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Low-Fat, High-Carbohydrate Diet Debated

January 02, 2008 | 12,625 views

Health experts are debating the value of a diet low in fat and high in carbohydrates for reducing the risk of heart disease, certain forms of cancer, and for losing weight. Both sides agree that Americans should eat more fruits, vegetables, and high-fiber foods. Both sides also lament the increased availability of fat-free products high in sugar

Replacement of fat with carbohydrates has not been shown to reduce the risk of coronary heart disease. Benefits are unlikely because this change similarly lowers HDL ('good') and LDL ('bad') cholesterol and reduces the intake of vitamin E and essential fatty acids. Moreover the beneficial effects of high-carbohydrate diets in reducing the risk of cancer or in maintaining body weight have not been substantiated. At present it appears prudent to replace saturated fats with monounsaturated fats because some experiments with animals hint at an increased cancer risk with a diet high in polyunsaturated fats.

They emphasize that Americans have already cut fat intake to 33 percent of total energy consumption, but the fat has been replaced largely with sugar, not with complex carbohydrates and fiber, fat intake should be reduced even further to 30%, but not any lower.

This information is so crucial to good health that I thought I would make an exception and actually print the entire section of the article supporting the case for the non-sense approach for increasing carbohydrates even more. I think this is powerful support printed in the most prestigious medical journal in the world for this position .

I agree nearly 100% with the high fat position. There are several cautions you should be aware of though. Be careful about reducing your saturated fat. It is likely that this will also cause its own problem. You will soon see many new articles supporting this position. Trans-fat is the fat that should be absolutely avoided at all costs. Read labels. ANYTIME you see partially hydrogenated that means trans-fat. The article recommends to use carbohydrates. I believe they should be mainly in the form of vegetables and you would best be served by reducing the grains in general. Although canola oil is a monounsaturate it is best to avoid canola oil. It is nowhere near as healthy as olive oil The Mediterranean countries studies described in the article used olive oil exclusively, canola oil did not exist till very recently. It has some serious problems that will likely show up in the next ten years.

(REPRINTED FROM NEW ENGLAND JOURNAL OF MEDICINE) We agree that the intake of fruits, vegetables, and high-fiber foods should be increased and that the high amounts of saturated and trans fatty acids consumed by Americans in the 1950s were unhealthful. However, one cannot generalize from those fats to all fats, because unsaturated fats, which make up the majority of fats in the current U.S. diet, lower LDL cholesterol levels. (1) Reductions in saturated fat and cholesterol in the diet cannot by themselves account for the decline in mortality due to coronary heart disease since the 1950s; increases in the consumption of unsaturated vegetable oils may have been important as well. (2)

Connor and Connor object to substituting unsaturated fats for unhealthful fats because fats produce postprandial lipemia. However, long-term substitution of carbohydrate, instead, does not reduce postprandial lipemia, (3,4) probably because high carbohydrate intake increases the levels of endogenous triglycerides that delay postprandial clearance of lipoproteins. HDL cholesterol levels are also reduced. In the study cited by Connor and Connor, a low-fat, high-fiber diet reduced weight after 12 weeks, but this effect was transient in longer studies. There is no good evidence that reducing total dietary fat will prevent cancer or hypertension. (5)

Like Connor and Connor, we lament the plethora of fat-free products high in sugar and the avoidance of foods such as nuts and oil-based salad dressing that provide n-3 fatty acids (flax). However, the failure to distinguish among types of fat and the emphasis on total fat reduction are the very causes of these problems.

Lower consumption of saturated and trans fats is desirable, but nonspecific recommendations to reduce total fat consumption have no strong scientific basis and could be harmful if unsaturated fats are avoided.

References

1. Mensink RP, Katan MB. Effect of dietary fatty acids on serum lipids andlipoproteins: a meta-analysis of 27 trials. Arterioscler Thromb 1992;12:911-9.

2. Hetzel BS, Charnock JS, Dwyer T, McLennan PL. Fall in coronary heartdisease mortality in U.S.A. and Australia due to sudden death: evidence for the role of polyunsaturated fat. J Clin Epidemiol 1989;42:885-93.

3. Blades B, Garg A. Mechanisms of increase in plasma triacylglycerolconcentrations as a result of high carbohydrate intakes in patients with non-insulin-dependent diabetes mellitus. Am J Clin Nutr 1995;62:996-1002.

4. Chen YD, Coulston AM, Zhou MY, Hollenbeck CB, Reaven GM. Why do low-fat high-carbohydrate diets accentuate postprandial lipemia in patients with NIDDM? Diabetes Care 1995;18:10-6.

5. Morris MC. Dietary fats and blood pressure. J Cardiovasc Risk 1994;1:21-30.

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