KARACHI, Jan29: If you were asked to name a few foods that promote healthy bones, you would probably list dairy products for their bone-building calcium and vitamin D. It is a lot less likely that prunes, onions and fermented soybeans would come to mind.
In fact, it has been known for some time that a high intake of fruits and vegetables helps keep bones strong and prevents fractures as people age, says a special report appearing in US newspaper Los Angeles Times.
Now nutrition scientists are trying to pinpoint the bioactive compounds in produce that appear to have this effect. And they are testing whether adding particular fruits and vegetables to the diet can keep osteoporosis at bay.
In a study under way at Florida State University, older women who have osteoporosis will be adding either a daily handful of dried apples or about 10 dried plums to their diet for a year. The investigators are betting that the prune eaters will have measurable restoration in their bone mass based on observations they made in a similar but shorter study.
Although that study was too brief to measure changes in bone density, something the new study will allow the women who ate 10 dried plums daily had significantly higher blood levels of two compounds (the hormone IGF-1 and the enzyme BSAP) that are associated with greater rates of bone formation.
What do prunes offer that other dried fruits don't? Various substances, and scientists don't yet know which among them is most important. Prunes contain small amounts of calcium and magnesium -- both bone-building minerals and some natural acids that could improve mineral absorption.
They are a rich source of antioxidant polyphenols, which also could be bone protective. They're also rich in boron, a bone-building mineral that is often lacking in the diet. (Boron prevents excretion of calcium and magnesium, which allows these minerals to be deposited in bone tissue.)
Fibre, too, could be important in the bone-produce connection: plant foods are rich sources of this. Studies have focused on a group of fibres known as fructans, which are plant carbohydrates found in some leaves, roots and tubers.
One fructan, inulin, is fermented by certain beneficial bacteria in the intestine, producing a more acidic environment that favours calcium absorption.
Inulin is found in leeks, garlic, artichokes, jicama and, especially, onions. This may explain some findings by researchers at the University of Bern in Switzerland who tested the benefits of various vegetables on bone.
Rats consuming a diet designed to mimic our typical Western fare u high in refined starch, sugar and fat u preserved more bone mass during a period of four weeks when dried vegetables were added to their chow. Brussels sprouts, tomatoes, garlic, parsley, carrots and a salad mixture all provided some benefit, but onions were the clear winner.
Onion-fed rats increased their total bone mineral content by more than 17 per cent. However, they were fed the human equivalent of about a quart of chopped onions a day. Further studies should help reveal the lowest beneficial dose.
There is also a growing body of research on the role played by vitamin K, which influences the binding of calcium to bone. Most of the vitamin K we consume is in a form called phylloquinone, found in green vegetables such as broccoli, lettuce and spinach. Another form, menaquinone, is obtained in much smaller amounts from certain foods (butter, cheese, liver, egg yolk) but can also be made by bacteria in our intestines.—PPI
