Everyone who lives in Wisconsin has participated in the running joke of our long winters wreaking havoc on our collective spirit. Our winters are harsh and the gray, sunless days stretch on for months. Lucky for us, summer is at its peak, which means the hardships of winter are far off (for now).
All humor aside, the thought that our moods are affected by the seasons is not far from fact. Vitamin D synthesis is triggered by ultraviolet B rays, or sunlight. According to a psychiatric study, vitamin D deficiency in older adults leads to a higher risk of mood disorders and decreased cognitive functioning. The study even indicated a greater risk for the onset of Alzheimer’s disease. Vitamin D also plays a key role in preventing osteoporosis and maintaining bone health both in children and adults.
It’s no wonder, then, why everyone seems happier in the summertime. More sun exposure leads to a better mood. However, if done properly, you can ensure that your body is vitamin D sufficient all year round. Technically, your body can accumulate and store enough vitamin D in the spring, summer, and fall through adequate sun exposure.
Here are some facts about vitamin D through sunlight:
- Complete cloud cover reduces UV energy by 50%; shade (including that produced by severe pollution) reduces it by 60%[i]
- UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin D[ii]
- Sunscreens with a sun protection factor (SPF) of 8 or more appear to block vitamin D-producing UV rays, although in practice people generally do not apply sufficient amounts, cover all sun-exposed skin, or reapply sunscreen regularly[iii]
I am one to always highly recommend sunscreen for various reasons, but in the case of vitamin D sufficiency, I suggest forgoing sun protection for only your first 30 minutes of sun exposure. Scientifically, you only need to be exposed to the sun for 5-30 minutes per day between the hours of 10 AM and 3 PM in order to meet your daily vitamin D intake.
In the summer, this requirement is easily met. In the spring and fall, try and make it outside whenever you see a break in the clouds. For instance, go for a 15-minute walk in the afternoon or take your lunch breaks outside at work. Ideally, your body will have enough vitamin D stored in normal layers of body fat to make it through the winter.
This is where it gets tricky. Older adults or those who cannot often leave their homes need to pay extra attention to sources of vitamin D. Because vitamin D is found in so very few foods, like the skin of swordfish, salmon, and tuna, a vitamin D supplement is something I recommend to my patients. I should note here that vitamin D is added to drinks like milk or orange juice, but with the rise of lactose sensitivities and the sugar content of orange juice, I still prefer supplements.
Supplements themselves can be confusing, but when you’re shopping for vitamin D, it’s helpful to know that both Vitamin D2 and Vitamin D3 are equivalent in their effectiveness. As for dosage, here’s a guide to who should be taking how much vitamin D:
- The American Academy of Pediatrics (AAP) recommends that exclusively and partially breastfed infants receive supplements of 400 IU/day of vitamin and all non-breastfed infants ingesting <1,000 mL/day of vitamin D-fortified formula or milk should receive a vitamin D supplement of 400 IU/day
- Children, men, and women, should take 15mcg or 600 IU of vitamin D per day if they are not meeting sun exposure requirements or eat an unbalanced diet
- Men and women over the age of 70 should take 20mcg or 800 IU of vitamin D per day
If you have any questions regarding particular brands of supplements, nutrition, or proper sun exposure, consult with me at Lifestyle Chiropractic. In the meantime, go outside and enjoy the sun! You now have a medical excuse to take that much-needed break outside.
[i] Wharton B, Bishop N. Rickets. Lancet 2003;362:1389-400.
[ii] Holick MF. Photobiology of vitamin D. In: Feldman D, Pike JW, Glorieux FH, eds. Vitamin D, Second Edition, Volume I. Burlington, MA: Elsevier, 2005.
[iii] Wolpowitz D, Gilchrest BA. The vitamin D questions: how much do you need and how should you get it? J Am Acad Dermatol 2006;54:301-17.
Best of health,
Dr. Chad M. Hoffman