What Are Some of the Bad Side Effects of CLA?

The most common side effects of CLA, or conjugated linoleic acid, are upset stomach, fatigue, nausea and diarrhea, according to WebMD. The supplement can worsen insulin resistance, negatively impact the liver, lower good cholesterol levels and increase inflammation.

Many people take this fatty acid as a weight loss aid, as studies of synthetic forms of CLA have been shown to reduce body fat, explains Holly Wagner for Research Communications from The Ohio State University. Most studies find that CLA decreases body fat and helps people feel fuller after eating, while typically not impacting BMI or weight. A study on mice taking the supplements found that CLA lowered body mass and blood sugar levels in diabetics. The mice developed excessive and dangerous amounts of fat in their livers, causing increased insulin resistance.

Any person considering taking CLA needs to talk to a doctor first to avoid negative interactions with their existing medications, as the supplement can interact with drugs for certain mental disorders, including schizophrenia. Due to a lack of evidence regarding the safety of conjugated linoleic acid, WebMD recommends that women who are pregnant or nursing do not take this supplement. It also does not recommend the supplement for children.