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Nutrition and bone health across the lifespan

The Westernized diet is now found to be responsible for more and more degenerative diseases. It is well known the link between diet and increased risk of cardiovascular disease and type 2 diabetes. New research is now implicating diet and nutrition to osteoporosis and Alzheimer’s disease. This article focuses on bone health and osteoporosis.

Bone health has become more important as osteoporosis has gotten to be a global health problem with increasing significance as people are living longer and the world’s population is increasing. More focus is on prevention of osteoporosis and its complications as priority to essential socioeconomics. Urgently needed is the development and implementation of nutritional approaches in prevention and treatment of osteoporosis.

Bone mass disease is osteoporosis and osteopenia both characterized by low bone mass and micro-architectural deterioration of bone tissue leading to bone fragility and increased susceptibility to fracture. Fragility fractures are the hallmark of osteoporosis and are particularly common in the spine, hip and distal forearm, although they can occur throughout the skeleton.

Osteoporotic fractures constitute a major public health problem. In the United States alone over 10 million people already have osteoporosis and 34 million have low bone mass we label as osteopenia, placing them at increased risk of fractures from this disorder. The estimated lifetime risk of fractures in Caucasian women at age 50 years for any fragility fracture is approaching 40 percent. In men it is 13 percent.

The incidence of vertebral and hip fractures increases exponentially with advancing age. The projected number of elderly population, 80 years and older in whom the incidence of osteoporotic fracture is higher, will grow to 26.4 million women and 17.4 million men by 2050. Between the increasing population and longer life expectancy this will have a large impact on the number of fractures that can be expected to occur in the next 30 years.

From an economic standpoint, the expense of hospital care and rehabilitation associated with osteoporotic fractures are a large drain for the health care system, exceeding those of other highly prevalent conditions of the elderly such as heart attack and stroke.

Many of the nutrients and food components we consume as part of a westernized diet can potentially have a positive or negative impact on bone health. They can influence bone by alternation of bone structure and change the rate of bone metabolism. These dietary factors range from inorganic minerals for example calcium, magnesium, phosphorus, sodium, potassium, and vitamins A, D, E, K, C, and certain B vitamins, along with macronutrients, such as protein and fatty acids.

Calcium is required for normal growth and development of the skeleton. Adequate calcium intake is critical to achieving optimal peak bone mass and modifies the rate of bone loss associated with aging. Besides the amount of calcium in the diet, the absorption of dietary calcium in foods is also a critical factor in determining the availability of calcium for bone development and maintenance.

Food components or functional food ingredients that may positively influence calcium absorption to ensure that calcium bioavailability from foods can be optimized need also to be identified. This approach may be of particular value in individuals with low dietary calcium and of those individuals with low efficiency of intestinal absorption of calcium. Calcium is absorbed through a multistep movement into cells which has a vitamin D dependent component. Most calcium absorption in humans occurs in the small intestine, although there is some small large intestine component of about 10 percent.

There are a number of food constituents which have been identified as potential enhancers of calcium absorption. Individual milk components such as lactose, lactulose, and casein phosphopeptides have been shown to enhance absorption of calcium. Additionally there is evidence to show that nondigestible oligosaccharides can improve calcium absorption. Examples of foods containing oligosaccharides are onions, garlic, leeks, legumes, wheat, and asparagus are a few.

Vitamin D is found naturally in very few foods. Synthesis of vitamin D which occurs when skin is exposed to UVB radiation from sunlight during summer is a principal determinant of vitamin D. However in latitudes above 40 degree north and 40 degrees south the skin photo-conversion to vitamin D occurs little if at all during 6 months of the year. During winter months here in Hamilton, Montana at latitude 46.247 degrees north there is increased reliance on dietary supply of vitamin D. This places many people at risk of low vitamin D status with possible consequences for bone health.

Vitamin D deficiency is characterized by inadequate mineralization, or demineralization of the skeleton causing osteomalacia or softening of bones. In addition the secondary hyperparathyroidism associated with low vitamin D status enhances mobilization of calcium from the skeleton. There is considerable evidence that vitamin D deficiency is an important contributor to osteoporosis through less efficient intestinal absorption of calcium, increased bone loss, muscle weakness, and a weakened bone microstructure. Increasing vitamin D intake can significantly reduce risk of bone fracture in older adults.

Estrogen deficiency is a major contributory factor to the development of osteoporosis in women and hormone replacement therapy (HRT) remains the mainstay for prevention of bone loss in postmenopausal women. Recently as a consequence of poor uptake and adherence of HRT as well as potential concerns over an increased risk of malignancy and other side effects associated with the use of HRT, attention has been focused on the dietary phytoestrogens as possible safe alternatives, or at least adjuncts to HRT.

hytoestrogens are nonsteroidal compounds naturally occurring in foods of plant origin, especially soy based foods that structurally resemble natural estrogens and compete with them for binding estrogen receptors. Recent critical review of the health effects of soybean phytoestrogens in postmenopausal women concluded that there is a suggestion, but no conclusive evidence that they have a beneficial effect on bone health. Further research is needed to clarify the role of dietary phytoestrogens in osteoporosis prevention.

About 90 percent of total adult bone mass is accrued by age 20, and a significant proportion of this is achieved during puberty alone. Thus gaining an understanding of the role of dietary components in bone metabolism and bone mass in these early life stages is important because finding new strategies to maximize the formation of bone during growth will help reduce the risk of osteoporosis in later life.

There is some concern about the proportion of adolescent girls who appear to be failing to meet the dietary recommended level of calcium 1300 mg daily. Adolescence also appears to be the life stage that has the highest prevalence of low vitamin D status. Severe vitamin D deficiency leads to rickets in children but less severe vitamin D deficiency may prevent children and adolescents from reaching their genetically programmed height and peak bone mass.

Increased emphasis on a preventative approach to degenerative diseases such as osteoporosis needs to include dietary strategies across the lifespan. In addition sun exposure and activity level including weight bearing exercise need to be a part of the prevention of osteoporosis. While the nutrients calcium and vitamin D have received the most attention there is growing evidence that wholefoods and other micronutrients have roles to play in primary and potentially secondary osteoporosis prevention.

Fruits and vegetables are still not being eaten in adequate amounts and yet contain micronutrients and phytochemicals useful for bone formation and resorption and are essential for reducing inflammation and oxidative stress. A balanced diet containing food groups and nutrients needed for bone health across the whole lifecycle may help to prevent osteoporosis.