Dr. Andrea Middleton - Is It Bad For You? Approved by Dr. Andrea Middleton

Is Lactic Acid Bad For You?



Short answer

Lactic acid is misunderstood; it's a natural, beneficial byproduct of anaerobic metabolism. It fuels muscles, buffers pH, and helps convert glucose, supporting energy production and delaying fatigue. Mistakenly blamed for soreness, lactic acid is cleared from muscles shortly after exercise, not causing the delayed onset muscle soreness (DOMS) typically experienced days later.



Long answer

Role of Lactic Acid in Exercise and Muscle Fatigue

Lactic acid often gets a bad rap, frequently blamed for the burning sensation in muscles during intense exercise and the subsequent muscle soreness. However, this perception is not only outdated but also misrepresents the nature of lactic acid and its actual role in the body’s physiological response to exercise.

Firstly, it's crucial to understand that during strenuous physical activity, the body requires energy to be produced rapidly. When oxygen levels are insufficient for aerobic metabolism, the body switches to anaerobic metabolism, leading to the production of lactate – the base form of lactic acid.

Lactate is then utilized in a few ways:

  • As a Fast-Energy Source: It can be quickly converted back into energy to fuel muscles when the demand is urgent, thus playing a significant role in energy production during anaerobic exercise.
  • Buffering Agent: Lactate acts to mitigate the drop in pH within muscles that could potentially impede continued muscular contraction and enzyme functioning.
  • Glucose Generator: Through the Cori Cycle, lactate can be transported to the liver, where it is converted back into glucose, thus contributing to sustained energy supply for muscle activity and recovery.

Recent studies emphasize lactate's role not as a fatigue agent but as a critical intermediary in metabolic processes. For instance, a research article published in the journal Sports Medicine outlines how lactate production acts to delay, not cause, muscle fatigue by compensating for the shortage of available energy substrates.

So, what about that familiar burn? The muscle discomfort experienced during exercise is now understood to be more closely linked to muscle strain and the accumulation of other metabolites rather than lactate itself. A study from the European Journal of Applied Physiology found that the process of lactate production and removal is quite efficient and does not directly correlate with muscle pain or cramps that may occur during or after rigorous activity.

Moreover, lactic acid does not linger in the muscles for long. It is quickly cleared from the muscles within an hour post-exercise, as conveyed in research published by the American Journal of Physiology. Therefore, the soreness felt days after a tough workout, known as delayed onset muscle soreness (DOMS), is due to microscopic muscle damage rather than lactic acid build-up.

While the understanding of lactic acid's role in exercise physiology has evolved, it is important to remember that lactic acid is not the enemy. Your body's ability to produce and clear lactate actually plays a role in how well you can perform physically and recover from exercise. The "burn" is a sign of your body effectively responding to energy demand, not a signal of harm or damage from lactic acid itself.

As always, the interpretation of physical sensations during exercise and the contributions of various biochemical processes must be grounded in scientific evidence, which shows that lactate production is a natural and beneficial component of the body's response to intense physical effort.

Misconceptions About Lactic Acid and Muscle Soreness

One of the most enduring myths in the realm of fitness and sports is the belief that muscle soreness, or Delayed Onset Muscle Soreness (DOMS), is caused by the accumulation of lactic acid in the muscles. This misconception has been debunked by numerous scientific studies, yet it persists in gym lore and casual conversation. Let's dissect the science to set the record straight.

First, it's crucial to understand what lactic acid actually is. Lactic acid is a byproduct of anaerobic glycolysis, a metabolic process that occurs when the body breaks down carbohydrates for energy without the use of oxygen. This process happens during intense exercise when the body's demand for oxygen exceeds its supply.

  • Lactic Acid's Role: Lactic acid helps provide short-term energy to muscles during strenuous activity.
  • Quick Conversion: Lactic acid quickly converts into lactate, a form that actually helps in fuel production, not muscle soreness.
  • Buffering Agent: Lactate acts as a buffering agent, helping to delay the onset of muscle fatigue during exercise.

Second, the association of lactic acid with muscle soreness arises from its presence in the muscles after intense exercise. However, DOMS is primarily due to microdamage in muscle fibers resulting from exertion beyond what the muscles are accustomed to. The soreness typically peaks 24 to 72 hours after the exercise, which corresponds not with lactic acid levels, but rather with the inflammation and repair processes occurring in the muscles.

In a study published in the Journal of Physiology, researchers indicated that lactate production is indeed associated with muscle fatigue; however, it is cleared from the muscles within an hour or so post-exercise, long before DOMS develops (source). Furthermore, an investigation in the Clinical Journal of Sport Medicine found no direct evidence of lactic acid causing muscle soreness (source).

We can conclude that the presence of lactate in the muscles is not the cause of DOMS, and lactic acid should not be vilified in this regard. The perpetuation of this myth is likely due to a misunderstanding of the body's metabolic processes and a tendency to oversimplify the causes of muscle soreness.

Correcting such misconceptions is important not only for the sake of accuracy but also to ensure that individuals do not avoid lactic acid-generating exercises, with the mistaken belief that they harm the muscles. In fact, these exercises are often high-intensity and can lead to significant improvements in strength, endurance, and overall fitness levels.

It's essential for fitness enthusiasts and athletes alike to be properly informed about the causes of muscle soreness to adopt the most effective recovery strategies, which should be based on rest, proper nutrition, and, when necessary, appropriate interventions like physical therapy, rather than unfounded fears of lactic acid.

Lactic Acid in Food: Understanding Fermentation Benefits

When you hear "lactic acid," you might initially think of the burn in your muscles during an intense workout. However, when it comes to food, lactic acid plays an entirely different role, one that's more beneficial than you might expect. Fermentation, a process vital in food preparation and preservation, is the primary source of lactic acid in our diet. Here, we delve into the world of fermented foods and the benefits that lactic acid can offer.

The Fermentation Process

Fermentation is a natural process through which microorganisms such as bacteria convert carbs like sugar and starch into alcohol or organic acids. In the case of lactic acid fermentation, specific strains of bacteria, predominantly Lactobacillus, convert sugars into lactic acid. This acid acts as a natural preservative, inhibiting the growth of harmful bacteria, thus extending the shelf-life of food products. Beyond preservation, fermentation also enhances the nutritional and organoleptic traits of these foods.

Nutritional Advantages of Lactic Acid Fermentation

Fermented foods rich in lactic acid have been linked to a variety of nutritional benefits:

  • Gut Health: Lactic acid acts as a prebiotic, stimulating the growth of healthy bacteria in the gut. Consuming fermented foods contributes to a balanced microbiome which is crucial for digestive health.
  • Improved Nutrient Profile: Fermentation can increase the levels of certain nutrients in food, such as B vitamins and omega-3 fatty acids.
  • Enhanced Digestibility: Fermented foods are often easier to digest than their non-fermented counterparts because fermentation breaks down complex proteins and sugars.
  • Increased Bioavailability: Fermentation can improve the bioavailability of minerals, making it easier for the body to absorb essential nutrients like iron, zinc, and calcium.

Probiotic Potential of Fermented Foods

Some lactic acid-fermented foods are probiotic, containing live microorganisms that, when ingested in adequate amounts, confer a health benefit on the host. The Lactobacillus and Bifidobacterium species are among the most common probiotics found in foods like yogurt, kefir, and some cheeses. Regular consumption of these probiotic-rich foods has been associated with improved immune function and decreased inflammation.

The Safety Aspect of Lactic Acid in Food

The presence of lactic acid in food is generally deemed safe and even beneficial. However, inflammation or soreness may not necessarily stem from lactic acid itself but could be indicative of an underlying intolerance or allergy. Individuals who suspect they might be sensitive to fermented products should consult a healthcare provider.

Environmental and Economic Factors

Beyond health benefits, lactic acid fermentation also has positive environmental and economic implications. This form of preservation reduces reliance on energy-intensive storage methods and diminishes food waste by prolonging shelf-life. Small-scale fermentation practices can enhance food sovereignty by enabling individuals and communities to preserve their own food without the need for industrial processing.

Overall, lactic acid in food, especially through the process of fermentation, brings a multitude of benefits that extend far beyond simple preservation. It encapsulates a historical wisdom that is increasingly supported by contemporary science, presenting a compelling case for the inclusion of fermented foods in a balanced diet.

Potential Skin Reactions to Topical Lactic Acid Use

Lactic acid, an alpha-hydroxy acid (AHA), found in over-the-counter skincare products and professional treatments, is a common ingredient hailed for its exfoliating properties that promote smooth and youthful-looking skin. Despite its widespread adoption and benefits in skincare routines, lactic acid is not free from the potential to cause skin reactions. Below, we delve into the variety of skin responses that can result from the topical use of lactic acid, highlighting what consumers should be vigilant about.

Common Skin Irritations

  • Redness: The application of lactic acid can lead to erythema or skin redness, particularly in individuals with sensitive skin or when used in higher concentrations. It can be a transient response or persist with continuous use.
  • Dryness and Flakiness: As an exfoliant, lactic acid accelerates the shedding of dead skin cells which could result in dry patches and flaky skin, especially if the skin's moisture barrier is not adequately supported with emollients or hydrating agents.
  • Burning or Stinging Sensation: Users may experience a tingling or stinging sensation upon application, often a sign that the acid is active on the skin. However, intense or ongoing discomfort suggests the product may not be suited to the individual's skin type or that the concentration is excessively high.

Allergic Reactions

  • Contact Dermatitis: Some individuals may develop allergic contact dermatitis, characterized by itching, blistering, or swelling in the area where lactic acid was applied. Though less common, this indicates a hypersensitivity to the ingredient.


Exposure to lactic acid makes the skin more prone to ultraviolet (UV) damage due to its exfoliating effect, which removes the uppermost protective layers of skin. Users must commit to regular application of sunscreen to avoid phototoxic reactions or long-term photoaging effects. Indeed, Journal of the American Academy of Dermatology emphasizes the necessity of photoprotection when using AHAs.

Risk of Chemical Burns

High concentrations of lactic acid, particularly in chemical peels performed without professional supervision, can lead to chemical burns. The severity of these burns can range from mild to severe and may be accompanied by blistering, peeling, and possibly scarring.

Interactions with Other Skincare Ingredients

Lactic acid can interact with other active ingredients in skincare products, such as retinol or vitamin C, which might amplify irritation, leading to increased inflammation and sensitivity. Users should be cautious when layering products to avoid such adverse interactions.

Varied Tolerance Among Users

It's important to note that skin reactions to lactic acid are not universal. Individual tolerance can greatly vary, with some users experiencing no adverse effects at all. Skin type, existing conditions, and past skincare routines play significant roles in how skin may react to lactic acid. Dermatologists often recommend patch testing and starting with lower concentrations to gauge skin's reaction.

Expert Opinions and Recommendations

Dermatologists generally advise introducing lactic acid slowly into skincare regimens to allow the skin to adapt and to mitigate potential irritation. A study in the International Journal of Cosmetic Science confirms that progressive skin acclimatization can minimize irritation potential. Those with sensitive or reactive skin types are particularly encouraged to follow a cautious approach or to seek alternatives.

In summary, while lactic acid can be a powerful ally in achieving radiant skin, the key to avoiding adverse reactions lies in understanding and respecting your skin's limits and employing sensible skincare practices. Awareness of the potential skin reactions can guide users to make informed choices and enjoy the benefits of lactic acid without compromising their skin health.

The Importance of Lactic Acid for pH Regulation in the Body

Lactic acid is a natural byproduct of metabolic processes in the body, often vilified due to its association with muscle fatigue and soreness. However, beyond these temporary effects, lactic acid plays a crucial, and often underappreciated, role in pH regulation within the body.

The body's pH balance, the measure of acidity or alkalinity, is a vital aspect of our overall health. Normal physiological pH values are tightly regulated, usually ranging between 7.35 and 7.45, slightly alkaline. Any significant deviation can lead to a state called acidosis or alkalosis, both of which can be detrimental to bodily functions. Lactic acid, produced during anaerobic respiration, is a key player in this balancing act.

During intense exercise or in situations where oxygen levels are low, our cells rely on anaerobic respiration to meet energy demands. This process converts glucose into energy and, as a side effect, produces lactic acid. The presence of lactic acid is often seen as unfavorable, as it's associated with the ‘burn’ felt during intense physical activity. However, this lactic acid production is an essential response to an immediate need for energy.

The body uses several mechanisms to manage the pH levels, including buffering systems—where lactic acid is a central component. Lactic acid can release hydrogen ions; the accumulation of these ions lowers the pH, signaling a shift towards acidity. This is where our body’s regulatory systems come into play:

  • Blood Buffer Systems: Hemoglobin and other proteins act as buffers, binding to excess hydrogen ions to mitigate changes in blood pH.
  • Respiratory Compensation: When lactic acid levels rise, the body compensates by increasing the rate and depth of respiration to expel more carbon dioxide (which is acidic when dissolved in blood) to raise the pH back towards normal levels.
  • Renal Compensation: The kidneys also regulate acid-base balance, selectively reabsorbing bicarbonate from urine and excreting hydrogen ions, to adjust the blood's acidity.

In fact, a study published in the Journal of Clinical Endocrinology & Metabolism demonstrated the intricate role of lactic acid in preventing acidosis during episodes of hypoxia, highlighting its importance in maintaining acid-base balance.

The misconception that lactic acid is only a harmful byproduct overlooks its essential role in our body's homeostasis. Lactic acid ensures that pH levels remain within a narrow range that is compatible with life and optimal function. It is a testament to the body's remarkable ability to regulate itself under varying conditions and demands.

As with many physiological processes, issues arise not from the presence of lactic acid itself but from an inability to effectively manage and clear it when production exceeds the body's threshold for clearance. Under normal conditions, lactic acid is swiftly processed and utilized or converted back into glucose in the liver through the Cori cycle, showcasing another layer of the body's sophisticated regulatory systems.

Understanding the role of lactic acid in pH regulation allows for a more nuanced perspective on its place within the complex puzzle of human biochemistry. Given the scientific evidence, lactic acid should not be considered inherently ‘bad’; instead, it is a vital component with significant regulatory functions that support our well-being. Targeted research has elucidated this fact, but public perception may still lag behind the science.

Frequently asked questions

Yes, lactic acid produced during the fermentation process acts as a prebiotic, promoting the growth of healthy gut bacteria. Consuming fermented foods that are rich in lactic acid can contribute to a balanced microbiome and overall digestive health.

The body utilizes buffers, such as hemoglobin in the blood and respiratory and renal compensation mechanisms, to manage excess lactic acid. These help to mitigate changes in blood pH by binding with hydrogen ions or by altering the excretion of carbon dioxide and hydrogen ions via breathing or urine, maintaining the body’s pH balance.

No, lactic acid is not responsible for the soreness that occurs days after a workout. That kind of soreness is known as delayed onset muscle soreness (DOMS) and is attributed to microscopic muscle damage and inflammation, not lactic acid build-up.

If you have sensitive skin, you should be cautious when using skincare products containing lactic acid. Consider patch testing and starting with lower concentrations to gauge how your skin reacts, and consult with a dermatologist if necessary. Lactic acid can cause irritation in some individuals with sensitive skin.

Ask a question about Lactic Acid and our team will publish the answer as soon as possible.

Possible short-term side effects

  • tingling
  • redness
  • dryness
  • flakiness
  • stinging
  • burning
  • chemical burns

Possible long-term side effects

  • allergic contact dermatitis
  • scarring from burns
  • increased photoaging

Commonly found in

  • skincare products
  • fermented foods
  • yogurt
  • kefir

Ingredients to be aware of

  • high concentrations in skincare
  • interactions with other skincare ingredients


  • energy source during exercise
  • buffering agent
  • glucose generation
  • gut health
  • improved nutrient profile
  • enhanced digestibility
  • increased bioavailability
  • skin exfoliation
  • smoother skin
  • ph regulation

Healthier alternatives

  • gradual introduction to skincare routine
  • lower concentrations
  • patch testing
  • sunscreen

Thank you for your feedback!

Written by Joey Conners
Published on: 12-14-2023

Thank you for your feedback!

Written by Joey Conners
Published on: 12-14-2023

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