Conjugated linoleic acid (CLA) is a potent anti-oxidant, anti-carcinogen, and anti-catabolite, as well as a powerful immune system enhancer. A deficiency of CLA in the diet may be a major factor in causing Americans to gain so many fat pounds. CLA is a potent anti-oxidant, but appears to prevent cancer via other mechanisms of action.
Yet there is no point in trying to increase your dietary CLA naturally because, even if all the theoretical benefits were confirmed, a person would have to consume at least 500g of fat, mostly saturated, each day to get meaningful amounts, which is at least three grams. That is over 4,500 fat calories each day just from eat CLA rich foods. Therefore if you want to boost your conjugated CLA intake to the levels used in scientific studies, you must use CLA supplementation.
In regards to CLA supplementation, it would be wise to use those whose isomer content is similar to naturally occurring CLA such as those consistently predominant of c9, t11 CLA, which are ones that are generally found in CLA that is available in stores.
While the t10, c12  isomer may exert a much more potent fat-reducing effect, there are simply too many unanswered questions over its possible health risks to recommend using large amounts at present time. Since CLA is similar to essential fatty acids, it would probably also be wise to make sure you dietary fats are up to par through foods such as sunflower seeds, almonds, peanuts, or EFA supplementation.
CLA is found mainly in dairy products and also in red meat, poultry, eggs, and, surprisingly enough, corn oil. There is also bacteria that lives in the intestine of humans that is able to produce CLA from linoleic acid, but supplementation of a rich source of linoleic acid did not product increases in blood levels of CLA in human study.  CLA is also available as a supplement. The table bellows shows the amount of CLA is common foods.
|Table 1: Conjugated Linoleic Acid content of common foods|
|FOOD||Typical mgs of CLA per gram of total fat||% of CLA present as c9, t11 isomer|
|Homogenized cow’s milk||5.5||92|
|Homogenized cow’s milk||4.8||84|
|Fresh ground beef||4.3||85|
|Sharp cheddar cheese||3.6||93|