Heart Health: Saturated Fat Should Not Be Restricted.
Written by Kevin Flatt
Assistant Professor Jeff S. Volek and his colleague Cassandra E Forsythe at the University of Connecticut, reporting in the August 2005 issue of the journal Nutrition & Metabolism, dispel common myths and provide a convincing argument that the restriction of saturated fat is not warranted on a low-carbohydrate diet because of their work showing favorable responses in clinical risk factors for diabetes and cardiovascular disease in low-carbohydrate diets that were rich in saturated fat.
They complimented Drs. Arora and McFarlane on their timely review of low carbohydrate diets in diabetes management, who had concluded that low carbohydrate diets compare more favorably, at least over the short term, to traditional low fat for improving glycemic control, insulin sensitivity and dyslipidemia of diabetes with reduction in triglycerides, increase in HDL cholesterol and modification of LDL to a less atherogenic form (i.e. a form where LDL Cholesterol is less likely to deposit in the arteries). (Nutr Metab (Lond) 2005, 2:16).
One point stressed by Arora and McFarlane was that mono and polyunsaturated fat should be emphasized over saturated fat as a way to achieve caloric balance on a carbohydrate-restricted diet.
Assistant Professor Jeff S. Volek and his colleague at the University of Connecticut, contended that the recommendation to intentionally restrict saturated fat is unwarranted and only serves to contribute to the misleading rhetoric surrounding the health effects of saturated fat.
They believe restriction of saturated fat is not warranted on a low-carbohydrate diet because of their work showing favorable responses in clinical risk factors for diabetes and cardiovascular disease in low-carbohydrate diets that were rich in saturated fat.
In addition, German & Dillard (Am J Clin Nutr 2004, 80:550-559) have reviewed several experimental studies of the effects of saturated fats and the results are found to be variable and there is a general failure to meet the kind of specific predictions that would justify the recommendation to reduce saturated fat in the population. Other critical reviews of the evidence have questioned whether public health recommendations for reducing saturated fat intake are appropriate. (J Clin Epidemiol 1998, 51:443-460, J Am Diet Assoc 2002, 102:1621-1630).
Professor Volek and colleague stated in their article that the critical issues are:
1. The atherogenic (the formation of plaques on the walls of the arteries) potential of saturated fats varies greatly depending on chain length and whether it is present alone or added in foods. Stearic acid is a major saturated fat found in beef, chicken, and pork and has repeatedly been shown not to raise LDL cholesterol levels (Am J Clin Nutr 1994, 60:986S-990S).
Even palmitic acid (a saturated fatty acid that is the major fat in meat and dairy products), the most abundant saturated fatty acid in the diet, does not raise LDL cholesterol in the presence of adequate linoleic acid (a liquid polyunsaturated fatty acid abundant in plant fats and oils; a fatty acid essential for nutrition). (Asia Pac J Clin Nutr 2002, 11 Suppl 7:S401-S407).
2. The effect of saturated fat cannot be assumed to be independent of specific dietary conditions. In particular, hypocaloric (low calorie) or low total fat diets may show different results than deduced from epidemiology (population studies). A recent report showed that for women on a relatively low fat diet, a greater saturated fat intake was associated with a reduced progression of coronary atherosclerosis. (Am J Clin Nutr 2004, 80:1175-1184). An editorial described this as “an American paradox”. (Am J Clin Nutr 2004, 80:1102-1103).
3. Evaluation of the overall health effects of saturated fat requires consideration of markers in addition to LDL-cholesterol. Replacement of carbohydrates with any type of fat, providing the same number of calories, results in decreased triglycerides and increased HDL-cholesterol, the effect on HDL-cholesterol being greater for saturated fat compared to unsaturated fat. (Am J Clin Nutr 1995, 61:1368S-1373S).
Reductions in saturated fat also adversely affect HDL subpopulations by decreasing larger HDL2-cholesterol concentrations. (Am J Clin Nutr 1999, 70:992-1000). Whereas increases in saturated fat increase this anti-atherogenic fraction. (Mayo Clin Proc 2003, 78:1331-1336, Am J Med 2004, 117:398-405).
Furthermore, very low-carbohydrate diets rich in saturated fat increase LDL cholesterol size and conversion from a high risk pattern B to a lower risk pattern A phenotype. (J Nutr 2005, 135:1339-1342).
4. Finally, there is the concern that recommendations to limit saturated fat would lead to their replacement with carbohydrate, which can have undesirable effects (increased triglycerides with decreased HDL cholesterol. (Am J Clin Nutr 1995, 61:1368S-1373S).
The authors concluded that for these reasons, they believe that the recommendation to restrict saturated fat in favor of unsaturated fat on a low-carbohydrate diet is unnecessary and may even diminish some of the beneficial physiological effects associated with carbohydrate restriction. At the very least, the food restriction required to reduce saturated fat will compromise the palatability of the diet and ultimately the acceptance of the approach to diabetes management recommended by Arora and McFarlane. (Nutr Metab (Lond) 2005, 2:16).
Adapted from: Jeff S Volek, Cassandra E Forsythe. The case for not restricting saturated fat on a low carbohydrate diet. Nutrition & Metabolism 2005, 2:21 (31 August 2005). © 2005 Volek and Forsythe, licensee BioMed Central Ltd.
http://www.nutritionandmetabolism.com/content/2/1/21.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/2.0 which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
