Vitamin Information Center

Research reports keep rolling in on the importance of vitamin D in our diet-beyond its familiar role in helping us to build strong bones. Here are some of the findings: Periodontal disease, in a dental study of 6,700 people from 13 to 90, the gums of patients with higher blood levels of vitamin D were 20 percent less likely to bleed. “The evidence on gingivitis and tooth loss suggests that vitamin D influences oral health by decreasing inflammation,” said Bess Dawson-Hughes, director of the Bone Metabolism Lab at the Human Nutrition Research Center on Aging at Tufts University.

Cancer. Studies by Reinhold Vieth at the University of Toronto have reported a substantial reduction in the rates of colon cancer as blood levels of vitamin D went up. Dr. Vieth suggests that vitamin D inhibits a mechanism by which cancer cells spread or it may boost the function of blood vessels or the immune system.

Diabetes. A number of studies have found that people with higher blood levels of vitamin D had a lower risk of diabetes than people with lower levels. Researchers have suggested that vitamin D seems to influence responsiveness to insulin.

Fitness. A study at the Wake Forest University School of Medicine found that people with low blood levels of vitamin D scored from 5 to 10 percent lower on tests measuring grip strength, balance and walking speed than those who had higher levels. Apparently vitamin D helps build and repair muscles as well as bones.

Longevity. People who take vitamin D supplements may also live longer, according to Sara Gandini, Ph.D., of the European Institute of Oncology in Italy, and Philippe Autier, M.D., of the International Agency for Research on Cancer in France. “The intake of ordinary doses of vitamin D supplements seems to be associated with decreases in total mortality rates,” they reported.

“The results are remarkable,” according to Edward Giovannucci, M.D., ScD., of the Harvard School of Public Health, in an editorial on vitamin D research in the Archives of Internal Medicine.

What to do. Adults should try to get 800 international units (IU) daily of vitamin D-or 1000 IUs a day if you are 70 or older. The average U.S. adult intake of vitamin D is 230 IUs daily, according to a study reported in the journal Nutrition Reviews. Vitamin D is available from sunlight, of course, and from foods such as fatty fish, eggs, fortified milk and fortified cereals as well as supplements.

-Sources: Bottom Line Health, CSPI Nutrition Action Letter, and Tufts University Health & Nutrition Letter

An adolescent’s vitamin K status could have important long-term implications on bone health, and a better status may protect them from osteoporosis later in life, suggests a new study.

An improved status of the vitamin was found to improve bone mineral content and bone mass in the whole body, according to the study with 307 healthy children with an average age of 11.2 published in the British Journal of Nutrition.

“As children grow the increase in bone mass may fail to keep up with the increase in height, or length of the bone, and as a consequence, this imbalance may result in fracture,” said lead author Marieke Summeren from University Medical Centre Utrecht.

“But the main threat of a long-term shortage of K vitamins is that peak bone mass may be compromised, and as we age and begin to lose bone density, the risk of fracture in later life is increased.”

Osteoporosis is characterized by low bone mass, which leads to an increase risk of fractures, especially the hips, spine and wrists. An estimated 75 million people suffer from osteoporosis in Europe, the USA and Japan.

Women are four times more likely to develop osteoporosis than men.

Potential reduction of osteoporosis has traditionally been a two-pronged approach by either attempting to boost bone density in high-risk post-menopausal women by improved diet or supplements, or by maximising the build up of bone during the highly important pubescent years.

About 35 per cent of a mature adult’s peak bone mass is built-up during puberty.

The new study followed the children for years and correlated vitamin K status, measured as a ratio of undercarboxylated osteocalcin (ucOC) to carboxylated osteocalcin (cOC), to bone mineral content (BMC) and markers of bone metabolism.

Osteocalcin is a vitamin K-dependent protein and is essential for the body to utilise calcium in bone tissue. Without adequate vitamin K, the osteocalcin remains inactive, and thus not effective.

Summeren and co-workers report that large variations were observed in the vitamin K status of the children, both at the start and end of the two-year study. Nonetheless, an improved vitamin K status over the time period, as was observed in 281 children, was associated with a significant increase in BMC.

“There are two types of vitamin K from dietary sources. Vitamin K1 is found in leafy green vegetables, and Vitamin K2, also called menaquinones, are predominately found in fermented cheeses, curd, and the fermented soy called natto,” explained co-author Leon Schurgers from VitaK and Cardiovascular Research Institute at the University of Maastricht.

“Vitamin K1 is mostly used by the liver where it is involved in the synthesis of certain blood clotting factors. Vitamin K2 is also equally active outside the liver, in tissues including bone. Thus it is important to have good sources of both types of vitamin K!”

The research adds to a growing body of science linking the vitamin to improved boned health, particularly in post-menopausal women. The Maastricht-based researchers previously reported that daily supplements of vitamin K2 maintained hipbone strength in postmenopausal women, while placebo led to weakening (Osteoporosis International, doi: 10.1007/s00198-007-0337-9).

The double-blind, placebo controlled study followed 325 healthy women with no osteoporosis for three years and also found that vitamin K2 supplements boosted the women’s bone mineral content (BMC), compared to placebo.

The new study also included researchers from VU University Medical Centre and the Danone Research Centre Daniel Carasso in France.

Source: British Journal of Nutrition
Published online ahead of print, doi:10.1017/S0007114508921760
“Vitamin K status is associated with childhood bone mineral content”
Authors: M.J.H. van Summeren, S.C.C.M. van Coeverden, L.J. Schurgers, L.A.J.L.M. Braam, F. Noirt, C.S.P.M. Uiterwaal, W. Kuis, C. Vermeer

Cod liver oil, a long-used source of vitamin D, may have the unexpected effect of lowering bone mass, a new study suggests.Norwegian researchers found that among more than 3,000 middle-aged women, those who took cod liver oil as children generally had lower bone mass than women who had not used the fish oil.

Because sunlight is needed to trigger the synthesis of vitamin D in the skin, people in Nordic countries are at particular risk of vitamin D deficiency. Cod liver oil is a traditional source of supplemental vitamin D, and is still widely used in Norway, where few foods are fortified with the vitamin.

Many people also take cod liver oil as a source of heart-healthy omega-3 fatty acids, or to ease arthritis symptoms.

Given the role of vitamin D in maintaining healthy bones, the new findings are “unexpected” and “paradoxical,” the researchers note in the American Journal of Epidemiology.

They speculate, however, that the high vitamin A content in cod liver oil could be to blame.

Vitamin A accumulates in body fat, and excessive levels may have a negative effect on bone metabolism and actually raise fracture risk, explained Dr Siri Forsmo, the lead researcher on the study and an associate professor at the Norwegian University of Science and Technology in Trondheim.

Too much vit A to blame
It’s possible that cod liver oil, on top of the traditionally vitamin A-rich Norwegian diet, provided some of these women with too much of the nutrient, Forsmo told Reuters Health.

Since 2002, Norway has required that cod liver oil producers cut the supplement’s vitamin A content by 75 percent - from 3,300 International Units per dose to 825 IU. Forsmo said she is unaware of any other countries that have made similar moves.

In the US, the recommended daily intake for vitamin A is 3,000 IU for men and 2,310 IU for women; for children, the recommendation is between 1,000 and 2,000 IU per day.

In contrast to the US and certain other countries, where milk and many breakfast cereals are fortified with vitamin D, relatively few foods in Norway have added vitamin D, Forsmo noted. Butter, margarine and one type of low-fat milk are the exceptions.

So cod liver oil remains a major source of vitamin D there, Forsmo said, adding that she still takes it during the winter.

Importantly, the researcher noted, the current study looked at bone mass, and not whether women who used cod liver oil as children actually had a higher rate of bone fractures. That is a question for future studies. - (Amy Norton/Reuters Health)

SOURCE: American Journal of Epidemiology, February 15, 2008.