Tue, Feb-11-03, 20:30
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Senior Member
Posts: 3,423
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Plan: Atkins (loosely)
Stats: -/-/-
BF:
Progress: 40%
Location: Ottawa, Ontario
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I ran into some interesting information regarding saturated fat. I guess I always assumed that saturated fat was a natural ever- present part of meat. I discovered that actually it's a rather recent phenomena, mostly due to the fact that livestock tends to be fed grain. This is good food for thought...
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Saturated/unsaturated fat composition of wild animal tissues, and consumption levels in modern vs. pre-agricultural peoples
Our data on the fatty-acid distribution in tissues of wild animals presented at a recent conference on the return of n3 fats to the food supply, held at the National Institutes of Health in Bethesda, Maryland has been recently published in World Review of Nutrition and Dietetics. [Cordain et al. 1998]. This data refutes contentions made by some that the overall PUFA in wild-animal tissues is low. To the contrary, it is relatively high in both brain (26%) and muscle (36%) as our data shows, and which corroborates earlier work of Crawford et al. [1969].
The difference in polyunsaturated fatty acids (PUFAs) between the Western diet and the so-called "paleolithic diet" is that the PUFAs in the Western diet are predominantly based upon 18-carbon lipids (vegetable oils) with huge amounts of 18:2n6 (linoleic acid) predominating. The PUFA content of the paleolithic diet is higher than that of the Western diet (19.2% vs. 12.7% [Bang and Dyerberg 1980]) with much higher levels of HUFA (>20-carbon lipids) of both the n6 and n3 families.
Once again, it should be emphasized as well that while pre-agricultural peoples certainly did consume saturated fat, it cannot compare with the levels consumed by modern Western populations. Bang and Dyerberg's data [1980] on Eskimo populations who ate a high-meat diet is particularly illustrative of this. Of the total dietary fats, saturated fats comprised 22.8% in Inuit people whereas saturated fats comprised 52.7% of the total dietary fats in a control population of Danes. To point to saturated fat consumption in pre-agricultural groups as license to eat freely of such fats ignores the ecological constraints that would have made modern levels of consumption highly unlikely for our paleolithic ancestors, and ignores as well the voluminous clinical data that shows their detrimental effects.
High levels of saturated fat consumption on a year-round basis only became possible when domesticated animals were bred and fed in a manner which allowed accumulation of depot fat on a year-round basis. Wild animals almost always show a seasonal variation in storage fat, and even the very fattest wild land mammals contain 60-75% less total fat than the average domesticated animal. Thus, until the advent of the "Agricultural Revolution" 10,000 years ago, it would have been extremely difficult, or perhaps impossible, to eat high levels of saturated fat on a daily basis throughout the year.
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Saturated animal fats in overall dietary context. However, I cannot agree with the statement that saturated fats from animals in modern diets have nothing to do with CHD. It may be possible that the hypercholesterolemic effects of saturated fats (12:0, 14:0, 16:0) can be negated or somewhat ameliorated by extremely low levels of dietary carbohydrates (particularly in insulin-resistant subjects) or by high levels of dietary protein (>20% of total calories) via protein's VLDL-suppressing effects [Kalopissis et al. 1995].
However, it is clear beyond a shadow of a doubt that dietary saturated fats (12:0, 14:0, and 16:0) elevate serum cholesterol levels within the context of the "average American diet." A recent meta-analysis of 224 published studies encompassing 8,143 subjects (many under metabolic ward conditions) has unequivocally demonstrated the hypercholesterolemic effect of dietary saturated fats [Howell et al. 1997]. The cellular basis for this observation stems from the regulation of low-density lipoproteins (LDLs). When the amount of cholesterol or saturated fat coming into the body is increased, there is an expansion of the sterol pools within liver cells, and to a lesser extent, peripheral cells, which causes a down-regulation of LDL receptors. As a consequence, LDL in plasma increases [Dietschy 1997].
Some have argued that increases in total plasma cholesterol and LDL may not necessarily have a direct relationship to mortality from CHD [Stamler et al. 1986]. Clearly, there are a wide variety of independent risk factors for CHD including hypertension, homocysteine (increased by deficiencies primarily in folate, vitamin B-6, and secondarily in B-12), catecholamines, n6/n3 fatty-acid ratio, antioxidant status (vitamins E, C, beta-carotene, phytochemicals, etc.), dietary fiber, cigarette smoking, and ethanol (alcohol) consumption, which influence a variety of physiological systems involved with CHD. However, there is powerful evidence (n = 356,222) to indicate that the relationship between serum cholesterol levels and the risk of premature death from CHD is, nevertheless, continuous and graded [Stamler et al. 1986].
Therefore, the recommendation by some that it is harmless to consume high levels of dietary saturated fats within the context of the "average American diet" appears to not only be erroneous, but probably deadly. Our hunter-gatherer ancestors consumed high levels of animal food (probably >55% of their total daily calories); however, the context under which this was done was much different than present-day conditions.
As I have previously mentioned, the carbohydrate content of the diet was low (~<35% of total calories) and composed of plant foods with high soluble fiber and low starch content. The protein content of the diet would have exceeded 20% and may have been as high as 30-40%. The polyunsaturated fats consumed would have had a low n6/n3 ratio, and there would have been both ample levels of 20 and 22-carbon fats of both the n6 and n3 variety. Since marrow contains 70-75% monounsaturated fats and was a favored food, it is likely that although the fat content of the diet may have been as high as 40%, it was composed of not only a much more favorable n6/n3 polyunsaturated fat ratio, but higher levels of monounsaturated fats and non-atherogenic saturated fats such as stearic acid (18:0) as well.
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You can find the reference here
Last edited by Angeline : Tue, Feb-11-03 at 20:32.
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coconut oil
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