The Sunshine Vitamin: Does Sunscreen Affect Vitamin D Synthesis?
It’s MS awareness month here in Canada, and with it comes a welcomed change in the weather. While my family took full advantage of the very wintery winter we just experienced, with lots of skiing, skating, and tobogganing, we’re nonetheless ready for some heat and sunshine. The sun making more regular appearances has me thinking about sunscreen. But is sunscreen a good idea for those of us living with MS?
When I was diagnosed with Optic Neuritis, the MS symptom which led to my diagnosis, my neuro-ophthalmologist told me to start supplementing 4,000 IU of Vitamin D3 per day. Why? He strongly suspected that MS was the underlying cause of my Optic Neuritis attack and he knew that Vitamin D deficiency is correlated to worse MS progression. When I first met with my neurologist at the St. Michael’s Hospital MS Clinic, he asked if I was supplementing Vitamin D3 and I advised that I had increased my Vitamin D3 supplementation from 800 IU per day to 4,000 IU per day on the advice of my neuro-ophthalmologist. My neurologist expressed that he was impressed with how knowledgeable my neuro-ophthalmologist appeared to be. He confirmed that I should continue to supplement 4,000 IU of Vitamin D3 per day. I have since learned that this level of supplementation of Vitamin D3 is the standard advice of most neurologists advising MS patients.
Vitamin D is one of the thirteen Vitamins discovered by doctors who were studying diseases caused by nutritional deficits in the early 20th Century. However, it’s not technically a Vitamin. Vitamins are organic compounds that are required in small quantities in the diet for normal physiological functioning, and which cannot be synthesized in sufficient amounts by the body. While Vitamin D is essential for health, it can usually be produced in sufficient amounts by the body. There are limited food sources for Vitamin D: fatty fish, egg yolks, beef liver, mushrooms that are exposed to sunlight, like maitake and portobello, and some cheeses. Nowadays many foods are fortified with Vitamin D: milk, cereal, orange juice, and yogurt. However, the primary source of Vitamin D for most people is synthesis through skin exposure to ultraviolet B (UVB) radiation from sunlight. UVB radiation converts 7-dehydrocholesterol in the skin into Vitamin D3 (cholecalciferol). The liver then converts the Vitamin D3 into 25-hydroxyvitamin D3 (calcidiol). The kidneys then convert it into the active form of Vitamin D, 1,25-dihydroxyvitamin D3 (calcitriol).
Vitamin D deficiency is known to be correlated to a higher risk for developing MS, as well as to a higher rate of MS progression in patients living with the disease. There are a number of studies demonstrating that being born and living near the equator significantly reduces the risk of several different autoimmune diseases, including MS. It’s important to remember that correlation does not equate to causation. While this known issue of Vitamin D deficiency in those living with MS, and particularly those living with aggressive MS, has resulted in neurologists recommending Vitamin D3 supplementation as a standard practice, increasingly randomized controlled clinical trials are undermining this advice.
A recent meta-analysis of randomized controlled trials sought to assess the impact of Vitamin D3 supplementation on clinical and radiological outcomes in MS patients and found no statistically significant reduction in patients’ Expanded Disability Status Scale (EDSS) score and no statistically significant reduction in patients’ annualized relapse rate. The authors of the meta-analysis conclude that there is no current evidence to support that Vitamin D3 supplementation impacts clinical outcomes in MS patients. However, they did point to a non-statistically significant reduction in patients’ development of T2 lesions to suggest that further research is warranted to evaluate whether this observation precedes a long-term clinical benefit.
Does all of this mean that we shouldn’t be supplementing Vitamin D3 anymore? Not so fast! Despite knowing that the evidence isn’t really checking out for the benefits of supplementing Vitamin D3 in the setting of MS, neurologists are still routinely advising MS patients to supplement Vitamin D3. Why? Because at low levels, Vitamin D3 supplements are extremely safe and unlikely to cause any harm. It is also an inexpensive and widely available supplement. So if there is even a modest chance that supplementing Vitamin D3 could help with an MS patient’s prognosis, it is likely worth doing.
Notably, this is not one of those scenarios in which some is good, so more is better. The reason why my neuro-ophthalmologist and my neurologist recommended that I take 4,000 IU of Vitamin D3 per day is that this dose is generally recognized as the safe upper intake limit for supplemental Vitamin D3 according to most health authorities. Overconsumption of supplemental Vitamin D typically only occurs when a person engages in prolonged use of megadoses. Vitamin D toxicity, also known as hypervitaminosis D, causes harmful levels of calcium to build up in your blood (hypercalcemia). This can have serious health consequences, including dehydration, kidney stones, or kidney damage or failure.
People who live at latitudes above 37 degrees North or below 37 degrees South of the equator don't get enough UVB energy from the sun to make all the Vitamin D that they require. As someone who lives above the 44th parallel North, that’s me. The same is true for people who spend most of their time indoors. Once again, as someone who spends a lot of time working at a desk, that is also me.
When supplementing Vitamin D, it is usually Vitamin D3 (cholecalciferol) that is recommended over Vitamin D2 (ergocalciferol). There’s a few reasons for this. First, Vitamin D3 increases and maintains serum 25-hydroxyvitamin D3 more effectively than Vitamin D2. It also has a longer half-life in the bloodstream, which results in more consistent levels over time. Vitamin D3 is the same form that your skin produces when exposed to sunlight.
Sun exposure is an important source of Vitamin D. However, sun exposure is also a leading cause of skin cancer. UVB radiation provides the energy that your skin needs to produce Vitamin D, but that very same energy can burn the skin and cause cell damage that can ultimately lead to skin cancer. The medical community warns us to avoid sun exposure between 10am and 2pm, wear wide-brimmed hats, and wear a broad spectrum sunscreen with an SPF of 30 or higher. This is to reduce our risk for skin cancer. As a freckled person so white that I get a sunburn just thinking about the beach, sunscreen is a must for me. But does all this skin cancer prevention put us at a higher risk of being Vitamin D deficient?
A recent meta-analysis of four experimental studies, three field trials (including two randomized controlled trials), and 69 observational studies, sought to evaluate whether sunscreen use reduced 25-hydroxyvitamin D3 concentration in the blood. While the experimental studies involving exposure to artificially generated UV radiation demonstrated considerable reduction in 25-hydroxyvitamin D3 production, the field trials and observational studies found no effect of daily sunscreen use on 25-hydroxyvitamin D3 concentration in the blood. Sunscreen can reduce vitamin D production, but in real-life use people rarely apply enough sunscreen to fully block UVB rays. Most people still make vitamin D even with sunscreen on. The authors of the meta-analysis conclude that concerns about Vitamin D deficiency should not negate skin cancer prevention advice when it comes to sunscreen. However, they do suggest further research as more potent sunscreen products enter the market.
As for me, I’m trying out a new brand of sunscreen this year as part of my efforts to buy more Canadian-made products. I just picked up some Green Beaver mineral sunscreen.
TL;DR: People with MS should not skip the sunscreen, but we should try to incorporate plenty of dietary sources of Vitamin D, we should ensure that we get limited and cautious sun exposure, and we should supplement Vitamin D3 in consultation with our doctors.
