Vitamin Information Center

Vitamin C might not keep you from catching a cold, but not getting an adequate amount of the vitamin can keep you from burning fat.

A study from Arizona State found that folks with low-blood concentrations of vitamin C, who walked on treadmills for a 60-minute session, burned 25 percent less fat than other participants with adequate amounts of C. Fortunately, a simple dose of vitamin C remedied the lackluster fat-burning potential of the participants. Vitamin C is necessary for creating the compound carnitine, which helps turn fat into fuel.

While the recommended daily intake of vitamin C is low, 90mg for men and 75mg for women, many health advocates recommend larger daily doses. Holistic health doctor Andrew Weil recommends 200mg daily, while the Linus Pauling Institute (named for the scientist that made the vitamin famous) recommends 400mg daily. The health team at Real Age recommends consuming 1,200mg daily between foods and supplements.

On this note, I am going to add some strawberries to my cereal tomorrow morning since a half cup contains 42mg of vitamin C.

Men who have their diet based on green vegetables, fruits and lentils have a higher chance of fathering a healthy child, a new research shows.

Scientists at the University of California, Berkeley and the Lawrence Berkeley National Laboratory found that men with relatively low levels of folate (a B Vitamin) had increased risks for sperm containing either too few or too many chromosome, a condition known as aneuploidy. This condition is connected to failure to conceive, miscarriages, and children born with conditions such as Down’s syndrome, Turner’s syndrome and Klinefelter’s syndrome.

“We looked at sperm to find different kinds of genetic abnormalities. The abnormalities we looked at here were having too few or too many chromosomes,” lead researcher Brenda Eskenazi, a professor of maternal and child health and epidemiology and director of the Center for Children’s Environmental Health at Berkeley’s School of Public Health said, according to the Washington Post.

The researchers analyzed sperm samples from 89 healthy, non-smoking men and questioned them about their daily intake of zinc, folate, vitamin C, vitamin E and beta-carotene. They found men with the highest intake of folate or folic acid (between 722 and 1150 micrograms a day) had 20 percent to 30 percent lower frequencies of aneuploidy compared to men with a lower intake. No correlation was made between the other vitamins and sperm aneuploidy.

The current recommended daily intake of folate for men over the age of 19 is 400 micrograms. Health experts recommend women of childbearing age maintain a healthy intake of folate because it is essential for healthy fetal developmental and to prevent neural tube birth defects such as spina bifida or anencephaly (severe type of brain damage). That’s the reason why folic acid is now added to bread, cereal, flour and other grain products in the U.S.

This study is the first to “say that male diet may be important for healthy offspring as well.”

“The emphasis related to the birth of a healthy baby has been weighted towards the health and diet of women, not just during pregnancy, but before. What we’re finding now is that a nutritious diet, specifically folate intake, may be beneficial for men as well when it comes to producing healthy offspring,” Dr. Eskenazi said.

She also adds that if other studies confirm her team’s findings of the link between folate intake and aneuploidy, scientists may recommend men tale folic acid for at least three months before trying to conceive.

The idea that diet can improve sperm quality is less well established. “There is increasing evidence from a number of studies to suggest that dietary factors can correlate with sperm health. The story so far suggests that dietary factors won’t help you make more sperm, but good diet might just improve that quality of the ones that are made,” said Dr. Allan Pacey, senior lecturer in andrology at the University of Sheffield and honorary secretary of the British Fertility Society, BBC News reported.

The study findings are published in the March 20 issue of the journal Human Reproduction.

People dealt with vitamin D deficiency at the turn of the 20th century. Who ever thought we’d be talking about rickets in 2008?

By Jennifer Fisher Wilson

Despite its familiarity, vitamin D is pretty puzzling. Not really a vitamin at all, it is actually a fat-soluble nutrient that is a prohormone (a precursor substance to a hormone). Milk is fortified with it, but it does not come in most other dairy products like cheese, yogurt, and ice cream, and it occurs in significant levels naturally in only a few foods like fatty fish and fish oils. To fulfill the recommended daily intake with milk alone may take as much as 6 to 8 glasses, far more than most people drink, and so most people get the majority of their vitamin D from sun exposure. But wearing sunscreen significantly impairs the sun’s ability to activate vitamin D — wearing SPF 8 can reduce the skin’s ability to produce vitamin D by about 95 percent.

Until recently, nobody thought much about whether they got enough vitamin D from drinking milk or other foods or from the sun. But getting the so-called “sunshine vitamin” does matter because it plays a far more complex role in our health than anyone could have imagined just a decade or two ago.

Of course scientists have known for a long time that vitamin D is important to keeping bones strong. Vitamin D signals the body to absorb calcium from food and so maintains normal blood calcium levels. When there isn’t enough vitamin D, the body doesn’t absorb enough calcium from the diet, and it instead removes calcium from stores in the bones, making them weak or brittle. Bone diseases linked to vitamin D deficiency include: rickets, the bone-deforming and potentially fatal condition that afflicted children for ages; osteomalacia, a muscle-weakening, bone-softening form of rickets that occurs in adults; and osteoporosis, the brittle bone disease.

Vitamin D’s role in bone health was pretty much the limit of scientific understanding back in the early 1990s when I met Michael F. Holick, professor of medicine, physiology, and biophysics at Boston University School of Medicine. The endocrinologist and vitamin D specialist met me in his office and told me about the discovery of vitamin D during the industrial age, when smoggy skies blocked the sun’s rays from people’s skin and led to an epidemic of rickets. Rickets mostly disappeared once doctors started prescribing cod liver oil and sunshine, and especially once governments mandated that milk be fortified with vitamin D in the 1930s. It doesn’t take much vitamin D to prevent rickets.

In between talking about vitamin D, Holick talked about his schooling in Wisconsin, about ice skating with his wife on their first date, about his adventures in industry developing a vitamin D-based psoriasis lotion, and about the glorious view of Boston from his office window. He introduced me to patients in his clinic that had bone disorders like osteoporosis. And he explained how rickets was now mostly confined to family pets like his own family’s iguana. Holick cured his captive reptile by serving it cream cheese and lettuce sandwiches, and by shining a sun lamp into the cage.

I was taken with this charismatic, energetic scientist. For a while I even tried to sell magazines an article on how to save pet iguanas from rickets. I was, not surprisingly, unsuccessful. But given time, a far larger and richer story about vitamin D has emerged, and much of it has come out of Holick’s office.

For one thing, rickets never really went away. Soon after our meeting, medical journals started reporting on cases diagnosed among children living in northern cities, as well as on a rise in cases of its adult form, osteomalacia. Scientists started to wonder if vitamin D deficiency was more common than they thought. A research group in Baltimore found that more than half of homebound adults over the age of 65 were severely vitamin D deficient.

To get sense of the scope of vitamin D deficiency in the wider community, Holick and colleagues measured vitamin D levels in younger people living in Boston. They found that it was surprisingly common. About 36 pecent of young adult city dwellers that worked office jobs were vitamin D deficient at the end of winter, and 11 percent were so at the end of summer. The emerging research also indicated that people with darker skin were more likely to be deficient than people with lighter skin, because they needed more time in the sun to convert vitamin D into an active hormone. Also, people who were overweight were more likely to be deficient, a result of the vitamin D becoming harder for the body to access from fat cells.

Suddenly, people again started paying attention to long-taken-for-granted vitamin D. Holick and others declared that the country was in the middle of a silent epidemic of vitamin D-deficiency, and warned that the health effects could be subtle but far-reaching. To combat the epidemic, Holick came out in 2004 with a book called The UV Advantage, which recommends sun exposure of 15 to 20 minutes a day while de-emphasizing skin cancer concerns. Some of his colleagues recoiled from his advice, feeling that people would take it as permission to sunbathe. After it also came to light that Holick received funding from the Indoor Tanning Association, he was forced to resign from the dermatology department at Boston University Medical School. (He still holds other positions there.)

Holick defended himself, saying his situation was no different than other doctors taking pharmaceutical money, and pursued his studies. Today he is still considered a leading expert in demystifying vitamin D. Building on what is now more than 30 years of research, last year he published a capstone review article in the New England Journal of Medicine that delineated just how important vitamin D is to the healthy body — and how many people need more of it.

Scientists now understand that most tissues and cells in the body have vitamin D receptors, including several that possess the machinery to convert it to the active form in the body. It is also now commonly believed that vitamin D helps maintain muscle strength and immune capability while also decreasing the risk for various chronic illnesses, including cardiovascular diseases, autoimmune diseases such as diabetes type 1 and multiple sclerosis, and various cancers including colon, ovarian, breast, and prostate. Among the evidence is the fact that the further away from the equator — and the sun — that people live, the greater their chance of developing some of these health problems. (Some very northern cultures like the Inuit naturally compensate for the reduced sun exposure with a diet rich in fish oil.)

The work is not without its doubters. A National Cancer Institute study based on survey data has found no relationship between vitamin D levels and the overall risk of dying from cancer based on a 10-year follow-up, although it did find an association between decreased risk of colorectal cancer death and higher vitamin D levels. The findings are not completely clear because of the complex contributions to risk from total diet and lifestyle.

Large studies are also still needed to confirm the strength of the links between vitamin D and chronic diseases. In recent years such studies of several other vitamins turned out to be disappointing for their role in improving health. But remember, vitamin D is not a classic vitamin, and so these vitamin studies may not be relevant.

Only time and additional studies will elucidate further whether we should be paying more attention to vitamin D. Maybe eventually it will become clearer whether we should be worrying less about skin cancer and more about whether our skin is soaking up enough rays to fulfill our sunshine vitamin quota.

In the meantime, I wonder if Holick still has that iguana — they can live for 20 to 30 years — and whether it really beat rickets for good. • 19 March 2008

SOURCES: “Vitamin D deficiency in homebound elderly persons.” Gloth FM 3rd, Gundberg CM, Hollis BW, et al. JAMA. 1995;274:1683-6. “Vitamin D insufficiency among free-living healthy young adults.” Tangpricha V, Pearce EN, Chen TC, & Holick MF. Am J Med. 2002;112:659-62. “Vitamin D Deficiency.” Holick MF. N Engl J Med 357; 266-81. Prospective Study of Serum Vitamin D and Cancer Mortality in the United States, Freedman DM, Looker AC, Chang S-C, & Graubard BI, J Natl Cancer Inst 2007; 99:1594-1602

A vitamin is a small organic molecule essential for normal metabolism and growth. Since it cannot be synthesized by the body in adequate amounts, it must be obtained in the diet. According to this definition, vitamin D isn’t even a vitamin, since very large amounts can be synthesized in the skin. However, many if not most people don’t make enough vitamin D and need to consume it in food or supplements.

Vitamin D has been in the news a lot partly because of this very problem. It turns out that the skin can synthesize vitamin D only if it is exposed to adequate amounts of sunlight. So, people who don’t get a lot of sun, such as patients in hospitals, or elderly people living in institutions, are often deficient in vitamin D. Even healthy active adults, who live in northern latitudes, such as in New England, are frequently deficient in vitamin D, as are people who live in sunny climates but habitually cover their skin. The UV rays that produce vitamin D in the skin are the very same UV rays that produce sunburn and that are blocked by sunscreen, shade, clothing and dark skin pigmentation, so even people who are active outdoors can be deficient in vitamin D.

Why do we care? Vitamin D is essential for regulating blood calcium levels and for promoting calcium absorption to maintain strong bones. It also regulates certain immune functions and can decrease the proliferation of normal and cancerous cells. This may explain why low vitamin D levels are associated with increased risks of certain kinds of cancer and other diseases, and why vitamin D supplementation has been shown to decrease the risk of some cancers in post-menopausal women.

Fortunately, it is easy to supplement vitamin D levels. The recommended daily intake of vitamin D3 is 400 IU daily, although many experts recommend intake of 800 IU daily for children and adults. There are several good dietary sources: a 3.5 ounce serving of fresh wild salmon has between 600 and 1000 IU of vitamin D3 (farm-raised salmon may only contain 100 to 250 IU in the same size serving); canned tuna contains about 230 IU in a 3.6 ounce serving (which is a little more than half a can). Fortified milk, yogurt, cheese, orange juice and breakfast cereals often contain 100 IU of vitamin D3 per serving. Over-the-counter supplements containing vitamin D3 are also widely available.

Finally, there is the option of careful, sensible sun exposure. It is difficult to calculate “adequate” sun exposure because the amount of sun needed for a person to synthesize enough vitamin D varies with season, latitude, time of day and skin pigmentation. These factors affect the amount of UV that reaches and is absorbed by the skin. Also, older skin has less capacity to synthesize vitamin D. For most people, 5 to 10 minutes of sun exposure on the arms and legs twice a week may be enough to maintain vitamin D levels. With sun exposure, moderation is key; too much UV exposure and sunburns increase the risk of skin cancer. So, it is still important to avoid excessive sun exposure and to use sunscreen daily to minimize this risk.

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.