Conjugated linoleic acid (CLA) is a fatty acid naturally occurring in dairy products and beef that has powerful positive health benefits. (1)
Large amounts of linoleic acid can be found in vegetable oils, and smaller amounts are found in other foods. Linoleic acid is a polyunsaturated fatty acid, and the most common of the omega-6 fatty acids.
But CLA has a different molecular structure: “conjugated” refers to the way the double bonds are arranged. For those of us who aren’t chemists, understanding how molecular bonds affect the way our bodies react to a substance can be a tough call, but just like with words, colors and facial features, arrangement is everything.
There are two different kinds of double bonds in CLA on the fatty acid chain. The placement of one of these types of bonds is structured in a way that classifies CLA as a trans fat, although it’s natural, and therefore not dangerous like industrially created trans fats that can cause damage in our bodies. (5, 6, 7)
Dietary CLA comes from the meat and dairy products of ruminant animals such as cattle, sheep and goats. The amount of CLA contained in these foods depends entirely on what the animals consumed. (8)
Keep in mind that the majority of animals meeting modern commercial demand for these foods are born and raised in industrial settings, eating mostly grains and soy products. In contrast, dairy animals of past times grazed and foraged, eating what they could find in their environment, including dried grasses and small amounts of grain during cold seasons.
There is a huge difference between the amount of natural CLA found in commercially raised animals and dairy products and grass-fed animals. The CLA content of products from grass-fed cows, including the meat after butchering, delivers between 300% and 500% more CLA than products from animals eating grains. (9)
The estimated average amount of CLA in a typical American diet today is about 150 mg for women and 200 mg for men. (10)
Supplemental CLA is chemically created by altering the molecular bonds in sunflower and safflower oils. This process distorts the ratio of different CLA forms found in natural sources (11, 12), so supplements won’t have the same beneficial effects.
Natural CLA Can Support Weight Loss
- Reduces the amount of calories consumed
- Increases the amount of calories burned
- Stimulates the breakdown of stored fat
- Inhibits the production of fat cells
Controlled randomized trials on the effects of CLA on weight loss show mixed results. Some indicate CLA can play a role in modifying body composition, reducing fat mass and sometimes even increasing muscle mass. (21, 22, 23)
When researchers correlated data from 18 controlled trials, the results for participants added up to between anywhere between .02 and 3 pounds weight loss per week over a six-month period. (27)
Some side effects were reported, including soft stools, diarrhea and constipation. With the range of different results, it’s possible CLA may have more pronounced effects on some people than others.
CLA and Chronic Disease
Observational studies can’t deliver the same level of evidence-based proof than randomized, controlled trials because of variable factors; that being noted, a number of observational studies indicate people who eat foods containing high levels of natural CLA may enjoy a reduced risk of developing chronic diseases.
People living in countries where cows are grass-fed have higher levels of CLA in their bodies; observational studies confirm their chances of suffering from heart disease are significantly lower. (31)
Whether or not the difference in the incidence of chronic disease is due to adequate levels of CLA has not been established. Grass-fed animal products are also rich in other nutrients with proven health benefits, such as vitamin K2, which affects the distribution of calcium in the body and may prevent heart disease by protecting the arteries.
Is CLA Right For You?
Evidence shows naturally-occurring CLA can provide health benefits ranging from supporting weight control to protecting against the development of chronic disease.
If you’re considering using supplemental CLA, remember that products are made from chemically altered CLA originating in unhealthy vegetable oils; these supplements have skewed ratios of the natural CLA components found in the meat and products of dairy animals and won’t deliver the benefits of the CLA you’ll get eating grass-fed meat and full-fat dairy products.
Studies show taking large doses of synthetic CLA can contribute to increased accumulation of fat in the liver, known as fatty liver disease. This may lead to type 2 diabetes and metabolic syndrome. (32, 33, 34)
Human and animal studies suggest that even though body fat levels decrease when higher CLA levels are achieved through supplementation, undesirable effects can also occur, including lower HDL cholesterol (the “good” kind), insulin resistance, and increased inflammation. (35, 36)
While the dosage levels in most of these studies were considerably higher than most people might use in a CLA supplement, some followed the recommended amount, so it’s something to consider.
A number of participants in the studies experienced side effects including stomach pain, flatulence, diarrhea and nausea. (37) The chances you’ll experience similar side effects are higher when you take more CLA.
The daily dose used in most studies ranged between 3.2 and 6.4 grams.
Summary: If you want to increase CLA intake and enjoy the potential benefits of regulating weight preventing chronic disease, the safest and most natural way to accomplish this is to buy meat and full-fat dairy products from grass-fed animals.