Vitamin D, not calcium, important in fracture reduction - Nutrition and Bone Health |
| Nutrition Research Newsletter, Feb, 2003 |
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| Calcium has long been proposed as the primary prevention of postmenopausal osteoporosis. There have been numerous clinical trials of calcium supplementation that demonstrated a reduction in bone loss and a lower risk of bone fracture. However, concomitant treatment with vitamin D makes it difficult to attribute benefits to calcium alone. Additionally, in contrast with the clinical data, most observational studies did not find a significant association between calcium intake and fracture risk or bone loss. Primarily on the basis of the clinical evidence, the Food and Nutrition Board of the National Academy of Sciences raised the adequate intake for calcium in women > 50 years of age to 1200 mg/day. |
| At low-to-moderate calcium intakes, vitamin D is essential for calcium absorption. Vitamin D insufficiency is common among older adults. On the basis of current research on the amount of dietary vitamin D required for maintenance of normal serum concentrations of 25-hydroxy vitamin D, the Food and Nutrition Board recently set the adequate daily intake of vitamin D at 10 micrograms for women aged 51 to 70 years and 15 micrograms for women aged > 70 years. Milk is a good and highly available source of both calcium and vitamin D and therefore might be expected to decrease osteoporotic bone low and fracture risk, yet research has not strongly supported this notion. |
| A recent study, using data from The Nurses' Health Study (NHS) was performed to examine calcium and vitamin D intakes, milk consumption, and use of calcium supplements during 18 years of follow-up in a large cohort of postmenopausal women. The analysis began in 1980 with the postmenopausal women who responded to the initial dietary questionnaire and had not reported a previous hip fracture or a diagnosis of cancer, heart disease, stroke, or osteoporosis. A total of 72,337 women contributed to the current study with follow-up through 1998. |
| The Subjects were asked to report all hip fractures and included information regarding date, exact bone site, and circumstances leading to the fracture. Cases in the current study included only fractures of the proximal femur that were caused by low or moderate trauma. Over the 18 years of follow-up, 603 hip fractures were determined among the study population. The median age at fracture was 65 years. |
| Participant's diets were assessed using a semiquantitative food-frequency questionnaire (FFQ). Total nutrient intakes were calculated by adding the amounts from multivitamins and front specific supplements to the intakes from food. Postmenopausal hormone use, smoking, and weight data were requested on all biennial questionnaires, and body mass index was calculated suing the initial height reported. Physical activity was also reported. |
| Women consuming = 12.5 micrograms vitamin D per day from food plus supplements had a 37% lower risk of hip fracture (RR = 0.63; 95% CI: 0.42, 0.94) than did women consuming < 3.5 micrograms per day. Total calcium intake was not associated with hip fracture risk (RR = 0.96: 95% CI: 0.68, 1.34 for = 1200 compared with < 600 mg per day). Milk consumption was also not associated with a lower risk of hip fracture (P for trend = 0.21 ). |
| Based upon results of this large-scale study, it appears that an adequate vitamin D intake is associated with a lower risk of osteoporotic hip fractures in postmenopausal women. Neither milk nor a high-calcium diet appears to reduce the risk of hip fractures in this group. As women generally consume less than the recommended intake of vitamin D, the researchers suggest that supplement use or dark fish consumption may be prudent. |
| D. Feskanich, W. Willett, G. Colditz. Calcium, vitamin D, milk consumption, and hip fractures: a prospective study among postmenopausal women. Am J Clin Nutr;77:504-511 (January, 2003). [Correspondence: D Feskanich, Channing Laboratory, 181 Longwood Avenue, Boston, MA 02115. E-mail: diane.feskanich@channing.harvard.edu]. |
| COPYRIGHT 2003 Frost & Sullivan |
| COPYRIGHT 2003 Gale Group |
