Skin is your largest organ and one that works pretty hard. Besides forming a barrier against infection and outside invaders, regulating hydration levels in your body, and keeping the rest of you contained, your skin plays a pivotal role in producing vitamin D.
When the sun hits your skin, it manufactures vitamin D. The sun’s UVB rays (the same waves that are responsible for sunburns) interact with a protein called 7-DHC in the skin. This interaction produces vitamin D3, the active form of vitamin D.
Sun exposure is critical to produce vitamin D. 50-90% of the vitamin D circulating in your bloodstream is made by the sun. Since sunscreen was first produced in 1944 (Red Vet Pet 1944, later bought by Coppertone), people have been blocking UVB rays.
The big question is does using sunscreen also block vitamin D?
There’s new research that challenges what we thought we knew and we’ll get to that shortly.
First, why is vitamin D so important?
Vitamin D regulates the absorption of calcium and phosphorus which helps keep your bones and teeth strong. A deficiency of vitamin D can lead to bone problems like osteomalacia (softening of the bones), osteoporosis (fragile bones), or fractures.
A vitamin D deficiency can also cause muscle aches, muscle weakness and bone pain.
Vitamin D is also critical to a well balanced immune system.
There are vitamin D receptors on all of your white blood cells. The way vitamin D works in your system is complex.
Bottom line: Low levels of vitamin D have been associated with:
- More frequent infections of colds and flus.
- autoimmune diseases (not as a causative factor but as an aggravating one)
- Many diseases including cancer, cardio vascular disease, diabetes (these are correlational studies so not scientific causative ones)
- depression and anxiety
Getting enough Vitamin D
For a vitamin that’s essential to health, it’s shocking how many people are low or deficient in vitamin D. Estimates are that 40-50% of Americans are deficient, with the numbers being even higher for people of color (who need more sun exposure to get adequate amounts), older people, and people with chronic disease.
Vitamin D doesn’t naturally occur in many foods, so it’s hard to get what you need from diet.
Because of this, some foods are fortified. This means that vitamin D has been added. Foods that contain vitamin D include:
- egg yolk
- milk (fortified)
- cereal (fortified)
- yogurt (fortified)
- orange juice (fortified)
Vitamin D supplements
You can also take supplements to up your vitamin D level. There are two forms of vitamin D available-D2 and D3.
Vitamin D2 is produced from plants sources. UVB light causes plants to produce vitamin D from ergosterol which is a compound in plant oils.
Vitamin D3 is what's produced by your own skin and is also found in animal based foods (see above).
Supplements can be really useful in the winter months and high latitudes where the angle of the sun doesn’t allow for optimal vitamin D production. Vitamin D3 has been found to be more effective at raising vitamin D levels in people.
Here’s the thing. You can’t overdo vitamin D that’s made by your own skin. Once your body has enough, it just stops making more.
This isn’t the case with supplemented vitamin D, so if you’re taking a high dose supplement or taking it for long periods of time, it’s important to get your blood levels checked. 4000 IU a day is considered the upper safe limit for vitamin D supplementation, 400-800 IU a day is the US recommended daily minimum.
The absolute best way to get the right amount of vitamin D is to get outside in the sun. Unfortunately, there is no exact dose of sun for optimal vitamin D production.
The American Academy of Dermatology’s 2009 position statement on vitamin D concluded “there is no scientifically validated, safe threshold level of UV exposure from the sun that allows for maximal vitamin D synthesis without increasing skin cancer risk.”
We do know it takes people with darker skin more time in the sun to produce the same amount of vitamin D as people with lighter skin. This is because darker skin has more of the pigment melanin.
It also depends on the amount of skin a person has exposed.
The (American) Skin Cancer Foundation recommends as little sun exposure as possible to reduce DNA damage.
But not everyone agrees.
Other government health councils (Australia, New Zealand, Britain) recommend a least a few minutes of direct sun exposure each day. They recommend exposing your arms and legs (areas that don’t get the constant exposure of your face) for short periods of time every day (from 5-20 minutes, although I’ve seen recommendations for 30 too).
One solution to the question of how much sun exposure is just right might be the Dminder app.
The Dminder app, uses factors like your location, skin type, and time of day to optimize the amount of sunlight you need for vitamin D production, and makes sure you stay safe by warning you of any risk to your skin getting burned.
The $99,000 question-will using sunscreen block vitamin D production?
I’ve always thought this is the elephant in the room. We’re told we need to avoid the sun because of skin cancer and premature skin aging risks, but we’re also warned of the dangers of vitamin D deficiency. Vitamin D is best gotten by sun exposure.
If we’re blocking UV rays with sunscreen, aren’t we also blocking vitamin D production?
Common sense (and just about everything on the internet) say yes.
Recent studies (see references below), say no. In fact, there has never been a study that has shown vitamin D blood levels to go down when sunscreen has been used.
One of the theories for this is that most people don’t apply sunscreen properly, so they’re still getting UVB rays. Another explanation is that even high SPF (a measure of UVB protection only) sunscreens don’t block 100% of UVB rays and the small percentage of rays that do get through are enough to keep vitamin D levels up.
UVA rays are important too
One of the main problems with the whole vitamin D, sun exposure, sunscreen issue is that we’re only talking about UVB rays and damage.
UVA rays are the more penetrating rays responsible for damaging the deeper layers of the skin and causing wrinkles, sagging, hyperpigmentation and photo-aging. And some skin cancers.
Undesirables for sure.
And another vote for sunscreen, especially on the areas that are constantly exposed to the sun (face, neck, hands). Broad spectrum sunscreen is what you need to screen UVA rays.
Like many things in life, balance and personal choice are keys. Sun is vital to health, too much sun is not. Vitamin D is crucial for immune and bone health at the least.
What you decide to do with all of the available information is up to you. An informed choice is your best choice.
Sunscreen on the face, neck, and hands for sure. They’re the parts of your body that are constantly exposed to the sun. And the parts that are most upsetting when they begin to show permanent signs of sun damage. I’ll use a mineral based, broad spectrum product that’s good for my skin and the environment.
I’ll let my arms and legs get some exposure, maybe 15-30 minutes most days. Less if it’s during the strongest part of the sun’s day. Maybe I’ll try the Dminder app (try it, it’s free) to get a good feel for how much sun I need to make enough vitamin D.
Then I’ll cover up or put on some sun screen and keep having fun outside.
How about you?
A.R. Young, J. Narbutt, G.I. Harrison, K.P. Lawrence, M. Bell, C. O'Connor, P. Olson, K. Grys, K. Baczynska, M. Rogowski‐Tylman, H.C. Wulf, A. Lesiak, P.A. Philipsen. Optimal sunscreen use, during a sun‐holiday with a very high UV index, allows vitamin D synthesis without sunburn. British Journal of Dermatology, 2019; DOI: 10.1111/bjd.17888