Seasonal Vitamin D
Do you know how to optimize your vitamin D levels for every season?
A growing body of knowledge shows that, at optimized levels, vitamin D functions as a hormone rather than a vitamin, with numerous notable effects on the body.
Vitamin D Supports:
- Healthy immunity
- Healthy mood
- Targeted support for over 2,000 genes
- Healthy bone formation
- Healthy glucose metabolism
- Musculoskeletal comfort
- Heart health
- Healthy skin
Many health experts consider the benefits of vitamin D to be one of the most important health discoveries of the past 100 years. In this article, I share new research on vitamin D deficiency—which affects 87% of Americans—and walk you through how to safely increase your levels.
History of Vitamin D Deficiency
Vitamin D deficiency, causing devastating bone-softening effects, was reported as far back as the 1600s. Originally treated with cod liver oil in the 1800s, it wasn’t until the 1930s that vitamin D deficiency was discovered as the cause.
Though called vitamin D, it is not really a vitamin, but a hormone. In fact, at optimized levels in the blood, the active form, known as calcitriol, is now understood as the most potent secosteroid hormone in the human body. At optimal levels, its effects may extend far beyond bone support, showing responsibility for many health-promoting processes in the body.
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Vitamin D Overflow
About ten years ago, researchers discovered people who live in climates where natural sun exposure is greatest experience greater longevity. In northern climates, studies show up to 61% of Americans are vitamin D deficient, going up to 87% in winter months.1,2
For the past 80 years, it was believed vitamin D was only important for regulating calcium and protecting bones. At levels below 45-50 ng/ml, this is vitamin D’s main role. However, new research reported by the Vitamin D Council has shown higher levels of vitamin D may have a much greater role to play. For example, when vitamin D3 levels are between 50-80 ng/ml, excess calcitriol (secosteroid hormone form of vitamin D) heads towards the cells (not the bones), where it targets over 2,000 genes (about 10% of the human genome).
This overflow of calcitriol has created a worldwide stir about the pervasive role of optimized vitamin D. At lower levels of sun exposure and vitamin D, this overflow simply doesn’t happen. The role of excess calcitriol in the cells is only now being understood.
No Sun = No Fun
During summer months, UVB rays are strongest between 10am-2pm. For most people, 10-15 minutes of direct sunlight on unprotected skin during these hours will be enough to manufacture ~10,000-20,000 IU of vitamin D3. Get just enough sun to turn your skin slightly pink. Darker-skinned people will have to get more sun to optimize their vitamin D levels.
How Your Body Uses Vitamin D3
From the skin, vitamin D3 (cholecalciferol) heads to the liver, where it is converted to calcidiol (25 hydroxyvitamin D). This is the form that circulates in the blood and is most accurately measured on a blood test.
From here, calcidiol heads to the kidneys, where it is converted to calcitriol (1,25-dihydroxyvitamin D), the most active form of vitamin D, which circulates to every tissue in the body.
Vitamin D Supports Immunity
Vitamin D expert Dr. John Cannell developed a theory that some immune issues are seasonal, due to seasonal variations in sunlight, which cause fluctuations in vitamin D levels.3,4Vitamin D activates genes that support an immune response to foreign entities in the body.5
Vitamin D has also been shown to support healthy respiratory immunity.6,7
Pro-inflammatory cytokines may be responsible for many lasting health issues. Vitamin D down-regulates cytokine activity and supports healthy inflammatory response.7
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Vitamin D Toxicity: Fiction or Fact?
Current understanding has it that the physiological requirement for vitamin D may be as high as 4-5,000 IU/day for adults. Although the Food and Nutrition Board established the tolerable upper intake level (UL) at 2,000 IU/day for adults, newer research demonstrates this amount is very conservative, and it appears unlikely that toxicity would occur in healthy people with doses less than 10,000 IU/day.8 For adolescents, 2,000 IU daily for a year has proven to be safe and efficacious.9
With many articles discussing that individual sensitivity issues may exist, it’s important to be aware that vitamin D toxicity is rare. One study showed 4,000 IU/day for several years was completely safe and only after taking 40,000 IU/day for several years is there risk of developing toxicity symptoms.5
That said, as I review the research, I am not so convinced that we can be casual about intake of high dosages of vitamin D supplements. Ideally, I think we should all do our very best to optimize vitamin D levels in summer, when UVB rays are available.
There is no vitamin D toxicity from the sun because UVA rays break down excess vitamin D. Vitamin D is stored in the fat, so we carry much of it into the winter months if we optimize the summer’s UVB rays. Unfortunately, most of us work indoors during midday summer hours, when the UVB rays are at their peak.
The Sunscreen Mistake
For the past 25 years, sunscreens have only blocked out skin-protecting UVB rays, but not UVA rays. It was mistakenly thought that UVB rays potentially caused abnormal cell division in the skin cells, so sunscreens were designed with SPF factors that reflect effectiveness of blocking only UVB rays. As it turns out, UVA rays are more abundant and penetrate deeper, making them more harmful than UVB rays.
Additionally, twenty years ago, SPF ratings were only at 10, but today they have risen up to 100, in the effort to make sunscreens more protective against abnormal cell growth. Sadly, all this time, sunscreens have been blocking protective UVB rays, while letting in harmful UVA rays.
Take a Vitamin D Test
While it is difficult to become toxic with vitamin D, experts believe it is ideal to keep levels at the higher end of normal, which is between 50-80 ng/ml. To maintain optimal levels, it is best to take a vitamin D test in the spring and fall. Once you establish the winter and summer dose of needed supplemental vitamin D3 that maintains levels in th 50-80ng/mL range you can reduce the frequency of vitamin D testing.
We offer an accurate Vitamin D Test Kit you can do at home. This test is inexpensive, safe, simple, accurate, and approved by the Vitamin D Council.
How to Optimize Vitamin D Levels + Prevent Deficiency
Summer Sun Exposure
Regularly receive midday sun exposure between 10am-2pm in late spring, summer, and early fall, exposing as much skin as possible for 10-15 minutes if you are fair-skinned, and longer if you are dark-skinned. Remember, you’ve had enough when skin shows the first sign of a pinkish change.
Supplementation: Depending on sun exposure and testing, I generally recommend a minimal vitamin D3 supplementation in the summer: perhaps 1,000-2,000 IU/day.
Test Your Levels: Test vitamin D levels to ensure you have optimized summer sun exposure.
The goal is to get vitamin D levels between 50-80 ng/ml and keep them there. Testing is the only way to know for sure you are maintaining these levels. Test yourself in the fall when levels are highest and in March when they are lowest. With those two numbers, everyone can safely calculate vitamin D supplement needs.
Children: Take 2,000 IU of vitamin D3 per day during winter.