What you read is correct. In a number of countries, including Japan, India, and Peru, the average daily calcium intake is only 300 mg. That's much less than the 1,000 mg recommended for adults between the ages of 19 and 50 in the U.S., yet the incidence of bone fractures in these countries is very low. In addition, evidence from some large studies indicates that calcium doesn't actually reduce the risk of osteoporosis as we once thought. For example, in two studies conducted by the Harvard School of Public Health, participants who drank one glass or less of milk per week had no greater risk of breaking a hip or forearm than those who drank two or more glasses of milk per week.
After reviewing this data and discussing it with Walter Willett, professor of nutrition and epidemiology at Harvard University's School of Public Health, I'm revising my calcium recommendation downward. In the past, I recommended 1,200 mg daily in divided doses and 1,500 mg for postmenopausal women who were not on hormone replacement therapy. I now suggest that women supplement with 500 to 700 mg of calcium citrate in two divided doses taken with meals, for a total daily intake of 1,000-1,200 mg from all sources. For men, I now suggest aiming for 500 mg from all sources, and that men probably do not need to supplement (higher amounts have been linked to increased risks of prostate cancer). Men should also watch their dairy intake. The Harvard study determined that men who drank two glasses of milk a day (that translates to about 1,000-1,200 mg of calcium) had twice the incidence of developing advanced prostate cancer.
Lower amounts of calcium should be sufficient to protect bones. However, the lifestyle measures listed below can help prevent bone loss as you get older (after 30 both men and women begin losing bone mass slowly; this accelerates for women after menopause):
- Get regular exercise, both weight-bearing exercise (walking, jogging or anything else you can do on your feet) and strength training for muscles. (Walter Willett says, "If you're concerned about bone health, forget about the milk and take your cow for a walk.")
- Be sure to get adequate vitamin D. I now recommend 2,000 IU of vitamin D3 daily. The ultraviolet B rays of the sun trigger your skin to make vitamin D (provided you're not wearing sunscreen). We don't get much D in our diets, so if you don't get regular sun exposure, it is necessary to supplement with this vitamin.
- Get adequate daily vitamin K (120 mcg for men, 90 mcg for women). Low intake has been linked to low bone density. You get vitamin K in broccoli, Brussels sprouts, dark green lettuce, collard greens and kale.
- Watch your protein intake. Too much can promote calcium loss from bones.
- Take supplemental vitamin A only in the form of beta carotene, as part of a mixed carotenoid product. Preformed vitamin A (identified on vitamin labels as "retinol" or "vitamin a palmitate") can weaken bones.
- Cut back on caffeine: too much can promote calcium excretion.
Andrew Weil, M.D.