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Fruit and vegetable intake linked to bone health

 

Bone mineral density and bone metabolism are affected by genetic, endocrine, mechanical and nutritional factors. Our understanding of nutritional influences on bone health is limited because most studies have focused on calcium. This study investigates the association between several micronutrients, bone mass and markers of bone metabolism.

Bottom line

This small study suggests an association between several nutrients found in fruit and vegetables (i.e. potassium, magnesium, B-carotene and vitamin C) and bone health. However, further investigations are needed to confirm these findings.

Reference

SA New et al. Dietary influences on bone mass and bone metabolism: further evidence of a positive link between fruit and vegetable consumption and bone health. American Journal of Clinical Nutrition 2000 71: 142-151.

Study

Participants were 62 women, aged 45 to 55 years, randomly selected from a health register. The women had not taken any medication or suffered from any condition likely to affect their bone metabolism.

Bone mineral density was measured by dual-energy X-ray absorptiometry at the lumbar spine and left femur and by peripheral quantitative computed tomography of the forearm (at the total, trabecular and cortical sites). Bone loss was calculated by measuring urinary excretion of pyridinoline and deoxypyridinoline and bone formation by measuring serum osteocalcin.

Both past and present intake of the following micronutrients was investigated: potassium, magnesium, fibre, vitamin C, ß-carotene, phosphorus and zinc. Usual dietary intake (over the previous 12 months) was assessed with a validated food-frequency questionnaire. Past dietary intake was assessed by asking about consumption of milk, milk products, cheese, fruit and vegetables during childhood (up to 12 years) and early adulthood (20 to 30 years). (These age groups were chosen because they are crucial stages in skeletal growth.) Nutrient intakes were grouped into quartiles.

Lifestyle factors (including physical activity and smoking) were measured with additional questions.

Results

The women were of average height and weight for the local population. Their average daily intake of nutrients were within the acceptable range for UK women of their age. All results were adjusted for age, weight, height and menstrual status.

Bone mineral density

No associations were found between current nutrient intakes and lumbar spine or hip bone mineral density. No differences were found in bone mineral density between women who consumed low amounts of milk, milk products cheese or vegetables in their childhood or early adulthood and those who consumed medium or high amounts. Significant differences were seen in femoral neck bone mineral density between women with high childhood intakes of fruit and those with medium or low intakes.

Average total forearm bone mineral density was greater with higher intakes of potassium, magnesium, fibre and alcohol. Average cortical bone mineral density increased with higher intakes of magnesium, potassium and alcohol. No differences in forearm bone mineral density were found according to past nutrient intakes.

Bone metabolism

Average pyridinoline excretion was lower with higher intakes of potassium, magnesium and ß-carotene. Average deoxypyridinoline excretion was lower with higher intakes of potassium, magnesium, ß-carotene and vitamin C.

Lifestyle factors

No associations were found between present or past physical activity levels or between smokers and non-smokers and bone mineral density or bone metabolism.

Comment

This study has two main limitations: it was conducted at a single point in time, so only associations, rather than causal relationships, can be inferred; and the number of participants is small, which may explain the lack of associations found.

Nevertheless, several nutrients were found to be associated with bone health, i.e. potassium, magnesium, ß-carotene and vitamin C, and these are found in fruit and vegetables. The associations found between alcohol intake and bone mass are perhaps surprising, but mechanisms have been suggested to explain this link (which include the induction of the adrenal production of androstenedione and its adrenal conversion to estrone). However, further research is needed to confirm these findings and to continue to investigate the influence of past dietary intake on bone health.