Taking a look at the details

The task force used a process called meta-analysis--a technique in which data from many studies are combined and analyzed together--to consider existing research on vitamin D and calcium in relation to cancer and fractures. Of the 137 studies selected for review, 16 randomized controlled trials were deemed of sufficient quality to include in the final analysis. Nearly all of the participants in these 16 studies were postmenopausal women, 65 years old and up.

While the main takeaway of the task force's study is the need for more research to better understand the relationship between these supplements and long-term effects on health, their finding of a weak association between these supplements and bone protection in postmenopausal women may point to the importance of knowing whether a person is deficient before supplementing.

Taking a look at the big picture

Older people living in care facilities are more likely to be vitamin D deficient, so it makes sense that providing them with extra D can improve bone health. For adults who aren't deficient, adding more vitamin D and calcium is unlikely to prevent fractures. The task force previously concluded that vitamin D supplementation is effective for preventing falls in older adults who are at increased risk for falls--an important benefit that should not be overlooked as people interpret these latest recommendations.

Although the report concluded that there isn't enough evidence to determine whether higher doses protect against fractures in postmenopausal women or other healthy adults, some research does in fact suggest a benefit. For example, a meta-analysis of five double-blind trials that included a total of 9,292 people at least 60 years old found that supplementation with 700 to 800 IU per day of vitamin D3 reduced the incidence of hip fractures by 26%.

It would be interesting to see whether the task force's conclusions would be different if more of the studies accounted for geography and lifestyle differences among participants. For example, a study of people living in Florida may be less likely to show a benefit with vitamin D supplements, because most people get enough D from being in the sun. This same study conducted in Minnesota may come to a different conclusion.

Dr. Bruce Hollis of the Medical University of South Carolina indicates that vitamin D, "has potential benefits in cancer prevention, cancer treatment, cardiovascular prevention, infection prevention, and prevention of autoimmune disease." Finally, some health experts feel that giving supplements to younger women to prevent later bone fractures may be more effective than giving supplements to older women with already thinning bones.

Cutting through the confusion

These are draft recommendations, so stay tuned; they may change prior to finalization. While waiting for more solid results, keep in mind that research suggests these nutrients may play a role in the prevention of other diseases. Dr. Bruce Hollis of the Medical University of South Carolina indicates that vitamin D, "has potential benefits in cardiovascular prevention, infection prevention, and prevention of autoimmune disease." To help you make smart decisions about calcium and vitamin D supplements, keep these tips in mind:

• If you have been taking calcium and vitamin D at the recommendation of your doctor, talk to him or her before deciding to stop. Findings from large studies don't always apply to individual needs.
• Consult with a dietitian who can do a thorough food and diet history, which will tell you whether you are coming up short on these nutrients. If you already get enough calcium from food, and enough vitamin D from a combination of food and sun exposure, you may not need supplements.
• If you do supplement calcium, take it in divided doses. For example, a supplement that provides 300 to 400 mg calcium per tablet or capsule can be taken with breakfast, lunch, and dinner, rather than in one large dose of 900 to 1,200 mg.
• Only supplement what you need: keep total calcium intake from food and supplements around 1,000 to 1,200 mg per day for adults, and keep total vitamin D intake from food and supplements around 600 IU per day for adults under age 70 and 800 IU per day for those older than 70.
• Though the task force did not include magnesium in its analysis, this mineral appears to play an important role in building strong bones and in overall health, and a person's calcium intake affects how it works. Eating too much calcium may reduce the amount of magnesium in the body, so making sure you get enough to maintain a better balance. To this end, nosh on magnesium-rich foods such as spinach, pumpkin seeds, beans, Brazil nuts, low-sodium tomato products, dark chocolate (65% or greater cocoa content), and whole grains--especially buck wheat, bulgur wheat, and oat bran.

(Vitamin D and Calcium Supplementation to Prevent Cancer and Osteoporotic Fractures in Adults: U.S. Preventive Services Task Force Recommendation Statement DRAFT; http://www.uspreventiveservicestaskforce.org/draftrec3.htm)