Vitamin D is a fat-soluble vitamin naturally present in very few foods, added to others for fortification and available as a dietary supplement in a couple different forms. While optimal serum concentrations of Vitamin D have not been established, the importance of having optimal Vitamin D levels is everywhere. It’s even hitting mainstream health news.
Do you know if you’re getting enough vitamin D? Do you know how to optimize your sun exposure for maximum Vitamin D production? And, if you’re supplementing, do you know if you’re taking the best type?
Natural Sources of Vitamin D:
- Sunlight exposure
- Fatty fish such as salmon, tuna, mackerel, sardines and swordfish
- Fish liver oils
- Egg yolks
- Beef liver
- Some mushrooms
Other Sources of Vitamin D:
- Fortified dairy (and dairy alternative) products
- Fortified grain products, such as cereal, rice, flour, etc.
Best Way to Get Vitamin D
The human body naturally produces vitamin D in response to sunlight exposure. Our early ancestors evolved close to the equator, where they were minimally clothed and got intense sun year-round.
There are 2 spectrums of sunlight – UVA and UVB. The UVB band is the sun's ultraviolet spectrum that enables our bodies to produce Vitamin D naturally. Since I always advocate natural choices, I believe that sunlight exposure is the best way to get the necessary Vitamin D.
Unfortunately, many people are indoors during peak sunlight hours (think cubicle life), they wear too much clothing that covers their skin or they slather their skin with sunscreen every day. So, these people do not naturally produce enough Vitamin D to promote optimal health.
The good news is that maximum Vitamin D production happens in just a few minutes in midday – so you don’t have to overexpose yourself to sunlight. Actually, you’ll make all of your Vitamin D for the day in approximately half of the time it takes for your skin to turn pink (that amount of time varies for each person – see recommendations below).
If you get the appropriate sun exposure in summer, it is possible to meet your body’s yearlong need for vitamin D during the summer months alone. But it’s important to note that everyone’s body synthesizes Vitamin D from the sun differently, and it’s key to understand the factors that relate to you.
10 Tips for Optimizing Sun Exposure
- Make sure at least 40% of your skin is exposed (not covered by clothing, hats or sunglasses) for optimal production.
- Do not wear sunscreen if you’ll be outside only for short times. An SPF of 8 can block up to 95% of the sun’s UVB rays (that means 95% of your body’s Vitamin D productsion).
- For vitamin D production, sun exposure should happen midday 10 a.m. and 3 p.m. – at least 2-3 days per week (for 5 to 10 minutes).
- The darker your skin, the longer it takes for your body to synthesize Vitamin D3 from the sun.
- The older you are, the longer it takes for your body to synthesize Vitamin D3 from the sun.
- You’ll synthesize Vitamin D faster at higher altitudes.
- Cloud cover and smog can filter UVB rays, making it harder for your body to produce Vitamin D.
- Glass blocks all UVB rays.
- While tanning beds are often villainized, they are only dangerous if used for long periods. If used for just a few minutes, studies show they can help optimize Vitamin D levels.
- You can make more Vitamin D during summer. During winter, it’s hard to synthesize Vitamin D. A good rule of thumb to remember is that if your shadow is longer than you are tall, you are not making much vitamin D.
Should You Supplement?
That is a decision you need to make with your doctor after having your Vitamin D levels tested. Since half of the population is deficient, if you feel you are at risk for deficiency, you should consider supplementation if you can’t get adequate sun exposure.
One thing you need to keep in mind is that Vitamin D taken orally via supplementation bypasses your body's built-in toxicity protection, so you can supplement with too much Vitamin D, whereas your body will not produce too much Vitamin D when exposed to the sun.
Dietary Supplements: Vitamin D2 or D3?
There are 2 forms of Vitamin D for fortified foods and supplements: D2 (ergocalciferol) and D3 (cholecalciferol). Vitamins D2 and D3 are generally considered to be equivalent in humans. However, some studies have shown that Vitamin D2 is much less effective than Vitamin D3 in humans.
So what’s the difference? Vitamin D3 is the form your skin naturally produces when exposed to the sun. However, Vitamin D3 can be manufactured by irradiating lanolin. This makes manufactured Vitamin D3 unsuitable for vegans. It’s also wise to note that D3 is not usually derived from US sources.
On the other hand, Vitamin D2 is manufactured by the UV irradiation of ergosterol in fungi (yeast or mushrooms). This was an eye opener for me to learn that those Vitamin D rich mushrooms at the store are irradiated – no wonder they last so much longer in my fridge lately!
It seems like both supplemental Vitamin D2 and D3 have their positives and negatives, and that neither come from natural food sources. If it helps, the Vitamin D Council believes that Vitamin D3 is the more natural choice of the two options, and recommends that you supplement with Vitamin D3. However, there is one natural Vitamin D supplement I recently learned about.
Fermented Cod Liver Oil
I have been reading Cure Tooth Decay, and the book talks a lot about fermented cod liver oil. I had read about it before, but now I'm very interested in trying it out since it is such a great natural source of natural fat soluble Vitamin D. Green Pastures is supposed to be the very best choice around.
Recommended Supplementation Levels
There are currently conflicting recommendations, so you can believe who you will, but given the statistics about deficiency, I personally err on the side of higher levels. Especially given the fact that studies show large quantities of Vitamin D3 – approximately 10,000 IU – are synthesized in your skin in response to full-body summer sun exposure.
Institute of Medicine (IOM)
The IOM recommended dietary allowance (RDA) of Vitamin D is:
- 600 IU for everyone aged 1-70
- 800 IU for adults older than 70
- The safe upper limit is currently 4,000 IU
Vitamin D Council
The Vitamin D Council recommends the following amounts of supplemental vitamin D3 per day in the absence of proper sun exposure:
- Healthy children under the age of 1 years: 1,000 IU
- Healthy children over the age of 1 year: 1,000 IU per every 25 lbs of body weight
- Healthy adults and adolescents: Minimum of 5,000 IU
- Pregnant and lactating mothers: Minimum of 6,000 IU
- People with chronic health conditions like autism, MS, cancer, heart disease or obesity may need up to double these doses