NEW YORK - Older women shouldn't take vitamin D and calcium supplements to prevent broken bones, and there's not enough evidence to say whether it would help anyone else either, says a U.S. government-backed panel.

Based on two reviews of past research, the U.S. Preventive Services Task Force waded into the debate over the two vitamins that are thought to strengthen bones to prevent against breaks.

"Calcium and vitamin D are important in general health and bone health. For this recommendation, we review data on whether supplements of vitamin D and calcium can prevent fractures in addition to dietary intake," said Dr. Jessica Herzstein, a member of the Task Force.

Approximately 1.5 million Americans suffer from breaks that are tied to brittle bones each year. And about half of all women over 50 years old will end up with a break that's linked to the bone-weakening disease osteoporosis.

That's a major concern, according to the Task Force, because broken bones are linked to chronic pain, disability and increased risk of sickness and early death.

Based on the reviews, the panel found there were no benefits but some risk for post-menopausal women taking low-dose vitamin D and calcium supplements - below 400 international units and 1,000 milligrams, respectively.

Specifically, taking low-dose supplements didn't change the older women's risk for broken bones, but was tied to a small increase in the risk of kidney stones.

They also found that there is not enough evidence to suggest higher doses of the vitamins would be effective or safer in older women, or that taking any dose of the supplements would help men or younger women.

For men and younger women, "We're not saying don't take it, we're just saying we don't know enough right now," said Herzstein, who is in charge of employee health at Air Products in Allentown, Pennsylvania.

She added that these recommendations do not apply to people who already have a diagnosis of osteoporosis, a history of fractures or are living in an assisted-living community.

Herzstein said it's important for people to talk with their doctors about the supplements.

Cara Welch, senior vice president of scientific and regulatory affairs for the Natural Product Association in Washington, D.C., told Reuters Health she agreed that people should talk to their doctors, but said the group disagrees with the new recommendation.

"We believe this recommendation is out of step with current research, and it really should not affect consumers who are trying to supplement their calcium and vitamin D intake with supplements," Welch said.

According to the most recent data from a national survey of Americans, 56 percent of women over 60 years old take vitamin D supplements, and 60 percent take calcium supplements.

The two vitamins are often sold together and are relatively inexpensive.

The Task Force already recommends women older than 65 years old be screened for the bone-weakening disease osteoporosis, and younger women who have a higher risk of broken bones.

The panel also recommends senior citizens with a history of falls and vitamin D deficiency take supplements to help strengthen muscles and help with balance.

Vitamin D has also been researched as a preventive measure against dementia, heart disease and cancer, but with mixed results. Herzstein said the panel will soon be issuing recommendations about the vitamin for some of those diseases.

Marion Nestle, a nutrition researcher from New York University who coauthored a commentary published alongside the recommendations in the Annals of Internal Medicine, said that good studies on vitamin D are hard to do, and any end to the debate over whether to take supplements or not is a long way off.

"These studies are so difficult to do and to interpret that scientific consensus seems impossible to achieve, especially in situations where entire organizations are devoted to convincing people to take high-dose vitamin D," she wrote in an email to Reuters Health.

Although vitamin D boosts the immune system, taking large doses of the nutrient does not appear to ward off colds, a new study from New Zealand says.

In the study, participants who took high doses of vitamin D supplements every month for more than a year were just as likely to catch colds as those who took a placebo.

Taking vitamin D supplements also did not reduce the length of time participants were sick, the severity of their illness or the number of workdays they missed.

The findings suggest vitamin D should join the list of therapies that researchers have deemed "ineffective for preventing or treating upper respiratory tract infections in healthy adults," Dr. Jeffrey Linder, of Brigham and Women’s Hospital in Boston, wrote in an editorial accompanying the study.

However, the study researchers noted that even the participants in their study who took a placebo had sufficient levels of the nutrient. People with a vitamin D deficiency may see more of a benefit from taking the vitamin, in terms of a reduced risk of colds, they said.

"Further research is required to clarify whether there is benefit from supplementation in other populations and with other dosing regimens," the researchers said.

The study and accompanying editorial will be published Wednesday (Oct. 3) in the Journal of the American Medical Association.

Earlier studies suggested a link between low vitamin D levels and an increased risk of respiratory tract infections such as tuberculosis; however, whether the vitamin reduced the risk of colds was not clear.

In the new study, 322 healthy adults were randomly assigned to receive either a high dose of vitamin D monthly for 18 months, or a placebo.  The vitamin D dose was 100,000 international units (IU) per month, which equates to 5 times the daily recommended allowance of 600 IUs a day for an adult.Participants were evaluated each month, and contacted the study researchers if they had cold symptoms. Samples from their noses were also tested for respiratory viruses.

Those who took vitamin D had increased blood levels of the vitamin that stayed constant throughout the study.

However, taking vitamins did not reduce the incidence or severity of colds in a meaningful way.

There were 593 upper respiratory tract infections in the vitamin D group and 611 in the placebo group. People in the vitamin D group had an average of 3.7 upper respiratory tract infections per person over the study period, compared with 3.8 per person in the placebo group.

It's not clear whether providing smaller, steady doses of vitamin D would have a different effect, the researchers said.

The study was conducted by researchers at the University of Otago in Christchurch, and was funded by the Health Research Council of New Zealand.

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Older people who take vitamin D supplements along with calcium may live longer than others, according to a new review of previous studies.

The researchers looked at data regarding the vitamin D intake  of more than 70,000 adults in their 60s and 70s. They found that people who took vitamin D, along with calcium supplements, were 9 percent less likely to die over a three-year period, compared with people who took neither supplement.

However, they found that taking vitamin D alone had no effect on mortality rates.

For every 151 people who took with daily vitamin D and calcium for three years, one life would be spared, according to the researchers' calculations.

The finding comes on the heels of several studies with conflicting results about the health benefits of vitamin D, including its possible effects on longevity. The new review is the largest of its kind, and included eight randomized controlled trials, said study leader Lars Rejnmark, of Aarhus University Hospital in Denmark. Such trials are considered the strongest type of scientific evidence.

The study confirms researchers' suspicions  that vitamin D may increase longevity, said Dr. Philippe Autier of the International Prevention Research Institute, who was not involved in the review.

Study participants were generally older people with health conditions, and possibly had inadequate nutrition. Therefore, it’s “not guaranteed that anyone in good health  who takes these vitamins would increase life expectancy,” Autier said.

In the review, the researchers found that 5.5 percent of the 35,412 people who didn't take vitamin D or calcium died during the study period, whereas 5.3 percent of the 35,116 people who took vitamin D died. 

Taking vitamin D, with or without calcium, had a significant effect on mortality rates only after three years; mortality rates were not significantly different among those taking the vitamin after one or two years, according to the study.

Vitamin D and calcium are important throughout life, because of their role in bone health, Rejnmark said. But he recommends people start paying particular attention to their intake "around menopause for women, and around the age of 50 for men."

While the review was based on studies of people who took supplements, Rejnmark said he does not believe the benefits would be any different for people who get the nutrients through food.

Autier noted that the greatest source of vitamin D is what the skin makes naturally when it is exposed to sunlight. People with darker skin tones, who are less able to produce vitamin D  in response to sunlight, should consider supplements as a viable option, he said.

A total of 87 percent of the studies' participants were female, but Rejnmark said this had no bearing on the results, and vitamin D and calcium are equally beneficial to both sexes in terms of preserving longevity.

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African-Americans are 25 percent more likely to die from cancer than white Americans are, and the reasons are numerous, including lower socio-economic status, poorer access to health care, and the cancer diagnosis coming at later, more deadly stages.

Still, health experts say these factors cannot fully explain the extent of disparities in survival for the most common cancers, such as breast, lung, colon and prostate cancers.

A paper published in the current issue of the journal Dermato-Endocrinology points the finger at a seemingly obvious but overlooked culprit: the sun.

The researchers' theory is that, in northern latitudes, the dark skin of African-Americans cannot absorb enough sunlight to generate adequate amounts of vitamin D, which is often called the "sunshine vitamin." The body uses ultraviolet rays from the sun to manufacture vitamin D in the inner layers of the skin.

Vitamin D is needed for strong bones; doctors nearly 100 years ago associated a lack of adequate sun exposure with rickets among child laborers, exemplified by bowed legs. Recent studies also have shown that low levels of vitamin D in the blood seem to contribute to a weak immune system and a host of diseases, such as cancer and multiple sclerosis. [ Infographic: The Power of Vitamin D ]

This lack of vitamin D could completely fill in the health disparity gap for cancer survival between white and black Americans, the researchers said.

Previous work by geneticist Rick Kittles at the University of Chicago suggests that upwards of 75 percent of African-Americans are deficient in vitamin D. Kittles says that African-Americans living north of the 37th parallel — just about anyplace north of central California, Texas, Tennessee or North Carolina — will have difficulty through most of the year absorbing enough sunlight to make vitamin D, because of the low angle of the rays reaching the Earth's surface.

Given this largely established fact, researchers Alan Peiris of East Tennessee State University and William Grant of the Sunlight, Nutrition and Health Research Center in San Francisco set out to look for a correlation between vitamin D and cancer death disparities. (In past research, Grant and a colleague suggested low levels of ultraviolet-B rays in Austria, paired with Mozart's nocturnal habits, may have led to vitamin D deficiency in the composer, who died at the age of 35.)

What they found in the new study is preliminary but warrants further investigation, they said. Relying solely on a scientific literature review, the researchers found that low vitamin D is independently associated with each of the cancer types for which an unexplained health disparity exists between African-Americans and white Americans.

Specifically, they found lingering disparities for 13 types of cancer after accounting for socioeconomic status, stage at diagnosis, and treatment: bladder, breast, colon, endometrial, lung, ovarian, pancreatic, prostate, rectal, testicular, and vaginal cancer; Hodgkin's lymphoma; and melanoma. For each one, there is a vitamin-D connection.

Few scientific studies have directly explored the link between cancer deaths and low vitamin D levels in African-Americans, though. One study published in the journal Cancer in 2011 indeed found that vitamin D deficiency contributes to excess African-American mortality from colon cancer. A Harvard study published in Cancer Epidemiology, Biomarkers and Prevention in 2006 found that African-Americans who are at risk for low vitamin D also had a higher risk for cancer death, particularly for digestive-system cancers.

The paucity of studies makes this a ripe topic for exploration, said Grant. If low vitamin D is the cause of this disparity in cancer deaths, thousands of lives could be saved annually by encouraging African-Americans to take a daily vitamin D supplement in the range of 1,000 to 4,000 IUs, he said. [ 9 Good Sources of Vitamin D ]

Peiris added that monitoring vitamin D levels should be routine. The issue becomes critical given that passive exposure from the sun simply is not enough for millions of African-Americans living in northern cities such as Washington, New York and Detroit. Air pollution filters sunlight, too; and many African-American children stay indoor for long hours, sometime over concerns of neighborhood safety.

Obtaining enough vitamin D through food, regardless of one's skin tone, can be difficult. Sources include fatty fish such as salmon, mackerel and wild catfish. At least the sources, aside from cod liver oil, tend to be tasty.

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