After a week of fun in the sun, I thought I’d shed some light on the “sunshine vitamin”: vitamin D, especially since I just wrote about calcium yesterday and the fact that our bodies require vitamin D to absorb calcium and promote bone growth. Vitamin D is essential for health. Additionally, vitamin D helps our immune system fight many chronic diseases, including osteoporosis, diabetes, multiple sclerosis, several cancers (including breast, colon, lung, lymphoma and prostate), high blood pressure, pregnancy complications and cardiovascular disease.
Vitamin D3 (cholecalciferol) is synthesized in our skin by exposure to ultraviolet-B (UVB) light. Exposure to UVA light does not synthesize vitamin D3 in our skin; only exposure to UVB synthesizes vitamin D in our skin. There’s more UVB toward the middle of the day (closer to noon), while there’s no UVB and only UVA early and late in the day.
Recommendations for vitamin D requirements and how to get enough vitamin D have changed since they were first published in the mid-1990s because we now understand much more about vitamin D than we did at that time. Those recommendations, which are still in use, are outdated and were intended to prevent rickets and osteomalacia (softening of bones).
Sun exposure is our best source of vitamin D, so get your vitamin D from mid-day sunlight whenever possible. Wearing a swimsuit is best as it maximizes skin exposure. Do not use sunscreen during the specified exposure time because sunscreen blocks UVB exposure, preventing synthesis of vitamin D. Afterwards, be sure to use some sort of sun block if you plan to remain in the sun, including sunscreen, clothing, hats, etc. According to Matt Lederman, M.D., here’s how much daily sun exposure (without sunscreen) you need, depending on the UV index (UVI) and your skin type.
If you always burn and never tan:
If you easily burn and rarely tan:
If you occasionally burn and slowly tan:
If you rarely burn and rapidly tan:
If you never burn and are always dark:
Your body will produce 10,000 – 15,000 IU of vitamin D per day when getting the recommended sun exposure based on the UVI and your skin type.
The brief exposure required to produce enough vitamin D is not enough to cause sun cancer. Some sun exposure may actually be protective against cancer. Burning is probably cancer-promoting, while no sun exposure seems to be cancer-promoting as well. Prevent burning by spending only the recommended times in the sun without sun protection and no more.
There are many reasons you may not be able to get daily sun exposure. You can also get vitamin D as a supplement. The recommended amount of vitamin D is 4,000 IU per day. Most of us typically get as much as 2,000 IU per day from sun exposure and fortified foods such as milks (including soy and almond milk), orange juice, and breakfast cereals. We can make up the difference by taking 1,000 to 3,000 IU per day as supplements. The upper limit (vitamin D toxicity) 10,000 IU/day from supplements. Interestingly, while your body synthesizes at least this much vitamin D from daily exposure to sunlight, overexposure to sunlight cannot cause vitamin D toxicity; only supplementation can cause vitamin D toxicity.
Time to go get some vitamin D for today!
Resources:
Vitamin D Frequently Asked Questions by Robert P. Hearney, M.D., internationally recognized expert on vitamin D, professor at John A. Creighton University, and co-founder of the Creighton University Osteoporosis Research Center.
Lecture notes from a course I personally attended by Matt Lederman, M.D., board-certified internal medicine physician and founder of Exsalsus Health and Wellness Center in conjunction with the T. Colin Campbell Foundation and eCornell.
Vitamin D3 (cholecalciferol) is synthesized in our skin by exposure to ultraviolet-B (UVB) light. Exposure to UVA light does not synthesize vitamin D3 in our skin; only exposure to UVB synthesizes vitamin D in our skin. There’s more UVB toward the middle of the day (closer to noon), while there’s no UVB and only UVA early and late in the day.
Recommendations for vitamin D requirements and how to get enough vitamin D have changed since they were first published in the mid-1990s because we now understand much more about vitamin D than we did at that time. Those recommendations, which are still in use, are outdated and were intended to prevent rickets and osteomalacia (softening of bones).
Sun exposure is our best source of vitamin D, so get your vitamin D from mid-day sunlight whenever possible. Wearing a swimsuit is best as it maximizes skin exposure. Do not use sunscreen during the specified exposure time because sunscreen blocks UVB exposure, preventing synthesis of vitamin D. Afterwards, be sure to use some sort of sun block if you plan to remain in the sun, including sunscreen, clothing, hats, etc. According to Matt Lederman, M.D., here’s how much daily sun exposure (without sunscreen) you need, depending on the UV index (UVI) and your skin type.
If you always burn and never tan:
- UVI 0-2: NA
- UVI 3-5: 10-15 min exposure
- UVI 6-7: 5-10 min exposure
- UVI 8-10 (and tanning): 2-8 min exposure
- UVI 11+: 1-5 min exposure
If you easily burn and rarely tan:
- UVI 0-2: NA
- UVI 3-5: 15-20 min exposure
- UVI 6-7: 10-15 min exposure
- UVI 8-10 (and tanning): 5-8 min exposure
- UVI 11+: 2-8 min exposure
If you occasionally burn and slowly tan:
- UVI 0-2: NA
- UVI 3-5: 20-30 min exposure
- UVI 6-7: 15-20 min exposure
- UVI 8-10 (and tanning): 10-15 min exposure
- UVI 11+: 5-10 min exposure
If you rarely burn and rapidly tan:
- UVI 0-2: NA
- UVI 3-5: 30-40 min exposure
- UVI 6-7: 20-30 min exposure
- UVI 8-10 (and tanning): 15-20 min exposure
- UVI 11+: 10-15 min exposure
If you never burn and are always dark:
- UVI 0-2: NA
- UVI 3-5: 40-60 min exposure
- UVI 6-7: 30-40 min exposure
- UVI 8-10 (and tanning): 20-30 min exposure
- UVI 11+: 15-20 min exposure
Your body will produce 10,000 – 15,000 IU of vitamin D per day when getting the recommended sun exposure based on the UVI and your skin type.
The brief exposure required to produce enough vitamin D is not enough to cause sun cancer. Some sun exposure may actually be protective against cancer. Burning is probably cancer-promoting, while no sun exposure seems to be cancer-promoting as well. Prevent burning by spending only the recommended times in the sun without sun protection and no more.
There are many reasons you may not be able to get daily sun exposure. You can also get vitamin D as a supplement. The recommended amount of vitamin D is 4,000 IU per day. Most of us typically get as much as 2,000 IU per day from sun exposure and fortified foods such as milks (including soy and almond milk), orange juice, and breakfast cereals. We can make up the difference by taking 1,000 to 3,000 IU per day as supplements. The upper limit (vitamin D toxicity) 10,000 IU/day from supplements. Interestingly, while your body synthesizes at least this much vitamin D from daily exposure to sunlight, overexposure to sunlight cannot cause vitamin D toxicity; only supplementation can cause vitamin D toxicity.
Time to go get some vitamin D for today!
Resources:
Vitamin D Frequently Asked Questions by Robert P. Hearney, M.D., internationally recognized expert on vitamin D, professor at John A. Creighton University, and co-founder of the Creighton University Osteoporosis Research Center.
Lecture notes from a course I personally attended by Matt Lederman, M.D., board-certified internal medicine physician and founder of Exsalsus Health and Wellness Center in conjunction with the T. Colin Campbell Foundation and eCornell.
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