Do You Really Need to Supplement Vitamin D?

by Dr. Cynthia Horner

The D Difference

The universal benefit from sunlight is its ability to activate the skin to produce vitamin D. There are three ways to get vitamin D, from food, from supplements and from the sun. Food supplies us with only small amounts of vitamin D therefore humans must count on the sun to allow their skin to produce vitamin D. Sun exposure has a positive effect on your health in that sun’s UVA and UVB rays are necessary for our bodies to make vitamin D.images


Two major forms of vitamin D have been discovered:

  •           D2 ergocalciferol               images (2)
  •                                           D3 cholecalciferol.

Similar but different

Some authorities say D3 is more effective than D2 in humans.

Because vitamin D is not abundant in food it is added to foods such as milk (then called fortified). The type of vitamin D used in fortifying most foods is D2, which is not the kind made by humans from exposure to the sun.

It is vitamin D3 that is synthesized in the skin when exposed to UVB light. The wavelengths needed to produce vitamin D is between 270 & 300 nanometers (sunburn is caused at about 290 to 400 nm). These lower wavelengths are present when the UV index is greater than 3.  When sunlight hits the skin for ten to fifteen minutes the reaction that produces vitamin D takes place within the next two to three days.

Low levels of vitamin D are associated with:

  • high blood pressure
  • most cancers
  • multiple sclerosis
  • osteoporosis
  • many autoimmune diseases

Melanin functions as a filter for the skin. Darker skinned people with more melanin in their skin require longer exposure to the sun to produce vitamin D. When light skinned individuals tan slowly they increase their melanin and create a natural sunscreen. Taking a supplement to add vitamin D to the body can be helpful if you are unable to get adequate sun exposure. A supplement in the amount of 2,000 to 4,000 IUs daily is the recommended dose. The optimal levels in the body  range from 40 – 60 ng/ml.


The D Facts

  1. Vitamin D is actually a prehormone, meaning that it has no hormone activity itself, but is converted to an active hormone.
  2. Helps body absorb calcium therefore needed for strong bones and muscles.
  3. Aids in reducing abnormal cell growth associated with cancer in the intestines, breast and prostate.
  4. Decreases inflammation throughout the body.
  5. At age 70 you produce about ¼ of the vitamin D you did at age 20.
  6. Dark skin decreases the body’s ability to produce vitamin D because melanin blocks UVA rays.
  7. About 5 to 15 minutes a day in the sun a few days a week is needed to produce vitamin.
  8. Most foods fortified with vitamin D are fortified with D2 not as potent as D3.
  9. Milk bottlers have switched to fortifying with D3.
  10. Clouds and smog block UV rays.
  11. D3 is found in:
  • egg yolks
  • fatty fish
  • liver

D2 is found in :

  • most plants

The D Timeline

1941 – Australian pathologist Frank Apperly found a link between vitamin D and cancer.

1998 – Doctors in Boston are shocked find 3 out of 5 elderly patients are vitamin D deficient.

2000 – Vitamin D was fortified in many foods other than milk.

2003 – A reemergence of rickets is experienced in America.

2004 – The book “The UV Advantage” by Michael Holick MD speaking out about the problems caused by avoiding the sun.

2005 – Harvard nutrition professor Edward Giovanni suggests vitamin D from the sun prevents many cancers.

The D Quiz

1)  Your age

a – over 50

b – under 50


2)  Describe your complexion

a –  dark

b – medium

c – light


3) If you drew a line from northern California through Denver Colorado and through Columbus Ohio to Philadelphia Pa, chose where you live.

a – north of the line

b –  right on the line

c   – below the line


4) How long do you spend outdoors most days?

a- Under 30 minutes a day

b- 30 minutes to 1 hour a day

c- Over I hour


5)  Describe your sunscreen habits

a – always wear sun screen

b – wear it only in the summer

c – never


6)  Do you tan indoors in a tanning salon?

a – never

b – several weeks a year


7)  Do you take a vitamin D supplement?

a – no  _______

b – yes _______


How did you score?

1) a = 1 point          b = 2 points

2) a = 1 point           b = 2 point            c = 3 points

3) a = 1 point           b = 2 points          c = 3 points

4) a = 0 points        b = 1 point             c = 2 points

5) a = 0 points        b = 1 point             c =2 points

6) a= 0 points         b = 2 points

7) a = 0 points       b = 3 points


If you scored 7 or less  = your body needs more vitamin D

If you scored 8 to 12  = your body is most likely making adequate but minimal vitamin D

If you scored 13 or more  =  your vitamin D levels are healthy


What my patients have taught me “People may benefit from good advice but they flourish when given the space to come to their own conclusions”



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