Vitamin D: Is It a Miracle? (Part 1)

What vitamin helps keep bones healthy, helps ease depression, and may prevent heart attacks, multiple sclerosis, rheumatoid arthritis, and Type 1 diabetes? You guessed it: vitamin D.


The media has given vitamin D an awful lot of attention lately, almost to the point of overdoing it. It seems like this oft-forgotten vitamin has appeared out of the woodwork with its head held high, on a crusade to battle all kinds of diseases. Many health experts are even claiming that the recommended intake for vitamin is too low. Let’s take a closer look and learn what vitamin D is all about.

What is Vitamin D?
Vitamin D, a fat-soluble vitamin, is sometimes called the “sunshine vitamin” because it’s made in the body when ultraviolet rays from the sun come in contact with the skin. Surprisingly, perhaps, this vitamin isn’t found in too many foods—salmon, mackerel, tuna, sardines, and cod liver oil are the main sources. Milk, margarine, and some cereals, yogurts, and orange juices are fortified with vitamin D; small amounts are also found in eggs and liver. Of course, vitamin D is available as a dietary supplement as well.

Vitamin D has to undergo some changes, biologically, before it can be used by the body. When you ingest vitamin D from food or supplements, or when you obtain vitamin D from the sun, the vitamin undergoes a conversion in the liver to a form called 25-hydroxyvitamin D. Then, this form of the vitamin gets converted in the kidneys to the active form that the body can actually use, called 1, 25-dihydroxyvitamin D, or calcitriol. Calcitriol is actually a steroid hormone, and vitamin D is sometimes called a precursor hormone, or the building block, for calcitriol.

What Does Vitamin D Do?
Miracles aside for a moment, one of vitamin D’s main roles in the body is to help maintain bone health. Vitamin D is required for calcium absorption in the intestines and to maintain the balance of calcium and phosphate in the body for bone mineralization.

We also need vitamin D for normal bone growth. You’ve probably heard of rickets, a bone disease that occurs in children due to a deficiency of this vitamin. Insufficient vitamin D leads to softening and weakening of bones. Rickets can manifest itself in the form of bow legs or a curving of the spine.

Osteomalacia is bone-softening that occurs in adults. Bone pain and muscle weakness are the main symptoms of this disease. Osteomalacia isn’t the same as osteoporosis, however. Osteomalacia results from a deficiency of vitamin D, which, in turn, affects the building of bones. Osteoporosis affects already-constructed bones.

Besides bone health, vitamin D plays a role in the function of the immune system and helps to reduce inflammation. Also, vitamin D is found in just about every cell in the body, meaning that this vitamin is needed for cell differentiation and growth.

How Much Vitamin D Do You Need?
Here’s where part of the debate comes in. The Dietary Reference Intakes (DRIs) for vitamin D vary, based on age:

  • Birth to 50 years: 200 international units (IU)
  • 51 to 70 years: 400 IU
  • 71+: 600 IU

Pregnant and lactating women need 200 IU of vitamin D.

Three and a half ounces of salmon contains 360 IU, 3 ounces of canned tuna in oil contains 200 IU, and 8 ounces of fortified skim milk contains 98 IU. Cod liver oil tops the charts at 1,360 IU per tablespoon; however, cod liver oil has its own set of potential problems, so it’s really not recommended to take this unless you’re careful and obtain it from a reputable source.

Are the DRIs for vitamin D high enough? The feeling from the medical community lately is that the established requirements for vitamin D aren’t enough, and that an intake between 800 to 1,000 IU would be better to aim for, especially for people at risk for deficiency, including older adults, those with limited sun exposure, those with gastrointestinal disorders, and people with darker skin.

More on vitamin D next week!

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  • CalgaryDiabetic

    Dear Amy.

    This is good timing for this article for all Canadians and most of your Yankee population. I was tested for vitamin D at the end of last May and was found deficient. Can you imagine what the reading would have been in February. I eat a lot of fish most Canadians would rather die. The milk in Canada is fortified with vitamin D but since my Diabetes I no longer drink prodigious amounts. Not sure what else is of course I eat oranges which are not and never drink orange juice. The test was done after a month of normal diet with no vitamin D tablets ingested.

    The GP suggested 1000 units per day all year around with maybe the exception of July, August and September. This July is rained a lot of the time. This may apply to the Canadians that live were banana plants survive (Yes I have seen them in certain areas of Vancouver). A friend of mine living in this semi-tropical paradise would get really depressed in winter months. Maybe vitamin D would be better than Wellbutrin.

  • dd0706

    After my doctor checked my vitamin D level and found me deficient, he prescribed 10,000 iu per day. After 6 months, with no other changes in my diabetes plan, my A1C dropped from 6.7 to 5.9. My D level is up at the high end of normal and the leg cramps I used to suffer are also gone.

  • Leonie Watt

    I to, recently had my Vitamin D levels checked and was found to be deficient. I come from sunny Australia, so this was some what of a surprise. But I am very fair skinned and tend to stay out of the sun. I am now taking Vitamin D supplements for the next 6 weeks in the hope to build up my Vitimin D levels and after that time I will have another blood test to see if my levels have improved. I jokingly call them my “sunshine pills”.

  • Linda

    My MD (internist/endo) put me on vitamin D about 6 months ago because I was deficient. I never realized that vitamin D deficiency can cause so much damage

  • Barbara

    I was once told that you “must” take another vitamin OR food supplement WITH Vitamin D.. If so, which one?? Thanx

  • acampbell

    Hi Barbara,

    Vitamin D is needed for calcium absorption in the gut, which is one reason that many calcium supplements also contain vitamin D. You could also eat a calcium-rich food, such as yogurt, milk, or leafy greens, with a food or supplement that contains vitamin D.

  • acampbell

    Hi Leonie,
    Just goes to show that sunlight is a prime source of vitamin D. And I like your nickname of “sunshine pills”!

  • Harry…………………………

    I started taking vitamin D about 1 and half years ago. I immediately felt my skin warm. (Something unusual for Buffalo) Then all my meds for two disabilities started working in synergy. Now even my cholesterol has somewhat lowered.

  • Leslie K

    Vitamin D is FAT SOLUBLE, so it is important to be tested for levels PRIOR to ANY supplementation. There are certain subsets of people for whom vitamin D deficiency is common.

    My son, who is on an amino-acid formula diet due to a GI/Immune disease (Eosinophilic Esophagitis) is in one of those subsets.

    “Vitamin D deficiency is more common in strict vegetarians (who avoid vitamin D-fortified dairy foods), dark-skinned people, alcoholics, and people with liver or kidney disease. People with liver and kidney disease can make vitamin D but cannot activate it.

    Vitamin D deficiency is more common in people suffering from intestinal malabsorption, which may have occurred following previous intestinal surgeries, or from celiac disease. People with insufficient pancreatic function (e.g., those with pancreatitis or cystic fibrosis) tend to be deficient in vitamin D. Vitamin D deficiency is also common in individuals with hyperthyroidism (Graves’ disease), particularly women.”

    Vitamin D Information