My mother has always been a big proponent of calcium supplements. She had me swallowing those green pills in elementary school and was equally diligent about taking them herself. As a physician, she knows the importance of calcium for healthy bones; as the daughter of an osteoporosis patient who has suffered multiple fractures, she knows of the pain caused by brittle ones.
After her bone density scan last October, however, my mother received disturbing news: She was diagnosed with osteopenia, a level of bone loss that is a gateway to osteoporosis. The T-score of her spine was - 1.65; her hip was even worse at -1.93. (Osteoporosis is defined at below -2.5, or two-and-a-half standard deviations below normal bone mass.) She decided to step up her efforts by adding to her regimen – and mine, of course – regular supplements of Vitamin D.
While Vitamin D has long been recognized as a nutrient essential to overall health, only now are researchers fully appreciating both its significance to a number of organ systems and the consumption levels required for us to benefit fully. Most recently, the National Osteoporosis Foundation raised its daily recommendations of Vitamin D intake to 800-1000 units for adults 50 and older. Previously, they had suggested 400-800 units for people of all ages.
Specifically, Vitamin D is very important to maintaining bone and mineral balance. It sends a message to intestines to absorb calcium, and numerous studies have shown that adequate intake can contribute to strong bones that are less likely to break in a fall.
"We are beginning to get a deeper appreciation for how important Vitamin D is to health," says Dr. Susan Nayfield, chief of the Geriatrics Branch at the National Institute on Aging in Bethesda, Md.
In addition to the bones, however, scientists have recently begun to understand the impact of Vitamin D receptors on muscles, including the small muscles in blood vessels, Dr. Nayfield says. While an outright Vitamin D deficiency can cause obvious medical problems, even a subtle deficiency, or "insufficiency" – in which the Vitamin D being used in the body exceeds intake – can play a negative role in one's well being.
This can pose a problem for older people whose sun exposure is limited, since the skin is able to produce Vitamin D with exposure to direct sunlight. However, as people age they cannot synthesize Vitamin D as efficiently, and their kidneys are less able to convert it to active form, according to the National Institutes of Health (NIH) Clinical Center. Also, individuals with darker skin, especially African-Americans, convert sunlight to Vitamin D less efficiently than those with fairer skin. Studies have shown that individuals with darker complexions can be especially prone to hypovitaminosis D, a term used to describe low blood levels of Vitamin D.
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Dr. Robert Recker, vice president of the National Osteoporosis Foundation, said the previous requirements were sufficient to prevent diseases associated with severe deficiency of Vitamin D, specifically rickets in children and osteomalacia in adults. "It takes a larger dose beyond that to supply all the other needs," says Dr. Recker, who is also chief of the Endocrinology Division at Creighton University Medical Center's Osteoporosis Research Center. "To put it simply, we have till now not realized what an adequate intake should be."
Especially of concern to individuals who already suffer from reduced bone mass, whether osteoporosis or osteopenia, are insufficiency's cumulative effects on a person's strength and reflexes. Inadequate levels of Vitamin D can cause muscle weakness and pain. "There is good evidence, unless you have Vitamin D, you have more propensity to fall," Dr. Recker says.
In fact, a recent study in The Journals of Gerontology found that among those 65 and older, those with a Vitamin D deficiency performed poorly on a battery of routine tasks, such as getting out of a chair and gripping with their hands.
"We're only just beginning to see the tip of the iceberg," of potential benefits of Vitamin D, said Dr. Recker, noting that it may be helpful in preventing a host of infections, cancers, diabetes, Alzheimer's disease and multiple sclerosis.
Dr. Recker says he believes the amounts recommended by the National Osteoporosis Foundation may be elevated further before long. Nevertheless, it is important to consult with your physician about what your optimal intake of Vitamin D should be.
It is worth considering that while recommended levels of the nutrient are good, more is not necessarily better. According to the NIH, Vitamin D toxicity can cause nausea, vomiting, constipation, weakness and weight loss. It can also raise calcium blood levels, which can lead to confusion, heart rhythm abnormalities, and calcinosis, in which calcium deposits in the body.
Most recently, there is now some evidence that high levels of consumption of calcium and Vitamin D are associated with brain lesions in those age 60 or older, according to research presented this week before the American Society for Nutrition.
"We found people who consumed more calcium and Vitamin D were more likely to have areas of brain damage believed to be due to loss of oxygen," said lead researcher Dr. Martha E. Payne of the Neuropsychiatric Imaging Research Laboratory at Duke University. The process, known as vascular calcification, can lead to dementia, stroke and cognitive impairment.
Dr. Payne stresses her group's research is very preliminary, and does not yet have any implication on Vitamin D recommendations since it did not show that calcium or Vitamin D caused the brain lesions observed. "We need to do more research to look at these possible negative consequences," she said. "With any kind of nutrient, there is some optimal level. In the future, medicine will be targeting individual risk factors."
Nayfield, of the Institute on Aging, says that research into Vitamin D's effects on the body is ongoing and will be important as experts fine-tune their recommendations for daily intake. "There are as many questions as answers," she says.
Published On: May 08, 2007