The Definition of Phytosterols

Phytosterols are plant compounds that form the membranes of cells, a role similar to that of cholesterol in animals. Intake of phytosterols helps reduce blood cholesterol levels. Phytosterols are abundant in plant oils and other plant foods, and have become a common food additive.

Sterols

Sterols are lipid compounds that are found in all animal and vegetable tissues. In vertebrates, cholesterol is the main component of the cell membranes and forms the backbone for steroid compounds such as testosterone, estrogen, and cortisol. Phytosterols have the same function in plants, and ergosterol forms the cell membranes in fungi.

Health Benefits

In 2003, the FDA approved the following claim for phytosterols: "Foods containing at least 0.4 gram per serving of plant sterols, eaten twice a day with meals for a daily total intake of at least 0.8 gram, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease." The beneficial effects of this compound have been demonstrated in numerous studies. The FDA approval allowed companies to add phytosterols to processed foods and to label those foods as healthy for the heart.

Effects

Phytosterols inhibit the intestinal absorption of cholesterol, thus lowering blood levels of total and LDL cholesterol. Phytosterols themselves have a lower intestinal absorption rate than cholesterol, and are mainly excreted into the bile. Cholesterol is a necessary compound, so when its absorption is inhibited, the body will work to synthesize more. However, the net result is still a decrease in LDL cholesterol (otherwise known as "bad" cholesterol).

Foods Containing Phytosterols

Phytosterols are found in all plant foods. Whole grains, legumes, nuts, and seeds have high concentrations of the compound. Oils made from these foods are especially good sources of phytosterols. It is estimated that the diets of earlier generations contained up to 1000 mg per day of the compound. In contrast, a review published in 2002 by Washington University in St. Louis estimated that the average diet in modern developed countries contains about 150 to 450 mg per day of phytosterols. Vegetarians and vegans have the highest intake.

Safety

Foods with natural phytosterols are safe for consumption. The FDA determined that food additives of phytosterols are safe, but recommends that intake not exceed 3 grams (3,000 mg) daily because there is no evidence of health benefits at higher amounts. Most of the studies on phytosterol additives were done using 1 to 3 grams daily.

Controversy

Some questions remain as to the safety of phytosterol additives. Increasing the amount of whole grains, beans, vegetables, and vegetable oils may be a better plan than consuming value-added foods. When phytosterols are ingested in their natural form, they come "packaged" with all the vitamins, minerals, and other benefits of the original food.

References

• The Cyberlipid Center
• Phytosterols in Human Nutrition; Ostlund RE Jr.; Annual Review of Nutrition; Apr 2002
• Linus Pauling Institute, Phytosterols