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Conjugated CLA linoleic acid is found mainly in animal products - milk, dairy products and ruminant meat. It is one of the best-studied bioactive compounds and has numerous pro-he alth effects: anti-cancer, anti-atherosclerotic, reducing adipose tissue, improving the immune system and increasing insulin sensitivity. The content of CLA in food products depends on many factors, and the way animals are raised is of key importance. To increase the proportion of these fatty acids in the diet, one should choose food from traditional small farms.


  1. CLA (conjugated linoleic acid) - formula. How is it made?
  2. CLA (conjugated linoleic acid) - occurrence. What are the sources of CLA?
  3. CLA (conjugated linoleic acid) - properties. Effect on he alth
  4. CLA (conjugated linoleic acid) - side effects and dosage

CLA( Conjugated linoleic acid , conjucted linolic acid) is an animal-derived fatty acid that contains 18 carbon atoms in the chain and 2 conjugated double bonds. Coupling 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 he alth-promoting effects, is believed to be unique in it.

It belongs to the group of trans fats, but it should not be equated with hydrogenated vegetable fats which are very harmful to he alth. The trans configuration in CLA is naturally formed and has no negative effects.

CLA (conjugated linoleic acid) - formula. How is it made?

There are several dozen different CLA isomers, however, they are common. he alth.

Dominant among CLA acids is the cis-9, trans-11 isomer (ruminal, rumenic acid), which accounts for 80-90% of all CLA isomers in meat and milk, and the second most frequent trans-10, cis -12 - 10-20%.

CLA linoleic acids are mainly produced by ruminants. Part ofthey are formed in the digestive tract (especially in the rumen) in the presence of appropriate symbiotic bacteria, e.g. Butyryvibrio fibrisolvens.

However, they are mainly produced in the tissues of polygastric animals and incorporated into the fat contained in their milk, muscles (invisible fat) and between muscles (visible fat). In animals with one stomach, CLA is synthesized, but at a much lower level.

This acid is also detected in human adipose tissue and breast milk. Presumably, it is not only supplied with food, but also to some extent produced in the body.

CLA (conjugated linoleic acid) - occurrence. What are the sources of CLA?

The main sources of conjugated linoleic acid are meat and milk fat from ruminants: cows, sheep, goats, as well as deer and kangaroos. Sheep milk has the highest content of the CLA cis-9, trans-11 isomer in milk, but due to the low availability of products made from it, it is not a significant source of CLA.

CLA is present in the diet mainly due to the consumption of cow's milk and its products (70% of CLA with food) and beef (25%). The average dietary intake of CLA acids ranges from 0.5 to 1.5 g / day, which is much less than the suggested dose positively influencing he alth - approx. 3 g / day.

The dose of CLA with a positive effect on he alth is approx. 3 g per day.

The most valuable are products from cows reared traditionally and grazed on pastures in the spring and summer period. In fish and poultry fat, the concentration of conjugated linoleic acid is much lower, and vegetable oils do not contain it at all.

The ability to produce CLA is shown by lactic acid bacteria, therefore the amount of this acid may increase in fermented milk products, e.g. yoghurts and kefirs.

CLA fatty acid content in foods [mg / g fat]
Cheddar cheese3,6
Cottage cheese4,5
Grana Padano cheese9.47
UHT milk5,5
Egg yolk0.6
Corn oil0,2
Peanut oil0,2
olive oil0,2

The content of CLA fatty acid in meat and dairy products depends on many factors. How the cattle are reared and fed, as well as their breed, are of key importance. The fat of traditionally farmed animals, i.e. pasture-grazed in summer and compound-fed in winter, is much more rich in CLA than that of animals fed with fodder all year round.

The content of CLA in products largely depends on the season. In summer it is even twice as high as in winter. As a result of the analysis of samples taken from cows traditionally bred on small farms in the Lubelskie Voivodeship and cows raised in a modern way in the Greater Poland Voivodeship, it was found that in the milk fat of cows traditionally bred in summer, the concentration of CLA was 10 mg / g, and 5.1 mg / g in winter, while in modern breeding cows: 5.3 mg / g in summer and 4.2 mg / g in winter.

The content of CLA in the fat of ruminants can be influenced by modifying their feed, which results in a 3-5-fold increase in the concentration of this acid. For this purpose, oils and oilseeds rich in linoleic acid are added, as well as fish oils rich in omega-3 acids.

CLA fatty acid content in Polish food products obtained from modern-farmed cows [mg / g fat]
Yellow cheeses2,4
Cheeses with blue mold1,9
Blue cheeses2,4
Goat cheese2,26
Cottage cheese3,0
Cheese1.21 - 2.400.51 - 1.1

Polish dairy products very often have a lower CLA content than, for example, Italian and Portuguese dairy products. This is due to a very large limitation of the natural grazing of animals and too little share of forage from grasslands.

About 90% of dairy products come from modern farms. Conversely, the fat of traditionally farmed cows is even 3-5 times more abundant in CLA.

CLA (conjugated linoleic acid) - properties. Effect on he alth

The scientific community shows great interest in the properties of conjugated linoleic acid andnew publications about him appear every now and then. Research on CLA acid dates back to 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 it. Currently, CLA is one of the best-studied bioactive substances and is assigned a broad spectrum of activity.

CLA Inhibition of Cancer Growth

The antitumor activity of the cis-9, trans-11 isomer of CLA acid has been confirmed in many animal models, as well as in humans. Clinical experiments in humans have not always yielded unequivocal results, which may be related to the dose of CLA taken, the type of neoplastic tumors, the age of the respondents, etc., however, it has been suggested that this relationship is important in the prevention and treatment of certain cancers and the prevention of metastasis.

Epidemiological studies conducted in Finland have shown a relationship between milk consumption (sources of CLA) and reduced incidence of breast cancer among women. In vitro studies confirm very high antitumor efficacy for human leukemia, melanoma, breast cancer, breast cancer, colorectal cancer, prostate cancer, ovarian and oral cancer.

CLA is approved by the National Academy of Sciences of the USA as the only anti-cancer fatty acid in animals.

Pariza, summing up the years of his research and the experience of other scientists, suggested that the impact of CLA on cancer development could be as follows:

  • by direct interference with the neoplastic process,
  • indirectly by reducing body fat,
  • by inhibiting cachexia (a state of severe cachexia) that accompanies many advanced cancers.

In many studies, CLA acids have a stronger effect on the inhibition of carcinogenesis than tocopherols and polyunsaturated fatty acids, omega-3 acids known for their antioxidant activity.

Antiatherosclerotic effects 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 its concentration in the blood, and lowers blood pressure.

These properties are exhibited only by the cis-9, trans-11 isomer. The trans-10, cis-12 isomer has a negative effect on the lipid profile - it worsens the ratio of HDL to LDL. Human studies are not conclusivepossibly due to the use of different isomers of conjugated linoleic acid.

However, in animal models, a reduction in atherosclerotic plaque as a result of CLA supplementation has been shown. It is important that the hypolipidemic effect of rumen acid is already manifested at low dietary levels (approx. 0.6 g / day). The antiatherosclerotic effect of CLA is probably related to its strong antioxidant activity, as cholesterol levels alone are not the only or the main risk factor for atherosclerosis.

Effect of CLA on body fat content

The trans-10, cis-12 CLA isomer is responsible for modifying the proportion 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 the body's energy expenditure even at rest,
  • 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 inflammatory markers,
  • increase in β-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 the treatment and the method of delivery (with the diet or in supplements).

Effect of CLA on the immune system

CLA affects the synthesis of eicosanoids (a type of lipid mediator) and thus modulates the immune system and prevents immunodeficiency in animals. In humans, it has a beneficial effect in some allergic and inflammatory reactions, reduces the concentration of inflammatory markers and increases the amount of protective antibodies.

Supplementation with a 1: 1 mixture of the two most common CLA isomers at a dose of 3 g / day for 12 weeks resulted in a decrease in pro-inflammatory cytokines (interleukin-1, tumor necrosis factor) and an increase in anti-inflammatory cytokines.

CLA (conjugated linoleic acid) - side effects anddosage

A dose of CLA having a positive effect on he alth is about 3 g per day. At the same time, it should be noted that already 0.6 g of rumen acid per day reduces the level of cholesterol in the blood.

The trans-10, cis-12 CLA isomer has a beneficial effect on the composition of body tissues (reduction of adipose tissue, increase in muscle mass), which is also hyperlipidemic and thus may contribute to cardiovascular diseases. When taken with food, CLA is considered safe, and possibly safe in supplements containing high doses of it.

Some studies indicate that high-dose CLA supplementation can cause fatty liver disease. Side effects of using CLA supplements include gastrointestinal discomfort, diarrhea, nausea and fatigue.

Children should take CLA in therapeutic doses for no longer than 7 months. When consumed with food, conjugated linoleic acid is safe during pregnancy and breastfeeding, while data on the effects of supplements are lacking. It is safer to avoid them during these periods.


CLA should not be taken by people with impaired blood clotting and taking medications to thin the blood, because the acid additionally reduces clotting. You should stop using it 2 weeks before the planned surgery, because it increases the bleeding.

You need to be careful and read labels carefully when taking CLA supplements. Often, completely inactive isomers of conjugated linoleic acid are found in pharmacy products. The type of isomer must also be selected according to the needs.

Due to the often inconclusive results of scientific research and suggested further research on the effects of CLA, supplementation should be considered and introduced wisely. It is worth increasing your CLA intake along with food sources. For this purpose, you should look for meat, milk and dairy products from small farms, where the animals are traditionally raised and grazed in the spring and summer.


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7. Karwat J. et al., CLA - he alth-promoting properties, General Medicine and He alth Sciences, 2013, 19 (4), 535-538

8. Janczy A., Conjugated linoleic acid cis-9, trans-11 CLA and atherosclerotic changes, Scientific Papers of Gdynia Maritime University, 2012, 73, 5-15

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10. Bartnikowska E., Conjugated linoleic acid dienes. Part I. Structure, formation, occurrence in food, Borgis - Safe Food, 2001,1

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12. Czekajło A. et al., Effect of conjugated linoleic acid on the risk of cancer formation and progression, Probl Hig Epidemiol, 2016, 97 (3), 207-212


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