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.
There are many different forms of it, but the two important ones are called c9, t11 (cis-9, trans-11) and t10, c12 (trans-10, cis-12) (3Trusted Source).
C9, t11 is most abundant in food, whereas t10, c12 is the form most often found in CLA supplements and associated with weight loss. T10, c12 is also present in foods, albeit in much smaller amounts (4Trusted Source).
CLAs contain omega-6 fatty acids. They are polyunsaturated fat, which the American Heart Association (AHA) say can have beneficial effects on the heart.
CLAs are also technically trans fats, which, in most cases, are unhealthful fats. However, CLA is a natural form of trans fat and does not seem to have the same negative health effects as artificially produced, industrial trans fats.
How does CLA help you lose weight? According to a 2009 report published in The Journal of Nutritional Biochemistry, it’s believed that CLA reduces adiposity (fat) because of its impact on 1) energy metabolism, 2) adipogenesis, 3) inflammation, 4) lipid metabolism and 5) apoptosis. In certain animal studies, CLA (specifically types 10 and 12) has also been found to lead to increased energy expenditure, increased fat oxidation and browning of subcutaneous white adipose tissue (aka white fat).
CLA has been investigated to be a fat burner and health promoting agent due to its effect on a molecular signalling receptor family named PPAR which is related to fat burning, steroid signalling, inflammation, and glucose/lipid metabolism.
However, human studies on CLA are very unreliable and the overall effects seen with CLA are not overly potent as well as sometimes contradicting. CLA is a good research standard to investigated fatty acids and the PPAR system, but its usage as a supplement for personal goals is quite lacklustre.
In fact, CLA may be one of the most comprehensively studied weight loss supplement in the world.
Animal studies suggest that CLA may reduce body fat in several ways (16Trusted Source).
In mouse studies, it was found to reduce food intake, increase fat burning, stimulate fat breakdown and inhibit fat production (17Trusted Source, 18Trusted Source, 19Trusted Source, 20Trusted Source).
CLA has also been studied extensively in randomized controlled trials, the gold standard of scientific experimentation in humans — though with mixed results.
Some studies indicate that CLA can cause significant fat loss in humans. It may also improve body composition by reducing body fat and increasing muscle mass (21Trusted Source, 22Trusted Source, 23Trusted Source, 24Trusted Source, 25Trusted Source).
Although CLA appears to reduce body fat mass in animals , results from human studies suggest that its effects are small and of questionable clinical relevance . One double-blind, placebo-controlled trial evaluated the effects of CLA supplementation (as a 50:50 mixture of c9t11-CLA and t10c12-CLA) in 180 overweight male and female volunteers (BMI 25–30) consuming an ad libitum diet . Participants received CLA as a free fatty acid (3.6 g CLA isomers), CLA as a triacylglycerol (3.4 g CLA isomers), or placebo daily for 1 year. At the end of the study, body fat mass dropped by significant amounts with both forms of CLA compared with placebo; reductions, on average, were 6.9% with CLA as a free fatty acid and 8.7% with the triacylglycerol form. Supplementation with CLA as a free fatty acid (but not as a triacylglycerol) also increased lean body mass compared with placebo.
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.
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.
As an antioxidant, CLA may have cancer-fighting properties. Studies have shown that women who get a lot of CLA from their diets have a lower risk of colorectal cancer; they may also have a lower risk of breast cancer. However, we don’t know if taking CLA supplements would have these benefits, too. More research is needed.
CLA does seem to lower bad LDL cholesterol. But since it also lowers good HDL cholesterol, it’s not a standard treatment.
People take CLA supplements for other reasons, ranging from dry skin to multiple sclerosis (MS). We don’t know if CLA will help with these conditions.
A study found that high intakes of both cis-9,trans-11 and trans-10,cis-12 CLA raised the level of HDL cholesterol in healthy women.
HDL cholesterol promotes low cholesterol levels and healthy heart function .
High levels of glucose result in major heart damage and heart disease. A study in rat cells found that cells pre-treated with CLA and then exposed to high glucose levels had reduced heart damage and a decreased risk of heart disease than cells not pre-treated in the same conditions .
In another study, mice with heart disease who were treated with a combination of nitrate and CLA prior to a heart attack had improved heart function post-heart attack .
FRIDAY, June 23, 2017 — Conjugated linoleic acid (CLA) supplementation is associated with an increase in serum C-reactive protein (CRP) concentration, according to a review and meta-analysis published online May 29 in Cardiovascular Therapeutics.
Tell your doctor about any supplements you’re taking, even if they’re natural. That way, your doctor can check on any potential side effects or interactions with medications.
CLA supplements may cause upset stomach, nausea, diarrhea, and fatigue.
Although conjugated linoleic acid supplements are considered safe, as with any nutritional supplement, you should consider the possible side effects. Excessive intake of CLA can increase the risk of diabetes in overweight individuals, or can lead to stomach and intestinal problems, nausea and diarrhea. Additionally, CLA can be harmful to infants and should not be used by pregnant women or nursing mothers. However, for relatively healthy individuals, CLA is considered an overall safe supplement.
Conjugated linoleic acid supplements are typically available as a solid capsule or in liquid form. CLA supplements vary in concentration, so you should look for a product that contains about 80 percent CLA. The recommended dosage of CLA supplements is 3.4g, or 3,400mg per day. Consuming conjugated linoleic acid supplements with high-protein foods such as milk can reduce the likelihood of experiencing nausea or diarrhea.
The majority of the studies outlined in research revolve around 5 grams of CLA daily for positive effects without harmful side effects.
Any greater amount per day could lead to serious side effects.
Supplements sold in the store are low in grams per pill. This limits the chance that somebody could overdose on CLA.