Vitamin D and Sunlight - What's The Big Deal?

by Dr. Joan Vernikos


What is It and How Does it Work?
Vitamin D3 is an oil-soluble steroid hormone that forms in your

skin when it is exposed to sunlight. Sunlight converts a cholesterol derivative into D3 also known as cholecalciferol. This is the most active form of Vitamin D. Over 80% is made in this way by the skin. Small amounts are in some foods, including fatty fish such as herring, mackerel, sardines and tuna and in smaller amounts in beef and chicken liver, cheese and egg yolks. In modern times small amounts of Vitamin D3 are added to milk and other dairy products, juices, and cereals. But diet alone won't provide enough Vitamin D to become Vitamin D sufficient.
     
During the darker months of the year, the modern habit of using sunscreen and our sardine habit not what it used to be, we have unknowingly become deficient in this crucial vitamin for health. The problem is most of us see inadequate sunlight directly above us from 10am to 3pm. Few expose enough skin that is not sprayed with sunscreen to protect ourselves from skin cancer and premature skin aging. Sunscreen reduces Vitamin D3 production by 98%. In the winter the sun is at too low of an angle over most of the US and all of Canada for us to produce adequate Vitamin D from sun exposure.

A bit of back-story: From the 1960’s NASA funded researchers to help us correct the loss of bone of astronauts in space. As part of this research, Michael Holick in Boston University and Bob Heaney at Creighton University, discovered Vitamin D3 was important for bone health by enabling the absorption of calcium from your gut. Without Vitamin D3 any calcium supplements you take simply go right through you unused. With Vitamin D3, calcium is absorbed into the blood from where together with Magnesium and Vitamin K2 it finds its way to bone, to build new bone. Together with calcium, Vitamin D helps protect older adults from osteoporosis. The amount of D3 commonly added to calcium supplements is too low for the job.
  
The Emerging Story on Vitamin D Preventing & Treating Illness
Since ancient times the sun was used to heal many conditions.  In 1933 medicine recognized 133 different conditions that were treated by sunlight. Without enough D3 circulating in your blood, your body simply does not function as it was intended – ridding the body of intruders, fighting disease, repairing cells. Muscles need it to remain strong and flexible, nerves need it to carry messages between the brain and every body part, and the immune system needs Vitamin D to fight off invading bacteria and viruses. It is used by cells throughout the body. That is its vital role in preventing a broad cross-section of diseases. Vitamin D is important to the body in many ways including, autoimmune disorders such as multiple sclerosis (MS),  Chronic Obstructive Pulmonary Disease(COPD), rheumatoid arthritis, inflammation, oxidative stress, autism, depression, dementia, pain and Alzheimer’s.

UV light exposure in sunshine has other health benefits that are independent of Vitamin D such as increased production of NO (nitric oxide) which lowers blood pressure, and setting the circadian clock. It is now established that Vitamin D3 is needed for each cell in the body to optimally access its own genetic DNA library. This is a big deal. The lower your Vitamin D3, the worse the problems from its deficiency you are likely to see during your lifetime. While sun exposure remains the most effective way to get Vitamin D3, the challenges of doing so coupled with its relative unavailability in foods, mean that we need to take supplements.

Who’s At Risk of Being Deficient?
In winter it is nearly impossible to gain adequate Vitamin D from the sun without spending long periods outside, and few of us do that! Even in the summer, as you might imagine, if you are someone who shuns being in the sun, or only allows a small part of your body to be exposed to the sun’s rays, you are probably deficient in Vitamin D. Even if you are a frequent swimmer or someone who works outside in the garden, if you religiously cover yourself with sunscreen you may still not be getting adequate Vitamin D3. Similarly if you live in more Northern latitudes (or Southern latitudes in the southern Hemisphere), you are also likely not getting enough Vitamin D3.
     
Black (dark) skin pigment needs 5-10 times more sun exposure than Caucasian (light) skin pigment to produce the same amount of D3. So if you are someone with dark skin or as you get older, you may need significantly more sun exposure to produce the same amount of Vitamin D3 as someone with pale skin. Know that burning is not at all required to get Vitamin D3!  People older than 65 are at highest risk of Vitamin D3 deficiency perhaps because they go outside less as they get older. Aging kidneys and less functioning skin receptors mean that less Vitamin D3 is synthesized. Additionally those who are obese are also at risk because their body fat binds to some Vitamin D3 and prevents it from getting into the blood.

How Much Vitamin D is Enough?
There are varying opinions on this but what I share here is my own options based on the science and what I have learned in a lifetime of work in the area of health.
In order to best know what actions you need to take you will have to have your blood levels measured. There are two vitamin D tests – 1,25(OH)D and 25(OH)D. The correct test is 25(OH)D,  also called 25-hydroxyvitamin D. This is the better marker of overall D status and health.
    
The recommended normal range is 50-70ng/ml of 25-OHD in the blood. The average person today is vitamin D3-deficient with a serum level around 25ng/ml 25-OHD. That’s what mine was at the end of a summer of swimming and sun. I was sure that my levels would have been much higher.
      
To achieve and maintain your blood level within this 50-70ng/ml range, you need to take approximately 5,000-6,000 IU’s/day of total Vit D3 from all sources – sun, food and supplements. Add up the amount from the labels of your food and supplements. If your level is low, I suggest you begin with 2,000 IU’s (or up to 4,000 IU’s/day for seniors) in supplements to increase your blood levels to the desirable range. If next time you measure it that was not enough, increase your supplement in steps of 1,000 IU's before you measure again. What matters is not what you take but whether your blood levels are in the right range. Therefore measuring your 25-OHD every 3-6 months is important until you know how to maintain a healthy level. You likely will not need as much supplementation after raising your level, but this will vary on an individual basis, so pay attention! The variations in sun exposure based on your location, the time of  day and of the year that you are outside, how much skin you expose, how old you are, how much sunscreen you use and how much you cover up (or don’t’) will all factor into your Vitamin D3 levels.

The growing body of work shows that to treat cancer or heart disease requires an even higher level of 25-OHD in the blood. Here are some guidelines that might help:

Levels of Vitamin D (25-OH Vitamin D)

  Deficient      Optimal    Treat Cancer and Heart Disease     Excess

         

 <50ng/ml      50-70ng/ml          70-100 ng/ml                        > 100ng/ml

                                                 or

<125nmol/L  125-175nmol/L      175-250nmol/L                       >250nmol/L

 
The amount you take in supplements needs to be carefully considered against how much you are getting from the sun itself. For instance if you frequently swim outside in the equatorial tropics  at noon for extended periods you likely will need much less supplementation that someone from Bangor, Maine who rarely goes outside. And know this: it is very difficult to get your Vitamin D3 levels to be too high for your overall health.

If  you want to measure your own blood levels every 6 months which is what I do, then simply purchase the D*Action Measurement Kit, part of the global non-profit Grassroots Project (www.GrassrootsHealth.net). This site will also help you stay up on the latest information.