The alpha linolenic acid content of flaxseed can prevent the atherogenic effects of dietary trans fat
The alpha linolenic acid content of flaxseed can prevent the atherogenic effects of dietary trans fat
Year: 2011
Authors: Bassett, C.M.C. McCullough, R.S. Edel, A. L. Patenaude, A. LaVallee, R.K. Pierce, G.N.
Publication Name: Am. J. Physiol. Heart Circ. Physiol.
Publication Details: doi:10.1152/ajpheart.00958.2010
Abstract:
Dietary intake of industrially hydrogenated trans fatty acids (TFA) has been associated with coronary heart disease. Dietary flaxseed can inhibit atherosclerosis induced by dietary cholesterol. The aim of this study was to determine if supplementing the diet with flaxseed could protect against atherosclerosis induced by a diet enriched in TFA. Low-density lipoprotein receptor deficient (LDL r-/-) mice were fed one of 14 experimental diets for 14 weeks containing one of two fat sources (regular (pork/soy) or trans fat) at two concentrations (4 or 8%) and supplemented with or without dietary cholesterol (2%), whole ground flaxseed or one of the components of flaxseed (alpha-linolenic acid (ALA), defatted fiber or lignan). Adding flaxseed to the diet partially mitigated the rise in circulating cholesterol levels induced by the cholesterol-enriched diet. Atherosclerosis was stimulated by TFA and/or cholesterol. Including milled flaxseed to an atherogenic diet significantly reduced atherosclerosis as compared to the groups that consumed cholesterol and/or TFA. ALA was the only component within flaxseed that could inhibit the atherogenic action of cholesterol and/or TFA on its own. Dietary flaxseed protects against atherosclerotic development induced by TFA and cholesterol feeding through its content of ALA. (Authors abstract)
The atherogenic process is affected by diet including the amount and type of fats. Epidemiological and interventional investigations have revealed a significant positive association between coronary heart disease and the consumption of trans fatty acids from industrially hydrogenated vegetable sources (iTFA). TFA intake has been associated with atherogenic risk factors, such as elevated plasma cholesterol and triglyceride levels and plasma markers of inflammation and endothelial dysfunction. Increasing the consumption of omega 3 (n3) fatty acids has been suggested to provide ardioprotection against atherosclerotic disease. ALA demonstrates significant cardioprotective effects. Flaxseed is also a good source of two other cardioprotective constituents; dietary fibre and phytoestrogens called lignans. The aim of this study was to examine the effects of consuming dietary flaxseed or one of its fractions on atherosclerotic plaque formation in the presence of iTFAs and/or dietary cholesterol in the LDL receptor deficient (LDLr-/-) mouse. The authors hypothesized that consuming dietary flaxseed would prevent atherosclerotic development induced by both dietary cholesterol and iTFAs. The source and dosage of TFA provided to the mice in this study included elaidic acid rich, partially hydrogenated vegetable shortening in either a moderate (T) or high (HT) dose provided 1.4% and 2.8% industrial source TFAs (iTFAs), representing 3.2% and 6.4% of caloric energy, respectively. Estimates of TFA intake range from 0.7 to 28.7 g/person/day with the average daily trans fat intake in North America reported as 5.8 grams or 2.6% of calories. The TFA dosages used were relevant to both the typical as well as a high TFA consumption levels in humans. The results showed that combining flaxseed with iTFAs in the diet protects against the initiation and progression of atherosclerotic development. This finding is particularly pertinent as the LDLr-/- mouse is an excellent model of human atherosclerotic disease. Both whole ground flaxseed and an ALA-rich flaxseed oil completely prevented the initiation of atherosclerotic development induced by the consumption of a moderate or high dose of iTFAs. Because the ALA and whole ground flaxseed had similar beneficial effects, it is reasonable to conclude that the ALA rich fraction was responsible for the majority of the cardioprotective effects of flaxseed. Dietary ALA from flaxseed provided preventative benefits in the presence of two atherogenic risk factors (cholesterol and iTFAs). The protective effect of ALA appears to be independent of changes in circulating cholesterol and triglyceride levels suggesting that flaxseed offers an anti-atherogenic protection via a mechanism other than a lipid lowering effect. All of the flaxseed fractions (oil, fiber and lignan) offered a lipid lowering effect in the presence of cholesterol when compared to their respective control diet (C+T) in the presence of two atherogenic agents. The addition of the lignan fraction reduced circulating triglyceride levels better than whole ground flaxseed. Despite warnings and legislation to reduce TFA content in foods, it may be impossible to completely avoid the ingestion of TFAs in today�s diet. From this study, the addition of whole ground flaxseed or flaxseed oil to the typical Western diet containing TFAs and cholesterol offers an effective dietary strategy to protect against atherosclerotic CVD. (Editors comments)
