Fats come in many shapes and sizes and not all fats are created equal. Some are strictly used for energy, others are cell membrane components and others have powerful health effects. Conjugated linoleic acid (CLA) is a member of the omega-6 fatty acid group and has many health benefits. It is naturally found in beef, eggs and dairy and more recently has been demonstrated to cause fat loss. CLA has actually become a very popular weight loss supplement around the globe and many people swear by it. It is important to know that there are at least 28 isomers of CLA. Two of these isomers have biological activity in humans and are known as c9t11 and t10c12 so these are the isomers of interest. It is important to know that these two isomers work differently in the body.
Studies prove that CLA side effects exist
Scientific studies done thus far have produced a wide range of results and in some cases look contradictory. Some of this is because some studies were done in rodents and others done in humans. Moreover, different isomers may have been involved which perform a different function. Some studies indicate that CLA can lower cholesterol levels and increase insulin sensitivity. On the other hand, some studies have demonstrated that CLA had adverse effects on cholesterol levels and insulin sensitivity creating insulin resistance. Other studies have found that CLA can damage the liver (creating a fatty liver) and may increase fat concentration in breast milk. All the studies above were reviewed and none of them demonstrated significant benefits of CLA for weight loss or body composition (building lean muscle). Other side effects of CLA include diarrhea, soft stools, nausea, gas, stomach pain and constipation.
In spite of the above results, other experiments are suggesting that CLA found in food is beneficial. For those of you wanting to take CLA supplements, know that the CLA comes from linoleic acid (not conjugated) from sunflower and safflower oils (the unhealthy vegetable forms). This linoleic acid is modified by a chemical process to create the conjugated form. Also keep in mind that some molecules/nutrients are beneficial coming from natural foods in small amounts but can become harmful when taking larger doses in supplemental form.
High dosage of CLA may cause side effects
Quite often animals studies used very high doses of CLA, in fact much higher than humans would ever supplement with. It is these high dose studies that demonstrate that CLA can cause an increase in fat deposits in the liver. This type of phenomena can lead towards metabolic syndrome and diabetes. Other studies in both animals and humans have demonstrated that CLA can lower body fat but increases inflammation, increases insulin resistance and lowers good cholesterol. Even though the animal studies used very high concentrations in animals the human studies used normal concentrations and some of these experiments demonstrated similar side effects. So, at the moment it would appear that the adverse side side effects of CLA should not be dismissed.
So, the upshot is that some studies have demonstrated some serious side effect from CLA such as an increase in fat deposits in the liver, insulin resistance and an increase in bad cholesterol. Other studies seem to contradict this but some of this may be due to the different isomer forms of CLA. Different isomers act differently in the body. Further testing will be required to determine what is actually going on. At any rate, many people believe that CLA can help them lose fat and build lean muscle. The recommended dose ranges from 3.2 to 6.4 gm daily. It would appear that the risk of side effects increases as you increase the dose.