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CLA as unhealthy as synthetic trans fatty acids

According to a meta-study by Dutch nutritionists, CLAs are just as bad for your heart and blood vessels as the dreaded synthetic trans fatty acids that the food industry has been using for years in cookies, margarines and junk foods. CLA’s popularity as a nutritional supplement is on the wane.

CLA as unhealthy as synthetic trans fatty acids
When you hear the words 'trans fatty acids' you probably think of ones like the formula at the top of the diagram here. This is elaidic acid, a trans fatty acid that is manufactured from a natural fatty acid. The advantage of trans fatty acids is that they don't go rancid quickly and they are what give bread and baked products a crispy texture. Nutritionists in the 1980s and 90s discovered that trans fatty acids increase the 'bad cholesterol' [LDL] in the body, and at the same time lower the 'good cholesterol' [HDL] thereby boosting the chance of a heart attack.

Milk and meat fats contain natural trans fatty acids, such as CLAs. The third structural formula in the diagram is of CLA. CLAs are produced in cows from vaccenic acid, another natural trans fatty acid in milk and meat, represented by the second structural formula in the figure above.

CLAs improve the body composition. They reduce the amount of body fat, probably by inhibiting fat cells' uptake of fatty acids. Instead the fatty acids end up in the muscle cells, which therefore get more energy and grow. Sounds good, but there's also a risk of the fatty acids getting into the organs – not healthy at all. The effect of CLAs on body composition has already been demonstrated, but is modest.

The Dutch nutritionists fear however that CLAs are just as risky as the trans fatty acids that the food industry has been putting in our food for years. For their publication in PLoS ONE, therefore, they analysed 39 trials in which people had been given trans fatty acids and the of these effects on heart and blood vessels had been measured. Seventeen of the studies were on CLAs, and six were on natural trans fatty acids like vaccenic acid.

The graph below shows that all sorts of trans fatty acids raised the concentration of the LDL by approximately the same amount. Statistical calculations produced the straight lines.

CLA as unhealthy as synthetic trans fatty acids

All sorts of trans fatty acids lowered the concentration of HDL.

CLA as unhealthy as synthetic trans fatty acids

Cardiologists look at the ratio between HDL and LDL. The smaller it is, the better. It won't come as a surprise that all trans fatty acids worsened the ratio by about the same amount.

CLA as unhealthy as synthetic trans fatty acids

Our diet does not contain terribly high amounts of natural trans fatty acids as we now eat less animal fat. If we could eliminate the last remaining trans fatty acids from our diet, then we might reduce our chance of heart and circulatory disease by 1.5 – 6 percent in theory. That's not a huge amount. In fact, the impact of long-term CLA supplementation may be more serious.

"Intakes from supplements can easily reach 3 grams of CLA a day", the researchers write in their conclusion. "This should increase the LDL to HDL cholesterol ratio by 0.050, which would correspond with a 3 to 12 percent increase in the risk of cardiovascular disease."

That's still not much. A rule of thumb in nutritional research is that something only becomes interesting if it doubles or halves risk. On the other hand though: CLAs are expensive and their effect is modest. If CLAs also increase your risk of cardiovascular disease it may be a reason for you to go in search of an alternative supplement.

PLoS ONE 5(3): e9434.

Bodybuilders progress faster with 5 grams CLA daily 15.12.2009