“From the standpoint of effects on blood lipids, there is no question that trans fatty acids are worse than any other possible source of calories in the diet.” [1]
-- Alberto Ascherio, MD, Dr. P.H., Harvard School of Public Health
Trans fats attack the circulatory system: Trans fats kill tens of thousands of Americans every year [2] and contribute significantly to mortality throughout the world [3]. They do this by raising the LDL/HDL ratio twice as much as saturated fats, and any amount of trans fats in the diet, however small, has been shown to have a negative impact [3]. Compared to saturated fats, trans fats also raise TG and Lp(a) levels [4-6] and increase the amount of small, dense LDL cholesterol particles (the worst kind of LDL) [7]. And trans fats uniquely (relative to saturated fat) lower HDL [8]. Thus, calorie for calorie, trans fats contribute more to hardening of the arteries and heart disease than any other macronutrient. Sadly, trans linolenic fat, which is produced in high amounts during deodorization of refined liquid vegetable oils, increases the LDL/HDL ratio six times more than would be expected from a standard mixture of trans fats in hydrogenated oils, making processed oils particularly unhealthy even when they are not hydrogenated [9]. But the impact of trans fats on shortening human life is so dramatic that a worse lipid blood panel cannot be the only explanation [10]. We now know that trans fats stimulate cellular processes related to insulin resistance and diabetes, including inflammation (e.g. involving tumor necrosis factor) [10,11]. Thus, trans fats also contribute more to diabetes than saturated fats, and they do so through different mechanisms (the alteration of expression of different genes) compared to saturated fats in peripheral tissues [12] and at the level of the pancreas [13]. There is a 39% increase in the risk for diabetes for those in the upper fifth of trans fat consumers (evaluated from 85,000 women in the Nurse’s Study) [14] and may be twice that amount for many, depending on their genetics [15]. The ‘upper fifth’ corresponds to eating more than a half dozen grams / day i.e. a couple fast-food meals or one serving of processed vegetable oil in one day. In addition, it appears that part of the poisonous effects of trans fats occur in the cell membranes into which they are incorporated; it is for this reason that some in the medical community now consider trans fats the equivalent of membrane-active drugs [16,17]. The membrane effects of trans fats specifically target the development of arrhythmias and contribute to sudden cardiac death [18].
Trans fats cause cancer of the prostate, breast and colon: Post-menopausal breast cancer is increased by a staggering 360% for those in the upper quarter of trans fat intake, but this effect is reduced when women also consume non-partially hydrogenated polyunsaturated fats [19]. A new case control study done at UCSF involving over 1000 subjects shows that men in the upper quarter of trans fat consumption have nearly triple the risk of prostate cancer (relative risk = 2.77, CI 1.60-4.79) but that for those with certain genetics (related to how cells respond to inflammation) have no increased risk from trans fats [20]. Previous work at the Fred Hutchinson Cancer Research Center had shown nearly twice the prostate cancer risk from trans fat intake [21]. Colon Cancer risk is increased by roughly 50% with trans fat intake [22].
Trans fats attack the liver: Saturated fat increases cell stress (endoplasmic reticulum) and lipid accumulation in liver cells. These negative effects are made worse in the presence of trans fats because they inhibit stearoyl-CoA desaturase. Thus, trans fats do not simply do what saturated fats do, but work by different mechanisms, augmenting the effects (symbiotically) of saturated fats to harm the liver [23].
Natural trans fats in meat and dairy: Most of the trans fats in our diet are from partially hydrogenated oils, but some are found naturally in meat (1-8% of total fats) because they are made by bacteria in the rumens of animals [24]. Interestingly, the results of four prospective studies have shown that trans fats from ruminants do not increase (and might even reduce) the risk of coronary heart disease [25-28]. Rumen bacteria make trans fats whenever their environment becomes more toxic to them [29], such as when cows are fed grain instead of grass. Comparing meats (all cuts) from cows fed only grass, grass with short-term grain feeding, or long-term grain feedlot rations shows that there is a successive decrease in the amount of omega-3 fats and an increase in the amount of trans fats as cows are fed more grain [30]. Although rumen bacterial trans fats have not been shown to be harmful, grass fed seems prudent.
My highest recommendation: Eliminate all partially hydrogenated vegetable oils from your diet. You must read the ingredients of the food products you buy: If trans fats are less than 0.5 g per serving, the trans fats will be listed as zero on the label even though the food contains trans fats. This is one of the many legal (FDA approved) ways in which the food industry can shorten our lives by misrepresenting the foods we are buying from them. Some food products will even go so far as to say on the front of their containers “Zero trans fats!” and then in tiny script so small you can barely read it underneath: “Per serving.” Ignore the lies. Read the ingredients. Eat no partially hydrogenated oils of any kind. If possible, use only food products containing oils that are cold pressed, not heat treated, and that have not been deodorized or processed in any other way. It is impossible to know the processing history of most oils since companies do not disclose everything they do. Just do your best when navigating oils, and at a minimum eliminate the hydrogenation. Although ruminant trans fats have not yet been correlated to disease, it is still worth considering consuming grass-fed beef. Many fast-food meals and ingredients in restaurants contain partially hydrogentated oils; we can’t always know. I occasionally (when not with friends who would be embarrassed) ask and a waiter finds out that trans fats are in their food.
References
1. Trans fatty acids and blood lipids. Ascherio A, Atherosclerosis 7 (2006) 25
2. Trans fatty acids and coronary heart disease. Ascherio A, Stampfer MJ, Willet WC, Harvard Schol of public Health (2004) 1.
3. Dietary saturated and trans fatty acids and cholesterol and 25-year mortality from coronary heart disease: the Seven Countries Study. Kromhout D et al., Prev Med 24 (1995) 308
4. Trans fatty acids and coronary heart disease. Ascherio A et al., N Engl J Med 323 (1999) 1994
5. Trans polyunsaturated fatty acids have more adverse effects than saturated fatty acids on the concentration and composition of lipoproteins secreted by human hepatoma HepG2 cells. Dashti N et al., J Nutr 132 (2002) 2651
6. Long-term effects of cis and trans monounsaturated (18:1) and saturated (16:0) fatty acids on the synthesis and secretion of apolipoprotein A-I- and apolipoprotein B-containing lipoproteins in HepG2 cells. Dashti N et al., J Lipid Res 41 (2000) 1980
7. Effect of different forms of dietary hydrogenated fats on LDL particle size. Mauger JF et al., Am J Clin Nutr 78 (2003) 370.
8. Trans(elaidic)fatty acids adversely affect the lipoprotein profile relative to specific saturated fatty acids in humans. Sundram KJ et al.,J Nutr 127(1997)514S
9. Dietary trans alpha-linolenic acid from deodorized rapeseed oil and plasma lipids and lipproteins in healthy men: the TransLinE Study. Vermunt SH et al., Br J Nutr 85 (2001) 27
10. Trans fatty acids and cardiovascular disease—edpidemiological data. Willet WC, Atherosclerosis 7 (2006) 5
11. Trans fatty acids—effects on systemic inflammation and endothelial function. Mozaffarian D, Atherosclerosis 7 (2006) 29
12. Differential effects of dietary saturated and trans-fatty acids on expression of genes associated with insulin sensitivity in rat adipose tissue. Saravanan N et al., Eur J Endocrinol. 2005 Jul;153(1):159-65.
13. Saturated and cis/trans unsaturated acyl CoA esters differentially regulate wild-type and polymorphic beta-cell ATP-sensitive K+ channels. Riedel MJ, Light PE. Diabetes 54 (2005) 2070
14. Diet, lifestyle, and the risk of type 2 diabetes mellitus in women. Hu FB et al., N Engl J Med 345 (2001) 790.
15. High incidence of type 2 diabetes in peroxisome proliferators-activated receptor gamma2 Pro12Ala carriers exposed to a high chronic intake of trans fatty acids and saturated fatty acids. Pisabarro RE et al., Diabetes Care 27 (2004).
16.Should trans fatty acids be viewed as membrane-active drugs? Katz AM, Atherosclerosis 7(2006)41
17. Trans fatty acids and coronary heart disease. Zaloga GP et al., Nutr Clin Pract 21 (2006) 505.
18. Trans-fatty acids and sudden cardiac death. Lemaitre RN et al., Atherosclerosis 7 (2006) 13
19. Adipose tissue trans fatty acids and breast cancer in the European Community Multicenter Study on Antioxidants, Myocardial Infarction, and Breast Cancer. Kohlmeier L et al., Cancer Epidemiol Biomarkers Prev 6 (1997) 705
20. Trans Fatty Acid Intake and Increased Risk of Advanced Prostate Cancer: Modification by RNASEL R462Q Variant. Liu X, Carcinogenesis 2007 Jan 18 [Epub ahead of print]
21. Serum trans-fatty acids are associated with risk of prostate cancer in beta-Carotene and Retinol Efficacy Trial. King IB et al., Cancer Epidemiol Biomarkers Prev 14 (2005) 988
22. Trans-fatty acids and colon cancer. Slattery ML et al., Nutr Cancer 39 (2001) 170
23. Saturated fatty acid-mediated endoplasmic reticulum stress and apoptosis are augmented by trans-10, cis-12-conjugated linoleic acid in liver cells. Wei Y et al., Mol Cell Biochem. 2007 Apr 11 [Epub ahead of print]
24. Medical progress: Trans fatty acids and cardiovascular disease. Mozaffarian D et al., N Engl J Med 354 (2006) 1601
25. Intake of fatty acids and risk of coronary heart disease in a cohort of Finnish men: the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. Pietinen P eet al., Am J Epidemiol 145 (1997) 876
26. Association between trans fatty acid intake and 10-year risk of coronary heart disease in the Zutphen Elderly Study; a prospective population-based study. Oomen CM et al., Lancet 357 (2001) 746
27. Intake or ruminant trans fatty acids and risk or coronary heart diseast. Jakobsen MU eet al., Am J Clin Nutr
28. Intake of trans fatty acids and risk of coronary heart disease among women. Willet WC et al., Lancet 341 (1993) 581
29. Formation of trans fatty acids is not involved in growth-linked membrane adaptation in pseudomonas putida. Hartig C et al., Applied Envir Microbio 71 (2005) 1915
30. Effect of feeding systems on omega-3 fatty acids, conjugated linoleic acid and trans fatty acids in Australian beef cuts: potential impact on human health. Ponnampalam EN et al., Asia Pac J Clin Nutr. 15 (2006) 21
This is very informative. Great job!
Posted by: Bob Brendon | October 12, 2010 at 05:41 PM