A PUFA-lipid paradoxon - tudomány és gyakorlat

Absztrakt

Human physiological judgment of dietary lipids (fats) is driven by the lipid-theory of Ancel Keys published in 1954. it says that higher fatty acid and cholesterol content of animal fats can be accused for the leading mortality factors just as cardiovascular diseases, in other terms hypertension and heart attack resulting from arteriosclerosis. Social effect of the theory was enormous. A cholesterol hysteria spread over the world (after some twenty years also in Hungary), cooking technologies changed, animal fat intake dropped by 25% while that of plant fats jumped four times higher, total fat intake increased by 30%. Rate of energy intake from fats in developed countries reached 40-42% instead of the recommended 30% value. In details it meant the blaming of animal and plant lipids with higher saturated fatty acids (SAFA) – among them milk fat (butter) – and the laudation of plant oils with high polyunsaturated fatty acid (PUFA, mainly omega-6) content. The scientific and practical dominancy of the theory was so strong that no remarkable (even nobel prize winning) findings could shake its position. Beginning from the last decade of the 20th century, however, three major breaking points appeared in the frontline of dietary fats. Even separately but also together these three findings gave the final jab to the theory. As an effect of the new findings lipids with saturated fatty acids and cholesterol became secondary risk factors while plant oils (saffron-, sunflower-, walnut-, wheat germ-, cotton seed-, soybean-, corn germ- and sesame seed oils) rich in PUFA became the primary ones. The three findings are as follows: - In 1992 the Harvard team of Willet alarmed the world that hydrogen treatment of plant oils result in formation of trans fatty acids and through the oxygenated ldl (oxldl) these acids are main factors of arteriosclerosis. In 2002 the institute of medicine of the National Academies declared that „trans fatty acid tolerance of human body is zero”. In some countries (Denmark, Canada, USA) legal regulations have been put in effect. - At the end of the century it was proved that omega-6 and omega-3 fatty acids if their ratio exceeds 3:1 or max 5:1 are potent factors of arteriosclerosis (beside causing other diseases and complaints just as allergy, psoriasis, migraine, periods pain, premature birth). In Hungary the same ratio is 97:1. - In 2005 the final jab to PUFA-rich oils was performed by prof. Ágnes Saari-Csallány of University of Minnesota when she and her team proved that during frying the PUFA oils formed highly citotoxic, mutagenic and carcinogenic aldehyd compounds (HNE, HHE, HOE, HDE). Toxic compounds can be found in fried meals (just as french fries, breaded meats) in the same concentration. Such compounds fail to form in lipids with low PUFA content. - The paradox quoted in the title has a dual meaning: first is that the practice failed to follow the science and the second is that the „extreme unction” for the lipid theory was given where the theory itself was born.