Dr. Thomas Dwan - Is It Bad For You? Approved by Dr. Thomas Dwan

Is Conjugated Linoleic Acid Bad For You?

Also Known As: CLA



Short answer

CLA, found in meat and dairy and available as a supplement, has potential benefits like modest fat reduction, but evidence is mixed and side effects like gastrointestinal issues, insulin resistance, and increased inflammation can occur. Its effectiveness and safety are still debated, with supplement forms potentially differing from natural sources.



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Long answer

Role and Benefits of Conjugated Linoleic Acid in the Body

Conjugated Linoleic Acid (CLA) is a term used to describe a group of positional and geometric isomers of linoleic acid, which is a polyunsaturated omega-6 fatty acid. CLA is naturally found in the meat and dairy products of ruminants, such as cows and sheep. Its role and purported benefits have been at the center of numerous studies, with investigations looking at its impact on body composition and various health parameters.

At a cellular level, CLA is believed to modulate the expression of certain genes involved in fat metabolism. One of the key roles of CLA is to inhibit lipoprotein lipase, an enzyme crucial for the uptake of fat from the bloodstream into fat cells, which may reduce fat storage. Moreover, CLA is thought to stimulate the breakdown of fats in adipocytes (fat cells) via the activation of another enzyme, hormone-sensitive lipase.

Let's take a closer look at the benefits of CLA that have been explored:

  • Weight Management: Some clinical trials have suggested that CLA supplementation can modestly reduce body fat mass in humans.
  • Muscle Mass: CLA has been associated with a potential to preserve lean muscle tissue during weight loss efforts, though results from studies have been mixed.
  • Immune Function: Animal studies have highlighted that CLA might bolster the immune system, but further human trials are needed to confirm these findings.
  • Anti-inflammatory Properties: CLA may exert anti-inflammatory effects, which could be beneficial for inflammatory conditions, according to some cell and animal research.
  • Anticarcinogenic Effects: Early animal studies have shown that CLA might reduce the development of cancer in various tissues, but it’s important to note that evidence in humans is limited and less conclusive.

Despite these potential benefits, the actual effectiveness of CLA in humans and its role in the body are subjects of debate. A meta-analysis published in the American Journal of Clinical Nutrition concluded that the evidence of CLA's efficacy for long-term weight loss is not compelling. Furthermore, the effects of CLA on muscle mass and immune function in humans remain inconsistent, with more robust clinical trials needed for conclusive results.

It is also essential to understand that the naturally occurring CLA in food sources may have different effects compared to the CLA often found in supplements, which is typically derived from vegetable oils and chemically altered. The distinction between these forms of CLA could be significant in terms of bioactivity and health impact.

To sum up, while CLA plays a role in lipid metabolism and has been associated with several potential health benefits, the evidence is mixed, and the scientific community still calls for caution and further research. Individuals considering CLA supplementation should consult with a healthcare provider, particularly in light of the varying effects of different forms of CLA and the lack of universally positive findings regarding its benefits.

Understanding the Sources of Conjugated Linoleic Acid

Conjugated Linoleic Acid (CLA) might sound like a man-made invention, but it's a naturally occurring fatty acid, one that's sparked a lot of interest for its purported health benefits and weight loss assistance. Let's cut through the hype and focus on the verifiable sources of CLA. This fatty acid is primarily found in the meat and dairy products of ruminants—that's cows, sheep, goats, and the like. Why these animals? It's thanks to the unique bacteria in their stomachs that help them digest their plant-based diets.

CLA exists in different forms, called isomers. The two most studied CLA isomers are known as c9,t11 (rumenic acid) which predominantly occurs in natural food sources, and the t10,c12, which is typically found in supplements. Here's a breakdown:

  • Natural Dietary Sources: The highest levels of naturally occurring CLA are found in grass-fed beef, butter, and cheeses. Full-fat dairy products and lamb also contain notable amounts.
  • Enhanced Foods: Some products have CLA added to them, although this is less common. These are usually marketed towards individuals looking to increase their intake of the fatty acid for its health claims.
  • Supplements: When it comes to supplements, CLA is derived either from plant oils, such as safflower and sunflower, or processed animal products. The form of CLA in supplements is different from the natural form found in foods, and it's essential to consider that when evaluating its impact on health.

A critical point to underscore here is the difference in bioavailability and potential health effects between naturally sourced CLA and synthesized CLA in supplements. Peer-reviewed studies, such as one published in the American Journal of Clinical Nutrition, suggest that the natural form, particularly the c9,t11 isomer, could have different and potentially more beneficial impacts on health than its synthetic counterparts.

What's interesting to note is that the content of CLA in these foods can vary widely based on the animals' diets. For instance, as stated in research published in the Journal of Dairy Science, cows grazing on fresh pasture have been shown to produce milk with up to 500% more CLA than those fed on grain. The bottom line? Not all sources of CLA are created equal, both in terms of quantity and potential health implications.

A critical reader should be wary of blanket statements regarding CLA. While the allure of a weight-loss wonder supplement is strong, it's key to examine the source, form, and evidence behind these claims. A meticulously informed approach to understanding CLA sources will serve consumers better than sensational marketing ever could. Remember, a supplement label is not a tell-all tale - thorough research is a consumer's best defense in a sea of oversimplified assertions.

Potential Adverse Effects of Conjugated Linoleic Acid Supplementation

Conjugated Linoleic Acid (CLA) is touted for its potential benefits in weight loss and bodybuilding. However, like any supplement, it's imperative to scrutinize its safety profile. A responsible approach to supplementation includes acknowledging possible side effects. The allure of CLA's promises should not eclipse the importance of understanding the risks associated with its consumption.

1. Gastrointestinal Issues:

  • Bloating: Some individuals report feelings of bloating and unease in the digestive tract.
  • Diarrhea: Increased stool frequency and looseness can occur, often linked with high doses of CLA.
  • Nausea: A sense of stomach discomfort and an inclination to vomit have been noted by some users.
  • Indigestion: Difficulty in digesting food properly can sometimes result from CLA supplements.

2. Metabolic Concerns:

  • Insulin Resistance: Despite the weight management claims, there's evidence suggesting CLA could impair insulin sensitivity, a concern flagged in a study published in the American Journal of Clinical Nutrition.
  • Lipid Profile Changes: Altered blood lipid levels, including increases in triglycerides, have been observed, potentially negatively impacting heart health.

3. Liver Health:

  • Hepatomegaly: An increase in liver size, indicative of strain or damage, has been associated with CLA in some animal studies.
  • Fatty Liver: Instances of steatosis, the buildup of fat in the liver, could potentially escalate into a more serious condition.

4. Inflammation and Oxidative Stress:

  • Inflammation: Paradoxically, although CLA is known for its anti-inflammatory properties, some studies hint at the possibility of pro-inflammatory effects with high or prolonged usage.
  • Oxidative Stress: CLA might prompt an increase in oxidative stress markers, which is a precursor for various chronic diseases.

5. Implications for Long-Term Health:

  • Concerns Over Cancer Risk: Debates exist in scientific circles regarding the implication of CLA in certain types of cancer, with animal studies sometimes showing an increase in tumor growth in response to CLA supplementation, such as research published in Carcinogenesis.
  • Weight Regain: Contrary to the weight-loss narrative, some users of CLA supplements report experiencing weight regain after discontinuing the supplement, which points towards a possible temporary effect of its usage on weight.

In the quest for transparency, it's critical to highlight that responses to supplements like CLA are individualized. Variances in genetics, existing health conditions, diet, and even the form or dose of CLA supplemented can sway the risk and severity of adverse effects. This dynamic highlights the importance of consulting with a healthcare provider before beginning supplementation, particularly for individuals with pre-existing health conditions or those taking other medications.

The conversation on CLA is far from closed. Ongoing research continues to peel back layers on its comprehensive effects. A constant vigilance and demand for high-quality, peer-reviewed scientific studies remain the cornerstone of understanding the full spectrum of impacts linked to CLA supplementation.

The Controversy Over CLA's Effectiveness in Weight Management

Conjugated Linoleic Acid (CLA) has been a hot topic in the diet and fitness world, with manufacturers claiming it can help reduce body fat, build muscle, and even improve overall health. However, scientific studies paint a mixed and often contradictory picture regarding its effectiveness in weight management. This section delves into the heart of the controversy, analyzing the evidence on both sides of the aisle.

First, let's address the proponent's perspective. Some studies suggest that CLA may affect body fat composition. For example, a meta-analysis published in the American Journal of Clinical Nutrition found that CLA supplementation modestly reduced body fat in humans. However, it's crucial to examine the nuances of these findings:

  • The amount of body fat reduction varied greatly among individuals.
  • The duration of the studies often influenced the outcomes, with longer interventions showing less pronounced effects.
  • Different isomers of CLA (namely, t10,c12 and c9,t11) were used in various studies, yielding inconsistent results.

On the flip side, detractors highlight several issues with the efficacy of CLA in weight management:

  • A considerable number of studies have failed to replicate the significant fat loss observed in some early research.
  • A review in the Journal of the International Society of Sports Nutrition concluded that "CLA does not appear to have a significant effect on body composition or weight loss."
  • Research points to potential negative side effects of CLA supplementation, including increased inflammation and insulin resistance in some individuals, particularly with the t10,c12 isomer.

Further clouding the debate, the dosage and form of CLA used in supplements vary and may not reflect the amounts used in successful studies. Additionally, the source of CLA (whether from natural foods like grass-fed beef and dairy or processed supplements) could impact its health benefits and risks.

To provide a balanced view, let's consider the evidence matrix:

Study Type Effectiveness of CLA References
Randomized Controlled Trials Varied outcomes, with some indicating modest fat loss and others showing no significant changes American Journal of Clinical Nutrition, Journal of Nutrition
Meta-Analyses Generally show a small reduction in body fat mass British Journal of Nutrition
Systematic Reviews Some suggest potential benefits, while others highlight a lack of convincing evidence Obesity Reviews, Journal of the International Society of Sports Nutrition

The intrigue surrounding CLA's weight management claims is not solely academic. It impacts consumers' wallets and health, as they navigate a minefield of marketing claims. As responsible guardians of truth in supplementation, it's our duty to lay out the facts and acknowledge that the jury is still out on CLA. We must advise consumers to approach CLA with a healthy dose of skepticism and a demand for more solid, long-term research before considering it a go-to weight management aid.

Dosage and Safety: Finding the Balance for Conjugated Linoleic Acid

When it comes to the consumption of Conjugated Linoleic Acid (CLA), the adage 'the dose makes the poison' couldn't be more relevant. The line between efficacy and safety can be thin, and it's crucial to understand how much CLA is considered both effective and safe.

Finding the optimum dosage for CLA is tricky, mainly because studies show a wide range of dosages used, from as low as 0.7 grams to as high as 6.8 grams per day. Most clinical trials tend to use doses around 3 to 4 grams per day, often finding a moderate level of effectiveness at these amounts. For example, a study published in the Journal of Nutrition in 2007 demonstrated that 3.4 grams of CLA per day reduced fat mass in overweight individuals.

  • Recommended Dosages: 3-4 grams per day based on research findings.
  • Minimum Threshold for Effect: Some studies suggest benefits may be seen with dosages as low as 0.7 grams per day.
  • Upper Safety Limit: Evidence is less clear, but dosages above 6 grams per day may increase the risk of side effects.

However, when it comes to safety, the narrative is less straightforward. Safety studies have found mixed results, with some reports indicating that high intakes of CLA could potentially lead to fatty liver, insulin resistance, and increased inflammation. A study by the American Journal of Clinical Nutrition in 2004 highlighted these concerns, particularly when doses exceeded 6 grams per day. This highlights the importance of staying within the recommended range and not assuming that higher doses will lead to better or faster results.

Dosage (grams per day) Potential Benefits Associated Risks
0.7 - 3.0 Mild fat loss effects Generally well-tolerated
3.0 - 4.0 Fat loss, lean muscle mass retention Increased risk of side effects
4.0 - 6.0+ Possible enhanced effects Fatty liver, insulin resistance, inflammation

Furthermore, individual variation must be considered in the equation. Factors such as age, sex, current health status, and concurrent use of other supplements or medications can influence how much CLA one should take and the subsequent effects on the body. Safety cannot be ensured across all populations, so consulting with a healthcare professional before starting CLA supplementation is a must—especially for pregnant or breastfeeding women, those with metabolic conditions, or those taking specific medications that could interact with CLA.

Finally, it's important to mention that the long-term safety of CLA has not been conclusively established. While short-term studies have provided some insight into appropriate dosages and potential benefits, the broader implications of prolonged use are not fully understood. Before incorporating any supplement into your regimen long term, especially one like CLA that has demonstrated potential side effects at high doses, a thorough risk-benefit assessment should be conducted.

Interactions with Medications and Underlying Health Conditions

The interaction between supplements and prescribed medications is an arena fraught with potential complications. More specifically, Conjugated Linoleic Acid (CLA), commonly found in dairy and beef products and widely available in supplement form, is touted for its weight loss benefits. However, it's pivotal to discern whether this purportedly beneficial supplement can play nice with your medication regimen or potentially exacerbate underlying health conditions.

Let's begin by delving into the interaction between CLA and blood-thinning medications, such as warfarin. Studies suggest that CLA has a blood-thinning effect, which could potentially enhance the efficacy of anticoagulant drugs—a double-edged sword, for sure. This can increase the risk of bleeding, a concern not to be taken lightly (Leatherdale et al., 2002). Individuals already on blood thinners must proceed with extreme caution, and only consider CLA supplementation under the direct supervision of a healthcare provider.

For those wrestling with metabolic disorders, such as diabetes, the waters are equally murky. CLA may influence glucose metabolism, which sounds promising, but the reality is that this can lead to unpredictable blood sugar levels—a diabetic's nightmare (Risérus et al., 2004). Therefore, diabetic individuals eyeing CLA for its purported benefits must do so under the watchful eye of an endocrinologist.

Furthermore, there is some evidence indicating that CLA supplementation could interact with medications used to treat high blood pressure. Specifically, CLA might negate the effects of antihypertensive drugs, thus elevating blood pressure in certain individuals (Whigham et al., 2003). This presents a clear and present danger to those battling hypertension, highlighting the necessity of professional guidance before integrating CLA into one’s health regimen.

Additionally, individuals with a history of liver disease should approach CLA with trepidation. Some studies have uncovered a potential for fatty liver induced by supplementing with CLA (Zambell et al., 2005). The liver's health is not something to be gambled with, and thus, CLA supplementation could represent a risk not worth taking for those with an already compromised hepatic system.

Lastly, we must consider the interaction with hormonal therapies. Given the complexity of the body’s endocrine system, and the delicate balancing act involved in hormonal treatments, the introduction of CLA could theoretically disturb this balance. The area is under-researched, but prudence dictates that those undergoing hormonal treatments should consult with their endocrinologist before considering CLA.

What becomes clear is that while some supplements may appear benign, they can have profound and sometimes unpredictable interactions with both medications and underlying health conditions. CLA is no exception. As always, the best course of action is to discuss with a healthcare provider before beginning any new supplement, especially if there is a pre-existing health condition or if other medications are being taken.

Frequently asked questions

Some concerns reported when ceasing CLA supplementation include potential weight regain. This suggests that the effects of CLA on weight may be temporary and cease with the discontinuation of the supplement. Additionally, any side effects experienced during supplementation should be monitored upon cessation. Consult a healthcare provider if you're considering stopping CLA supplementation, as the transition should be managed appropriately.

The evidence on CLA’s potential to preserve or increase muscle mass is mixed. Some studies suggest CLA may support muscle mass retention during weight loss due to its effects on fat metabolism, while others have not found significant muscle-building effects. Muscle preservation may occur, but this doesn't necessarily translate to increased muscle growth, and results may depend on factors like dosage, diet, and exercise.

Ensuring the safety of CLA supplementation involves several steps: sticking to recommended dosages (generally 3-4 grams per day), being cautious about long-term usage, monitoring for possible side effects, and consulting healthcare professionals, especially if you have pre-existing conditions or are taking other medications. Also, consider the source of CLA, with food-derived CLA potentially showing a different safety profile from supplement-derived CLA.

The efficacy of CLA may differ between food and supplement forms due to variations in isomer content and bioavailability. Naturally occurring CLA in foods like grass-fed dairy and meats contains mostly the c9,t11 isomer, which has been suggested to offer more health benefits than the t10,c12 isomer typically found in supplements. Moreover, the natural form of CLA in dietary sources may be more bioavailable and thus potentially more beneficial for health than the processed form in supplements. However, individual response can vary, and more research is needed.

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

Possible short-term side effects

  • bloating
  • diarrhea
  • nausea
  • indigestion
  • insulin resistance
  • lipid profile changes
  • inflammation
  • oxidative stress

Possible long-term side effects

  • hepatomegaly
  • fatty liver
  • potential increase in certain cancers
  • weight regain
  • impaired glucose metabolism
  • elevated blood pressure

Ingredients to be aware of

  • synthetic cla isomers
  • high doses


  • modest body fat reduction
  • potential to preserve muscle mass
  • possible immune support
  • anti-inflammatory effects
  • anticarcinogenic properties (in animals)

Healthier alternatives

  • natural dietary sources (grass-fed beef, full-fat dairy, lamb)

Our Wellness Pick (what is this?)

Sports Research CLA

  • Enhances fat loss
  • Supports muscle retention
  • Non-GMO
  • Soy & Gluten Free
  • 95% CLA potency
Learn More!

Thank you for your feedback!

Written by Joey Conners
Published on: 02-28-2024

Thank you for your feedback!

Written by Joey Conners
Published on: 02-28-2024

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