Dietary Sources of Natural CLA
For centuries, humans have consumed conjugated linoleic acid (CLA) naturally through their diet, primarily from animals that graze on pasture. The bacteria in the rumen of these animals convert omega-6 fatty acids from green plants into CLA, which is then stored in the animal's fat and milk. Focusing on high-quality, whole-food sources is often considered the safest and most effective way to obtain this beneficial fatty acid.
Ruminant Meat and Dairy
Foods from ruminant animals like cows, sheep, and goats are the richest dietary sources of natural CLA. The content can vary significantly based on the animal's diet and farming practices, with grass-fed animals consistently producing more CLA than grain-fed ones.
- Grass-fed beef and lamb: These are among the most potent sources. For example, beef from grass-fed cattle can have substantially higher CLA content than conventional beef.
- Dairy products from grass-fed animals: Milk, cheese, and butter from cows and sheep fed a diet of fresh pasture contain higher levels of CLA. Dairy products like milk and cheese are major contributors to dietary CLA intake.
- Cooking methods: Interestingly, cooking beef at higher internal temperatures has been shown to increase total CLA concentrations due to moisture loss, while the beneficial isomer profile remains stable.
Other Animal Sources
While ruminant products are the best sources, some other animal foods contain smaller amounts of CLA.
- Ground turkey: Contains a moderate amount of CLA.
- Veal: Another source of CLA, though often in lesser quantities than beef or lamb.
- Pork and chicken: Generally contain much lower levels of CLA compared to ruminant meat.
Vegetarian Sources
Vegetarians can find minimal amounts of CLA through certain foods, though the quantity is not comparable to ruminant sources.
- Pomegranate seed oil: A plant-based source known to contain specific CLA isomers.
- Some mushrooms: White button mushrooms are mentioned as a vegetarian source.
Synthetic CLA Supplements
Given the relatively low concentration of CLA in most modern diets, many people turn to supplements to achieve higher intake levels. These supplements are typically produced by chemically altering linoleic acid from plant-based oils.
Production and Isomer Differences
Most commercial CLA supplements are derived from vegetable oils rich in linoleic acid, such as safflower oil. The process results in a mixture of isomers that is significantly different from the natural balance found in grass-fed dairy and meat.
- Natural CLA: Primarily composed of the cis-9, trans-11 (c9, t11) isomer, which makes up 80–90% of the CLA in ruminant foods.
- Supplemental CLA: Often contains a roughly 50:50 mix of the c9, t11 and trans-10, cis-12 (t10, c12) isomers. The t10, c12 isomer is the one most associated with body fat reduction in animal studies, but also with potential negative side effects in humans.
Comparing Dietary and Supplemental CLA
Choosing between food and supplements depends on individual goals, desired dosage, and risk tolerance. The table below summarizes the key differences.
| Feature | Natural Food Sources (Grass-fed) | Supplemental CLA | References |
|---|---|---|---|
| Primary Isomer | Primarily c9, t11 | Roughly 50:50 mix of c9,t11 and t10,c12 | |
| Dosage | Relatively low, average daily intake is ~150-212 mg | High, typically 3-6 grams per day in studies | |
| Associated Risks | Generally safe; comes with other nutrients | Potential risks at higher doses (e.g., insulin resistance, fatty liver) | |
| Weight Loss Effects | Modest contribution from diet; not for targeted fat loss | Modest effect observed in some human studies; results are inconsistent | |
| Convenience | Requires intentional dietary choices and effort | Easy to take in concentrated form | - |
Risks, Side Effects, and Safety Considerations
While CLA from food is generally considered safe, supplements come with considerations, especially at the higher dosages needed for a potential effect on body composition.
Potential Side Effects
Several human studies have reported side effects, primarily associated with the supplemental form and high doses.
- Gastrointestinal Issues: Upset stomach, nausea, diarrhea, and bloating are commonly reported.
- Metabolic Concerns: Research suggests high doses of supplemental CLA can lead to insulin resistance, particularly in individuals with pre-existing metabolic syndrome or diabetes.
- Liver Effects: Animal studies and some human data suggest a risk of increased fat accumulation in the liver with supplemental CLA.
Important Precautions
Certain individuals should be cautious or avoid CLA supplementation altogether without medical supervision.
- Individuals with diabetes or metabolic syndrome: The risk of worsening insulin sensitivity is a significant concern.
- People with bleeding disorders: CLA supplements may slow blood clotting, increasing the risk of bruising and bleeding.
- Pregnant and breastfeeding women: There is insufficient evidence to determine safety, so avoiding supplements is recommended.
Conclusion: Your Best Strategy for Getting CLA
For most people, the safest and most beneficial way to get conjugated linoleic acid is through a balanced diet rich in natural sources. Prioritizing meat and dairy from grass-fed animals will provide a more wholesome form of CLA, complete with other beneficial nutrients, and without the potential risks associated with high-dose supplements. While the levels in food are much lower than in supplements, the natural isomer profile and lower overall intake are not linked to the adverse metabolic effects seen in some studies involving synthetic versions.
If pursuing CLA supplementation, it is crucial to first consult a healthcare provider. While some may experience modest fat loss, the effects are often small and inconsistent across human studies. The decision should weigh the potential for minor benefits against the known and potential risks, particularly with synthetic isomers and high dosages. Ultimately, a whole-food, balanced diet remains the gold standard for overall health and for obtaining conjugated linoleic acid naturally.
To optimize your intake of natural CLA:
- Prioritize meat and dairy from grass-fed animals whenever possible.
- Consider fermented dairy products like yogurt and cheese, as fermentation can enhance CLA content.
- Don't rely on CLA as a miracle weight-loss solution; focus on overall diet and exercise for more sustainable results.
- Remember that whole foods provide a complex matrix of nutrients, offering synergistic health benefits that are not replicated in isolated supplements.
For more detailed information on comparing food-based nutrients with supplements, see this resource on nutrients found in animal products.
