Ask Tufts Experts: Beans and cholesterol … Chlorella … Biotin
Q: I have high cholesterol and my doctor told me to eat more beans. Why?
A: Nicola McKeown, PhD, associate professor at the Friedman School, answers: “Beans (and other foods high in viscous soluble fiber, such as apples and barley) can be helpful for lowering blood cholesterol levels. This type of fiber thickens and forms a gel-like substance in the digestive tract. The gel traps bile acids which are needed for the digestion and absorption of fats and fat-soluble vitamins in the small intestine. The trapped bile acids are eliminated from our bodies via our feces. Once bile acids are excreted, this signals our liver to make more bile acids, which requires cholesterol, thus leaving less circulating cholesterol available to be incorporated into unhealthy low-density lipoproteins (LDL cholesterol).
“In addition to beans, many plant foods are good sources of soluble fibers, including apples, pears, plums, and citrus fruits, oats and oat-based products, barley, shitake mushrooms, and seaweed. Another viscous soluble fiber, psyllium is added to various foods such as ready-to-eat cereals and is also available in concentrated form as an isolated fiber in over-the-counter products such as Metamucil (which should only be taken under the direction of your physician). A diet rich in a variety of beans, nuts, seeds, fruits, vegetables, and whole grains will deliver a wide array of cholesterol-lowering soluble fibers.”
Q: What is chlorella, and can it really do any of the things it’s advertised to do?
A: Judith C. Thalheimer, RDN, LDN, managing editor of Tufts Health & Nutrition Letter, answers: “Chlorella is a type of algae. It is harvested and processed into nutritional supplements. As long as the cell walls are broken down before ingestion, chlorella provides protein, fat, carbohydrate, fiber, vitamins, minerals, and chlorophyll, but the actual amount of these compounds in a given supplement is small and varies widely. When consumers purchase a chlorella supplement, it’s difficult to know exactly what they’re getting. “These supplements are advertised to do just about everything—increase energy, control blood pressure and cholesterol, reduce joint pain, help with digestion and regularity, improve memory and mood, balance blood sugar, and even improve bad breath. In fact, there is insufficient evidence to say definitively that chlorella does any of these things.”
Q: Can you tell me what biotin is and how much people need?
A: Alice H. Lichtenstein, DSc, executive editor of the Tufts Health & Nutrition Letter, answers: “Biotin is a water-soluble vitamin also called vitamin B7. It is essential to certain steps in metabolism and is a key regulator of gene expression. Adequate intake of biotin for people over age 19 is 0.3 milligrams (mg) a day. Since it is estimated that most U.S. adults get 0.4 to 0.6 mg a day from foods, biotin deficiency is rare in healthy individuals. Egg yolks are a major source of biotin, with about 0.25 mg in just one large egg. Biotin is also found in smaller amounts throughout the food supply. “There is only limited evidence of biotin’s affect on the skin, hair, and nail disorders it is marketed to treat. The U.S. Food and Drug Administration has issued a warning that high supplemental doses of biotin can cause false negatives on diagnostic tests, including an important test for heart attacks. Talk to your doctor if you are currently taking biotin or are considering adding biotin, or a supplement containing biotin, to your diet.”
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