LACTIC ACID

LACTIC ACID

CAS No. : 50-21-5
EC No. : 200-018-0

Synonyms:
2-Hydroxypropanoic acid; Lactic acid; Milk acid; lactate; Acetic acid; Glycolic acid; Propionic acid; 3-Hydroxypropanoic acid; Malonic acid; Butyric acid; Hydroxybutyric acid; 1-Propanol; 2-Propanol; Propionaldehyde; Acrolein; Sodium lactate; Ethyl lactate; Hydroxybutyric acid; Acids in wine; Alanine cycle; Biodegradable plastic; Dental caries; MCT1, a lactate transporter; Thiolactic acid; Lactic acid bacteria; LAB; AHA; alpha-hydroxy acid; lactic acid; 2-hydroxypropanoic acid; DL-Lactic acid; 50-21-5; 2-hydroxypropionic acid; Milk acid; Polylactic acid; lactate; Ethylidenelactic acid; Lactovagan; Tonsillosan; LACTIC ACID; Racemic lactic acid; Propanoic acid, 2-hydroxy-; Ordinary lactic acid; Milchsaeure; Acidum lacticum; Kyselina mlecna; DL-Milchsaeure; Lactic acid USP; 1-Hydroxyethanecarboxylic acid; Aethylidenmilchsaeure; alpha-Hydroxypropionic acid; Lacticacid; Lactic acid (natural); FEMA No. 2611; 26100-51-6; Kyselina 2-hydroxypropanova; Milchsaure [German]; Propionic acid, 2-hydroxy-; 598-82-3; (RS)-2-Hydroxypropionsaeure; CCRIS 2951; HSDB 800; (+-)-2-Hydroxypropanoic acid; FEMA Number 2611; Kyselina mlecna [Czech]; Propanoic acid, hydroxy-; SY-83; DL- lactic acid; Propel; Purac FCC 80; Purac FCC 88; Kyselina 2-hydroxypropanova [Czech]; EPA Pesticide Chemical Code 128929; (R)-2-Hydroxy-propionic acid;H-D-Lac-OH; Poly(lactic acid); C3H6O3; 2-hydroxy-propionic acid; DL-Lactic acid, 90%; E 270; (+/-)-Lactic acid; alpha-Hydroxypropanoic acid; C01432; Milchsaure; Polactide; Lacticum acidum; D(-)-lactic acid; Cheongin samrakhan; Cheongin Haewoohwan; Cheongin Haejanghwan; Lactic acid [JAN]; Lactic acid [USP:JAN]; lactasol; Propanoic acid, 2-hydroxy-, homopolymer; 1-Hydroxyethane 1-carboxylic acid; Biolac; Whey; 2-Hydroxy-2-methylacetic acid; Cheese whey; Lactide Polymer; Milk serum; Chem-Cast; Whey, cheese; L- Lactic acid; DL-Polylactic acid; Lactate (TN); 3B8D35Y7S4; 2-Hydroxypropionicacid; 4b5w; Lactic acid, tech grade; Propanoic acid, (+-); DL-Lactic Acid, Racemic; HIPURE 88; (.+/-.)-Lactic acid; EC 200-018-0; Lactic acid (7CI,8CI); 2-Hydroxypropanoic acid; Lactic acid; Milk acid; lactate; Acetic acid; Glycolic acid; Propionic acid; 3-Hydroxypropanoic acid; Malonic acid; Butyric acid; Hydroxybutyric acid; 1-Propanol; 2-Propanol; LACTIC ACID; Propionaldehyde; Acrolein; Sodium lactate; Ethyl lactate; Hydroxybutyric acid; Acids in wine; Alanine cycle; Biodegradable plastic; Dental caries; MCT1, a lactate transporter; Thiolactic acid; Lactic acid bacteria; LAB; AHA; alpha-hydroxy acid; lactic acid; 2-hydroxypropanoic acid; DL-Lactic acid; 50-21-5; 2-hydroxypropionic acid; Milk acid; Polylactic acid; lactate; Ethylidenelactic acid; Lactovagan; Tonsillosan; Racemic lactic acid; Propanoic acid, 2-hydroxy-; Ordinary lactic acid; Milchsaeure; Acidum lacticum; Kyselina mlecna; DL-Milchsaeure; Lactic acid USP; 1-Hydroxyethanecarboxylic acid; Aethylidenmilchsaeure; Lactic acid (JP17/USP); Lactic acid, 85%, FCC; Lactic Acid, Racemic, USP; NCIOpen2_000884; L-( pound<<)-Lactic acid; .alpha.-Hydroxypropanoic acid; .alpha.-Hydroxypropionic acid; KSC269O0T; (RS)-2-hydroxypropanoic acid; Lactic Acid (Fragrance Grade); INS NO.270; L-(+)-Lactic acid, 98%; CC(O)C([O])=O; CHEMBL1200559; DTXSID7023192; Lactic acid, natural, >=85%; (+/-)-2-hydroxypropanoic acid; Lactic Acid, 85 Percent, FCC; DL-Lactic acid, ~90% (T); INS-270; DL-Lactic acid, AR, >=88%; DL-Lactic acid, LR, >=88%; L-(+)-Lactic Acid, High Purity; Lactic Acid, 10 Percent Solution; EINECS 295-890-2; Propanoic acid, 2-hydroxy- (9CI); DL-Lactic acid, 85 % (w/w), syrup; Propanoic acid,2-hydroxy-,(.+/-.)-; Lactic Acid, 85 Percent, Reagent, ACS; L0226; Lactic acid solution, ACS reagent, >=85%; Lactic acid solution, USP, 88.0-92.0%; LACTIC ACID; Lactic acid solution, p.a., 84.5-85.5%; Lactic acid, meets USP testing specifications; D00111; DL-Lactic acid, SAJ first grade, 85.0-92.0%; Propanoic acid, 2-hydroxy-, (+-)-, homopolymer; Q161249; DL-Lactic acid, JIS special grade, 85.0-92.0%; Lactic acid solution, Vetec(TM) reagent grade, 85%; Lactic acid, United States Pharmacopeia (USP) Reference Standard; ALPHA/BETA HYDROXY ACIDS (ALPHA/BETA HYDROXY ACIDS); Lactic acid, Pharmaceutical Secondary Standard; Certified Reference Material

Lactic Acid

Lactic acid is an organic acid. It has a molecular formula CH3CH(OH)COOH. It is white in the solid state and it is miscible with water.[2] When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as natural sources. Lactic acid is an alpha-hydroxy acid (AHA) due to the presence of a hydroxyl group adjacent to the carboxyl group. It is used as a synthetic intermediate in many organic synthesis industries and in various biochemical industries. The conjugate base of lactic acid is called lactate.

In solution, it can ionize, producing the lactate ion CH3CH(OH)CO−2. Compared to acetic acid, its pKa is 1 unit less, meaning lactic acid is ten times more acidic than acetic acid. This higher acidity is the consequence of the intramolecular hydrogen bonding between the α-hydroxyl and the carboxylate group.
Lactic acid is chiral, consisting of two enantiomers. One is known as l-(+)-lactic acid or (S)-lactic acid and the other, its mirror image, is d-(−)-lactic acid or (R)-lactic acid. A mixture of the two in equal amounts is called dl-lactic acid, or racemic lactic acid. Lactic acid is hygroscopic. dl-Lactic acid is miscible with water and with ethanol above its melting point, which is around 16, 17 or 18 °C. d-Lactic acid and l-lactic acid have a higher melting point. Lactic acid produced by fermentation of milk is often racemic, although certain species of bacteria produce solely (R)-lactic acid. On the other hand, lactic acid produced by anaerobic respiration in animal muscles has the (S) configuration and is sometimes called "sarcolactic" acid, from the Greek "sarx" for flesh.

In animals, l-lactate is constantly produced from pyruvate via the enzyme lactate dehydrogenase (LDH) in a process of fermentation during normal metabolism and exercise.[6] It does not increase in concentration until the rate of lactate production exceeds the rate of lactate removal, which is governed by a number of factors, including monocarboxylate transporters, concentration and isoform of LDH, and oxidative capacity of tissues.[7] The concentration of blood lactate is usually 1–2 mM at rest, but can rise to over 20 mM during intense exertion and as high as 25 mM afterward.[8][9] In addition to other biological roles, l-lactic acid is the primary endogenous agonist of hydroxycarboxylic acid receptor 1 (HCA1), which is a Gi/o-coupled G protein-coupled receptor (GPCR).
In industry, lactic acid fermentation is performed by lactic acid bacteria, which convert simple carbohydrates such as glucose, sucrose, or galactose to lactic acid. These bacteria can also grow in the mouth; the acid they produce is responsible for the tooth decay known as caries.[12][13][14][15] In medicine, lactate is one of the main components of lactated Ringer's solution and Hartmann's solution. These intravenous fluids consist of sodium and potassium cations along with lactate and chloride anions in solution with distilled water, generally in concentrations isotonic with human blood. It is most commonly used for fluid resuscitation after blood loss due to trauma, surgery, or burns.

History
Swedish chemist Carl Wilhelm Scheele was the first person to isolate lactic acid in 1780 from sour milk.[16] The name reflects the lact- combining form derived from the Latin word lac, which means milk. In 1808, Jöns Jacob Berzelius discovered that lactic acid (actually l-lactate) also is produced in muscles during exertion.[17] Its structure was established by Johannes Wislicenus in 1873.
In 1856, the role of Lactobacillus in the synthesis of lactic acid was discovered by Louis Pasteur. This pathway was used commercially by the German pharmacy Boehringer Ingelheim in 1895.
In 2006, global production of lactic acid reached 275,000 tonnes with an average annual growth of 10%.[18]

Production
Lactic acid is produced industrially by bacterial fermentation of carbohydrates, or by chemical synthesis from acetaldehyde.[19] In 2009, lactic acid was produced predominantly (70–90%)[20] by fermentation. Production of racemic lactic acid consisting of a 1:1 mixture of d and l stereoisomers, or of mixtures with up to 99.9% l-lactic acid, is possible by microbial fermentation. Industrial scale production of d-lactic acid by fermentation is possible, but much more challenging.

USAGE areas of lactic acid
Cosmetics (make-up, creams, moisturizers, sun protectors...)
Foods
Cleaning products
Forgery
Pharmaceutical and cosmetic applications
Sports

Fermentative production
Fermented milk products are obtained industrially by fermentation of milk or whey by Lactobacillus bacteria: Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus delbrueckii subsp. bulgaricus (Lactobacillus bulgaricus), Lactobacillus helveticus, Lactococcus lactis, and Streptococcus salivarius subsp. thermophilus (Streptococcus thermophilus).
As a starting material for industrial production of lactic acid, almost any carbohydrate source containing C5 and C6 sugars can be used. Pure sucrose, glucose from starch, raw sugar, and beet juice are frequently used.[21] Lactic acid producing bacteria can be divided in two classes: homofermentative bacteria like Lactobacillus casei and Lactococcus lactis, producing two moles of lactate from one mole of glucose, and heterofermentative species producing one mole of lactate from one mole of glucose as well as carbon dioxide and acetic acid/ethanol.[22]

Chemical production
Racemic lactic acid is synthesized industrially by reacting acetaldehyde with hydrogen cyanide and hydrolysing the resultant lactonitrile. When hydrolysis is performed by hydrochloric acid, ammonium chloride forms as a by-product; the Japanese company Musashino is one of the last big manufacturers of lactic acid by this route.[23] Synthesis of both racemic and enantiopure lactic acids is also possible from other starting materials (vinyl acetate, glycerol, etc.) by application of catalytic procedures.

Polymer precursor
Main article: polylactic acid
Two molecules of lactic acid can be dehydrated to the lactone lactide. In the presence of catalysts lactide polymerize to either atactic or syndiotactic polylactide (PLA), which are biodegradable polyesters. PLA is an example of a plastic that is not derived from petrochemicals.

Pharmaceutical and cosmetic applications
Lactic acid is also employed in pharmaceutical technology to produce water-soluble lactates from otherwise-insoluble active ingredients. It finds further use in topical preparations and cosmetics to adjust acidity and for its disinfectant and keratolytic properties.

Foods
Lactic acid is found primarily in sour milk products, such as koumiss, laban, yogurt, kefir, and some cottage cheeses. The casein in fermented milk is coagulated (curdled) by lactic acid. Lactic acid is also responsible for the sour flavor of sourdough bread.
In lists of nutritional information lactic acid might be included under the term "carbohydrate" (or "carbohydrate by difference") because this often includes everything other than water, protein, fat, ash, and ethanol.[40] If this is the case then the calculated food energy may use the standard 4 kilocalories (17 kJ) per gram that is often used for all carbohydrates. But in some cases lactic acid is ignored in the calculation.[41] The energy density of lactic acid is 362 kilocalories (1,510 kJ) per 100 g.[42]
Some beers (sour beer) purposely contain lactic acid, one such type being Belgian lambics. Most commonly, this is produced naturally by various strains of bacteria. These bacteria ferment sugars into acids, unlike the yeast that ferment sugar into ethanol. After cooling the wort, yeast and bacteria are allowed to “fall” into the open fermenters. Brewers of more common beer styles would ensure that no such bacteria are allowed to enter the fermenter. Other sour styles of beer include Berliner weisse, Flanders red and American wild ale.[43][44]

In winemaking, a bacterial process, natural or controlled, is often used to convert the naturally present malic acid to lactic acid, to reduce the sharpness and for other flavor-related reasons. This malolactic fermentation is undertaken by lactic acid bacteria.
While not normally found in significant quantities in fruit, lactic acid is the primary organic acid in akebia fruit, making up 2.12% of the juice.
As a food additive it is approved for use in the EU,[46] USA[47] and Australia and New Zealand;[48] it is listed by its INS number 270 or as E number E270. Lactic acid is used as a food preservative, curing agent, and flavoring agent.[49] It is an ingredient in processed foods and is used as a decontaminant during meat processing.[50] Lactic acid is produced commercially by fermentation of carbohydrates such as glucose, sucrose, or lactose, or by chemical synthesis.[49] Carbohydrate sources include corn, beets, and cane sugar.[51]
Forgery
Lactic acid has historically been used to assist with the erasure of inks from official papers to be modified during forgery.[52]

Cleaning products
Lactic acid is used in some liquid cleaners as a descaling agent for removing hard water deposits such as calcium carbonate, forming the lactate, Calcium lactate. Owing to its high acidity, such deposits are eliminated very quickly, especially where boiling water is used, as in kettles. It also is gaining popularity in antibacterial dish detergents and hand soaps replacing Triclosan.

Related chemicals
Hydroxybutyric acid
Acids in wine
Alanine cycle
Biodegradable plastic
Dental caries
MCT1, a lactate transporter
Thiolactic acid

Everything You Need to Know About Lactic Acid Peels
What is lactic acid?
Lactic acid is an antiwrinkle and pigmentation-fighting ingredient found in over-the-counter (OTC) and professional-grade skin care products.
Derived from milk, lactic acid belongs to a class of anti-aging ingredients called alpha-hydroxy acids (AHAs). Other examples of AHAs include glycolic acid and citric acid.
Keep reading to learn how a lactic acid peel can improve your skin, OTC products to try, what to expect from a professional peel, and more.

How can a lactic acid peel benefit your skin?
A chemical peel works by using a chemical — in this case, lactic acid — on bare skin. It removes the top layer of skin (epidermis). Some stronger formulas may also target the middle layers of skin (dermis).
Despite the name, your skin doesn’t noticeably “peel” off. What is noticeable, though, are the effects underneath the removed epidermis: smoother and brighter skin.
Lactic acid is specifically used to treat hyperpigmentation, age spots, and other factors that contribute to a dull and uneven complexion. Other benefits of AHAs like lactic acid include improved skin tone and reduced pore appearance.
However, unlike AHAs such as glycolic acid, lactic acid is a bit milder. This makes a lactic acid peel a better choice for sensitive skin. Lactic acid may also be an option if you’ve tried another AHA in the past and found the product too strong.

Are side effects possible?
Despite the milder nature of lactic acid, it’s still considered a powerful AHA.
Its “peeling” effects will make your skin more vulnerable to the sun’s ultraviolet (UV) rays, so sunscreen is key. Make sure you apply sunscreen every morning and reapply as needed throughout the day.
Over time, unprotected sun exposure can lead to more age spots and scarring. It may even increase your risk for skin cancer.
Lactic acid peels can also cause irritation, rash, and itchiness. These effects are usually mild and improve as your skin gets used to the product. If your side effects persist after the first few applications, discontinue use and see your doctor.
You shouldn’t use a lactic acid peel if you have:
eczema
psoriasis
rosacea
If you have naturally darker skin, talk to your doctor or dermatologist before use. Chemical peels may increaseTrusted Source your risk of hyperpigmentation.

How to use a lactic acid peel
Instructions for use vary based on a product’s makeup and concentration. Always read the product label and follow the manufacturer’s directions.
Purchase
For a lighter peel, look for a product with a 5 percent acid content. Medium peels can range from 10 to 15 percent lactic acid, and deeper (professional) peels have even higher concentrations.
As a rule of thumb, the higher the concentration, the stronger the results. You may not have to use stronger peels as often, but any subsequent irritation may last longer.

Preparation and use
It’s important to do a skin patch test before your first full application. This can help reduce your risk of side effects.
To do this:
Apply a dime-sized amount of product to the inside of your forearm.
Cover the area with a bandage and leave it alone.
If you don’t experience any irritation or inflammation within 24 hours, the product should be safe to apply elsewhere.
If you do experience side effects, discontinue use. See your dermatologist if your side effects worsen or last more than a day or two.
Lactic acid peels are designed for evening application. Like other AHAs, lactic acid increases sun sensitivity, so you should never use them in the morning.

Protection
You should wear sunscreen every day when using lactic acid. For best results, apply sunscreen every morning and reapply as needed throughout the day. You can use a sunscreen-containing daytime moisturizer as well as a foundation with an SPF.
Lactic acid products to try at home
Lactic acid peels are widely available in drug stores, beauty supply stores, and online retailers.

Popular options include:
Dermalogica Gentle Cream Exfoliant. Suited for more sensitive skin, this cream-based lactic acid exfoliant also contains salicylic acid. These two ingredients remove dead skin cells that can lead to a pigmented, dull complexion.
Juice Beauty Green Apple Peel Full Strength. This all-encompassing peel targets wrinkles and hyperpigmentation with the help of lactic acid and other AHAs. It also contains willow bark, a natural type of salicylic acid, and vitamins A and C. This peel is not recommended for sensitive skin.
Patchology Exfoliate FlashMasque Facial Sheets. These lactic acid-based disposable face sheets work by sloughing off dead skin to improve overall appearance and texture. As a bonus, the facial sheets are easy to use, with no extra steps or rinsing required.
Perfect Image Lactic Acid 50% Gel Peel. If you’re looking for a deeper lactic acid peel, this product might be a home-based option for you. It contains 50 percent lactic acid to improve your complexion, and the gel is easy to manage without the product running off your face. It’s a professional-grade peel, so consult your dermatologist before use.
QRx Labs Lactic Acid 50% Gel Peel. Considered a professional-grade product, this gel-based peel also contains a higher concentration of lactic acid at 50 percent. Although the company promises professional results, it’s a good idea to run this by your dermatologist first to prevent side effects.

Consider getting a professional lactic acid peel
Despite the availability of at-home lactic acid peels, the Mayo Clinic says that deeper chemical peels offer the best results. The effects also last longer than OTC peels, so you don’t have to use them as often.
You might consider getting a lactic acid peel from your dermatologist or skin care specialist if you aren’t seeing results from OTC versions but don’t want to use a stronger AHA.

Before getting a professional lactic acid peel, talk to your dermatologist about all the medications you take as well as your level of sensitivity. These can all factor into the strength of the peel your dermatologist or skin care specialist chooses. This can help prevent side effects and complications, such as irritation and scarring.
Also know that it can take up to two weeks to recover from a professional lactic acid peel. Mild peels may cause side effects that last a day or so, but after a deeper peel, your skin may need to be bandaged for a couple of weeks.
Lactic acid peels can vary in cost, and they aren’t covered by insurance. That’s because they’re considered cosmetic treatments and not medically necessary therapies. However, you may be able to work out a payment plan with your dermatologist’s billing department.

The bottom line
Lactic acid is used to create a mild chemical peel that can help even out your skin tone. It can help address age spots, melasma, and rough texture, along with fine lines.
Although OTC options are available, it’s important to discuss your skin care needs with a dermatologist before trying a lactic acid peel at home. Certain skin conditions may increase your risk of side effects.
If you do try an OTC peel, make sure you do a skin patch test before your first full application. You should also apply sunscreen every morning and reapply as needed throughout the day.

USES of Lactic Acid
This medication has 2 types of ingredients (emollient, keratolytic) that work together to treat or prevent dry, rough, scaly, itchy skin (such as that caused by eczema, keratosis, xerosis). Dry skin is caused by a loss of water in the upper layer of the skin. Emollients are substances that soften and moisturize the skin and decrease itching and flaking. Emollients/moisturizers work by forming an oily layer on the top of the skin that traps water in the skin. Petrolatum, lanolin, mineral oil, and dimethicone are common emollients.
Lactic acid, salicylic acid, and urea are keratolytics. They increase moisture in the skin by softening/dissolving the horny substance (keratin) holding the top layer of skin cells together. This helps the dead skin cells fall off and helps the skin keep more water in. Higher strengths of urea are used to treat corns, callous, and some nail problems (e.g., ingrown nails). Urea is also used to help remove dead tissue in some wounds to help wound healing.

How to use Lactic Acid 10 % Topical Cream
Use this product as directed. Follow all directions on the product package and prescription label. If you have any questions, ask your doctor or pharmacist.
Some products need to be shaken before use. Check the label to see if you should shake the bottle well before using. Apply to the affected areas of the skin, usually 1-3 times a day or as directed by your doctor. Rub in well until absorbed. How often you apply the medication will depend on the product and your skin condition.

Apply to the skin/nails only. Avoid sensitive areas such as your eyes, lips, inside your mouth/nose, and the vaginal/groin area, unless your doctor directs you otherwise. Ask your doctor or check the label for directions about any areas or types of skin where you should not apply the product (e.g., on the face, any areas of broken/chapped/cut/irritated/scraped skin, or on a recently shaved area of the skin). Consult your doctor or pharmacist for more details.
Use this medication regularly to get the most benefit from it. Most moisturizers need water to work well. Apply the product after bathing/showering/shampooing while the skin is still damp. For very dry skin, your doctor may instruct you to soak the area before using the product. Long, hot, or frequent bathing/washing can worsen dry skin.

Production and Application of Lactic Acid
Lactic acid is an important organic acid used in the chemical, pharmaceutical, and food industries. Its production by biotechnological routes is preferable to chemical processes mainly because of the possibility of obtaining pure isomers (d- or l-lactic acid). l-Lactic acid is easily assimilated by the human body, which is why it is the most common commercial form. Another important application of l-lactic acid is in polymerization to obtain highly crystalline poly-l-lactic acid, which is suitable for fiber and film production. Many efforts have been concentrated on the improvement of production procedures, including process conditions, cost reduction, and productivity increase. Among these, can be mentioned the screening of new strains, genetic amelioration of strains, and use of cocultures. The use of alternative substrates, use of renewable resources, and development of new bioreactor configurations and downstream processing appear as new strategies for lactic acid production improvement. This chapter discusses the main topics concerning the importance, applications, production, and recovery of lactic acid.

What is lactic acid? (And where does it come from?)
Lactic acid, or lactate, is a chemical byproduct of anaerobic respiration — the process by which cells produce energy without oxygen around. Bacteria produce it in yogurt and our guts.  Lactic acid is also in our blood, where it's deposited by muscle and red blood cells.
It was long thought that lactic acid was the cause of muscle soreness during and after an intense period of exercise, but recent research suggests that's not true, said Michael Gleeson, an exercise biochemist at Loughborough University in the U.K., and author of "Eat, Move, Sleep, Repeat" (Meyer & Meyer Sport, 2020). 
"Lactate has always been thought of as the bad boy of exercise," Gleeson told Live Science. 
Contrary to that reputation, lactic acid is a constant, harmless presence in our bodies. While it does increase in concentration when we exercise hard, it returns to normal levels as soon as we're able to rest — and even gets recycled back into energy our body can use later on, Gleeson said.

How muscles produce lactic acid
Throughout most of the day, our body burns energy aerobically — that is, in the presence of oxygen. Part of that energy comes from sugar, which our muscle cells break down in a series of chemical reactions called glycolysis. (We also get energy from fat, but that involves a whole other chemical process). The end product of glycolysis is pyruvate, a chemical that the body uses to produce even more energy. But energy can be harvested from pyruvate only in the presence of oxygen. That changes during hard exercise.
Related: Muscle spasms and cramps: Causes and treatments

When you break into an all-out sprint your muscles start working overtime. The harder you work, the more energy your muscles need to sustain your pace. Luckily, our muscles have built-in turbo-boosters, called fast-twitch muscle. Unlike slow-twitch muscle, which we use for most of the day, fast-twitch muscle is super-effective at producing lots of energy quickly and does so anaerobically, Gleeson said. Fast-twitch muscle also uses glycolysis to produce energy, but it skips harvesting energy from pyruvate, a process that takes oxygen. Instead, pyruvate gets converted into a waste product, lactic acid, and released into the bloodstream.
It's a common misconception that muscle cells produce lactic acid when they can't get enough oxygen, Gleeson said. "That's not the case. Your muscles are getting plenty of oxygen," he said. But in times of intense energy needs, muscles switch to anaerobic respiration simply because it's a much quicker way to produce energy.

Other sources of lactic acid
Muscle cells aren't the only sources of lactic acid. Red blood cells also produce lactic acid as they roam the body, according to the online text Anatomy and Physiology published by Oregon State University. Red blood cells don't have mitochondria — the part of the cell responsible for aerobic respiration — so they only respire anaerobically.
Many species of bacteria also respire anaerobically and produce lactic acid as a waste product. In fact, these species make up between 0.01-1.8% of the human gut, according to a review published in the Journal of Applied Microbiology. The more sugar these little guys eat, the more lactic acid they produce. 

Slightly more insidious are the lactic acid bacteria that live in our mouths. Because of the acidifying effect they have on saliva, these bacteria are bad news for tooth enamel, according to a study published in Microbiology.
Finally, lactic acid is commonly found in fermented dairy products, like buttermilk, yogurt and kefir. Bacteria in these foods use anaerobic respiration to break lactose — milk sugar — into lactic acid. That doesn't mean that lactic acid itself is a dairy product, however — it's 100% vegan. It happens to get its name from dairy simply because Carl Wilhelm, the first scientist to isolate lactic acid, did so from some spoiled milk, according to a study published in the American Journal of Physiology.

Your body on lactic acid
It's common to feel a burning in your legs after you squat with heavy weights, or complete a hard workout. But contrary to popular belief, it's not lactic acid that causes the soreness, Gleeson said. 

Lactic acid is processed by the liver and the heart. The liver converts it back into sugar; the heart converts it into pyruvate. During exercise, concentrations of lactic acid in the body do spike because the heart and liver can't deal with the waste product as quickly as it's produced. But as soon as we're done exercising, lactic acid concentrations go back to normal, Gleeson said.
Related: Feel the pain? Don't blame lactic acid. 
Muscle soreness after exercise most likely has more to do with tissue damage and inflammation, Gleeson said. Hard exercise physically breaks down your muscles, and it can take days for them to recover.
Lactic acid can build up to life-threatening levels in the body, according to a review published in the Mayo Clinic Proceedings. But this condition, called acute lactic acidosis, happens because of acute illness or injury, not exercise. When tissues are deprived of blood due to a heart attack or sepsis, for example, they tend to go into anaerobic respiration, producing lactic acid.
"They get starved of oxygen," Gleeson said.
But Gleeson said he's never heard of a case of life-threatening lactic acidosis because of exercise. "That would be most unusual."  

Additional resources: 
Read about anaerobic respiration on Khan Academy.
Find out why you feel so sore after a workout.
Learn about acute lactic acidosis on Medscape. 

Lactic Acidosis and Exercise: What You Need to Know
Muscle ache, burning, rapid breathing, nausea, stomach pain: If you've experienced the unpleasant feeling of lactic acidosis, you likely remember it.
Lactic acidosis caused by intense exercise is usually temporary. It happens when too much acid builds up in your bloodstream.

Symptoms
The symptoms may include a burning feeling in your muscles, cramps, nausea, weakness, and feeling exhausted. It's your body's way to tell you to stop what you're doing
The symptoms happen in the moment. The soreness you sometimes feel in your muscles a day or two after an intense workout isn't from lactic acidosis. It's your muscles recovering from the workout you gave them.

Causes
Intense Exercise. When you exercise, your body uses oxygen to break down glucose for energy. During intense exercise, there may not be enough oxygen available to complete the process, so a substance called lactate is made. Your body can convert this lactate to energy without using oxygen. But this lactate or lactic acid can build up in your bloodstream faster than you can burn it off. The point when lactic acid starts to build up is called the "lactate threshold."

Medical Conditions. Some medical conditions can also bring on lactic acidosis, including:
 Cancer
 Seizures
 Liver failure
Vitamin B deficiency
 Sepsis (a whole-body inflammation caused by severe infection)
Shock
Medications. Some drugs, including metformin, a drug used to treat diabetes, and all nucleoside reverse transcriptase inhibitor (NRTI) drugs used to treat HIV/AIDS can cause lactic acidosis. If you are on any of these medications and have any symptoms of lactic acidosis, get medical help immediately.

Uses Of Lactic Acid
Lactic acid is used as a humectant, or moisturizer, in some cosmetics and as a mordant, a chemical that helps fabrics accept dyes, in textiles. It is also used in making pickles and sauerkraut, foods for which a sour taste is desired. Lactic acid is used in the dairy industry not only in making yogurt but in making cheese as well. It is also used in tanning leather. Lactic acid is important in the pharmaceutical industry as a starting material for other substances and is involved in the manufacturing of lacquers and inks. A related compound that is made from lactic acid is calcium stearoyl-2-lactylate, which is used as a food preservative.

What is lactic acid?
Lactic acid is a hydrating alpha hydroxy acid (AHA) commonly derived from milk, but there are alternative vegan sources, like fermented corn starch, beets, and other sugar-rich foods. Synthetic forms of this ingredient are often found in peels and serums.

What does lactic acid do for skin?
Lactic acid brightens, smooths, and evens skin, while also making it look firmer. It helps reduce the appearance of fine lines, wrinkles, and dark spots.

How does it work exactly?
It exfoliates by loosening the bonds between dead skin cells to reveal a more radiant complexion.

How do I use it?
It’s generally recommended for nighttime use, and suggested frequency varies from product to product. Check the packaging for specific instructions.

Are there any potential side effects?
You may experience slight tingling, stinging, and/or redness. (Don’t worry—this is normal.)

What can I pair it with?
While it can be used with many other ingredients and products, sunscreen’s an essential when lactic acid is a part of your routine. Another important step: cleansing the morning after you use lactic acid to sweep away dead skin cells.

Anything I shouldn’t pair it with?
Don’t use it on days you use retinol since both are potent ingredients. Alternate between the two to avoid irritation.

Preventing Lactic Acidosis
Begin any exercise routine gradually. Pace yourself. Don't go from being a couch potato to trying to run a marathon in a week. Start with an aerobic exercise like running or fast walking. You can build up your pace and distance slowly. Increase the amount of exercise each week so your body builds up a tolerance. This will increase your "lactate threshold," making it less likely you'll get lactic acidosis.
Make sure you drink lots of water. It helps get rid of any excess acid. Eat a balanced diet which includes lots of fruits, vegetables, whole grains, and lean meats. Get plenty of sleep at night and give yourself time to recover between bouts of exercise. How long that is depends on how you feel.
If your lactic acidosis is caused by a disease or medication, talk to your doctor. You may be able to make changes that will help you avoid the problem. And talk to your doctor before starting a new exercise routine.

What is lactic acidosis?
Lactic acidosis is a form of metabolic acidosis that begins when a person overproduces or underutilizes lactic acid, and their body is not able to adjust to these changes.
People with lactic acidosis have problems with their liverTrusted Source (and sometimes their kidneys) being able to remove excess acid from their body. If lactic acid builds up in the body more quickly than it can be removed, acidity levels in bodily fluids — such as blood — spike.

This buildup of acid causes an imbalance in the body’s pH level, which should always be slightly alkaline instead of acidic. There are a few different types of acidosis.
Lactic acid buildup occurs when there’s not enough oxygen in the muscles to break down glucose and glycogen. This is called anaerobic metabolism.
There are two types of lactic acid: L-lactate and D-lactate. Most forms of lactic acidosis are caused by too much L-lactate.
There are two types of lactic acidosis, Type A and Type B:
Type A lactic acidosis is caused by tissue hypoperfusion resulting from hypovolemia, cardiac failure, sepsis, or cardiopulmonary arrest.
Type B lactic acidosis is caused by impairment of cellular functioning and localized areas of tissue hypoperfusion.
Lactic acidosis has many causes and can often be treated. But if left untreated, it may be life-threatening.

What are the symptoms?
The symptoms of lactic acidosis are typical of many health issues. If you experience any of these symptoms, you should contact your doctor immediately. Your doctor can help determine the root cause.
Several symptoms of lactic acidosis represent a medical emergency:
fruity-smelling breath (a possible indication of a serious complication of diabetes, called ketoacidosis)
confusion
jaundice (yellowing of the skin or the whites of the eyes)
trouble breathing or shallow, rapid breathing
If you know or suspect that you have lactic acidosis and have any of these symptoms, call 911 or go to an emergency room right away.

Other lactic acidosis symptoms include:
exhaustion or extreme fatigue
muscle cramps or pain
body weakness
overall feelings of physical discomfort
abdominal pain or discomfort
diarrhea
decrease in appetite
headache
rapid heart rate
What are the causes?
Lactic acidosis has a wide range of underlying causes, including carbon monoxide poisoning, cholera, malaria, and asphyxiation. Some common causes include:
Heart disease
Conditions such as cardiac arrest and congestive heart failure may reduce the flow of blood and oxygen throughout the body. This can increase lactic acid levels.

Severe infection (sepsis)
Any type of severe viral or bacterial infection can cause sepsis. People with sepsis may experience a spike in lactic acid, caused by reduced oxygen flow.
HIV
HIV medications, such as nucleoside reverse transcriptase inhibitors, can spike lactic acid levels. They also may cause liver damage. This makes it harder for the body to process lactate.
Cancer
Cancer cells create lactic acid. This buildup of lactic acid may accelerate as a person loses weight and the disease progresses.

Short bowel syndrome (short gut)
While rareTrusted Source, people with short gut may experience a buildup of D-lactic acid, caused by bacterial overgrowth in the small bowel. People who’ve had gastric bypass surgery may also get D-lactic acidosis.

Acetaminophen use
Regular, frequent use of acetaminophen (Tylenol) can cause lactic acidosis, even when taken in the correct dosage. This is because it can cause an accumulation of pyroglutamic acid in the blood.

Chronic alcoholism
Drinking alcohol to excess over an extended period of time can lead to lactic acidosis and alcoholic ketoacidosis. Alcoholic ketoacidosis is a potentially fatal condition if left untreated, but it can be combated with intravenous (IV) hydration and glucose.
Alcohol increases phosphate levels, which negatively impact the kidneys. This makes the body’s pH more acidic. If you’re having trouble reducing your alcohol intake, support groups can help.

Intense exercise or physical activity
A temporary buildup of lactic acid can be caused by vigorous exercise if your body doesn’t have enough available oxygen to break down glucose in the blood. This can cause a burning feeling in the muscle groups you’re using. It can also cause nausea and weakness.

Lactic acidosis and diabetes
A specific class of oral diabetes medication, called biguanides, can cause a buildup of lactic acid levels.
Metformin (Glucophage) is one of these drugs. It’s used to treat diabetes and may also be prescribed for other conditions, such as renal insufficiency. Metformin is also used off-label to treat polycystic ovarian syndrome.
In people with diabetes, lactic acidosis may be more of a concern if kidney disease is also present. If you have diabetes and experience any symptoms of lactic acidosis, call 911 or go to an emergency room immediately.

How is it diagnosed?
Lactic acidosis is diagnosed through a fasting blood test. Your doctor may instruct you to not eat or drink anything for 8 to 10 hours before taking the test. You may also be instructed to curb your activity level in the hours leading up to the test.
During the test, your doctor may tell you not to clench your fist, as this may artificially spike acid levels. Tying an elastic band around the arm may also have this result.
For these reasons, the lactic acidosis blood test is sometimes done by finding a vein on the back of the hand instead of the arm.

What are the treatment options?
The best way to treat lactic acidosis is by treating its root cause. For that reason, treatments vary.
Lactic acidosis sometimes represents a medical emergency. This requires treating symptoms, regardless of their root cause. Increasing oxygen to the tissues and giving IV fluids are often used to reduce lactic acid levels.
Lactic acidosis caused by exercising can be treated at home. Stopping what you’re doing to hydrate and rest, often helps. Electrolyte-replacement sports drinks, such as Gatorade, help with hydration, but water is usually best.

What is the outlook?
Based on the root cause, treatments for lactic acidosis often result in full recovery, particularly if treatment is immediate. Sometimes, kidney failure or respiratory failure may result. When left untreated, lactic acidosis can be fatal.

Preventing lactic acidosis
Lactic acidosis prevention is also determined by its potential cause. If you have diabetes, HIV, or cancer, discuss your condition and the medications you need with your doctor.
Lactic acidosis from exercise can be prevented by remaining hydrated and providing yourself with long resting periods between exercise sessions.
It’s vitally important to avoid misusing alcohol. Discuss rehabilitation and 12-step program options with your doctor or counselor.

What is lactic acid?
When working out, it’s important to avoid overexerting yourself. This can lead to injury and lactic acid building. Lactic acid is produced in your muscles and builds up during intense exercise. It can lead to painful, sore muscles.
Lactic acid buildup due to exercise is usually temporary and not cause for a lot of concern, but it can affect your workouts by causing discomfort. Read on to learn how to get rid of lactic acid after it’s built up in your muscles and what you can do to prevent it from building up in the future.

1. Stay hydrated
Make sure you’re staying hydrated, ideally before, during, and after strenuous exercise. Proper hydration is important when working out because it may help:
replenish any fluids that you lose when working out
rid your body of lactic acid
allow nutrients to create energy
relieve sore muscles
prevent muscle cramps
keep your body performing at optimal levels
Drink at least eight glasses of water a day, and increase this amount when you exercise.

2. Rest between workouts
While exercising regularly can help you maintain consistency, getting enough rest between workouts is important for muscle recovery. It also gives your body the chance to break down any excess lactic acid.
Have at least one full day of rest per week. It’s ok to do some light exercises or movement on rest days, just keep it to a minimum.

3. Breathe well
Get in the habit of improving your breathing technique. A 1994 studyTrusted Source found that athletes who practiced breathing exercises increased their athletic performance without increasing lactic acid levels.
For a simple breathing technique, inhale slowly through your nose and exhale out through your mouth. You may wish to retain your breath for a few seconds after each inhalation, but do this only if it feels comfortable.
You can also try one of these simple breathing exercises to get in the habit of breath awareness while increasing your lung capacity.
Practice these breathing techniques while you’re working out and throughout the day. This may help to deliver more oxygen to your muscles, slowing down the production of lactic acid and helping to release any buildup.

4. Warm up and stretch
Take time to warm up and stretch your muscles before and after your workout. Doing a few light stretches in the morning and evening can also help. Even if it’s only for a few minutes at a time, your muscles will thank you.
Stretching can help to stimulate circulation, increase flexibility, and relieve tension. This helps bring more oxygen to your muscles, which can reduce lactic acid production and rid your muscles of any accumulation of lactic acid.

5. Get plenty of magnesium
Increasing your magnesium intake may help to prevent and relieve muscle soreness and spasms that may accompany lactic buildup. It can also help optimize energy production so that your muscles get enough oxygen while you’re exercising.
A small 2006 studyTrusted Source on 30 male athletes found that magnesium supplementation had a positive effect on their athletic performance over a four-week period. This is thought to be because lower levels of lactic acid led to less exhaustion. Larger studies are needed to confirm these results.
Foods rich in magnesium include nuts, legumes, and leafy greens. Taking a magnesium flake or Epsom salt bath is another way to absorb magnesium. It can also help to promote relaxation, boost energy levels, and relieve soreness, especially if you do it on a regular basis.

6. Drink orange juice
Adding a glass of orange juice to your pre-workout routine may be beneficial in reducing lactate levels and improving your athletic performance.
In a small 2010 study, researchers asked 26 middle-aged women who were overweight to exercise three times a week for three months. Half of the women were asked to drink orange juice before their workout. The other half did not have any orange juice.
The group that had the orange juice showed lower levels of lactic acid, which suggests that they had less muscle fatigue. They also showed improved physical performance and lowered their cardiovascular risk.
Researchers believe these improvements were due to the participants increased intake of vitamin C and folate. More research is needed to confirm these results.
How to know if you have lactic acid buildup
When lactic acid builds up in your muscles, it can make your muscles feel fatigued or slightly sore. Other symptoms may include:
nausea
vomiting
weakness
muscle soreness or cramping
burning sensation in the muscles
rapid or shallow breathing
shortness of breath
cramps
numbness
tingling
yellowing of the skin or eyes
If your symptoms are severe or persist, it may a sign of lactic acidosis. This condition can become serious. See your doctor if your suspect lactic acidosis.

Lactic acid can cause fatigue and soreness as a way of protecting your body. This can be a reminder for you to slow down and take it easy.
Taking steps to manage lactic acid buildup can help you to develop healthy habits for both your daily life and your exercise program.
Always talk to your doctor before beginning a new workout plan, and See your doctor if you have pain or discomfort after exercising that doesn’t subside after a few days, or if you experience any unusual or severe symptoms.

Applications of Lactic acid
Starter cultures for fermented foods
Fermented foods are produced through fermentation of certain sugars by Lactic acid and the origins of them are lost in antiquity. The most commonly Lactic acid used as starter cultures in food fermentations are shown in Table 1. It is well-known that the greatest proportion of them belong to the category of dairy products, namely cheese, yoghurt, fermented milks, while fermented meat products, fish products, pickled vegetables and olives and a great variety of cereal products are manufactured, nowadays, using starter cultures. These products, were produced in the past through back slopping and the resulting product characteristics depended on the best-adapted strains dominance, whereas, the earliest productions of them were based on the spontaneous fermentation, resulting from the development of the microflora naturally present in the raw material and its environment. Today, the majority of fermented foods are manufactured with the addition of selected, well defined, starter cultures with well characterized traits, specific for each individual product. For a detailed classification of starter cultures see.21−23

Adjunct cultures
Secondary cultures, or adjunct cultures or adjuncts, are defined as any cultures that are deliberately added at some point of the manufacture of fermented foods, but whose primary role is not acid production. Adjunct cultures are used in cheese manufacture to balance some of the biodiversity removed by pasteurisation, improved hygiene and the addition of defined-strain starter culture.24,25 These are mainly non-starter Lactic acid which have a significant impact on flavour and accelerate the maturation process.24,25

Extracellular polysaccharides (EPSs) are produced by a variety of bacteria and are present as capsular polysaccharides bound to the cell surface, or are released into the growth medium.26 These polymers play a major role in the production of yogurt, cheese, fermented cream and milk-based desserts27 where they contribute to texture, mouth-feel, taste perception and stability of the final products. In addition, it has been suggested that these EPSs or fermented milks containing these EPSs are active as prebiotics,28 cholesterol-lowering29 and immunomodulants.30 EPS-producing strains of Streptococcus thermophilus and Lactobacillus delbreuckii ssp. bulgaricus have been shown to enhance the texture and viscosity of yogurt and to reduce syneresis.31
For the production of wine, Lactic acid are involved in the malolactic fermentation, that is a secondary fermentation, which involves the conversion of L-malate to L-lactate and CO2 via malate decarboxylase, also known as the malolactic enzyme, resulting in a reduction of wine acidity, providing microbiological stabilization and modifications of wine aroma.32,33

Bio-protective cultures
Certain Lactic acid have been found to produce bacteriocins, namely, polypeptides synthesized ribosomally by bacteria that can have a bacteriocidal or bacteriostatic effect on other bacteria.34,35 In general, bacteriocins lead to cell death by inhibiting cell wall biosynthesis or by disrupting the membrane through pore formation.36 Bacteriocins are therefore important in food fermentations where they can prevent food spoilage or the inhibition of food pathogens. The best known bacteriocin is nisin, which has gained widespread application in the food industry and is used as a food additive in at least 50 countries, particularly in processed cheese, dairy products and canned foods.37 Examples of useful bacteriocins produced by Lactic acid are lacticin 314738−41 from lactococci, macedovicin from Streptococcus macedonicus ACA-DC 198,42,43 reuterin from Lactobacillus reuteri,44 sakacin M from Lactobacillus sake 14845 curvacin A, curvaticin L442 and lactocin AL705 from Lactobacillus curvatus LTH1174,46 pediocin PA-1/AcH from Pediococcus acidilactici,47 plantaricins (A, EF and JK) from Lactobacillus plantarum.47 The above bacteriocins have proved effective in many food systems for the control of food spoilage or pathogenic bacteria.

Antifungal activities of Lactic acid have been reported.48−50 In addition; Lactic acid strains also have the ability to reduce fungal mycotoxins, either by producing anti-mycotoxinogenic metabolites, or by absorbing them.50
For Lactic acid to be used as bio-protective starter cultures, they must possess a range of physical and biochemical characteristics, and most importantly, the ability to achieve growth and sufficient production of antimicrobial metabolites, which must be demonstrated in the specific food environment.48

Probiotic culture
Lactic acid are considered as a major group of probiotic bacteria;51,52 probiotic has been defined by Fuller53 as "a live microbial feed supplement which beneficially affects the host animal by improving its intestinal microbial balance". Salminen et al.54 proposed that probiotics are microbial cell preparations or components of microbial cells that have a beneficial effect on the health and well-being of the host. Commercial cultures used in food applications include mainly strains of Lactobacillus spp., Bifidobacterium spp. and Propionibacterium spp. Lactobacillus acidophilus, Lactobacillus casei, Lb. reuteri, Lactobacillus rhamnosus and Lb. plantarum are the most used Lactic acid in functional foods containing probiotics.55,56 Argentinean Fresco cheese,57 Cheddar58 and Gouda59 are some examples of applications of probiotic Lactic acid, in combination with bifidobacteria, in cheeses.

The health-promoting effects of Lactic acid are shown in Table 2. Apparently, these effects are species and strain specific, and the big challenge is the use of probiotic cultures composed of multiple species.60 In addition, Lactic acid, as part of gut microbiota ferment various substrates such as biogenic amines and allergenic compounds into short-chain fatty acids and other organic acids and gases.61
In recent years, the genomes of several probiotic species have been sequenced, thus paving the way to the application of ‘omics’ technologies to the investigation of probiotic activities.60 Moreover, although recombinant probiotics have been constructed, the industrial application of genetically engineered bacteria is still hampered by legal issues and by a rather negative general public opinion in the food sector.