There are 28 different forms of CLA. It is technically a trans fat, but very different from industrial trans fats.
The main dietary sources of CLA are animal foods from ruminants, such as cows, goats and sheep. However, it’s important to recognize that the CLA in supplements is not derived from natural foods. It is made by chemical alteration of safflower and sunflower oils, which are unhealthy vegetable oils. The linoleic acid in the oils is turned into conjugated linoleic acid via a chemical process. The balance of the different forms is significantly distorted in supplements. Foods are mostly c9, t11, while the supplements are very high in t10, c12, which is never found in large amounts in nature. As such, CLA found in supplements does not have the same nutritional value and effects on health as CLA obtained from foods.
Some studies have shown that CLA can cause significant fat loss in humans and also improve body composition, with a reduction in body fat and sometimes increases in muscle mass, whereas many other studies show absolutely no effect of CLA on weight and body composition. In a large review paper that pooled the data from 18 controlled trials, CLA was found to cause modest fat loss. The effects are most prominent during the first 6 months of administration, after which it slowly plateaus for up to 2 years.
A rule of thumb: some molecules and nutrients are beneficial when found in natural amounts in real foods, but become harmful when we start taking them in large doses. CLA supplements are no exception, according to some studies. These studies have demonstrated that large doses of supplemental CLA can cause increased accumulation of fat in the liver, which paves the way towards metabolic syndrome and diabetes. There is also evidence from many studies, in both animals and humans, demonstrating that despite lowering body fat, CLA can drive inflammation, cause insulin resistance and lower HDL (the “good”) cholesterol.
CLA can also cause other less serious side effects like diarrhea, stomach pain, nausea and flatulence. Most of the studies used doses ranging from 3.2 to 6.4 grams per day. Remember that the risk of side effects increases as the dosage increases.
Carnitine, derived from an amino acid, is found in nearly all cells of the body. Carnitine is the generic term for a number of compounds that include L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine.
Carnitine plays a vital role in energy production.
The human body produces enough quantities of carnitine to meet the needs of the different functions. Healthy children and adults do not need to consume carnitine from food or supplements, as the liver and kidneys produce sufficient amounts from the amino acids lysine and methionine to meet daily needs.
Animal products like meat, fish, poultry, and milk are the best sources of carnitine. In general, the redder the meat, the higher its carnitine content. Dairy products contain carnitine primarily in the whey fraction.
Carnitine has been studied extensively because it is important to energy production.
Some athletes take carnitine to improve performance. However, twenty years of research failed to establish consistent evidence that carnitine supplements can improve exercise or physical performance in healthy subjects—at doses ranging from 2–6 grams/day administered for 1 to 28 days. (The total body content of carnitine is about 20 grams in a man weighing around 75 Kg, almost all of it in the skeletal muscle).
Doses of approximately 3 g/day, carnitine supplements can cause nausea, vomiting, abdominal cramps, diarrhea, and a "fishy" body odor. Rarer side effects include muscle weakness in uremic patients and seizures in those with seizure disorders.
Some research indicates that intestinal bacteria metabolize carnitine to form a substance called TMAO that might increase the risk of cardiovascular disease. This effect appears to be more pronounced in people who consume meat than in vegans or vegetarians. The implications of these findings are not well understood and require more research.