Do We Need Vitamin D in Sunny Climates?
Why we can fall short even in a warm climate.
Vitamin D deficiency in Sunny Climates
Did you know that lots of us here in sunny southern California suffer from Vitamin D insufficiency? We’d expect that in Portland Oregon right, but why in Santa Monica?
Shed Some Light on the Facts
It turns out we need to watch our Vitamin D levels, regardless of which sun-infused skies we enjoy. In fact, almost 50% of the worldwide population (about 5 Billion) across all temperature zones suffer from vitamin D deficiency.
A major source of vitamin D for most humans is synthesized from the exposure of the skin to sunlight typically between 1000 h and 1500 h in the spring, summer, and fall. Vitamin D produced in the skin may last at least twice as long in the blood compared with ingested vitamin D.
When an adult wearing a bathing suit is exposed to one minimal erythemal dose of UV radiation (a slight pinkness to the skin 24 h after exposure), the amount of vitamin D produced is equivalent to ingesting between 10,000 and 25,000 IU. A variety of factors reduce the skin's production of vitamin D3, including increased skin pigmentation, aging, and the topical application of sunscreen. An alteration in the sun's zenith angle caused by a change in latitude, the season of the year, or time of day dramatically influences the skin's production of vitamin D3.
Do You Have a Good Latitude?
Well yes, the latitude (distance from the equator) seems primary, but besides that, there is a range of other factors that can affect vitamin D synthesis in the skin, such as gender, adiposity (body fat), clothing habits, cloud cover, pollution, skin pigmentation, and genetic factors. One or more of those factors can significantly affect how much Vitamin D we can synthesize.
When Sun Protection Works Against Us
Surprisingly, our great diligence in protecting our skin from harmful sunlight exposure in order to decrease the risk of skin cancer, especially in sunny countries, has a double-edged effect. Sun avoidance and/or covering protection and regular use of sunscreen are encouraged in many countries, and rightfully so, this may have had an adverse effect on our ability to absorb vitamin D. This only makes sense, right; if we cover our skin and block the harmful rays, we cannot activate the mechanisms to unlock Vitamin D.
Lifestyle Causes of Vitamin D Deficiency
No surprise but the rise of the D deficiency pandemic is mostly due to lifestyle and environmental factors which reduce exposure to sunlight. The big deal about sunshine is that it is the mechanism required for ultraviolet-B (UVB)-induced vitamin D production in the skin.
With us being so much more diligent these days about skin protection with an enormous selection of sunscreen and deflective clothing, both of which are critical to reducing the risk of deadly melanoma, and let’s face it, wrinkle prevention. However, the challenge is getting enough direct sunshine to make the necessary amounts of Vitamin D, which are likewise critical for our general health and disease prevention. For example, using sunscreen with an SPF of 30 reduces vitamin D synthesis in the skin by more than 95%. And people with a naturally dark skin tone have natural sun protection and they require three to five times longer exposure to make the same amount of vitamin D as a person with a white skin tone.
Vitamin D from Direct Sunshine - Safely
With intention, we can safely get the sun exposure we need by following a few guidelines. To maintain healthy Vitamin D blood levels, aim for 10–30 minutes of midday sunlight depending on your skin color and sensitivity, and where you live including altitude. Optimum is several times per week, directly on the exposed skin, without sun cover. People with darker skin may need a little more than this. Your exposure time should depend on how sensitive your skin is to sunlight.
People with Limited Sun Exposure - at Risk
Homebound individuals, women who wear long robes and head coverings for religious reasons, and people with occupations that limit sun exposure are unlikely to obtain adequate vitamin D from sunlight. Plus sunscreen does play a role in reducing vitamin D synthesis.
People with dark skin
Larger amounts of the pigment melanin in the epidermal layer result in darker skin and reduces the skin's ability to produce vitamin D from sunlight. It has not been proven that lower levels of 25(OH)D for persons with dark skin have significant health consequences. Intake of RDA levels of vitamin D from foods and/or supplements will provide adequate amounts of this nutrient to these individuals if there is a concern.
People who are obese
A BMI value of ≥30 is associated with lower serum 25(OH)D levels compared with non-obese individuals. Obese people may need larger than usual intakes of vitamin D https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3356951/ to achieve 25(OH)D levels comparable to those of normal weight. Greater amounts of the subcutaneous fat sequester (captivate) more of the vitamin and alter its release into the circulation.
Gastric bypass surgery
Individuals who have undergone gastric bypass surgery may become vitamin D deficient over time without a sufficient intake of vitamin D from food or supplements; moreover, part of the upper small intestine where vitamin D is absorbed is bypassed.
Fat malabsorption
Vitamin D is fat-soluble, therefore it requires some dietary fat in the gut for absorption. Individuals with reduced ability to absorb dietary fat might require vitamin D supplements. Fat malabsorption is associated with a variety of medical conditions including some forms of liver disease, cystic fibrosis, and Crohn's disease.
Vitamin Supplementation
First of all, getting your Vitamin D levels checked is as easy as getting a blood test done. And that means regularly, not every few years as Vitamin D levels can change quickly. Having regular blood work is a really good way to get accurate levels especially for people with osteoporosis or certain other health conditions.
Recommendations for how much daily vitamin D adults need through diet have changed over the years and currently, you can find many different opinions. The Institute of Medicine has placed the recommended dietary allowance, or RDA, for vitamin D at 600 international units (IU) per day for young adults and 800 IU per day for adults older than 70. That seems low to me, especially if I am spending time in Oregon. Other experts suggest that adults’ vitamin D needs are much higher. For example, the Endocrine Society recommends up to 2,000 IU of vitamin D daily for adults. It’s important to meet with a doctor or naturopath who will consider all of the factors as we have mentioned above.
