Vitamin Information Center

Oily fish: Mackerel is a good source of vitamin D

Vitamin D may offer protection against the most common form of diabetes.

New research shows that, in particular, men with the highest blood level of the vitamin were 72 per cent less likely to develop type 2 diabetes.

There was a reduced effect among women.

Scientists in Finland monitored several thousand people, aged 40 to 74, for 22 years, during which time 412 developed the disease.

Results showed that those with higher levels of vitamin D had the lower risk of diabetes.

It is thought that low levels of vitamin D affect the body’s ability to produce insulin.

Diabetes type 2 is a growing health problem.

There are 1.9 million adults in the UK with diagnosed diabetes, and it is estimated there are another 589,000 unidentified sufferers.

Risk increases with age - less than one per cent of people under 34 have diagnosed diabetes compared with 10 per cent aged 75 and over.

Mothers everywhere probably will not be surprised to hear that they were right. Drinking your milk is, of course, good for you. Not only is milk chock-full of calcium, most milk has been fortified with vitamin D — and both nutrients are necessary for good bone health, among other things. And in recent years, a growing body of research has caused experts to conclude that many adults, particularly those over 50, are not getting enough calcium or vitamin D, says Dr. Michelle Germain, a part-time faculty member in the Department of Gynecology and Division of Urogynecology at Greater Baltimore Medical Center.

What is vitamin D?

Vitamin D is a fat-soluble vitamin. It is absorbed from food through the GI [gastrointestinal] tract and also is made by the body. The body needs it because it helps with absorption of calcium and phosphorus, both of which the body needs for bone health.

You said that, in addition to absorbing vitamin D from food, the body also manufactures it. How does the body make vitamin D?

The skin manufactures the vitamin D with the help of ultraviolet rays from the sun. So you need sun exposure to make it. Once we have vitamin D in our bodies, the liver and the kidneys convert the vitamin D into the active form that is used for bone health.

What foods contain vitamin D?

Cod-liver oil is the best way to get vitamin D, but we don’t see many people taking that these days. So other really great sources of vitamin D are fish, such as salmon, mackerel and tuna, and vitamin D-fortified foods, such as dairy products and cereals.

What happens if we don’t get enough vitamin D?

You can become vitamin D-deficient. Children can develop “rickets,” in which the bone doesn’t properly mineralize, and the children develop very soft bones and deformities of their skeleton. In adults, too little vitamin D can lead to osteoporosis. [Too much vitamin D, on the other hand, can make the intestines absorb too much calcium.]

How pervasive is rickets?

In developed countries like the United States, it is pretty uncommon because we fortify so many foods with vitamin D. But there has been a resurgence of rickets in African-American infants and children in poorer states, especially in the South such as Tennessee and Mississippi. The resurgence is being caused by poverty and poor nutrition. It also has to do with darker pigmentation of the skin, which converts sunlight less effectively into vitamin D.

Rickets also is more prevalent in immigrants from Africa, the Middle East and Asia because of their diets before they arrive in the United States and because they may not have enough money to afford good nutrition once here. Again, if they have darker skin, they are not converting UV rays into vitamin D as effectively as people with lighter skins.

Are there other populations for which vitamin D is particularly important?

Older women. If older women are vitamin D-deficient then they are at increased risk for osteoporosis. This is of special concern for menopausal women because once their estrogen levels drop, they begin to lose bone. The vitamin D is necessary to absorb calcium and utilize it in bone formation. And people who have any kind of gastrointestinal illness like Crohn’s disease or celiac disease or any kind of liver disease also are at increased risk for vitamin D deficiency.

Are there any symptoms of vitamin D deficiency that might occur before bone loss?

Unfortunately, there are really no symptoms of it until you are diagnosed with osteoporosis.

What do you tell your patients about vitamin D?

Children and young adults need to consume a diet that is rich in vitamin D-fortified foods. At least 15 minutes of exposure to sunlight twice a week should be adequate to make sufficient amounts of vitamin D. But I also tell them that if you put on sunscreen with an SPF greater than 8, it can interfere with making vitamin D, so diet is very important. Particularly in winter, they should concentrate on eating a diet with plenty of vitamin D-rich foods.

What do you tell adults?

If a woman has osteoporosis, she should ask the doctor if she is potentially vitamin D-deficient. Very often, after a woman has a hip fracture, we check her vitamin D level, and it turns out to be ridiculously low. So, if you have osteoporosis or a fracture, ask about your vitamin D level.

How much vitamin D do we need?

Last year, the National Osteoporosis Foundation released new recommendations about vitamin D. The National Institutes of Health also are due to release this spring new guidelines. According to the National Osteoporosis Foundation, adults under age 50 need 400 to 800 IU [International Units] of vitamin D3 daily. [Also called cholecalciferol, vitamin D3 is the kind of vitamin D that best enhances healthy bones.] And menopausal women and adults over the age of 50 need 800 to 1,000 IU of vitamin D3 daily.

Sixty-year-old Darlene Yates has had two hip replacements, a knee replacement and this past year shattered her left femur while she was walking in her neighborhood. Her diagnosis seemed obvious — osteoporosis. But it turns out she had bone weakness caused by a vitamin D deficiency.

“I thought with my age and all my broken bones that I definitely had osteoporosis,” Yates said. “The low vitamin D levels really took me by surprise.”

Vitamin D promotes the absorption of calcium and phosphorus. It regulates how much calcium remains in the blood and how much makes its way to the bones and teeth. It also has been found to reduce the risk of breast, colon and ovarian cancer. Vitamin D deficiency contributes to osteoporosis by reducing calcium absorption and osteoporosis is an example of the long-term effects of vitamin D deficiency.

In a recent review of women with osteoporosis hospitalized for hip fractures, 50 percent were found to have signs of vitamin D deficiency. Low levels are most often seen in older women; however, times appear to be changing.“I am seeing many active, young women and men who have dangerously low vitamin D levels,” said Dr. Kenneth Mathis, chairman of orthopedic surgery with The Methodist Center for Orthopedic Surgery. “I believe if these people begin taking the daily recommended amount of vitamin D when they are younger, and get their levels tested regularly, that they might be able to prevent osteoporosis and certain cancers when they get older.”

Sources of vitamin D include fortified milk, cod liver oil, fish such as sardines, tuna, salmon and mackerel, some yogurt and breakfast cereals, and the sun. However, if you wear an SPF of eight or more, you will have a tough time converting the sunlight into vitamin D.

Most adults over age 50 need to take a daily supplement of vitamin D if they don’t think they are getting the daily recommended amount. Adults under age 50, including pregnant women, need 200 IU of vitamin D daily. A person over age 50 needs 400 IU daily and it goes up to over 600 IU at age 70.

Mathis says taking the correct amount is important because too much vitamin D can be toxic. Vitamin D is stored in the liver and in the fat tissue. When you take too much it cannot leave the body as easily as water soluble vitamins such as vitamin C. The excess vitamin D can lead to too much calcium in the blood, which can cause kidney stones and/or kidney failure.

Yates has begun a strict vitamin D regimen to build up her levels. She says she has more energy than she ever has and is feeling better.

“I’m hoping that I can get to where I don’t break any more bones and have to have any more surgeries,” Yates said. “If I would have known about the link between vitamin D and bone weakness 40 years ago, you can bet I would have done something about it.”

Medical and nutrition experts offers some ways to get more vitamin D in your life:

The National Institutes of Health recommends getting about 10 minutes of sun exposure on your arms, legs and hands two to three times a week without using sunscreen. Eat oily fish such as salmon or mackerel. Just 3.5 ounces of either provides 90 percent of the daily value for vitamin D.

Eat vitamin D-fortified foods such as milk, some cheeses, yogurts, juices and cereals. Check labels to see which ones contain vitamin D.

Take a vitamin D supplement. The government’s current recommendation for vitamin D is 200 IUs (international units) a day for people up to age 50, 400 IUs to age 70, and 600 IUs for people over 70. Although some scientists believe these dosages are too low, most caution not to exceed 1,000 IUs daily from supplements, because too much vitamin D can be toxic.

Take vitamin D-3 (cholecalciferol form) instead of D-2. Vitamin D-3 is more potent and more easily absorbed by the body than D-2.

– R.J. IGNELZI

Unless you are lucky enough to live in a location that enjoys year-round sunshine and mild temperatures, you are likely to experience a drop in your Vitamin D levels during the winter. Getting direct sun on your skin is one of the chief ways in which you get vitamin D. With the colder weather, we spend less time outdoors and when we are outdoors, we try to cover as much skin as possible.
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Ninety percent of the vitamin D in your body is a result of your skin’s exposure to ultraviolet light. This makes vitamin D one of the only vitamins you don’t really have to pay for. The other 10 percent can come from a supplement or certain foods, but really a 15-minute walk is more beneficial than either of these things.

Although this is the exact opposite of what skin cancer warnings tell us, limiting that exposure to 10 to 15 minutes will keep you safe and full of vitamin D. It is a soluble fat, which means it is stored and dissolved in body fat rather than water soluble, which is not stored. Vitamin D stays in your body for months and that means taking the 15-minute walk in the sunshine will provide you with the beneficial affects of vitamin D for months to come.
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