Conjugated linoleic acid (CLA) is highly found in fats from ruminants, and it appears to modify the body composition and cardiometabolic risk factors favorably. The capacity of CLA to reduce the body fat levels as well as its beneficial actions on the glycemic profile, atherosclerosis and cancer has already been proved in experimental models. Furthermore, CLA supplementation may modulate the immune function, help re-synthesize of glycogen and potentiate the bone mineralization. CLA supplements also could increase the lipolysis and decrease the accumulation of fatty acids on the adipose tissue; the punitive mechanisms involved may be its action in reducing the lipase lipoprotein activity and to increase the carnitine-palmitoil-transferase-1 activity, its interaction with PPARγ, and to raise the expression of UCP-1. Although studies made in human have shown some benefits of CLA supplementation as the weight loss, the results are still discordant. Some have shown adverse effects, such as the glucose metabolism and lipid profile. The primary purpose of this article is to demonstrate the available data and benefits of CLA on the energetic metabolism and body composition, emphasizing action mechanisms.
Though many researchers have studied and found significant evidence about functional foods, their benefits to health have often been talked about, calling the attention of the scientific community. Even though several studies were performed claiming that functional foods are essential for health and have helped reduce the risk of developing various chronic diseases. This useful property concerns the metabolic or physiological role played by the nutrient or non-nutrient in growth, development, maturity and other standard functions of the human organism. However, studies on nutraceuticals, which are foods with a medicinal function lack further explanation, especially regarding the associated protective effects. The doses indicated generate doubts that these results will be achieved, and also regarding the possible adverse effects of their long term use.
Many different classes of substance that are naturally found in foods or produced by food technology have functional properties. One of the substances is conjugated linoleic acid or CLA, which is a fatty acid which gives a linoleic acid isomer (C18:2, n-6) and has been considered an anti-obesity agent, and can be useful in the weight reduction process. Though the initial result that was found only in an animal model, more recent research on humans suggests that CLA would act to reduce adiposity through modulating properties in the lipid metabolism. But some doubts remain as to the action mechanics of CLA in adipocytes, which leads to the reduction of body fat and, the safety of supplements of this compound.
Which means the purpose of this review is to demonstrate the effect of CLA supplementation on body composition, in particular on the reduction of adiposity, focusing on possible action mechanisms.
Conjugated linoleic acid
Conjugated linoleic acid or CLA is a term that describes a group of fatty acids with 18 atoms of carbon, and the geometric isomers consist of linoleic acid. This is a common name given to a group of position isomers with two double bonds separated by a methylene group. This conjugation of the double bond is generally in positions 9 and 11 or 10 and 12 and may be a cis or trans configuration.
Isomer structure represents CLA 10-trans and 12-cis; indicate CLA 9-cis and 11-trans; C18:2 9-cis and 12-cis
CLA is produced naturally in the digestive tract of animals such as cattle, goats, sheep, buffalo, and to a lesser degree in pigs, chickens, and turkeys. The synthesis occurs due to fermentative bacteria, like Butyrivibrio fibrinogens, which isomerizes the linoleic acid in CLA or by synthesis via α9-desaturase of 11-trans octadecanoic acid. The fat in beef contains about 1.7 to 10.8 mg CLA/g of fat with 9-cis and 11-trans isomers. It is also found in dairy products like milk and derivatives.
CLA can be obtained using enzyme α9-desaturase which promotes the desaturation of the 11-trans octadecanoic acid. Many different isomers of CLA such as 11-trans and 9-cis are the best acids that we know of because they are found in food. It is also possible to obtain CLA in a modern form, through the partial hydrogenation of linoleic acid or by thermal treatments, aiming to produce a compound with maximum biological activity and with a defined chemical composition.
CLA has a significant role in the lipid metabolism, especially as regards the oxidative cellular system, which explains many physiological properties of fatty acids. The action on the lipid metabolism is associated with the inhibition of entry of the glucose into the adipocytes and may lead to changing the insulin metabolism and cause situations of hyperinsulinemia, as well as the increase of inflammatory markers.
There are many investigations to evaluate the influences of CLA on the energetic metabolism, promoting significant changes in the lipid metabolism and body composition. As a result, some effects can be cited such as reduction of body fat, improved insulin resistance, anti-thrombogenic and anticarcinogenic effects, reduction of atherosclerosis, improved lipid profile, modulation of the immune system and stimulation of bone mineralization, and also reduced blood glucose. The most studied CLA supplement effect is the capacity to alter the body composition, promoting an increase in lean mass and reduction of the fat mass.
6 Benefits of Conjugated Linoleic Acid
1. Helps with Weight Loss and Fat-Burning
People find it hard to believe, but it turns out butter is a fat-burning food. CLA has shown to help fat loss in many animals and human studies when in its concentrated form it’s one of the most popular weight loss supplements in the world. According to a 2009 report that was published in The Journal of Nutritional Biochemistry, it is believed that CLA reduces fat because of its impact on, energy metabolism, adipogenesis, inflammation, lipid metabolism, and apoptosis.
Supplementation with a CLA mixture or the isomer alone decreases body fat mass, according to a result of numerous animal studies. Within the two major isomers, 10,12 specifically seems to be responsible for the antiobesity effects of CLA.
Within human studies, the results for CLA on weight loss have been auspicious. One study found that supplementation of a CLA mixture in overweight and obese people with three to four grams a day for about 24 weeks decreased body fat mass and increased the lean body mass.
Some people believe that they experience better results than others due to the fact they include CLA isomer combination rather than individual isomers, CLA dose and duration of treatment, gender, weight, age and metabolic status of the subjects. One possible potential mechanism by which CLA reduces body fat mass might be that it will decrease energy intake or increases energy expenditure. A study that was demonstrated that mice supplemented with a CLA mixture for four weeks reduced their food intake and experienced liver function improvements, although studies are still happening in humans.
2. Regulates Blood Sugar and Helps Improve Insulin Function
There’s substantial evidence that an inverse association exists between CLA intake in someone’s diet and diabetes risk. The theory is that CLA may be involved in insulin regulation. We also know that the best food sources with CLA, include healthy fats like butter or grass-fed beef, which can stabilize blood sugar and help someone stick to a low-sugar, low-carb diet that is very beneficial for controlling diabetes.
3. Improves Immune Function and Could Potentially Help Fight Cancer
Conjugated lipoic acid has shown immune-enhancing effects and anticarcinogenic activities in several animal studies. CLA that is in saturated fatty foods could offset the adverse effects of the saturated fat content and benefit everything from blood sugar control to hormone regulation to even natural cancer prevention.
Researchers repeatedly found that the quality of fatty acids in someone’s diet is exceedingly important for reducing overall cancer risk, and conjugated linoleic acids have proved to increase the health in several ways, especially lowering inflammation. Lower inflammation is a sign of less free radical damage or oxidative stress, and that is linked to lower cancer risk.
CLA modulates immune and inflammatory responses as well as improve bone mass. Researchers found the effects of conjugated linoleic acid for preventing breast cancer is somewhat conflicting, but early research shows that higher intake of CLA from natural foods is linked with a lower risk of developing breast cancer. Other study results indicate that it can be very beneficial for fighting cancer of the digestive organs and can improve detoxification via healthier liver function too.
4. Reduces Allergies and Asthma Symptoms
Consuming CLA from food or taking CLA supplements for 12 weeks seems to improve symptoms and overall health in people with seasonal allergy symptoms. Some research shows that people with asthma could use CLA to be a natural treatment method for asthma-related symptoms. Twelve weeks of supplementation seems to improve airway sensitivity and better cardio.
5. Improves Rheumatoid Arthritis Symptoms
Early research has been showing that CLA is beneficial for lowering inflammation and autoimmune disorders like rheumatoid arthritis. Taking CLA alone or along with other supplements like vitamin E benefits those with arthritis by reducing symptoms, including pain and morning stiffness. Pain and inflammation including swelling have been improved for adults with arthritis taking CLA compared to their pre-treatment symptoms or people not taking CLA, meaning CLA can naturally treat arthritis.
6. Improve Muscle Strength
Some researchers found that taking conjugated linoleic acid alone or along with supplements like creatine and whey protein can help increase strength and improve lean tissue mass. This is why CLA is added to some bodybuilding supplements, protein powders or weight loss formulas.
Best Sources of Conjugated Linoleic Acid
According to a report published in The Journal of Food Composition and Analysis, the top food sources of CLA include:
Butter from grass-fed cows (ideally organic)
Full-fat, preferably raw, dairy products like cream, milk, yogurt or cheese
Grass-fed beef (preferably organic)
Also found in dairy products from sheep or goats, in addition to cows
Found in smaller amounts in grass-fed lamb, veal, turkey and seafood
The proportion of CLA ranges from 0.34–1.07 percent of the total fat found in dairy products, making it the highest source which is followed by about 0.12—0.68 percent of the total fat in raw or processed beef products. Although, when it comes to animal products, the breed and the in particular quality of the animal’s diet and lifestyle affect the fat that you will obtain when you eat the animal. In other words, not all beef or dairy is created equal when it comes to supplying us with healthy fats.
What the animal was eating and the conditions it was living in highly affect how much CLA and other healthy fats or nutrients it supplies. Even the season, quality of the soil on the farms and age of the animal affect the CLA content. For example, one study found that the CLA content in beef and dairy from grass-fed cows is 300–500 percent higher compared to grain-fed cows!
Grass-fed beef contains much higher levels of CLA and even more omega-3 fats and vitamins than meat from factory farm-raised animals. The same goes for dairy products we get from cows, such as cream or butter. The best way to find high-quality grass-fed beef is to purchase it directly from small town farms, whether visiting farmer’s markets, joining a community-sponsored agriculture group or even looking online. If you can’t find the perfect product, for example, 100 percent organic and grass-fed beef, do the best you can while also focusing on limiting industrial and human-made fats from your diet.
According to a study, the effect of CLA is not the same in all animal models. Rats supplemented with 0.5 % of CLA, for instance, presented a small, but fast (7 days) reduction of adipose tissue, compared to mice.
Scientists evaluated the effects of supplementation with CLA on the body composition of healthy Wistar rats supplemented for three weeks with CLA at the concentrations of 1 %, 2 % and 4 % on the daily supplement of the diet and control group which was 2 % linoleic acid. At the end of the period, the groups that were supplemented at a concentration of 2 % and 4 % with CLA had a bigger body fat reduction compared to the control group.
Other researchers evaluated that coconut oil, corn oil, and CLA. In this study, 28 rats were allocated to 4 different diets, which were supplementation with coconut oil, and CLA, corn oil and maize oil and CLA. After 28 days, total cholesterol, HDL–c and triglycerides were evaluated. It was found that the triglycerides diminished in the diet supplemented with coconut oil and CLA, and HDL-c decreased with the maize oil diet. The total cholesterol concentrations were lowest in the rats on the coconut oil and CLA diet, but not in the diet with corn oil and CLA. This study suggests that the CLA might diminish adiposity and improve the lipid profile under some conditions.