By Kimberly Beauchamp, ND
Healthnotes Newswire (November 17, 2005)—Inulin, a type of natural dietary fiber, may increase calcium absorption and help build stronger bones in teenagers, reports a study in the American Journal of Clinical Nutrition (2005;82:471–6).
Inulin is a nondigestible carbohydrate found in plants such as onions, leeks, asparagus, Jerusalem artichoke, and chicory. Inulin is considered a “prebiotic,” a food source for the beneficial colonic bacterium Bifidobacterium. Inulin and related compounds called fructo-oligosaccharides may also promote healthy gut function by increasing the production of butyrate, a substance thought to protect against colon cancer.
Calcium is necessary for the growth of bones and teeth, as well as for proper nerve conduction, blood clotting, and muscle contraction. It is especially important to get enough calcium during the periods of rapid skeletal growth that occur in early childhood and adolescence.
Several studies have shown that inulin may increase calcium absorption. The new study evaluated the effects of long-term inulin supplementation on calcium absorption and the process by which new bone is formed (bone mineralization) in 100 children whose average age was 12 years. The participants received either: 8 grams of a mixed inulin/fructo-oligosaccharide supplement each day for one year, or placebo. The inulin supplement or placebo was mixed in milk or a calcium-fortified orange juice.
At the beginning of the study, calcium absorption, bone mineral density, and bone mineral content of the children were measured. Calcium absorption was measured again after eight weeks and after one year, and bone mineral measurements were repeated after one year of supplementation. Since vitamin D status is linked to calcium absorption in the body, and since variations in a gene that regulates vitamin D function in the body (the vitamin D receptor gene) can influence calcium absorption, analyses of the vitamin D receptor gene were also performed.
Calcium absorption was significantly greater in the inulin group compared with the placebo group after eight weeks and after one year. This effect was enhanced among children who had variations in the vitamin D receptor gene that are associated with greater calcium absorption. Bone mineral content and bone mineral density increased significantly more in the inulin group than in the placebo group, reflecting the laying down of about 11 additional grams of new calcium in the skeleton over one year.
Currently, food makers add inulin to products such as yogurt, both as a fiber source and with the hope of increasing calcium absorption. The Food and Nutrition Board of the National Academy of Sciences recently increased the recommended daily calcium intake for teenagers from 1,200 mg to 1,300 mg. It is estimated that 86% of adolescent girls and 65% of adolescent boys do not get enough calcium. The addition of inulin to different foods is one way to increase calcium absorption in this at-risk population.
Kimberly Beauchamp, ND, earned her bachelor’s degree from the University of Rhode Island and her Doctorate of Naturopathic Medicine from Bastyr University in Kenmore, WA. She cofounded South County Naturopaths in Wakefield, RI. Dr. Beauchamp practices as a birth doula and lectures on topics including whole-foods nutrition, detoxification, and women’s health.
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