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30.12.2008


Live longer with healthy fats

Linoleic acid is bad and the health risks of saturated fats are stories made up by Unilever: thatís still pretty much the view of alternative nutrition experts. A recent Scandinavian study, in which epidemiologists monitored a group of men for thirty years, shows otherwise. According to the study, a diet with high quantities of saturated fats shortens life expectancy and a diet that is high in linoleic acid does the opposite.


In the seventies the Swedes, working at Uppsala University, measured the concentrations of a dozen fatty acids and three enzymes involved in fatty acid metabolism in the blood of 1900 men aged 50.

The researchers looked at stearoyl-CoA desaturase (SCD), an enzyme that converts fatty acids into mono-unsaturated oleic acid. Oleic acid is found in olive oil, and itís widely present in the human body. A high level of active SCD in your blood indicates that you eat large amounts of saturated fatty acids.

The simplified table below shows the relation between the concentrations of the fatty acids and enzymes measured and mortality. An increase in the relative mortality risk is the result of a 1 SD increase in the fatty acid or enzyme level.



Palmitic acid increases the mortality risk the most, and linoleic acid reduces the mortality risk the most. The concentration of SCD is a good predictor of the mortality risk. Fatty acids affect the heart and blood vessels. Healthy, unsaturated fatty acids improve cholesterol levels and inhibit inflammatory processes; saturated fatty acids do the opposite.

The figure below shows the effect of linoleic acid on the risk of mortality. The right-hand curve represents the mortality risk for the fifty percent of the group of men with high levels of linoleic acid, the left-hand curve represents the mortality risk for the fifty percent with low levels of linoleic acid.



According to the alternative nutritionists in the fatty acids debate, linoleic acid is a bad fatty acid. The main reason given is that it is a precursor of inflammatory factors. This is the case, the researchers confirm. But linoleic acid Ė or rather arachidonic acid, which is made from linoleic acid Ė is also a precursor of lipoxines and these inhibit inflammation.

The bottom line of the Swedish study confirms the consensus view of mainstream nutritionists: a diet that is rich in saturated fatty acids is not healthy. These are found mainly in fatty meat products (not in fish) and in fatty snacks.

Sources:
Am J Clin Nutr. 2008 Jul;88(1):203-9.