Dr. Mirkin's Special issue on vitamin D

[Guest guest]

Dr. Gabe Mirkin's Fitness and Health e-Zine

April 6, 2008

Vitamin D ­ Special Issue

Over the

last few years I have reported on numerous

studies linking vitamin D deficiency with various diseases:

diabetes, heart attacks, at least 30 types of cancer, and

autoimmune disease such as lupus and rheumatoid arthritis

(a list of these reports appears below).

This

winter I have had a series of baffling exercise-

associated muscle injuries. My blood levels of vitamin D have

been extremely low, even though I spend a lot of time outside

riding my bike. I reviewed my diaries and found that wintertime

 

injuries have been a lifelong pattern for me. I have not been able

 

to find any strong evidence that lack of vitamin D causes muscle

injuries. However, it is associated with muscle weakness, falling in

 

older people, bone deformities and fractures.

People get

most of their vitamin D from sunlight. The skin

has an enormous capacity for vitamin D production and supplies

the body with 80-100 percent of its vitamin D. However, a

recent

study showed that a high percentage of people in sunny Arizona

are vitamin D deficient (American Journal of Clinical Nutrition,

March 2008). How can this be? A clue to the problem is that a

large percentage of the people who were deficient were

African-

American, Hispanic, elderly or overweight.

We know that

people who have dark skin need more vitamin D because dark

skin blocks the sun's UVB rays that make vitamin D. Another

study showed that almost 50 percent of African Americans in

Boston had low vitamin D in March. We also know that obesity

can cause vitamin D deficiency because body fat removes vitamin

D from circulation. Furthermore, as people age, skin cannot

synthesize vitamin D as efficiently and the kidneys are less able to

 

convert vitamin D to its active hormone form.

An article

from Australia showed that 15 out of 18

gymnasts in Australia suffered from vitamin D deficiency (Clinical

Journal of Sport Medicine, March 2008). These athletes spend a

 

lot of time training indoors. Even if you spend several hours

a

day outside in winter, you probably will not get enough sun to

meet your vitamin D needs. At our latitude the sun's rays reach

 

earth at an angle so they have to penetrate a thick layer of the

earth's atmosphere and fewer rays get through. Also, when the

weather is cold we cover most of our skin with

clothing.

 

My personal plan and recommendations

While we

wait for the scientific community to resolve

whether lack of vitamin D causes cancers, heart attacks and so

forth, or is just a marker for other risk factors such as lack of

activity or excess weight, I think you should be aware of your own

vitamin D status and take action if you are deficient.

If you

seldom go outdoors, have dark skin, are over 50 or

are overweight, I recommend that you ask your doctor to do blood

tests for vitamin D3 and D2. D3 is made by your skin from

ultraviolet light (UVB) or from the vitamin D you get in foods or

supplements. D2 comes just from food or supplements.

Your

total blood level of vitamin D should be over 50. If it is

below 50,

you may need to take a tropical vacation, use a tanning bed or

take vitamin D supplements. A safe dose appears to be 1000 IU

per day during the winter.

Until

summer arrives and my vitamin D levels return to

normal, I have chosen to use a tanning salon. I am reluctant to

 

take supplements because one study from Australia suggests that

they may suppress the body's ability to synthesize vitamin D.

 

Tanning lamps emit both UVA and UVB. However, because UVB

are the primary rays that cause skin cancer, most tanning beds

are high in UVA which does not make vitamin D and low in UVB

that makes vitamin D. Ask the tanning center about the amount of

 

UVB in their lamps. Some have 70 percent UVA and 30 percent

UVB, but some emit less than five percent UVB. If you use a

tanning bed, start at very low exposure, preferably with less than

five minutes on your first visit. You won't know if you have burnt

 

yourself until that evening. Then add only two minutes per

exposure and don't go every day. After a couple of weeks, you

can repeat your blood test. Stop using tanning bed when your

total level reaches 50. If it does not reach 50 in a month, you

 

should stop the tanning bed and take vitamin D supplements.

I will

report to you from time to time on the progress of my

training program, injuries and vitamin D levels; and I will continue

 

to survey the scientific literature for studies on the association

between vitamin D and various health problems.

****************************************************

My previous reports on vitamin D:

Heart attacks and vitamin D

 

http://www.drmirkin.com/public/ezine012708.html

Cancer and vitamin D

 

http://www.drmirkin.com/public/ezine101407.html

 

 

http://www.drmirkin.com/public/ezine031107.html

 

 

http://www.drmirkin.com/nutrition/1337.html

 

http://www.drmirkin.com/men/9431.html

Diabetes and vitamin D

 

http://www.drmirkin.com/public/ezine072907.html

 

 

http://www.drmirkin.com/diabetes/vitamins_minerals.html

 

http://www.drmirkin.com/diabetes/2279.html

 

http://www.drmirkin.com/diabetes/9570.html

Other vitamin D studies

 

http://www.drmirkin.com/public/ezine092307.html

 

 

http://www.drmirkin.com/public/ezine120306.html

 

 

http://www.drmirkin.com/public/ezine051505.html

 

 

http://www.drmirkin.com/nutrition/8362.html

 

http://www.drmirkin.com/joints/2347.html

 

 

http://www.drmirkin.com/joints/vitaminD.html

 

 

http://www.drmirkin.com/nutrition/1074.html

 

 

http://www.drmirkin.com/nutrition/9873.html

 

 

http://www.drmirkin.com/nutrition/9613.html

 

 

http://www.drmirkin.com/nutrition/8941.html

 

 

http://www.drmirkin.com/nutrition/8564.html

 

 

http://www.drmirkin.com/nutrition/8288.html

 

http://www.drmirkin.com/archive/6914.html

 

http://www.drmirkin.com/archive/6355.html

More information on vitamin D:

 

http://en.wikipedia.org/wiki/Vitamin_D

 

http://ods.od.nih.gov/factsheets/vitamind.asp

 

 

http://www.ncbi.nlm.nih.gov/pubmed/11991436