What You Don’t Know About Saturated Fat That Could Harm You

by Paul Rogers on December 3, 2008

What you probably do know is that most dietary recommendations say that you should keep your consumption of saturated fat and cholesterol in food low in order to lower your blood cholesterol and consequently your risk of heart disease.

The usual recommendations are that saturated fat should be no more than 10% of total calories and cholesterol less than 300 milligrams each day — and for people with existing signs of heart disease, less than 7% saturated fat and under 200 milligrams of cholesterol each day.

If you read widely of internet health and nutrition sites, you may also be aware that fringe movements exist that say this is not true; that it’s a government conspiracy and so on, and that saturated fat and cholesterol are as harmless as soft fruit. You can read one of my responses to that. It’s surprising how many otherwise knowledgeable pundits get taken in by this stuff.

What you may not know is that too much saturated fat in the diet has other adverse effects beyond how it raises blood cholesterol. Here is a short summary.

Saturated Fats Cause Dementia

Here is what one research team has to say about saturated (and trans) fat and cognitive function.

“Diets high in fat, especially trans and saturated fats, adversely affect cognition, while those high in fruits, vegetables, cereals, and fish are associated with better cognitive function and lower risk of dementia. While the precise physiologic mechanisms underlying these dietary influences are not completely understood, modulation of brain insulin activity and neuroinflammation likely contribute.” (Ann N Y Acad Sci. 2007 Oct;1114:389-97.)

And another:

“Moderate intake of unsaturated fats at midlife is protective, whereas a moderate intake of saturated fats may increase the risk of dementia and AD, especially among ApoE epsilon4 carriers. “ (Dement Geriatr Cogn Disord. 2006;22(1):99-107. )

Saturated Fats Cause Insulin Resistance

This conclusion provides a pointer to findings from several similar studies:

“A change of the proportions of dietary fatty acids, decreasing saturated fatty acid and increasing monounsaturated fatty acid, improves insulin sensitivity . . . ” (Diabetologia. 2001 Mar;44(3):312-9.)

And:

“Therefore, prevention of the metabolic syndrome has to be targeted . . . and . . . to improve insulin sensitivity and associated metabolic abnormalities through a reduction of dietary saturated fat, partially replaced, when appropriate, by monounsaturated and polyunsaturated fats.” (Clin Nutr. 2004 Aug;23(4):447-56.)

 Saturated Fat Slows Blood Flow in the Arteries

Here is what recent studies found about how saturated fat essentially clogs the arteries. (The endothelium is the layer of cells lining the inside of blood vessels and arteries. It is important in regulating blood flow.)

“High SFA (saturated fat) caused deterioration in FMD (flow-mediated dilation) compared with high PUFA, MUFA, or CARB diets. Inflammatory responses may also be increased on this diet.” (Arterioscler Thromb Vasc Biol. 2005 Jun;25(6):1274-9.)

And:

 “Consumption of saturated fat reduces the anti-inflammatory potential of HDL and impairs arterial endothelial function. In contrast, the anti-inflammatory activity of HDL improves after consumption of polyunsaturated fat.” (J Am Coll Cardiol. 2006 Aug 15;48(4):715-20.)

And:

“Consumption of an SAFA-rich meal is harmful for the endothelium, while a MUFA-rich meal does not impair endothelial function in subjects with type 2 diabetes.” (Diabetes Care. 2008 Dec;31(12):2276-8.)

Overall, you should be able to see that the case against too much saturated fat in the diet is convincing — one way or another — and it’s not just about cholesterol. Bear in mind that vegetable sources of saturated fat are not inconsequential. Olive and soy oil are about 15%, corn and sunflower about 12% and peanut oil around 20%. However, consuming saturated fat and cholesterol together in animal foods may present the greatest combined risk, and whole nuts or seeds, even with some saturated fat, the least risk.

- Parrott MD, Greenwood CE. Dietary influences on cognitive function with aging: from high-fat diets to
healthful eating. Ann N Y Acad Sci. 2007 Oct;1114:389-97. Review.
– Laitinen MH, Ngandu T, Rovio S, et al. Fat intake at midlife and risk of dementia and Alzheimer’s disease: a
population-based study. Dement Geriatr Cogn Disord. 2006;22(1):99-107.
– Morris MC, Evans DA, Bienias JL, et al. Dietary fats and the risk of incident Alzheimer disease. Arch Neurol. 2003 Feb;60(2):194-200. Erratum in: Arch Neurol. 2003
– Vessby B, Unsitupa M, Hermansen K, et al. Substituting dietary saturated for monounsaturated fat impairs insulin sensitivity in healthy men and women: The KANWU Study. Diabetologia. 2001 Mar;44(3):312-9.
– Riccardi G, Giacco R, Rivellese AA. Dietary fat, insulin sensitivity and the metabolic syndrome. Clin Nutr. 2004 Aug;23(4):447-56. Review.
– Keogh JB, Grieger JA, Noakes M, Clifton PM. Flow-mediated dilatation is impaired by a high-saturated fat diet but not by a high-carbohydrate diet. Arterioscler Thromb Vasc Biol. 2005 Jun;25(6):1274-9.
– Tentolouris N, Arapostathi C, Perrea D, et al. Differential effects of two isoenergetic meals rich in saturated or monounsaturated fat on endothelial function in subjects with type 2 diabetes. Diabetes Care. 2008 Dec;31(12):2276-8.
– Nicholls SJ, Lundman P, Harmer JA, et al. Consumption of saturated fat impairs the anti-inflammatory properties of high-density lipoproteins and endothelial function.J Am Coll Cardiol. 2006 Aug 15;48(4):715-20.

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