Sun & Vitamin D: A Slightly Different Angle

What are we supposed to do about sun exposure?

There is conflicting information out there regarding those invisible ultraviolet rays from our sun.

How does vitamin D fit in?


UVA rays (the bad guy) have a long wavelength and constitute 90-95% of the sun's ultraviolet light. They penetrate the furthest into the skin and are the primary inducer of tanning in humans. UVA rays are constant during all hours of daylight the entire year.

UVB rays (the good guy) are partially absorbed by the ozone layer and window glass and have a medium wavelength. They contain more energy than UVA rays and activate the synthesis of vitamin D in the skin. UVB rays are the primary cause of sunburn and of the most concern for skin and eye damage. UVB rays are low in morning and evening and high at midday. UVB rays are influenced by season, the lowest being between November and March.

If you are avoiding the sun by going out early in the morning or late in the day, you're getting lots of UVA and not much UVB. This practice appears safe on the outside, but greatly interferes with the body's production of vitamin D.

Safe sunlight exposure (UVB rays) has been shown to protect against as many as 16  types of cancer, including breast, colon, endometrial, esophageal, ovarian, bladder, gallbladder, gastric, pancreatic, prostate, rectal and renal cancers, as well as non-Hodgkin's lymphoma.

Is our sunlight dangerous? In the northern statesm vitamin D synthesis is greatly decreased because of the seasonal angle of the sun's rays. They're too low to efficiently allow UVB radiation to penetrate the atmosphere and activate vitamin D synthesis. This deficiency of vitamin D is of epidemic proportions for the people living in the northern latitudes above the Tropic of Cancer (23.5 degrees).  Redding is at latitude 40.6 degrees.

Do sunscreens really help? Wearing a sunscreen on your uncovered skin blocks your body's production of vitamin D. In fact, sunscreens reduce vitamin D production by as much as 97.5 to 99.9%. Most chemical sunscreens block UVB rays preventing sunburn but are transparent to UVA rays, the real enemy. Sunscreens are definitely no miracle cure to prevent skin cancer.

Many of us spend our lives indoors or in vehicles, which keeps us from UVB rays that are vital to our body's production of vitamin D. Here are a few options to protect yourself from vitamin D deficiency:

1. Apply window film to the glass where you spend most of your time. This blocks 99% of the UVA rays that destroy vitamin D and mak you more susceptible to cancer, diseases and influenza. (Visit for more info.)

2. Get 10 - 15 minutes' exposure from direct sunlight to large portions of your body (between 10 a.m. - 3 p.m.) every day.

3. Contact your doctor to determine if your vitamin D blood levels (25-Hydroxyvitamin D3) are optimal (40-60 ng/ml). A blood spot test from can be ordered for only $40. This will help support your immune system during the influenza season and may prevent and/or treat many cancers and/or diseases.

4. Supplement with vitamin D3. Dosages from 1000 to 5000 IU/day are a reasonable recommendation when you know your vitamin D blood level.


5. The best food source of vitamin D is cod liver oil, since it is difficult in today's society to get enough vitamin D from our food. Cod liver oil contains more vitamin D per unit weight than any other common food.

6. Limiting sun exposure, wearing protective clothing, and using a non-chemical sunscreen may reduce the risks of skin cancer and other harmful effects of the sun. (Visit for non-chemical sunscreen information.)

(, articles - Douglas Laboratories, Confronting the Worldwide Epidemic of Vitamin D Deficiency, 10/2008.)

Ed Roberts, DC, spent 12 years as a mechanical engineer on the space shuttle before his chiropractic career in Redding. He has a thriving practice that uses many of the problem-solving skills he used as a NASA engineer to find the cause his patients' spinal problems. Check out his website at

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9 Responses

  1. This calculator helps you work out the necessary exposure to sunshine required for 1000iu.

    Remember the darker tanned or brown/black your skin is the longer exposure will be required and the least tanned skin is the most efficient and making vitamin d.

    To work out your total daily vitamin d requirement you need roughly 1000iu for each 25lbs you weigh + 100iu/daily for each remaining 25lbs. This is useful for working out amounts for children.

    While cod liver oil may be the best dietary source of D3 you are unlikely to get more than 10% of you daily amount from diet so if the weather isn't warm enough for sun exposure a D3 supplement of equivalent strength is required.

    This Utube video from one of the Grassrootshealth scientists explains the dangers of sunscreen use.

    YouTube – Skin Cancer/Sunscreen – the Dilemma

  2. Pete says:

    Use vitamin d3 supplements not cod liver oil. To get 5000IU a day from the cod liver oil in my cupboard would need 25 spoonfuls a day. That is a lot of oil and a vast amount of vitamin A. The D3 supplements are made the way the body does it. Also as most D containing foods contain D as a supplement you might as well take it in tablet form.

  3. Mike says:

    If you are interested in vitamin D you should take a look at The Canadian Cancer Society now recommends that everyone take vitamin D to prevent cancer. The site has good summaries of the data and offers a new preparation of vitamin D in a micro-pill formulation. The pills have been formulated with cellulose which absorbs water very quickly. This ensures that the pill breaks up very quickly to provide for maximum absorption. The micro pill is tiny and tasteless. Many vitamin D pills on the market have very poor dissolution properties resulting in poor absorption.

    The site also offers to supply customers with a free supply of 400IU for their children and it also has a good newsletter.

    • Ed Roberts says:

      Thanks for mentioning Cancer. There is a growing mountain of evidence that is suggesting that at least 16 cancers cound be prevented by optimizing our levels of Vitamin D. Look for that article in the future.

  4. I forgot to put in the link to the Vitamin d from sunshine calculator.While Mike 's Vitamin D3 website is excellent and well worth a visit you will find that <a>The cheapest source of Vitamin D3 5000iu is here and CODE WAB666 earns you a further $5 discount.
    For those who want to learn more about how vitamin d reduces cancer incidence this you tube video is a good place to start.
    <a>How Vitamin D Reduces Incidence of Cancer: DINOMIT Model

  5. It's not often spoke about but, vitamin D is a great supplement to take as proper supplementation prevents you from catching a cold, especially if you are prone to a lot of allergies. If you have adequate amounts of vitamin D in your diet, you are less subject to cancer and other illnesses than you would normally be.

  6. Martha says:

    Good article, thanks. I am very surprised though, given that Ed is an engineer and a space shuttle one at that, that he declares UVB to be lowest "between November and March" when for precisely 50% of planet Earth the opposite is true! It's lowest in the darker half of the year, whenever that may be for you.

    • Dr. Ed says:

      The UVB is incrementally lower for two reasons:

      1) as the latitude increases from the equator the incident angle of the sun decreases.

      2) during the Fall – Winter season the incident angle of the sun decreases.

      It's all about the incident angle of the sun.

      "On a minute-by-minute basis, the amount of UV radiation is dependent on the angle of the sun."

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