Plant sterols don’t get that much hype for some reason, but they can be an effective way to lower cholesterol as this article on the Denver Nutrition Examiner illustrates.
Phytosterols are plant derived compounds that are similar in structure to animal cholesterol. Early human diets likely included about 1 gram per day, while current average natural consumption is about 250 mg/day. Some vegetarians may still consume about 1 gram per day.
This is not that different that average dietary intake of cholesterol, but blood levels of phytosterols stay much lower than cholesterol, and < 10% of phytosterols are absorbed compared to ~50% of cholesterol).∞
Basically, the plant sterols compete with cholesterol in the digestive tract in forming mixed micelles (the vehicle for lipid absorption), ultimately this results in a reduced amount of absorbed cholesterol. The affinity of plant sterols for micelles is greater than that of cholesterol. There are other proposed mechanisms, but, they are more or less the same result.
There are a few caveats to using plant sterols though:
- There have been some reports of decreased levels of plasma alpha & beta carotene, a-tocopherol, and/or lycopene as a result of consuming foods containing both stanol esters and sterol esters*
- Most recent research shows a 10% decrease in a-tocopherol levels, but, when adjusted for decreases in LDL was not a significant change**
- There is a genetic condition which could cause an individual to absorb excessive amounts of sitosterol, and results in hypercholesterolemia
- Beta sitosterol has been though to exert an estrogenic influence
- Sterols and stanols have not been proven safe in pregnant women or in children
The article in the Examiner gives specific recommendations on therapeutic levels of plant sterols, or you can find out what the American Heart Association recommends as part of the Therapeutic Lifestyle Change Diet at this link..
∞Gylling H, Miettinen TA. The effect of plant stanol- and sterol-enriched foods on lipid metabolism, serum lipids and coronary heart disease. Ann Clin Biochem. 2005 Jul;42(Pt 4):254-63.
*Lichtenstein AH, Deckelbaum RJ. Circulation. 2001 Feb 27;103(8):1177-9. AHA Science Advisory. Stanol/sterol ester-containing foods and blood cholesterol levels. A statement for healthcare professionals from the Nutrition
**Tuomilehto J, Tikkanen MJ, Högström P, Keinänen-Kiukaanniemi S, Piironen V, Toivo J, Salonen JT, Nyyssönen K, Stenman UH, Alfthan H, Karppanen H. Safety assessment of common foods enriched with natural nonesterified plant sterols.Eur J Clin Nutr. 2008 Feb 13. [Epub ahead of print]
*** Belamarich PF, Salen G, Starc TJ, et al Committee of the Council on Nutrition, Physical Activity, and Metabolism of the American Heart Association.. Response to diet and cholestyramine in a patient with sitosterolemia. Pediatrics. 1990;86:977–981
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