What is a natural conjugated linoleic acid?

November 21, 2025 •

3 min read

Natural conjugated linoleic acid (CLA) is a complex mixture of fatty acid isomers predominantly found in meat and dairy products from grass-fed ruminant animals. Unlike man-made supplements, this natural form is created through a complex biohydrogenation process involving bacteria in the animal's digestive system.

Quick Summary

Explains natural conjugated linoleic acid (CLA), its origin in ruminant animals through bacterial biohydrogenation, its key isomer (rumenic acid), and how it differs from synthetic products.

Key Points

Ruminant Origin: Natural CLA is primarily produced in the digestive systems of ruminant animals like cows, sheep, and goats through a process called biohydrogenation.
Rumen Bacteria Role: Gut bacteria in the rumen convert dietary linoleic acid from grasses into various fatty acid intermediates, which include CLA isomers.
Endogenous Synthesis: The animal's own tissues, especially the mammary gland, further synthesize CLA from an intermediate called trans-vaccenic acid, accounting for a large portion of the CLA in milk.
Main Isomer: The most prevalent isomer of natural CLA is cis-9, trans-11, also known as rumenic acid, which comprises over 80% of CLA in ruminant fats.
Natural vs. Synthetic Differences: Natural CLA is predominantly cis-9, trans-11, whereas synthetic supplements are chemically altered from plant oils and contain a roughly 50:50 mixture of two main isomers.
Health Effects are Nuanced: Research on CLA's health benefits, including body fat reduction and anti-cancer effects, shows mixed and often modest results in humans compared to more pronounced effects observed in animal studies.

The Natural Origin of Conjugated Linoleic Acid

Conjugated linoleic acid (CLA) refers to a group of isomers of the essential omega-6 fatty acid, linoleic acid. Natural CLA is produced biologically in ruminant animals, unlike synthetic CLA from vegetable oils. The concentration of CLA in meat and dairy depends on the animal's diet, with grass-fed animals having higher levels.

The Role of Rumen Bacteria

Natural CLA is primarily formed through biohydrogenation in the rumen of animals like cows and sheep. Rumen bacteria, particularly Butyrivibrio fibrisolvens, convert dietary polyunsaturated fatty acids like linoleic acid into more saturated fats. CLA is an intermediate in this process, with cis-9, trans-11 CLA (rumenic acid) being the most favored isomer. Endogenous synthesis also contributes significantly to CLA in milk.

Endogenous Synthesis in Mammals

Animals also synthesize CLA in their tissues. Approximately 64% of the CLA in milk fat is produced in the mammary gland. This involves the enzyme delta-9 desaturase converting trans-vaccenic acid, a bacterial intermediate, into cis-9, trans-11 CLA. Humans can also perform this conversion, but less efficiently.

Key Isomers: Rumenic Acid vs. Synthetic CLA

The isomer composition of CLA varies between natural sources and synthetic supplements. Natural CLA from dairy and meat is mainly cis-9, trans-11 CLA (rumenic acid), often exceeding 80%. Synthetic supplements, made from plant oils like safflower oil, typically have a 50:50 mix of cis-9, trans-11 and trans-10, cis-12 isomers. These different ratios can influence biological effects.

Comparison of Natural and Synthetic CLA


Feature	Naturally Produced CLA	Synthetically Produced CLA
Origin	Ruminant meat and dairy (e.g., beef, lamb, milk, cheese).	Chemically derived from plant oils (e.g., safflower, sunflower).
Primary Isomer Ratio	Dominated by cis-9, trans-11 (Rumenic Acid), typically >80%.	A mix of approximately 50% cis-9, trans-11 and 50% trans-10, cis-12.
Concentration	Relatively low concentrations in whole foods.	Highly concentrated in supplement form.
Dietary Impact	Higher levels in products from grass-fed animals.	Not influenced by animal diet; depends on supplement dosage.
Health Effects	Associated with general dietary benefits of ruminant products.	Variable effects, with some studies showing mixed or modest benefits, particularly in humans.

Potential Health Effects and Research Insights

Research on CLA's health effects began with its discovery as an anticarcinogen in cooked meat. While animal studies showed promise for various conditions, human studies are less conclusive.

Animal Studies vs. Human Trials

Animal studies indicated CLA could reduce body fat, fight cancer, boost immunity, and prevent atherosclerosis. However, these results haven't consistently appeared in humans. For instance, human studies on fat loss show only modest or no significant effects, potentially due to different isomer ratios and doses compared to animal research.

Isomer-Specific Effects

Different CLA isomers have distinct activities. The natural cis-9, trans-11 isomer is linked to anti-cancer and immune effects. The trans-10, cis-12 isomer, common in supplements, is associated with body fat regulation but has also been linked to negative effects like increased insulin resistance in some human studies at high doses.

Top Natural Food Sources of CLA

To increase natural CLA intake, prioritize foods from grass-fed ruminants:

Beef and Lamb: Higher CLA in meat from grass-fed animals.
Dairy Products: Grass-fed dairy is a major source of natural CLA.
Other Sources: Smaller amounts are found in non-ruminant products and some plants like mushrooms, but they are not primary dietary sources.

Conclusion: Embracing Natural Dietary CLA

Natural conjugated linoleic acid, specifically rumenic acid, is a fatty acid found in grass-fed dairy and meat, produced through a biological process involving ruminants and their gut bacteria. While research on its health benefits, including body composition and disease prevention, has been extensive, human evidence is not as strong as animal studies. Differences in isomer profiles and concentrations between natural foods and supplements likely contribute to these varying outcomes. Focusing on natural sources from grass-fed ruminants is a balanced approach, as results from synthetic supplements are mixed. For further research details, resources like the National Institutes of Health can provide insights.

Frequently Asked Questions

The primary natural sources are meat and dairy products from ruminant animals, such as beef, lamb, milk, cheese, and yogurt, especially those from grass-fed animals.

Ruminants produce natural CLA through a two-step process: microbial biohydrogenation of dietary fatty acids in the rumen and subsequent endogenous synthesis of CLA from metabolic intermediates in their tissues, particularly the mammary gland.

Natural CLA is produced biologically in ruminants and is rich in the cis-9, trans-11 isomer. Synthetic CLA is produced chemically from plant oils and contains a roughly 50:50 mix of the cis-9, trans-11 and trans-10, cis-12 isomers.

While some animal studies suggest CLA can reduce body fat, human studies on natural CLA from food sources show modest effects. The impact of the different isomer ratios and concentrations found in supplements is still under investigation.

Rumenic acid is the common name for the cis-9, trans-11 isomer, which is the most abundant and primary natural form of CLA found in ruminant products.

While natural CLA is predominantly animal-derived, some lesser-known sources include certain types of mushrooms and pomegranate seed oil, although these are not as significant for dietary intake.

Obtaining CLA from whole food sources like grass-fed dairy and meat provides the natural cis-9, trans-11 isomer in a balanced form. Supplements contain different isomer ratios and may have inconsistent effects, with some high-dose studies raising concerns.