Wednesday, May 6, 2015

Desire for Whiter Skin Possibly Connected to Vitamin D Deficiency in China

After mentioning the vitamin D deficiency she developed after moving to Beijing, Alyssa Abkowitz described a study indicating many others in China have the same deficiency:
A recent study conducted by seven Chinese hospitals across five cities found that more than half of the Chinese population suffers from the same problem. The study measured vitamin levels in more than 2,000 volunteers and found that only about 5% of participants had healthy levels of Vitamin D, which is crucial for strong bones and a healthy immune system. That’s compared to about 67% of the U.S. population whose Vitamin D levels are deemed sufficient, according to a 2011 Centers for Disease Control and Prevention report.
In a fact sheet for health professionals, the National Institutes of Health in the U.S. explains the important connection between sun exposure and vitamin D:
Most people meet at least some of their vitamin D needs through exposure to sunlight. Ultraviolet (UV) B radiation with a wavelength of 290–320 nanometers penetrates uncovered skin and converts cutaneous 7-dehydrocholesterol to previtamin D3, which in turn becomes vitamin D3. Season, time of day, length of day, cloud cover, smog, skin melanin content, and sunscreen are among the factors that affect UV radiation exposure and vitamin D synthesis. Perhaps surprisingly, geographic latitude does not consistently predict average serum 25(OH)D levels in a population. Ample opportunities exist to form vitamin D (and store it in the liver and fat) from exposure to sunlight during the spring, summer, and fall months even in the far north latitudes.

Complete cloud cover reduces UV energy by 50%; shade (including that produced by severe pollution) reduces it by 60%. UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin D. Sunscreens with a sun protection factor (SPF) of 8 or more appear to block vitamin D-producing UV rays.
Unsurprisingly, the researchers in China suggest people spending less time outdoors and high levels of smog as causes for the large number of people with a vitamin D deficiency. But a possible contributing factor not discussed in the journal article exists as well.

In addition to people using mobile phones while driving motorbikes, this is something else I recently saw on a bridge in Hengyang, Hunan province:

young woman walking while holding a red bag over her head
I moved to the side just in time.

She was not hiding from my camera as she walked down the sidewalk. Instead, most likely she was trying to avoid the bright sun that day. I saw multiple similar examples, all involving females, just minutes apart on the same bridge. None of this surprised me in the least, since many women in China desire whiter skin or, at the very least, don't want their skin to become darker.

advertisement for skin whitening cream in Shenzhen
Advertisement for skin whitening cream which previously appeared in a set of scenes from Shenzhen

In addition to skin whitening cream for sale, a big business, in many parts of China it is common to see younger women using umbrellas outside on sunny days. When an umbrella isn't available, a variety of items, such as bags, extra clothing, and paper flyers, may instead be used as shields from the sun. So even if they are outside on a sunny day, they are missing out on a prime opportunity for vitamin D.

This type of behavior probably doesn't account for all of the researchers' findings, such as the significantly lower vitamin D levels for males in Beijing aged 49 to 59 years. Again, other factors such as time spent indoors and levels of smog likely play a role. Yet the well-established connection between UVB exposure and vitamin D levels, the prevalence of people actively blocking the sun's rays while outside, and the study's finding that vitamin D levels were overall "much worse among women and younger participants" make it more than fair to suspect the desire for whiter skin has contributed to China's vitamin D problem.

In the near future, I doubt many people who now prefer lighter skin would rethink their views and seek more outdoor UVB exposure, even if the air quality and their schedules allow it. Instead, as Abkowitz suggests, increased demand for vitamin D supplements and fatty fish, one of the better natural food sources for vitamin D, is far more likely. I can't imagine how much their prices would go up if they were found to also cause lighter-colored skin.

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