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    Avoid High-Dose Calcium Supplements


    Americans constantly are being urged to consume more calcium in an effort to reduce our epidemic of osteoporosis. It is hoped that increasing calcium consumption will help people maintain bone density, reducing the high rate of hip fractures and spinal compression fractures in the elderly. An adult woman with a life expectancy of 80 years has a 16 percent lifetime risk of sustaining a hip fracture. The death rate in the first year after a hip fracture is 15 to 20 percent, so this really is a serious problem.

    The risk of a hip fracture correlates well with bone density. Studies show that women with the lowest bone density have a much greater risk of severe injury in a fall. Because most hip fractures result from falls, the ability to identify women at higher risk of falling as they age is important. Special care should be given to those who have low bone density. Everyone agrees that something needs to be done, but the controversy is whether or not women should be taking 1000 to 2000mg of calcium in the form of dairy products or supplements, as is recommended by most health authorities.

    The problem is twofold. One, the focus on calcium intake shifts the emphasis away from other more critical factors that promote calcium loss in the urine. These include excess consumption of sodium, animal protein, coffee, junk food, and vitamin A in supplements and in fortified foods. Research indicates the dangers of vitamin A supplementation, but vitamin A is still found in most supplements and is added to milk and soy milk. Also, when you consider the epidemic of vitamin D (essential for bone health) deficiency in our country and our relatively sedentary lifestyles, it is easy to see that simply increasing calcium intake while ignoring other important factors is not going to produce the results we are seeking. Secondly, taking such high doses of calcium has not been shown to be more effective than lower—but still adequate—doses, and the high dose potentially can have negative health effects as well.

    We advise getting most of your calcium from vegetables (which are an excellent source) and that additional calcium supplementation should not be excessive. When you get calcium from greens, you get a symphony of nutrients for optimal health, including folate, phosphorus, vitamin K, and phytonutrients, all of which have positive effects on bone health.

    How Much is Enough?
    When advising whether calcium supplementation is necessary at all and if so, which dose should be recommended, different scientific approaches have yielded different estimates, and there is significant disagreement here among authorities. Government advisory panels that reviewed calcium balance studies (which examine the point at which the amount of calcium consumed equals the amount of calcium excreted) suggest that an adequate intake of calcium is about 550mg per day.

    To ensure that 95 percent of the population gets this much calcium, the National Academy of Sciences has made the following daily recommendations:1

    1,000 mg ages 19-50
    1,200 mg age 50 or over
    1,000 mg if pregnant or lactating

    Supplements Too High
    Supplement manufacturers (and most consumers) make the assumption that a person taking the calcium supplement consumes little or no calcium in their diet. As a result, supplements typically supply 800 to 1200mg of calcium daily.

    Unfortunately, most calcium balance studies are short-term and therefore have important limitations. To detect how the body adapts to different calcium intakes over a long period of time requires studies of longer duration. The results from such long-term studies may be surprising to some. While they do not question the importance of calcium in maximizing bone strength, they cast doubt on the value of consuming the large amounts of calcium that currently are recommended for adults. Long-term studies suggest that increasing the calcium dose above 800 mg per day doesn’t lower a person’s risk for osteoporosis. For example, in the large Harvard studies of male health professionals and female nurses, individuals who drank one glass of milk (or less) per week were at no greater risk of breaking a hip or forearm than were those who drank two or more glasses per week.2 Other studies have found similar results. Adding to the confusion is the fact that milk is usually fortified with both vitamin A and vitamin D, and excess vitamin A has a powerful negative effect on bone health. It is possible that the reason long-term studies show that milk consumption hurts women’s bones is because the women are being exposed to bone-damaging levels of vitamin A.

    Additional evidence also supports the idea that American adults may not need as much calcium as is currently recommended. For example, in places such as India, rural China, and Japan, where average daily calcium intake is about 300-400 mg per day, the incidence of hip fractures is comparatively very low. Of course, these countries differ in other important factors as well—such as level of physical activity and amount of sunlight—which could account for their low fracture rates. Health authorities in different countries around the world recommend varying amounts of calcium ranging from 500 to 1000 mg. In 1998, the Expert Committee of the European Community in the Report on Osteoporosis—Action on Prevention, has given the recommended daily dietary allowances (RDA) for calcium for the elderly population, above age 65, as 700-800 mg per day. The British medical authorities agreed.

    Despite the debate surrounding milk and osteoporosis and how much calcium is ideal, one thing is clear: Adequate calcium is important for reducing the risk of osteoporosis. When women supplement their diet with extra calcium, hip fractures do decrease, and the combination supplement containing both 800mg of vitamin D and calcium has been shown to reduce both bone loss and hip fractures. However, one long-term,18-year analysis showed that 600 mg of calcium was as effective as 1200 mg in preventing osteoporosis as long as adequate vitamin D was present. Low-serum vitamin D levels correlated best with fracture risk.3

    We recommend calcium should not be used in excessive doses, and supplemental calcium should be in the 400-600 range, not the 1000-2000 range. Excessive ingestion of calcium could interact with minerals such as iron, zinc, magnesium, and phosphorus and create a potential for risk of mineral depletion in vulnerable people. A 1998 National Academy of Sciences report, Establishing Upper Intake Levels for Nutrients, stated, “Like all chemical agents, nutrients (e.g., calcium) can produce adverse health effects if intakes from any combination of food, water, nutrient supplements, and pharmacologic agents are excessive. Iron absorption can be decreased by as much as 50 percent by many common forms of calcium and by milk ingestion when consumed at the same time as iron-containing foods. Calcium citrate, calcium ascorbate, or calcium chelates do not decrease iron absorption.”4 But it is possible that increased intakes of specific sources of calcium might induce iron deficiency in individuals with marginal iron status.

    In conclusion, a modest increase in calcium via supplementation is appropriate for most people, but real food should supply a good percentage of your calcium intake to achieve the right balance of supportive nutrients to maximize bone health. Practices that might encourage total calcium intake to approach or exceed 2,000 mg per day seem more likely to produce adverse effects and should be avoided.


    1. Optimal Calcium Intake. NIH Consensus Statement Online 1994 June 6-8; 12(4): 1-31.

    2. Owusu W, Willett WC, Feskanich D, Ascherio A, Spiegelman D, Colditz GA. Calcium intake and the incidence of forearm and hip fractures among men. J Nutr 1997; 127:1782-7. Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Milk, dietary calcium, and bone fractures in women: a 12-year prospective study. Am J Public Health 1997; 87:992-7.

    3. Feskanich D, Willett WC, Colditz GA. Calcium, vitamin D, milk consumption, and hip fractures: a prospective study among postmenopausal women. Am J Clin Nutr 2003 Feb;77(2):504-11.

    4. Whiting SJ. The inhibitory effect of dietary calcium on iron bioavailability: a cause for concern? Nutr Rev 1995 Mar;53(3):77-80.