And now for
something completely different, I'm going to nerd out and share an academic
article with you. Don't worry, though, I'll make it painless; you really do
need to know about this.
(Note for
readers: if you want to reference the study I'm writing about, there are quotes
in italics throughout and a link in the next paragraph. If you just want my summary and opinion,
that's in plain text.)
Writing in
the recent Journal of the American College of Nutrition, a group of authors
have published "Sunlight and Vitamin D: Necessary for PublicHealth." Head on over if you'd like
to geek out on the whole thing, but I'm going to give you the most important
points.
Basically,
the authors examine the fact that many recommendations from the American Cancer
Society, the World Health Organization, and the like, focus on encouraging sun
avoidance and sunscreen use during the very hours of the day that our bodies
are most primed to make use of the sun:
"Though
these recommendations, all focused on reduction of skin cancer, are accompanied
by brief acknowledgement of the importance of vitamin D for health, they
persist in urging avoidance of the sun at the precise times when vitamin D can
be synthesized in the skin—the hours between 10 am and 3 pm—and suggest that
all necessary vitamin D can be obtained through food and dietary
supplements."
And yet,
there are compelling reasons to get your Vitamin D from the sun. Take a look at
this introductory paragraph:
"These
recommendations are understandable from the viewpoint of preventing the 3.5
million new cases of and 2000 deaths from nonmelanoma skin cancer in the United
States each year, but they neglect the fact that we have a long cultural
history of appreciation of the sun and use of UV radiation for healing
purposes. Moreover, they neglect that we have evolved with physiological
adaptations to help protect the skin from the sun when we are mindful of our
exposure and do not burn. They neglect the fact that increased sun exposure,
based on latitude, has been associated with protection from several different
types of cancer, type 1 diabetes, multiple sclerosis, and other diseases. They
also neglect the fact that exposure to the sun induces beneficial physiological
changes beyond the production of vitamin D. Though adherence to the current
sun-protective recommendations would likely result in the reduction of
nonmelanoma skin cancer, that reduction would likely be overshadowed by the
potential reduction in deaths from other cancers and from cardiovascular
disease, which could be achieved by doubling average blood concentrations of
25-hydroxyvitamin D (25(OH)D) to 40 ng/mL through a combination of sun exposure
and supplements."
Let's break
that down a bit. Basically, we're saying
that, in our zeal to protect ourselves from approximately 2000 nonmelanoma skin
cancer deaths a year, we are turning our backs (no pun intended) on our
cultural and biological adaptations that allow us to appreciate the sun and use
it for healing. Additionally, we are increasing our risk of other types of
cancer, type 1 diabetes, multiple sclerosis, and other conditions.
For example,
look at these benefits:
"When
the skin is stimulated with UVA radiation, nitric oxide is released, stimulating
vasodilation and lowering of blood pressure. During active exposure to UVA,
diastolic blood pressure in one study fell by roughly 5 mmHg and remained lower
for 30 minutes after exposure. A reduction of diastolic blood pressure by 5
mmHg decreases risk for stroke by 34% and coronary heart disease by 21%."
"Additionally,
human skin produces beta-endorphin in response to UVB exposure; these opioid
peptides have the result of increasing a feeling of well-being, boosting the
immune system, relieving pain, promoting relaxation, wound healing, and
cellular differentiation. Light signals received through the eye regulate
production of melatonin and serotonin for circadian rhythm control and also
play a role in seasonal affective disorder."
Short form: sunlight
contains both UVA and UVB radiation. The
UVA radiation can lower blood pressure enough to decrease risk for stroke and
coronary heart disease. UVB radiation can improve mood, help with certain
depressive conditions, improve the immune system, relieve pain, and help with
healing.
Are we sure
we want to keep avoiding the sun?
Look, no one
is going to tell you to go try to get a sunburn. And if vitamin D supplements
make sense to you, go for it. But the
sun has been getting a bad rap lately.
And, there
are reasons for seeking the sun:
"The
full solar spectrum is essential to optimal health and well-being. Humans are
physiologically adapted to produce vitamin D in response to sun exposure,
specifically UVB radiation; other regions of the spectrum seem to confer
benefit as well. Though some vitamin D comes from our diet (and more recently
from supplements), we should not ignore the natural capacity that we possess to
produce our own. We are of the opinion that moderate sun exposure (less than
the time required to burn) to the arms, shoulders, trunk, and legs should be
sought rather than avoided."
I agree with
the authors. Bottom line, the full
spectrum of sunlight seems to confer many health benefits, and our bodies are
designed to make vitamin D from this exposure. So go outside wearing a tank top
and shorts. Mow the lawn, hang the laundry, take a bike ride. Do so between the
hours of 10 am and 3 pm for maximum formation of vitamin D. As long as you don't allow yourself to burn,
you will very likely be helping your health far more than you might possibly
harm it.