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Several recent articles on Medscape (a site for medical professionals) highlight the debate over vitamin D. The question: Does daily vitamin D supplementation have positive health benefits or not? Everyone agrees that if there is an actual deficiency, then it has positive health effects. But how about the average person with levels above the deficiency level?

Numerous observational studies find that low levels of vitamin D are associated with all sorts of health problems (e.g., cancer, heart disease), but randomly controlled trials (RCT) where people are randomly assigned to different groups with no one knowing what they are getting - just aren't finding health benefits. The strongest evidence so far has been for vitamin D supplementation resulting in lower incidence of upper respiratory illnesses.

What is going on? Some suggest that low vitamin D levels are a marker for ill health (the illness reduces the vitamin D levels), and that vitamin D levels go down when there is chronic inflammation. It could also be a proxy for sun exposure (the more sunlight, the higher the vitamin D levels). Note that sunlight may have additional benefits compared to just vitamin D supplementation (e.g, blue light is immune boosting).

John M. Mandrola, MD writes for Medscape, and his articles tend to be thought-provoking. Some excerpts of a Commentary by Dr. John Mandrola from Medscape: Why Is Vitamin D Hype So Impervious to Evidence?

The vitamin D story exudes teaching points: it offers a master class in critical appraisal, connecting the concepts of biologic plausibility, flawed surrogate markers, confounded observational studies, and slews of randomized controlled trials (RCTs) showing no benefits on health outcomes.

Yet despite the utter lack of benefit seen in trials, the hype continues....

My questions are simple: Why doesn't the evidence persuade people? How many nonsignificant trials do we need before researchers stop studying vitamin D, doctors stop (routinely) measuring levels, and patients stop wasting money on the unhelpful supplement? What are the implications for this lack of persuasion?  ...continue reading "Some Large Studies Find No Benefit From Vitamin D Supplements"

We've all been warned over and over to avoid sunlight in order to avoid skin cancer, but... conflicting with that advice are studies linking higher sunlight exposure to lower levels of other cancers, health benefits (e.g. lower blood pressure), and early death (mortality). One such recent study found that higher sun exposure over the years is associated with a lower risk of breast cancer in women.

The Univ. of Buffalo and Univ. of Puerto Rico researchers conducted the study in Puerto Rico, where people live with high year round sun exposure. 635 women participated in the study.

From Medical Xpress: Study in Puerto Rico finds lower risk of breast cancer with more sun exposure

The sun is almost always shining during the day in San Juan, Puerto Rico, and that makes the findings of a new study on breast cancer and sun exposure particularly noteworthy.  ...continue reading "Study Finds Lower Risk of Breast Cancer With Higher Sunlight Exposure"

Another study found that increased sun exposure in children and young adults is linked to lower levels of multiple sclerosis. This was the main finding of a study conducted at multiple centers in the United States by a team of American and Australian researchers.

The researchers in the study stated that not only does sunlight boost vitamin D levels, it also "...stimulates immune cells in the skin that have a protective role in diseases such as multiple sclerosis." In addition, they found an association with the intensity of sunlight and estimated that residents of Florida would be 21 percent less likely than residents of New York to have multiple sclerosis. Sun exposure appears to be dose dependent - the longer the exposure, the lower the risk of multiple sclerosis.

Earlier studies also found immune boosting properties of sunlight. Sunlight has low levels of "blue light" which energizes T cells that play a central role in human immunity. T cells are a type of white blood cell, are part of the immune system, and help protect the body from infection and cellular abnormalities (cancer). 

Bottom line: In this study getting at least 30 minutes (up to 1 hour) of sunshine daily, especially in the summer, seems to be key in terms of protective effects.

From Medical Xpress: Sunshine may shield children, young adults from MS

Living in sunny locations and spending time outdoors may raise the risk for skin cancer, but a new study led by UC San Francisco and the Australian National University shows that in children and young adults, sun exposure may protect against multiple sclerosis. The study follows previous work by other researchers that has demonstrated an association between increased ultraviolet exposure in childhood and lower odds of adult MS ...continue reading "Sunshine and Multiple Sclerosis in Children and Young Adults"

Researchers in Canada found that sunlight (or UVB light) on the skin changes the gut microbes (gut microbiome), especially in people with lower levels of vitamin D, that is, who are vitamin D deficient. UVB (Ultraviolet B light) exposure increased beneficial gut microbe diversity and richness in these people, as well as increasing their vitamin D levels. However, people who had been taking vitamin D supplements prior to the study, and who had sufficient vitamin D levels, did not have significant gut microbiome changes.

The researchers viewed the study results as evidence that there may be a skin-gut axis. As the researcher Vallance said: “It is likely that exposure to UVB light somehow alters the immune system in the skin initially, then more systemically, which in turn affects how favorable the intestinal environment is for the different bacteria,” suggested Vallance.

The researchers also thought that these study results (which was conducted in Vancouver, Canada, in healthy human volunteers) could help explain the protective effect of UVB light against inflammatory diseases such as multiple sclerosis (MS) or inflammatory bowel disease (IBD). And how did the researchers know what bacteria were in the gut in the study participants? They analyzed the feces with modern genetic sequencing methods. By the way, these results match what has been found in earlier studies in humans and mice.

Bottom line: Sunlight on the skin is beneficial to the gut microbiome, by increasing gut bacteria linked to health. In the study the increases in bacteria (after UVB light exposures) were in the Lachnospiraceae, Ruminococcus, and Clostridiaeae families. And nope, none of those are found in currently available probiotics. By the way, this study was conducted in winter in Canada, so the effects of UVB light were clearly seen in the healthy volunteers. This study supports getting some sunlight exposure (on the skin), and perhaps supplementing with vitamin D in the winter.

From Medical Xpress: Where the sun doesn't shine? Skin UV exposure reflected in poop  ...continue reading "Exposure To Sunlight Improves Gut Microbes and Vitamin D Levels"

Are we looking at vitamin D and sunlight the wrong way? Back in 2016 I posted about the results of a long-running Swedish study that made me rethink everything I knew about sunlight and health. (The prevailing view of dermatologists at the time and now is: to always use sunscreen if going outdoors in order to lower the risk of skin cancer. In other words, that sunlight is always harmful.)

The Swedish study followed women for 20 years and found that: Women who had more sunlight exposure experienced a lower mortality rate than women who avoided sun exposure. However, they were at an increased risk of skin cancer. But those with more sun exposure lived longer due to a decrease in heart (cardiovascular) disease and other noncancer reasons. And the most surprising finding: Nonsmokers who avoided sun exposure had a similar life expectancy as smokers with the highest sun exposure. In other words: avoidance of sun exposure = cigarette smoking when looking at life expectancy. And the results of sun exposure was dose-dependent, with the more, the better for longer life expectancy.

The researchers suggested that  a person's vitamin D levels might be just a marker of sun exposure, which other studies and articles now also suggest. So while we measure vitamin D levels in studies, maybe we should instead be looking at sunlight exposure.

Since then I read more studies that found other benefits of sunlight exposure, such as sunlight having low levels of "blue light" which energizes T cells. T cells are a type of white blood cell, are part of the immune system, and help protect the body from infection and cellular abnormalities (cancer). An earlier study found that exposing skin to sunlight may help to reduce blood pressure and thus cut the risk of heart attack and stroke.

This year I read the following two nicely written articles about this whole issue, both a little different - so worth reading both to get a good idea about the research and the debate.

1) From Outside: Is Sunscreen the New Margarine?

2) From Elemental Medium: What If Avoiding the Sun Is Bad for You?

And once again, a link to the 20 year Swedish study, from the Journal of Internal Medicine: Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort

Two more studies found that higher levels of vitamin D in the blood are associated with better health outcomes - one study found a lower risk of breast cancer, especially among postmenopausal women, and in the other - better outcomes after a metastatic melanoma diagnosis.

The breast cancer study suggested that a fairly high blood level of vitamin D (25(OH)D serum level>38.0 ng/mL) was associated with a lower risk of breast cancer. But overall they found that women supplementing with vitamin D (more than 4 times a week) at any dose had a lower risk of breast cancer over a 5 year period than those not supplementing with vitamin D. From Environmental Health Perspectives:

Serum Vitamin D and Risk of Breast Cancer within Five Years

Vitamin D is an environmental and dietary agent with known anticarcinogenic effects, but protection against breast cancer has not been established. We evaluated the association between baseline serum 25-hydroxyvitamin D [25(OH)D] levels, supplemental vitamin D use, and breast cancer incidence over the subsequent 5 y of follow-up. From 2003-2009, the Sister Study enrolled 50,884 U.S. women 35-74 y old who had a sister with breast cancer but had never had breast cancer themselves. Using liquid chromatography-mass spectrometry, we measured 25(OH)D in serum samples from 1,611 women who later developed breast cancer and from 1,843 randomly selected cohort participants.

We found that 25(OH)D levels were associated with a 21% lower breast cancer hazard (highest versus lowest quartile). Analysis of the first 5 y of follow-up for all 50,884 Sister Study participants showed that self-reported vitamin D supplementation was associated with an 11% lower hazard. These associations were particularly strong among postmenopausal women.

In this cohort of women with elevated risk, high serum 25(OH)D levels and regular vitamin D supplement use were associated with lower rates of incident, postmenopausal breast cancer over 5 y of follow-up. These results may help to establish clinical benchmarks for 25(OH)D levels; in addition, they support the hypothesis that vitamin D supplementation is useful in breast cancer prevention.

The first sentence in the melanoma study lays out what is widely known: "Vitamin D deficiency (≤20 ng/mL) is associated with an increased incidence and worse prognosis of various types of cancer including melanoma." Studies show that the relationship between vitamin D, sunlight exposure, and melanoma is complicated in a number of ways, including: sun exposure may be associated with increased survival in patients with melanoma. which may mean that vitamin D has a protective role in patients with melanoma. Several studies suggest that vitamin D may delay melanoma recurrence and improve overall prognosis. The study also found that metastatic melanoma patients with vitamin D deficiency who are unable to or don't raise their vitamin D blood levels (25(OH)D3) have a worse outcome compared to those who are are able to markedly increase (by greater than >20 ng/mL) their 25(OH)D3 levels. From Oncotarget:

Vitamin D deficiency is associated with a worse prognosis in metastatic melanoma

Vitamin D deficiency (≤20 ng/mL) is associated with an increased incidence and worse prognosis of various types of cancer including melanoma. A retrospective, single-center study of individuals diagnosed with melanoma from January 2007 through June 2013 who had a vitamin D (25(OH)D3) level measured within one year of diagnosis was performed to determine whether vitamin D deficiency and repletion are associated with melanoma outcome.

A total of 409 individuals diagnosed with histopathology-confirmed melanoma who had an ever measured serum 25(OH)D3 level were identified. 252 individuals with a 25(OH)D3 level recorded within one year after diagnosis were included in the study .... A worse melanoma prognosis was associated with vitamin D deficiency, higher stage, ulceration, and higher mitotic rate. In patients with stage IV metastatic melanoma, vitamin D deficiency was associated with significantly worse melanoma-specific mortality. Patients with metastatic melanoma who were initially vitamin D deficient and subsequently had a decrease or ≤20 ng/mL increase in their 25(OH)D3 concentration had significantly worse outcomes compared to non-deficient patients who had a >20 ng/mL increase. Our results suggest that initial vitamin D deficiency and insufficient repletion is associated with a worse prognosis in patients with metastatic melanoma.

I've frequently mentioned that when taking vitamin D supplements, the one to take is vitamin D3, and not D2. Medscape (the medical site) has an article explaining that results of a recent study showed that vitamin D3 is twice as effective as D2 in raising blood levels of vitamin D. The vitamin D3 form is derived from animal products, while vitamin D2 is plant-based. So check any supplements you purchase because many contain the vitamin D2 form of vitamin D.

Of course, sunlight is the best because it has more benefits than vitamin D - such as also having low levels of "blue light" which energizes T cells (which are part of the immune system). From Medscape:

Vitamin D3, Not D2, Is Key to Tackling Vitamin D Deficiency

Vitamin D3 is significantly more effective at raising the serum biological marker of vitamin D status than vitamin D2 when given at standard doses in everyday food and drink, say UK researchers — findings that could have major implications for both current guidelines and the supplement industry.

In a randomized controlled trial of vitamin D supplements, vitamin D3, which is derived from animal products, was associated with significantly higher serum total 25-hydroxyvitamin D [25(OH)D] levels after 12 weeks than vitamin D2, which is plant-based and currently used in the vast majority of vitamin D supplements.

"The importance of vitamin D in our bodies is not to be underestimated, but living in the UK it is very difficult to get sufficient levels from its natural source, the sun, so we know it has to be supplemented through our diet," explained lead author Laura Tripkovic, PhD, department of nutritional sciences, University of Surrey, Guildford, United Kingdom, in a press release.

She added, "Our findings show that vitamin D3 is twice as effective as D2 in raising vitamin D levels in the body, which turns current thinking about the two types of vitamin D on its head." "Those who consume D3 through fish, eggs, or vitamin D3-containing supplements are twice as likely to raise their vitamin D status [compared with those] consuming vitamin Drich foods, such as mushrooms, vitamin Dfortified bread, or vitamin Dcontaining supplements, helping to improve their long-term health." [Original study.]

I'm starting to see studies questioning whether some of the beneficial health effects that many attribute to vitamin D may actually be due to sunlight. In the first study, researchers said that sunlight also has low levels of "blue light" which energizes T cells. T cells are a type of white blood cell, are part of the immune system, and help protect the body from infection and cellular abnormalities (cancer). So the blue light in sunlight had a positive effect on the T cells.

The second study examined whether it was low levels of vitamin D that is linked to multiple sclerosis (which is the widely accepted medical view) or was it low exposure to sunlight? They found that vitamin D is not associated with multiple sclerosis risk in blacks or Hispanics (but is in whites). But sun exposure is protective in all three racial/ethnic groups (blacks, Hispanics, whites). Thus it was the sunlight that was important in protecting against multiple sclerosis rather than vitamin D. Bottom line: for various beneficial health reasons, go out in sunshine frequently (20 minutes a day is fine). Remember, sunlight is the "natural source" for vitamin D (the ultraviolet light hitting our bare skin allows us to make vitamin D).

From Dec. 2016 in Science Daily: Sunlight offers surprise benefit: It energizes infection fighting T cells

Sunlight allows us to make vitamin D, credited with healthier living, but a surprise research finding could reveal another powerful benefit of getting some sun. Georgetown University Medical Center researchers have found that sunlight, through a mechanism separate than vitamin D production, energizes T cells that play a central role in human immunity.

Their findings, published today in Scientific Reports, suggest how the skin, the body's largest organ, stays alert to the many microbes that can nest there. They specifically found that low levels of blue light, found in sun rays, makes T cells move faster -- marking the first reported human cell responding to sunlight by speeding its pace.

"T cells, whether they are helper or killer, need to move to do their work, which is to get to the site of an infection and orchestrate a response," Ahern says. "This study shows that sunlight directly activates key immune cells by increasing their movement."

"We know that blue light can reach the dermis, the second layer of the skin, and that those T cells can move throughout the body," he says. ...."We found that sunlight makes hydrogen peroxide in T cells, which makes the cells move. And we know that an immune response also uses hydrogen peroxide to make T cells move to the damage," Ahern says. "This all fits together." Ahern says there is much work to do to understand the impact of these findings, but he suggests that if blue light T cell activation has only beneficial responses, it might make sense to offer patients blue light therapy to boost their immunity.

From Medscape: Is It Time to Rethink Low Vitamin D as a Contributor to MS?

The idea that vitamin D deficiency may contribute to multiple sclerosis (MS) has been well established in the literature and has, for the most part, been etched into recent neurology dogma. Yet, research by Annette Langer-Gould, MD, PhD—a clinical assistant professor at the University of Southern California's Keck School of Medicine in Los Angeles—suggests that the association might not be that simple. ....As background, the vitamin D–multiple sclerosis hypothesis originated from the observation that the prevalence of MS increases with increasing distance from the Equator, as ultraviolet radiation (UVR) from the sun becomes less intense. But this is also where more white people live.

The main result of our study is that vitamin D is not associated with MS risk in blacks or Hispanics, regardless of genotype. In contrast, sun exposure is protective in all three racial/ethnic groups.

Exposing skin to sunlight may help to reduce blood pressure and thus cut the risk of heart attack and stroke.

From the January 17, 2014 Science Daily: Here Comes the Sun to Lower Your Blood Pressure

Exposing skin to sunlight may help to reduce blood pressure and thus cut the risk of heart attack and stroke, a study published in the Journal of Investigative Dermatology suggests.

Research carried out at the Universities of Southampton and Edinburgh shows that sunlight alters levels of the small messenger molecule, nitric oxide (NO) in the skin and blood, reducing blood pressure... "NO along with its breakdown products, known to be abundant in skin, is involved in the regulation of blood pressure. When exposed to sunlight, small amounts of NO are transferred from the skin to the circulation, lowering blood vessel tone; as blood pressure drops, so does the risk of heart attack and stroke."

While limiting sunlight exposure is important to prevent skin cancer, the authors of the study, including Dr Richard Weller of the University of Edinburgh, suggest that minimising exposure may be disadvantageous by increasing the risk of prevalent conditions related to cardiovascular disease.

Cardiovascular disease, often associated with high blood pressure, accounts for 30 per cent of deaths globally each year. Blood pressure and cardiovascular disease are known to vary according to season and latitude, with higher levels observed in winter and in countries further from the equator, where ultraviolet radiation from the sun is lower.