What Exactly Does CLA (Conjugated Linoleic Acid) Do and Is It Harmful?

Conjugated linoleic acid (CLA) is a type of omega-6 fatty acid that is believed to be good for health. Several studies show that taking up to 6 grams of conjugated linoleic acid daily is safe and doesn’t lead to any serious health risks.

Conjugated linoleic acid (CLA) is a type of omega-6 fatty acid that is believed to be good for health. It’s popular in weight loss and sporting communities as a solution for burning fat, building muscle, and boosting energy. Despite its widespread use, experts don’t recommend using it as a dietary and fitness supplement. This is because there is not enough evidence to prove the health benefits of CLA. Moreover, studies show that taking large doses of CLA — like the quantities found in supplements — can be harmful.

Conjugated linoleic acid is a slightly modified form of the essential fatty acid called linoleic acid. Linoleic acid is one of the most common types of omega-6 fatty acids. You can find it in large amounts in vegetable oils made from soybean, sunflower, and corn, as well as in seeds, nuts, and dry fruits.

The word “conjugated” refers to the fact that the double bonds in these fatty acids are arranged in various ways. These varied arrangements result in 28 distinct forms of CLA, each having a slightly different structure and properties.

Since CLA is made up of multiple double bonds, it can also be classified chemically as trans fat. Keep in mind, though, that this is a natural trans fat, similar to what you can find in various healthy foods.  Such naturally occurring trans fats are different from trans fats in certain industrially produced foods, which are known to harm human health when taken in large amounts.

Conjugated linoleic acid is made by the microbes living within the gut of ruminant animals like cows, sheep, and goats. You can naturally get CLA by adding to your diet the meat and milk from these animals. 

Note that the amount of CLA in these food products depends on what was fed to these animals. Studies show that the dairy and beef from grass-fed cows contain 300% to 500% greater CLA content compared to that from grain-fed cows. To some extent, CLA is also found in vegetable oils like safflower oil and corn oil. By cooking your food in such oils, you can increase the fatty acid content in them. 

You can also get artificial conjugated linoleic acid in the form of CLA supplements. The fatty acids in these supplements don’t come from natural sources like beef and dairy products, though. Manufacturers make them by chemically modifying plant-based linoleic acid. This is why CLA supplements don’t offer the same health benefits that naturally occurring CLA does.

Marketers often promote conjugated linoleic acid as a fitness and dietary supplement. 

These are some of the uses that CLA is most famous for:

Helpful in weight loss. Several studies have been done on CLA, making it one of the world’s most researched weight-loss supplements. Scientists have found conjugated linoleic acid to be helpful in reducing body fat when tested on animals. For example, studies on mice show that CLA can cause fats to burn and break down, interfere with fat production, and lower the urge to eat.

However, human studies on CLA have shown mixed results. In some randomized controlled trials, people with obesity lost significant amounts of body fat after taking CLA supplements for many months. Other studies found no effect of CLA on human body fat. There have also been studies that show that taking CLA could lead to moderate fat loss — about 0.2 pounds/ week — but only during the first 6 months.

Keep in mind that while these weight loss effects might be significant from a research point of view, they don’t make much difference in everyday life. As per some studies, there could also be some side effects of CLA supplements. This is why experts don’t recommend taking supplemental CLA, even to those who wish to lose weight or reduce body fat.

Improving athletic performance. While CLA is popular among many sportspeople and bodybuilders, enough research hasn't been done to determine its effect on muscle mass.

Some controlled human trials found that conjugated linoleic acid caused only a slight increase in muscle strength and size when taken by weight-training men. Other studies on trained men and women showed that taking CLA supplements could lower the fat levels in the upper arm.

However, further research using more robust techniques is needed to properly understand the effects of CLA on body composition. 

People take conjugated linoleic acid for various reasons other than to get in shape. Many use it to treat dry skin, asthma, hay fever, diabetes, common cold, and even multiple sclerosis, but there isn’t enough research to support it as a treatment. 

There are some health benefits of CLA that have been studied by scientists. These include:

Regulating cholesterol levels. A few studies indicate that CLA could lower the levels of triglycerides in the blood. If present in high amounts, these fats could increase your risk of stroke, heart attack, and heart disorder. 

However, conjugated linoleic acid has also been found to lower the amounts of HDL (good cholesterol) in the blood. This is why CLA is not considered a good treatment for those with cholesterol problems.

Reducing the risk of cancer. Various animal and test-tube studies have found antioxidant properties in CLA, which allow it to fight cancer cells in the body. Preliminary research has found it helpful in reducing the risk of breast cancer, lung cancer, colon cancer, and prostate cancer. 

However, it should be noted that it’s the CLA in foods that offer most of these benefits, not those present in supplements. Also, since only a few human-based studies have been done on it, more clinical trials are needed to understand the usefulness of CLA for cancer treatment. 

CLA has been found to be safe for most adults when it’s taken in its natural form, like what is found in milk and meat. However, supplements contain the artificial form of this fatty acid. Moreover, the doses that you get from CLA supplements are much higher compared to what you get from natural sources.  

Scientists have found that such high doses of supplemental CLA can cause the fat in your liver to build up. This can lead to other medical conditions like diabetes and metabolic syndrome. Research on animals also points toward the negative effects of conjugated linoleic acid. Such studies reveal that when large amounts of this fatty acid are given to animals, they face an increased risk of inflammation and experience decreased levels of good cholesterol, as well as reduced sensitivity to insulin.

Mild side effects of CLA supplements have also been seen in some human-based clinical trials. These studies indicate that even moderate doses of supplemental CLA could cause health issues like nausea, diarrhea, and stomach upset.

The U.S. Food and Drug Administration (FDA) classifies conjugated linoleic acid as GRAS (generally regarded as safe). This means it’s safe to add CLA to foods, but only in moderate amounts. 

There is no official information available regarding the recommended dosage of CLA. However, you can follow the dosage levels mentioned in the reputed research publications. Scientists have found these doses of CLA to be safe and helpful for improving human health. 

For example, several studies show that taking up to 6 grams of conjugated linoleic acid daily is safe and doesn’t lead to any serious health risks. Another review suggests that those who wish to lose weight can take 3 grams of CLA per day.

Keep in mind that taking more than the established dosage levels of CLA can increase your risk of having side effects, so if you’re planning to use artificial sources of this fatty acid, first figure out how much you already get through your diet. 

In the US, women typically get about 151 milligrams of CLA per day while men take about 212 milligrams of CLA per day. Since up to 6 grams is considered safe for human use, you can get the remaining amount of CLA from its supplements.

People belonging to a particular age group and those with certain medical conditions face the risk of getting worse if they take supplemental CLA. 

Those people include:

Children: There isn’t enough evidence that shows that the long-term use of supplemental CLA is safe for children. Instead of supplements, feed them natural sources of CLA like beef and butter.

People with heart disease: High amounts of CLA can trigger cell-damaging processes in the heart. If this occurs in those who already have heart disorders, it can make their condition worse. 

People with diabetes: In some cases, CLA causes insulin resistance and leads to an increase in blood sugar levels. This can worsen the symptoms of diabetes. 

People taking blood-thinning medications: Since CLA is known to interfere with the process of blood clotting, it can add to the effect of anticoagulants and lead to excess bleeding and bruising.

Most people take CLA supplements either to lose weight or to build their muscles, but studies haven’t found any significant effect of conjugated linoleic acid on weight loss or muscle mass. Moreover, there is a concern that the supplemental CLA could pose serious health risks if taken for a long time.

Since the demerits of conjugated linoleic acid outweigh its merits, medical experts suggest avoiding the use of CLA supplements. For those who wish to lose weight, there are various other, better weight loss methods that have no negative effects on human health. 

If the goal is to increase CLA intake, it’s best to eat natural sources of CLA like dairy products and meat. Doing so would not only help you lose weight but also benefit your health.

However, if you still plan to use CLA supplements, make sure you talk to your doctor before taking them. They can warn you about any potential side effects or negative interactions of CLA with your current medications.