A toast to good bone health
Many Americans have insufficient intake of vitamin D and calcium, along with insufficient exercise. Most physicians are aware of the need for calcium, vitamin D and exercise for bone health, but inadequate intakes of magnesium, silicon, vitamin K and boron are prevalent and are also important for bone health.
Calcium is the major bone nutrient because a large proportion of bone is made up of calcium. Review the amounts of calcium needed and the recommended advice to get most of our daily calcium from foods in Boning Up with Calcium. Moving to other bone nutrients, it is helpful to think of these nutrients as dancers in a complex dance arrangement! Calcium is needed for the basic foundation of bone, but we must have Vitamin D in order to absorb the calcium. Picture calcium as the ballerina who must be lifted by the male dancer (Vitamin D) in order to fulfill her role as the beaming star of the lift. Without Vitamin D, calcium is ineffective in performing its role. Vitamin D is also ineffective without calcium, in aiding bone structure and strength. Both calcium and vitamin D are needed for adequate calcium absorption for bone building and maintenance.
There are more supporting roles in the bone building ballet. In addition to supporting the absorption of calcium, vitamin D facilitates the absorption and use of several additional essential inorganic elements. Other nutrients involved in building and maintaining bone include minerals, such as magnesium, copper, zinc, iron, selenium, manganese and phosphorous and vitamins, such as vitamin K and vitamin C.
Each of these micro-nutrients has an important role, and recent research indicates that the entire group of nutrients must be present in adequate amounts to ensure adequate bone formation and retention, and to prevent osteoporosis (resulting in weak bones). Most research on nutrients for bone health has focused almost exclusively on calcium and vitamin D. Though the National Academy of Sciences recommends only 600 IU vitamin D for ages 1-70 and 800 IU for ages 70 and up, some osteoporosis experts recommend 800 to 1,200 IU of vitamin D per day. This level can reduce the risk of bone fracture by 20% in elderly people and can lower the risk of falls. The tide of scientific opinion is moving toward consuming larger amounts of vitamin D (vitamin D3 form) as a supplement. As concern increases in relation to possible skin cancer from excess exposure to sunlight, there is a need to ensure adequate vitamin D intake due to sun avoidance and sunscreen application, as well as reduced absorption by those with darker skin. Greater rates of deficiency levels are being seen, especially during winter months and in northern latitudes. Vitamin D is somewhat difficult to find in the diet, as 8 oz. of fortified milk has about 100 IU, and the other food sources may not be eaten regularly, such as tuna/salmon/sardines and breakfast cereals that have been fortified with vitamin D. Individuals can be tested for adequate vitamin D levels through their healthcare provider.
Other Minerals Important in Bone Health
Zinc, manganese and copper have a role in bone health, and are present in the typical diet in adequate amounts. Phosphorous, too, is plentiful in meats, dairy products, whole grains, seeds and nuts - adequacy is not a concern for the general public. Magnesium, on the other hand, once thought to be plentiful in the diet, is proving to be inadequate for many Americans due in part to the consumption of more highly processed foods, which can reduce magnesium intake. Boron, selenium and silicon are other minerals which have roles in bone health, but may be in short supply in the diet of the general population. Dietary sources of silicon include whole grains and whole grain cereals, carrots, and green beans. Boron is found in fruits, leafy vegetables, nuts and legumes. Brazil nuts are the richest source of selenium, offering 7 times the full Daily Value per ounce of nuts, with much smaller amounts in tuna, seafood, meats and poultry.
Other Vitamins Important in Bone Health
Vitamin K and vitamin C are involved in building cartilage and connective tissues and for collagen production, the first step in bone formation. Vitamin K is found in green leafy vegetables, and the Third National Health and Nutrition Examination Survey (HANES III) showed that about half of the men and women in the US consume less than the recommended amount of vitamin K. Vitamin K is also necessary for blood coagulation, however excess amounts of it do not result in an increased risk of blood clots, though people on blood thinner therapy should avoid excess amounts of it. Vitamin C is widely dispersed in fruits and vegetables, such as citrus fruit, kiwi, and cabbage, among others.
Promising research has shown that certain combinations of micro-nutrients may be as beneficial as some osteoporosis drug therapies. For the present time, it is difficult to determine what levels of supplementation beyond calcium and vitamin D would be the most beneficial. The full interplay of the bone nutrients is not completely understood, so look for more guidance as the functions and interactions of each micro-nutrient are clarified.