The Vitamin D Story. An Old Dog with Some New Tricks.


Mention Vitamin D to most people and they will try not to yawn. One of the less glamorous vitamins it is known as the sunshine vitamin because our skin, when exposed to the ultraviolet rays in sunlight, manufactures vitamin D. Not unexpectedly sunscreen on the skin blocks this production. The remainder of our body’s supply of this vital vitamin comes from a limited number of foods. The main role of vitamin D is thought to promote intestinal absorption of calcium. Calcium is crucial for bone development. Children without enough vitamin D suffer from a disorder of abnormally soft bones known as rickets resulting in extreme bowing of the legs and dental problems. Adults with vitamin D deficiency can develop low blood calcium levels, osteoporosis, as well as softening of the bone known as osteomalacia.

Recent studies however, have shown that Vitamin D may serve many other important functions in the body. Several investigators found that low Vitamin D plays a role in “seasonal affective disorder” which is a form of depression occurring during the winter when little sunlight is available. Low levels of Vitamin D can be found in Alzheimer’s patients, and some researchers believe low levels of this vitamin may contribute to loss of muscle tone and frequent falling in the elderly. Recent studies link low Vitamin D levels in pregnant women to the development of preeclampsia (toxemia of pregnancy). Vitamin D was also shown to help lung function and to delay a common but serious eye disorder known as macular degeneration.

Studies also show that Vitamin D may help benefit the immune system and help reduce the incidence of certain cancers. Recent studies suggest vitamin D may help prevent or delay colon, breast and ovarian cancer. One study showed that 1000 IU of vitamin daily could cut the risk of colon cancer by 50% while another study found a similar risk reduction for pancreatic cancer in those who took vitamin D supplementation. Results of these studies are still inconclusive and require verification but point to an important role of vitamin D in cancer protection.

Until recently the recommended daily allowance of Vitamin D was 400 IU. Some researchers now state that this amount is too low and advocate a daily intake of 1000 IU. Vitamin D can be found in Vitamin D supplemented milk, many multivitamins and calcium supplements. Yoghurt, margarine, cooking oils, breakfast cereal and bread may also be fortified with vitamin D. Oily types of fish such as salmon, tuna, and sardines are excellent sources of vitamin D. In particular the fish liver stores much of the vitamin, hence “cod liver oil” is an excellent vitamin D source.

The vitamin D we ingest in pills and food is an inactive form of the vitamin which then must be activated in the kidney. For this reason those with kidney disease frequently must receive medication with activated vitamin D to prevent bone disease or other conditions related to low calcium levels in the blood.

A note of caution about vitamin D is sounded by some experts. While there is still plenty of debate about the amount of vitamin D which could be toxic, most authorities believe that up to 2000IU daily should be safe.

Only you and your doctor can decide on what medical treatments are best for you. The articles on metabolism.com such as this one are meant for educational purposes only and should not be used to guide you in your medical care. Speak to your health professional before undertaking to change or initiate medical treatment plans.

Gary Pepper M.D.
Editor-in-Chief
Metabolism.com

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  • annette

    I had a Bilio Pancreatic Diversion surgery done in 1990. My Vitamin D level is low, at 15.
    My Dr. has me on 50,000 iu of Vit D every other day, 4,000 iu on the other days.

    May I ask you, what is your opinion on this amount of Vit. D. The 50,000 iu capsules are by prescription.

    Thanks so Much,

    AS

  • Dr. G. Pepper

    Vitamin D deficiency is a serious problem and has been largely overlooked in the general population until recently. Vitamin D is not only important for bone health but we are learning it is important for the immune system and may help protect against certain cancers. In my medical practice in Florida I am finding an alarming number of my patients with very low and borderline low levels of Vitamin D that were totally unexpected. I assume it is because everyone knows that sunlight is bad because it causes wrinkles and skin cancer. The further north you live the weaker the sunlight so the incidence of vitamin D deficiency is higher.

    Until recently the recommended daily Vitamin D allowance was 400 IU but recently this was increased to 800 IU and some authorities recommend higher amounts.
    10,000 IU levels daily for the average normal person is thought to be an upper limit before toxicity can be seen. Vitamin D is a fat soluble vitamin so in people who have problems absorbing fat, such in your case after intestinal bypass surgery, higher amounts are needed. Vitamin D doses of 50,000 IU at a time are not unusual but are usually given only a few times weekly or monthly, depending on needs. A handy tip is that deficient Vitamin D causes serum calcium levels to be low, so many clinicians will monitor serum calcium levels to help adjust the prescription.

    Although I can’t recommend medical therapy in this forum I have some thoughts I can share. Why not get another blood vitamin D level measured to see if the amount you are getting is okay? Calcium levels go up in vitamin D excess so a serum calcium level that is elevated can be an indication of too much vitamin D.

    Hope that helps. Keep us posted.

    The metabolism.com website disclaimer applies to this and all my posts.

    G. Pepper

  • Triskelion

    I need to know what is the difference between Vitamin D and Vitamin D3 ? Are they the same thing and if not please let us know what the differences are.

    thanks!