Nutritional factors in bone health in elderly subjects: methodological and contextual problems

Article Abstract:

There is currently much interest in the bone disease osteoporosis, which is characterized by diminished bone mass and increased risk of fractures. In the elderly, if the bones are not strong enough to support the individual's weight and movement, they may fracture easily. Prevention of fractures is the primary reason for promoting bone health in the elderly. Bone fragility results not only from decreased bone mass, but also from mechanical fatigue and other factors. Bone mass is influenced by various factors including dietary calcium intake, physical activity (which strengthens bones), genetic factors and female hormones. Adequate amounts of calcium are needed for maintenance of the skeleton, but calcium alone cannot overcome other influences on bone mass. Much controversy has developed over what level of calcium intake is adequate for different age and sex groups. Evidence is accumulating that suggests white women in particular should be consuming more calcium than they currently do. Experts have suggested 1000 mg/day for women around menopause who have adequate estrogen levels, and 1500 mg/day for women after menopause with depleted estrogen levels; actual average intakes of American women over age 50 are about 500 mg/day. Primitive humans may have consumed even more calcium and the human body was apparently accustomed to these intakes. Some individuals adapt to lower nutrient intakes better than others. The time lag between nutritional inadequacy and bone disease is very long, perhaps 20 to 30 years. In conclusion, bone mass is only one influence on bone strength and bone mass itself is affected by many factors. Methodological issues concerning the assessment of bone health in the elderly are discussed.

Diseases, Bone diseases, Osteoporosis, Aged women, Elderly women

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Calcium absorption from kale

Article Abstract:

It is generally assumed that dairy products, such as milk and cheese, are the best dietary sources of calcium. Certain vegetables are high in calcium, but some of them also contain substantial amounts of oxalates, compounds that bind the calcium and reduce the ability of the intestines to absorb it. Spinach is high in both calcium and oxalates, with the net effect of poor calcium absorption. However, calcium absorption from vegetables low in oxalates has not been measured. Kale, a calcium rich, low-oxalate vegetable, was studied. Eleven healthy young women participated. Their absorption of calcium from kale and milk was measured on two separate occasions. The calcium in these foods was labelled with radioactive isotopes, making it possible to trace how much was absorbed and how much was excreted. Forty-one percent of the calcium from kale was absorbed, which was considered excellent bioavailability. Calcium absorption from milk was actually lower, at 32 percent; for practical purposes these two foods can be considered equally good calcium sources. In conclusion, green leafy vegetables, such as kale, that are high in calcium and low in oxalates appear to be excellent sources of calcium. Other vegetables in the same family are turnip, collard, mustard greens and broccoli. (Consumer Summary produced by Reliance Medical Information, Inc.)

Measurement, Food, Calcium, Dietary, Kale

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Soybean phytate content: effect on calcium absorption

Article Abstract:

Phosphorus is stored in seeds as phytic acid, and phytic acid is thought to interfere with the absorption of minerals from cereals and legumes (such as beans). Phytic acid binds to the mineral and decreases its bioavailability, or the amount accessible for the body's metabolic needs. The bioavailability of zinc decreases with increases in the intake of phytic acid. But the effects of phytate on calcium absorption have not been extensively studied. Although studies suggest that phytate decreases calcium absorption in humans, it does not appear to affect calcium absorption in rats. Unlike humans, rats have an enzyme called phytase in their intestines, which breaks down the phytate-mineral complex, thereby increasing the bioavailability of the mineral. The relationship between dietary intake of phytate and absorption of calcium from soybeans was assessed in 16 normal women. The absorption of calcium from milk was also studied for comparison in 15 of the 16 women. Fractional calcium absorption was 0.31 from soybeans containing high levels of phytate; 0.41 from soybeans containing low phytate levels; and 0.38 from milk. These findings show that calcium absorption is lower with high dietary phytate intake than with low dietary intake of phytate. (Consumer Summary produced by Reliance Medical Information, Inc.)

Calcium in the body, Soybean, Soybeans, Phosphorus in the body, Phosphorus (Nutrient), Phytic acid

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