Updated July 20, 2006

Boning Up on Bone Health

by Belinda O’Connell, M.S., R.D., C.D.E.

Age. Because the ability of the body to build bone decreases as you age, the older you are, the greater your risk of osteoporosis. People who reach a higher peak bone mass when they are young are better protected against age-related bone loss.

Ethnicity. People of Latino and African-American heritage have a lower risk for osteoporosis than people of Caucasian and Asian ethnicity. But this does not mean that osteoporosis is not a concern for Latinos and African-Americans; it is, and they also need to control the risk factors that they can.

Body size. The size of your bones influences your risk of developing osteoporosis. People with small bones and a thin body build are at greater risk than people who have large, dense bones. People who weigh more often have stronger bones because bone is stimulated to grow and make new tissue by weight-bearing activity. Women who weigh more may also produce greater amounts of estrogen. Eating disorders like anorexia can cause severe loss of bone tissue and greatly increase the risk of having osteoporosis at a young age.

Hormone levels. The sex hormones, estrogen in women and testosterone in men, protect against bone loss. When hormone levels are low, the rate of bone loss increases. Hormone levels are decreased in amenorrhea (the abnormal loss of menstrual periods in young women) and menopause. Medroxyprogesterone (brand name Depo-Provera), an injectable contraceptive, may also cause bone loss.

Nutrition. Adequate levels of many nutrients, including calcium, vitamin D, magnesium, and vitamin K, are necessary to build healthy bones. The most important of these are calcium and vitamin D. Bones and teeth hold more than 99% of the body’s calcium stores. If your dietary calcium intake is low, the body pulls calcium from bone stores to perform other necessary functions in the body. Chronic low calcium intakes cause calcium loss from bones, weakening them. Vitamin D is necessary for absorption and use of calcium in the body, and low levels are also associated with increased osteoporosis and fractures. (For more about calcium, read “The Calcium Connection.”)

Conditions such as food allergies, Crohn disease, and intestinal surgery that limit food intake or decrease absorption of nutrients can also increase risk of osteoporosis. In addition, excessive intake of retinol, a form of vitamin A, has been shown to interfere with normal bone metabolism and to increase the risk of fractures. The upper intake limit for retinol is 600 micrograms for children up to 3 years, 900 micrograms for children 4-8 years, 1700 micrograms for children 9–13 years, 2800 micrograms for teens 14–18 years, and 3,000 micrograms for people 19 and older. The upper intake level does not include beta-carotene, a nutrient found in plant foods that is converted to vitamin A in the body. Retinol is found in animal products; vitamin supplements; fortified foods such as milk, cereals, and energy bars; and skin preparations.

Activity level. A low physical activity level is a risk factor for osteoporosis. Exercise, particularly weight-bearing activities where your body is working against gravity, can help keep bones strong. Weight-bearing activities include walking, dancing, climbing stairs, and weight training. Balance exercises are also useful to prevent falls that could lead to fractures.

Smoking. Smoking can decrease estrogen levels and may promote early menopause in women. Smoking-related bone loss is a major risk factor for osteoporosis.

Alcohol intake. Regular consumption of more than one to two servings of alcohol a day can be toxic to bone cells and can prevent bone from growing and rebuilding itself. Alcohol use can also decrease absorption of nutrients from food, change calcium and vitamin D metabolism, and increase risk of falls and incidence of fractures.

Belinda O’Connell is a Diabetes Nutrition Specialist at the International Diabetes Center in Minneapolis, Minnesota, and a freelance health and science writer.

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