Health Benefits of Conjugated Linoleic Acid

Can the weight loss aid deliver on its promise?

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Conjugated linoleic acid (CLA) is a fatty acid often marketed as a weight loss aid. Naturally found in dairy products and beef, CLA can be synthesized in the lab as a dietary supplement. Proponents claim that CLA can reduce fat, build muscle, and increase energy and endurance.

Others believe that CLA can enhance immune function while improving high cholesterol and blood pressure levels. Despite its popularity among some athletes, the evidence remains split on whether CLA can deliver on these promises.

Health Benefits

Conjugated linoleic acid is found in a plethora of weight loss supplements, either on its own or co-formulated with other ingredients, such as caffeine or guarana. While the supplement is mainly used for weight loss, CLA is believed to have other health benefits.

Weight Loss

A 2007 review of studies published in the American Journal of Clinical Nutrition concluded that CLA, taken at a dose of 3.2 grams per day, produced only a modest loss in body fat (average 0.05 pounds) compared to a placebo.

In the same year, another review published in Public Health Nutrition reported no difference between the body weight or composition of those who took CLA versus those who took a placebo.

What's more, a component of CLA supplements, known as trans-10,cis-12, was found to have a negative impact on blood sugar and could potentially contribute to the development of insulin resistance and atherosclerosis (hardening of the arteries).

So conflicting is the research that scientists have a tough time even suggesting how CLA is meant to work. While CLA is believed to suppress appetite, few studies have shown this to have any effect on weight or body fat composition.

Based on current evidence, a 2015 review published in Nutrition and Metabolism concluded that CLA offered no "promising or consistent health effects so as to uphold it as either a functional or medical food."

Other Health Benefits

Beyond its use in weight loss, proponents of CLA supplementation believe that it can enhance athletic performance by stimulating testosterone production in the Leydig cells of the testicles. While it is true that CLA has this effect, the level of stimulation rarely translates to increased energy expenditure.

A 2014 study from the University of Nebraska reported that athletes provided a daily, 800-mg dose of CLA for six weeks showed no improvement in endurance (as measured by the VO2 max) compared to athletes given a placebo.

Other health benefits are also largely unsupported, including CLA's use in treating diabetes, the common cold, allergic rhinitis (hay fever), or asthma.

Similarly, while an increased intake of CLA was once linked to a reduction in breast cancer risk, a 2016 review of studies was unable to show any association between CLA levels in breast tissue and the risk of cancer, metastasis, or death.

Where CLA may be beneficial is as adjunctive therapy for high blood pressure. When used with Altace (ramipril), CLA was shown to achieve better control of hypertension compared to Altace alone, according to a 2009 study from China.

Possible Side Effects

Conjugated linoleic acid supplements are generally considered safe if taken as prescribed. Some people may experience side effects, usually mild, including stomach upset, diarrhea, nausea, fatigue, headache, and backache.

CLA is mainly metabolized in the liver. On rare occasion, CLA may cause liver toxicity (usually in people with underlying liver disease). Large doses can also trigger the accumulation of fat in the liver, leading to fatty liver disease, diabetes, and metabolic syndrome.

Conjugated linoleic acid may also slow blood clotting. Taking a CLA supplement along with an anticoagulant ("blood thinners") or nonsteroidal anti-inflammatory drug (NSAID) can further enhance this effecting, leading to easy bruising and bleeding.

Possible drug interactions include:

  • Advil (ibuprofen)
  • Aleve (naproxen)
  • Aspirin
  • Advil (ibuprofen)
  • Coumadin (warfarin)
  • Fragmin (dalteparin)
  • Heparin
  • Lovenox (enoxaparin)
  • Plavix (clopidogrel)
  • Voltaren (diclofenac)

Dosage and Preparation

Conjugated linoleic acid supplements are typically produced as a gel cap and filled with either sunflower or safflower oil. CLA is classified by the U.S. Food and Drug Administration as GRAS ("generally regarded as safe") and typically prescribed at between 3 grams and 6 grams per day. Doses greater than 6 grams may increase the risk of side effects.

What to Look For

Conjugated linoleic acid is not considered an essential nutrient like vitamins and minerals. Taking them or not taking them will likely have little tangible impact on your health.

If you do decide to use them, talk with your doctor to understand the potential risks and benefits of treatment. This is especially true if you have diabetes or are on blood thinners. In cases like these, CLA may cause more harm than good.

Instead of supplements, you can get plenty of CLA from milk and grass-fed beef and lamb. There are also CLA-fortified eggs in some grocery stores. Portobella mushrooms and acorn mushrooms are good plant-based sources of CLA.

If you decide to give CLA supplements a try, find a brand tested and approved by a recognized certifying body such as U.S. Pharmacopeia (USP), NSF International, or ConsumerLab. Doing so can ensure the highest quality and safety possible.

Other Questions

When approaching any weight loss strategy, focus on diet and exercise before turning to potentially useless or even harmful supplements. As much as we'd like to think there are shortcut solutions, most promise more than they can actually deliver.

The problem with rapid weight loss is that it almost invariably causes the accumulation of fat in the liver. This, in turn, increases the risk of insulin resistance and type 2 diabetes. A slow and steady approach, focusing on good nutrition, routine exercise, and positive reinforcement, will serve you far better than reaching for any weight loss aid.

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