The beginning of spring marks the beginning of the longer, warmer days, and that means one thing to many people: getting a taste of sunlight. Many of the health benefits of small doses of sunshine are reasonably well known, particularly those attached to vitamin D and its production in the body. We know, for instance, that it's necessary to help stave off osteoporosis and bone aging because of vitamin D's importance in the body's production of calcium. (We also know, of course, that too much sun raises the risk of melanoma.) But there are other aspects to sunshine's impact on our physical selves that are less publicized, though no less important to our general health in the summer months.
The right amount of sunshine exposure every day remains rather an imprecise figure. While it's clear to the scientific community that a full day without shade or protection is a horrible idea, estimates for the just-right quantity of sunlight vary quite a lot. They also differ depending on skin color; those with greater melanin content in their skin need more exposure time to produce the same amount of vitamin D as somebody with lighter skin. And if you live closer to the equator, you're likely to find it easier to produce vitamin D than those who exist in far-flung regions.
So don't let anybody tell you that "a standard 20 minutes a day" is the exact prescription; but also don't wander around without protection or sunscreen the second it becomes warm enough to wear a sundress. Yes, I recognize the temptation.
There May Be A Relationship Between Sunshine & Higher Suicide Rates
The relationship between sunshine and serotonin is an intriguing one. The debate on whether seasonal affective disorder, the depression-like dip in mood associated with colder temperatures and less sunlight, actually exists continues to play out in medical circles. But there does seem to be a definite link between levels of serotonin, a crucial neurotransmitter for human mood, and sunlight exposure. A little may go a long way, but an intriguing 2014 study posed a more serious side effect of lengthening days and greater time in the sun: the possibility of higher suicide rates.
Establishing cause and effect, particularly when it comes to human mood, is a notoriously difficult business, so the people behind the 2014 study made a lot of caveats. Their study of nearly 70,000 suicides in Austria between 1970 and 2010 (note, not a highly sunny or warm country) found that there was a positive link between high levels of sunlight and a suicide date. They also found, however, that high levels of sunlight 14 to 60 days beforehand seemed to have a kind of "protective" effect.
Just because there's a correlation, though, doesn't necessarily mean there's a cause, or that it's a direct one. People who have set out to die make strange choices and are often not around to discuss their motivations with scientists afterwards. It's an intriguing possibility, though, that for deeply depressed people a range of sunny days may not be the boon it might seem (or may give a depressed person the boost of energy they "need" to carry out the act).
Nitric Oxide May Help Diabetes & Heart Health
The most famous chemical reaction in the body to sunlight is, of course, the production of vitamin D. There is, however, another kind of chemical reaction that also seems to have distinct effects on human health. Nitric oxide is produced in response to skin exposure to UV light, and it's proven to be a very important factor in various aspects of bodily health; it's strongly involved in the heath of our airways, for instance. And sun exposure seems to be giving us some benefit through its nitric oxide-producing ways.
One surprising effect is in the cardiovascular system. A study by the University of Edinburgh found that UV light helped to lower blood pressure in patients through its stimulation of nitric oxide production, though only through a 20-minute exposure. (A full day tanning will not be good for you.) The same university also discovered that there may be sun-related benefits for human rates of weight gain and how soon we develop diabetes; mice exposed to UV light, or given a cream containing a dose of nitric oxide for the skin, were both slower to get fat and less likely to show abnormal glucose levels. That study's only been conclusive on mice, though, so pre-diabetic people shouldn't rely on doses of sunshine to help their situation.
Some Sun Exposure Gives A Bit Of Cancer Protection
Oddly, while many of us have been given repeated warnings about the dangers of skin cancer (in Australia, the seriousness of the warnings have gone so far that people are now developing illnesses from vitamin D deficiency), emphasis is often not given to the cancer-busting benefits of brief doses of sunshine. Moderation, it appears, is likely the best way forward for most of us.
A review of the science in 2008 found that greater sunshine levels in everyday life correlated with lower cancer rates:
"Living at higher latitudes increases the risk of dying from Hodgkin lymphoma, as well as breast, ovarian, colon, pancreatic, prostate, and other cancers, as compared with living at lower latitudes.... Moreover, although excessive sun exposure is an established risk factor for cutaneous malignant melanoma, continued high sun exposure was linked with increased survival rates in patients with early-stage melanoma".
This effect, the reviewers also point out, seems to be particularly heightened in post-menopausal women. A 2007 study found that daily vitamin D doses prompted huge reductions in the cancer rates of post-menopausal women, which is a big bloody deal considering how many people breast and ovarian cancer kill.
Certain Medications May Be Made Less Effective By The Sun
In a fascinating study, scientists at the Karolinska Institute in Sweden decided to look at something rarely targeted: whether or not higher levels of sunshine and corresponding shifts in the body might change the way in which we metabolize medication. What they found was a bit odd, and requires a bit of unpacking.
They examined the levels of three immunosuppressant drugs in the blood of 70,000 patients in periods of most and least sunshine, and found that higher levels of vitamin D actually seem to stimulate how the body metabolizes drugs. In July to September, people had lower drug concentrations in their systems compared to January to March. They think it's due to vitamin D's activation of an enzyme that stimulates liver function (the liver, of course, is a major player in how the body processes medication). It's just a focus on immunosuppressants at the moment, but if you feel as if your regular medication may not be working so well in the sunny months, it's possible you're not imagining it.