Vitamin D3: The Controversial Vitamin
The compound
we call vitamin D can no longer properly be considered a vitamin. For
most mammals, it is not in any sense even a nutrient. Nevertheless,
vitamin D resembles true vitamins in as much as humans -- who are cut
off from the critical solar ultraviolet wavelengths by reason of
latitude, clothing, or shelter-- depend on an external source of the
substance, just as they do for the true essential nutrients.
What is Vitamin D?
Vitamin D,
calciferol, is a fat-soluble vitamin. It is 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 with a different activity. Some
forms are relatively inactive in the body, and have limited ability to
function as a vitamin.The liver and kidney help convert vitamin D to its
active hormone form.
The major
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 in concert 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, which are
skeletal diseases that result in defects that weaken bones.
What are the sources of vitamin D?
Food sources
Fortified
foods are the major dietary sources of vitamin D. Prior to the
fortification of milk products in the 1930s, rickets (a bone disease
seen in children) was a major public health problem in the United
States. Milk in the United States is fortified with 10 micrograms (400IU) of vitamin D per quart, and rickets is now uncommon in the US.
Exposure to sunlight
Exposure to
sunlight is an important source of vitamin D. Ultraviolet (UV) rays from
sunlight trigger vitamin D synthesis in the skin.
Season,
latitude, time of day, cloud cover, smog, and suncreens affect UV ray
exposure. For example, in Boston the average amount of sunlight is
insufficient to produce significant vitamin D synthesis in the skin from
November through February.
Sunscreens with a sun protection factor of 8 or greater will block UV rays that produce vitamin D.
Vitamin D
supplements are often recommended for exclusively breast-fed infants
because human milk may not contain adequate vitamin D.
Vitamin D and Bone Health
It is
estimated that over 25 million adults in the United States have, or are
at risk of developing osteoporosis. Osteoporosis is a disease
characterized by fragile bones. It results in increased risk of bone
fractures.
Rickets and
osteomalacia were recognized as being caused by vitamin D deficiency 75
years ago; their prevention and cure with fish liver oil constituted one
of the early triumphs of nutritional science. The requirement for
vitamin D has been pegged to these disorders ever since.
Having normal
storage levelsof vitamin D in your body helps keep your bones strong and
may help prevent osteoporosis in elderly, non-ambulatory individuals,
in post-menopausal women, and in individuals on chronic steroid therapy.
Researchers
know that normal bone is constantly being remodeled (broken down and
rebuilt). During menopause,the balance between these two systems is
upset, resulting in more bone being broken down (resorbed) than rebuilt.
Vitamin D
deficiency has been associated with greater incidence of hip fractures. A
greater vitamin D intake from diet and supplements has been associated
with less bone loss in older women. Since bone loss increases the risk
of fractures, vitamin D supplementation may help prevent fractures
resulting from osteoporosis.
The use of
vitamin D is well accepted, but the mere absence of clinical rickets can
hardly be considered an adequate definition either of health or of
vitamin D sufficiency.
The fact that
it takes 30 ormore years to manifest itself makes it no less a
deficiency condition than a disorder that develops in 30 days. It is
easy to understand how long-period deficiency diseases could never have
been recognized in the early days of nutritional science, but with
modern methods and a better grasp of the relevant physiology, failing to
recognize a slowly developing condition as a true deficiency state, can
no longer be justified.
Vitamin D
nutrition probably affects major aspects of human health, as listed
below, other than its classical role in mineral metabolism. The rest of
the article addresses some of the newly recognized uses of vitamin D.
Cancer
Today, it is
well established that besides playing a crucial role in the
establishment and maintenanceof the calcium in the body, the active form
of vitamin D also acts an effective regulator of cell growth and
differentiation in a number of different cell types, including cancer
cells.
Laboratory,
animal, and epidemiologic evidence suggest that vitamin D may be
protective against some cancers.Clinical studies now show vitamin D
deficiency to be associated with fourof the most common cancers:
- Breast (23)
- Prostate 24-27
- Colon 28-31
- Skin 32,33
Diabetes
Vitamin D
deficiency has been associated with insulin deficiency and insulin
resistance. (1-3) In fact, last year it was shown that vitamin D
deficiency is likely to be a major factor for the development of type
one diabetes in children. (4)
Heart Disease
Insulin
resistance is also one of the major factors not only leading to the
cancers mentioned above, but also to the number one killer in the US,
heart disease. Northern countries have higher levels of heart disease
and more heart attacks occur in the winter months. (5,6)
Arthritis
Progression of degenerative arthritis of the knee and hip is faster in people with lower vitamin D concentrations (33-34)
Infertility and PMS
Infertility is
associated with low vitamin D(7), and PMS has been completely reversed
by addition ofcalcium, magnesium and vitamin D.(8)
Fatigue, Depression and Seasonal Affective Disorder
Activated
vitamin D in the adrenal gland regulates tyrosine hydroxylase, the rate
limiting enzyme necessary for the production of dopamine, epinephrine
and norepinephrine.
Low vitamin D
may contribute to chronic fatigue and depression. (9-10) Seasonal
Affective Disorder has been treated successfully with vitamin D. In a
recent study covering 30 days of treatment comparing Vitamin D and 2
hour daily use of 'lightboxes', depression completely resolved in the D
group, but not in the light box group.(11)
Autoimmune Disorders
Multiple
Sclerosis, (12) Sjogren's Syndrome, rheumatoid arthritis, thyroiditis
and Crohn's disease have all been linked with low vitamin D levels.
Single, infrequent, intense,skin exposure to UV-B light suppresses the immune system and causes harm.
However
chronic low-level exposurenormalizes immune function and enhances immune
cell production. This reducesabnormal inflammatory responses such as
found in autoimmune disorders,and reducing occurrences of infectious
disease. (14-18)
Obesity
Vitamin D
deficiency has been linked with obesity. (18, 19) Vitamin D has recently
been shown to lower leptin secretion. (20) Leptin is a hormone produced
by fat cells and is involved in weight regulation. It is thought that
the hormone signals the brain when fat cells are "full," but exactly how
the hormonecontrols weight is not entirely clear.
Additionally,
obesity by itself probably further worsens vitamin D deficiency due to
the decreased bioavailabilityof vitamin D(3) from skin and dietary
sources, because of its being deposited in body fat. (36)
Syndrome X
Vitamin D
deficiency has been clearly linked with Syndrome X. (21) Syndrome X
refers specifically to a group of health problems that can include
insulin resistance (the inability to properly deal with dietary
carbohydrates and sugars), abnormal blood fats (such as elevated
cholesterol and triglycerides), overweight, andhigh blood pressure.
Vitamin D and Steroids
Steroids, like
prednisone, are often prescribed to reduce inflammation from a variety
of medical problems. These medicines may be essential for a person's
medical treatment, but they have potential side effects, including
decreased calcium absorption.
There is some
evidence that steroids may also impair vitamin D metabolism, further
contributing to the loss of bone and development of osteoporosis
associated with steroid medications. For these reasons, individuals on
chronic steroid therapy should consult with their physician or
registered dietitian about the need to increase vitamin D intake through
diet and/or dietary supplements.
For the latest on vitamine D3 click here.
| Vitamin D Dose Recommendations | |
| Age | Dosage |
| Below 5 | 35 units per pound per day |
| Age 5 - 10 | 2500 units |
| Adults | 5000 units |
| Pregnant Women | 5000 units |
WARNING: There is no way to know if the above recommendations are correct. The ONLY way to know is to test your blood. You might need 4-5 times the amount recommended above. Ideally your blood level of 25 OH D should be 60ng/ml. | |
