Bone Health

Hip fractures associated with osteoporosis result in approximately 300,000 hospital admissions and an estimated $9 billion annually in the United States (82). Calcium and vitamin D are well established as important nutrients associated with bone metabolism but less is known about the effect of other nutrients and dietary constituents on bone health.

In 1999, Swiss researchers fed vegetable mixtures containing lettuce, tomato, cucumber, onion, and several herbs to rats for 4 weeks and found a significant reduction in bone resorption (83). Onion feeding improved bone mineral content, density, and cortical thickness by 14-18%. In ovariectomized rats (a model of estrogen withdrawal similar to menopause), onion intake attenuated the hormone-mediated bone resorption in a dose-dependent manner. The investigators suggested that the effect of onion on acute bone resorption was comparable to that of calcitonin (83). It is not clear what specific compounds in vegetables might account for these observations. Some investigators have speculated that phenolic compounds, including quercetin derivatives, may be important in inhibiting bone loss in ovariectomized rats (84), although this has been debated (85).

Two cross sectional studies of human subjects have suggested that fruit and vegetable consumption may contribute to the maintenance of bone density. In a recent study of elderly men and women in the Framingham Heart Study, fruit and vegetable intake was positively associated with bone mineral density at three out of four sites in the hip and forearm of men and two sites in women (86). In the same subjects followed for a four-year period, higher intake of fruits and vegetables was associated with less decline in bone mass at one hip site in men, but not in women. This study showed a strong correlation between potassium and magnesium intake and bone density suggesting that fruits and vegetables may play a role in bone health due to their content of these two micronutrients. Potatoes, orange juice, bananas, and tomatoes were among the top 6 sources of potassium for these subjects; bananas and orange juice were among the top 6 foods providing magnesium.

“… In a recent study of elderly men and women in the Framingham Heart Study, fruit and vegetable intake was positively associated with bone mineral density at three out of four sites in the hip and forearm of men and two sites in women.”

A cross-sectional study of 62 healthy women (45-55 years) in the United Kingdom demonstrated that several nutrients found in fruits and vegetables predicted bone mineral density as well as markers of bone metabolism (87). Women in the highest quartile of potassium and magnesium intake had significantly lower excretion of pyridinoline and deoxypyridinoline, two urinary markers of bone resorption. There was no significant association between specific foods or nutrient intake and bone mineral density in lumbar spine and hip. However, women who reported having high intakes of fruits during childhood tended to have higher femoral neck bone mineral density than women with low intakes, although the authors admit that these data are subject to recall bias. Mean bone mineral density of forearm was significantly greater with a higher intake of potassium, magnesium, fiber, and alcohol compared to women with lower intake of each of these.

The mechanism for a potential protective effect of fruit and vegetables on bone health is not clear. It has been proposed that a diet favoring alkaline ash, (including fruits, vegetables, vegetable protein, potassium, and magnesium) might decrease the rate of bone attrition by decreasing the need for bone mineral as a buffer for acid load from mixed diets (86).

In conclusion, current available data suggest that there may be a link between bone health and fruit and vegetable consumption, although further investigation is needed to confirm the mechanisms and specific constituents in fruits and vegetables that might account for the association.