Conjugated CLA linoleic acid is found mainly in animal products – milk, dairy products and meat derived from ruminants. It is one of the best-studied bioactive compounds and has numerous pro-health effects, anti-cancer, anti-atherosclerotic, reducing adipose tissue, improving the immune system and increasing insulin sensitivity.
What is CLA?
CLA (Conjugated Linoleic Acid) is an animal-derived fatty acid that contains 18 carbon atoms and 2 conjugated double bonds in its chain. Conjugation means that the double bonds on the carbon atoms are separated by only one single bond. It is a rare property in nature and the uniqueness of CLA acid, which has a number of health-promoting effects, is believed to be unique in it.
It belongs to the group of Trans fats, but it should not be compared with hydrogenated vegetable fats which are very harmful to health. The Trans configuration in CLA is naturally formed and has no negative effects.
What are the sources of CLA?
The main sources of conjugated linoleic acid are meat and milk fat from cows, sheep, goats, deer and kangaroos. Sheep milk is characterized by the highest content of the CLA cis-9, trans-11 isomer among milk, but due to the low availability of products made from it, it is not an important source of CLA.
CLA is present in the diet mainly due to the consumption of cow’s milk and its products (70% of the CLA taken with food) and beef (25%). The average dietary intake of CLA is from 0.5 to 1.5 g/day, which is much less than the suggested dose positively influencing health – approx. 3 g/day.
The dose of CLA positively influencing health state is about 3 g per day.
CLA (conjugated linoleic acid) – properties. Impact on health
The scientific community shows great interest in the properties of conjugated linoleic acid and new publications about it appear every now and then. Research on CLA acid began in the 1970s, when M.W. Pariza, a professor at the University of Wisconsin-Madison, isolated from fresh and fried ground beef a compound that inhibited the development of epidermal cancer in mice.
In the following years, he identified and named him. Currently, CLA is one of the most studied bioactive substances and is assigned a broad spectrum of activity.
Antiatherosclerotic action of CLA
The results of many researchers indicate the antiatherosclerotic effect of CLA. This acid contributes to an increase in the level of good HDL cholesterol and a decrease in triglycerides. It also reduces cholesterol oxidation and cholesterol levels in the blood, and lowers blood pressure.
Only the cis-9, trans-11 isomer exhibits these properties. The trans-10, cis-12 isomer has a negative effect on the lipid profile – it worsens the ratio of HDL to LDL fraction. Human studies are not conclusive, possibly due to the use of different isomers of conjugated linoleic acid.
However, in animal models, a reduction in atherosclerotic plaque has been demonstrated with CLA supplementation. It is important that the hypolipidemic effects of rumen acid is already manifested at low levels in the diet (approx. 0.6 g/day). The anti-atherosclerotic activity of CLA is probably related to its strong antioxidant activity, as the level of cholesterol itself is not the only or the main risk factor for atherosclerosis.
Effect of CLA on the content of adipose tissue
The trans-10, cis-12 CLA isomer is responsible for modifying the share of adipose tissue in the body and it is the only isomer that shows the ability to reduce body fat. In clinical trials from 2000, CLA at a dose of 3.4 g daily for 12 weeks was shown to significantly reduce body fat in obese people. Weight loss occurs through several mechanisms
- Increasing energy expenditure by the body even at rest state
- Reducing the ability to accumulate triglycerides in adipose tissue cells by inhibiting the action of lipoprotein lipase – an enzyme necessary to store triglycerides in adipocytes
- Increase in the death of fat cells (adipocytes)
- Modulating adipose tissue hormones and markers of inflammation
- An increase in beta-oxidation (the use of fat as an energy source) in skeletal muscle
CLA and insulin resistance
Numerous studies show that CLA is effective in increasing the sensitivity of tissues to insulin and reducing hyperinsulinemia. At the same time, the experience of other authors shows that the use of CLA does not affect insulin and glucose metabolism. The divergent effects of conjugated linoleic acid may depend on the dose of CLA in the diet, the isomer used, the length of treatment and the method of delivery (with diet or supplements).