Why The Official Recommended
Intake for Vitamin D is Too Low
Vitamin D has been a natural part of man's experience forever,
and 90% of vitamin D is derived from solar ultraviolet-B (UVB)
irradiance. The health effects of vitamin D can be and have been
determined from a variety of studies including ecological, observational
(case-control and cohort), and cross-sectional studies.
Vitamin D helps both to prevent and to treat chronic diseases
including many types of cancer, cardiovascular disease (coronary
heart disease, stroke, etc.), congestive heart failure, diabetes
mellitus (types 1 and 2), osteoporosis, falls, and fractures.
It is also effective against infectious diseases including both
bacteria and viral infections: bacterial vaginosis, pneumonia,
dental caries, periodontal disease, tuberculosis, sepsis/septicemia,
Epstein-Barr virus, and influenza type A such as A/H1N1 influenza.
The autoimmune diseases include asthma, type 1 diabetes mellitus,
multiple sclerosis, and perhaps rheumatoid arthritis.
Pregnancy outcomes are also adversely affected by low serum D
levels. 40% of primary Cesarean-section deliveries in the United
States are linked to low D levels (9% of births in the United
States involve primary C-section), and preeclampsia is also linked
to low serum levels of D. In regards to cancer, vitamin D helps
cells fit into the organs properly or commit suicide (apoptosis),
and also reduces angiogenesis (new blood vessel growth) around
tumors and reduces metastasis. For metabolic diseases, the mechanisms
include increased insulin sensitivity and insulin production.
For infectious diseases, vitamin D induces production of cathelicidin
and defensins, which have antimicrobial and antiendotoxin activities.
Due to current lifestyles in the United States, most people do
not spend sufficient time in the sun to produce the higher serum
D levels associated with optimal health. Black-Americans are particularly
vulnerable to low levels due to their darker skin, which reduces
the amount of UVB that reaches the 7-dehydrocholesterol in the
lower epidermis to produce previtamin D. Black-Americans have
a 25% higher mortality rate than White-Americans, and this difference
may be explained in terms of lower serum 25(OH)D levels. Solar
UVB is an excellent source of vitamin D during about half of the
year. The way to take advantage of the sun as a source of vitamin
D is to expose as much of the body as possible without sunscreen
near solar noon, the time when one's shadow is shorter than one's
height, for 10-30 minutes depending on skin pigmentation, being
careful not to turn pink or red or burn. (https://www.doctoryourself.com/holick.html
Supplements represent an efficient way to obtain sufficient vitamin
D. African-Americans should consider taking 3000 International
Units (IU) per day while White-Americans should consider taking
2000 IU/day. The current dietary guideline, approximately 400
IU/day, was based on the amount of vitamin D in a spoonful of
cod liver oil, which prevented rickets.
There are few adverse effects of vitamin D. With whole-body exposure
to the sun, one can make at least 10,000 IU/day in a short time.
Adverse effects such as hypercalcemia have been found in general
only for 20,000-40,000 IU/day for very long periods. However,
those with certain diseases such as adenoma of the parathyroid
gland, granulomatous diseases, lymphoma, sarcoidosis, and tuberculosis,
should limit their vitamin D intake or production due to the fact
that the body's innate immune system produces too much 1,25-dihydroxyvitamin
D in the serum, which can raise serum calcium levels too high.
Several studies have examined how much mortality rates and economic
burdens of disease could be lowered if the population had more
vitamin D. These studies were for Western Europe, Canada, the
Netherlands, and the United States. They generally found that
mortality rates could be reduced by about 15%.
During pregnancy and lactation, women should be taking about
6000 IU/day. The current US "Adequate Intake" recommendation
is a mere 200 IU/day. Bruce W. Hollis and Carol L. Wagner, Medical
University of South Carolina, recently completed a randomized
controlled trial vitamin D supplementation for pregnant and nursing
women and found that even 2000 IU/day was inadequate, and that
there were no adverse effects with 6000 IU/day.
For the text of a Vitamin D Scientists' Call to Action, please
go to https://www.grassrootshealth.net
William B. Grant earned his PhD in physics at UC Berkeley.
For 15 years he was a physicist at NASA Langley Research Center's
Atmospheric Sciences Division. He has authored or coauthored over
180 papers in peer reviewed journals. Since he began his work
on UVB/vitamin D and cancer in 2000, the list of vitamin D-sensitive
cancers has grown from 5 to at least 16. His paper in Cancer in
2002 identified 10 additional vitamin D-sensitive cancers. Dr.
Grant directs the Sunlight, Nutrition, and Health Research Center
February 24, 2010