trans Fatty acids (TFA) are unsaturated fatty acids that possess a trans configuration on one or more of their double bonds (here). Evidence suggesting that TFA are detrimental to health has been growing for a number of years thanks to the tireless research and campaigning by scientists such as Mary Enig. In response manufacturers have been quietly removing TFA from foods, although their percentage in most foods are not provided on labels. Despite this researcher have shown that margarines and shortening can contain between 7 and 41% TFA, whereas cooking oils can contain between 1 and 79%. Naturally occurring TFA such as trans-vaccenic acid from ruminants are not though to pose a problem to health because they occur in human diets in low amounts and because the trans double bond is in the n-7 position which may not be detrimental to health.
Linoleic acid (LA, C18:2 (n-6)) is an essential fatty acid that is required for optimal health. Vegetable naturally contain high levels of LA, which can be converted to various trans fatty acids during the hydrogenation of vegetable oils to produce shortenings and margarine. The main fatty acid in hydrogenated vegetable oil is trans elaidic acid (EA, t-C18:1 (n-9)) and the main TFA in partially hydrogenated fat is trans, trans-linoelaidic acid (LEA, t,t-C18:2 (n-6). Of these, EA in particular has been identified as having some important negative health effects. High intakes of TFA results in their accumulation in human body tissues. Subjects consuming a typical Western diet were shown to have 4 to 14% TFA in heart tissue and 5 to 10% TFA in arterial tissue. The accumulation of TFA in heart and arterial tissue may have implications for cardiovascular disease.
Epidemiological research is increasingly linking the consumption of TFA to the development of cardiovascular disease. To investigate the mechanisms by which TFA might have detrimental health effect, researchers have used cell models to understand their biochemistry. For example, researchers1 from the university of Illinois added various concentrations of trans and non-trans fatty acids to cultured endothelial cells. When the cells were harvested the amount of calcium influx, a possible step in the development of atherosclerotic plaques, was assessed. The results showed that the percentage of fatty acids incorporated into the cell membranes was proportional to their concentration in the cell culture medium. Further, the amount of TFA and LA incorporated into the endothelial cells was proportional to the ratio of these fatty acids in the culture medium. Influx of calcium to the endothelial cells was increased significantly when they were cultured in trans, compared to non-trans fatty acids
Interestingly, the researchers performed the experiments at both high and low concentrations of magnesium, with high concentrations of magnesium reducing the influx of calcium to the endothelial cells even in the presence of TFA. This may be because magnesium is required to maintain the physical structure of the membranes, and magnesium deficiency results in a breakdown of proper membrane function. This study shows that trans fatty acids may contribute to this cellular disturbance of the membrane, perhaps by displacing LA from its normal position in phospholipids. There are a large number of papers in the literature that link magnesium deficiency to ischaemic heart disease. The low intakes of magnesium in Western diets may therefore be contributing to the high rate of cardiovascular disease, perhaps due to low intakes of whole grains, which are a rich source of magnesium.
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