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Vitamin D Healthy Bone
The Benefits of Vitamin D (calciferol)
By: Dr. Obikoya
Vitamin D, also known as calciferol, is a fat-soluble vitamin
found in food, but also can be made in your body after exposure to ultraviolet
rays from the sun. Vitamin D exists in several forms, each form acting
differently, some actually relatively inactive in our body. The liver and kidney
help convert vitamin D to its active hormone form.
There are two main types of vitamin D. Vitamin D2 is formed by the action of
UV-B on the plant precursor ergosterol. It is found in plants and used to be
added to irradiated cows milk. Most milk today contains D3. Vitamin D3 or
cholecalciferol is found in animal foods. Both forms of vitamin D have been used
successfully to treat rickets and other diseases related to vitamin D
insufficiency.
Vitamin D3 is often thought to be the preferred vitamin because it has more
biological activity. Vitamin D3 as found in food or in human skin always has
various metabolites or isomers that may have biological benefit. There may be as
many as 12 metabolites or isomers in the vitamin D found in animal foods. When
vitamin D is taken in the form of fish oil, or eaten in foods such as eggs or
fish, these metabolites will be present.
When we take in vitamin D from food or sunlight, it is converted first in the
liver to the form 25(OH) D and then in the kidney to 1, 25 (OH) D. These active
forms of vitamin D are available by prescription. They are given to those with
liver or kidney failure or those with a hereditary metabolic defect in vitamin-D
conversion.
The main biologic function of vitamin D is to maintain normal blood levels of
calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to
form and maintain strong bones. It promotes bone mineralization along with a
number of other vitamins, minerals, and hormones. Without vitamin D, bones can
become thin, brittle, soft, or misshapen. Vitamin D prevents rickets in children
and osteomalacia in adults, skeletal diseases that result in defects that cause
weak bones and muscles.
Vitamin D deficiency can occur when dietary intake of vitamin D is insufficient,
when there is limited exposure to sunlight, when the kidney cannot convert
vitamin D to its active form, or when someone cannot adequately absorb vitamin D
from the gastrointestinal tract.
Canadian researcher, Dr. Reinhold Vieth, argued that current vitamin D
recommendations are woefully inadequate. The recommended dose of 200-400
international units (IU) will prevent rickets in children but does not come
close to the optimum amount necessary for vibrant health.1 According to Dr.
Vieth, the minimal daily requirement of vitamin D should be in the range of
4,000 IU from all sources, rather than the 200-400 currently suggested, or ten
times the Recommended Daily Allowance (RDA).
Osteoporosis is not uncommon in the US. It is a disease characterized by fragile
bones, which increases a person’s risk of bone fractures. Normal levels of
vitamin D helps keep your bones healthy and strong and may help prevent
osteoporosis in elderly, the bed-ridden, in post-menopausal women, and those on
chronic steroid therapy. Vitamin D deficiency is relatively common in
post-menopausal women and seniors. This might explain the higher incidence of
hip fractures among these groups of people, who should, therefore, take higher
amounts of vitamin D. Research evidence suggests that vitamin D may protect
against some cancers, particularly colon cancer.
Steroids commonly used as anti-inflammatory medications used in a variety of
medical conditions lower calcium absorption and impair vitamin D metabolism,
further contributing to the loss of bone and development of osteoporosis
associated with steroids. Persons on chronic steroid therapy may, therefore,
need to take extra vitamin D.
Persons with Alzheimer’s disease have increased risk of hip fractures, perhaps
because many of these individuals often stay home and get little sunlight.
Furthermore, this condition is more prevalent in the elderly whose skin’s
capacity to convert vitamin D to its active form is much less due to the aging
process. These individuals are also prone to developing hip fractures. It is,
therefore, important to give these individuals vitamin D supplements as part of
their overall treatment regime.
The standard American diet provides vitamin D only in very low quantities. We
need to supplement our diets with vitamin D. In persons that lived till a
hundred years old, high levels of vitamin D in the blood and normal thyroid
function were the strongest markers of health and longevity. The Food and
Nutrition Board of the Institute of Medicine considers an intake of 25 mcg
(1,000 IU) for infants up to 12 months of age and 50 mcg (2,000 IU) for
children, adults, pregnant, and lactating women to be the tolerable upper intake
level (UL).
Adequate calcium and magnesium, as well as other minerals, are important parts
of vitamin D therapy. Without calcium and magnesium in sufficient quantities,
vitamin-D supplementation will withdraw calcium from the bone and will allow the
uptake of toxic minerals. It is therefore important to supplement and sunbathe
when you are certain you have sufficient calcium and magnesium to meet your
daily needs.
Also important about using vitamin D is that the assimilation and utilization of
vitamin D is influenced by the kinds of fats we consume. If you increase the
levels of both polyunsaturated and monounsaturated fatty acids in your diet, you
will decrease the binding of vitamin D to D-binding proteins. Saturated fats
such as those found in butter, tallow and coconut oil, and the omega-3 fats do
not have this effect.
References
1. Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and
safety Am.J.Clin.Nutr. 1999; 69: 842-56.
