We should give the human body more credit than it sometimes gets. People don’t shrivel, shatter, or shut down at the first sign of stress. Instead, the human body operates on the “overload principle”—when subjected to outside forces, it adapts by getting stronger. Examples of this phenomenon abound in the human body.
Your muscles don’t pop and your bones don’t break if you regularly lift weights—they get bigger and more powerful so they can handle a heavier load.
Your heart and lungs don’t explode or collapse if you go running every morning
—they become more efficient and your lung capacity expands. Your ligaments and tendons don’t snap if you do stretching exercises—they get more flexible.
The same goes for your skin’s exposure to sunshine. If your skin receives regular, moderate exposure to sunshine, it adapts by producing melanin to absorb the sun’s radiation, thereby protecting itself against a future burn. It also induces DNA repair enzymes to spring into action. This is the human body’s natural adaptation to outside stress. Of course, sudden and extreme exposure to strong sunshine after an extended period of nonexposure will result in sunburn in the same way that exposure to sudden and extreme physical activity can result in damage to the muscle-bone system or the heart.
Remember, too, that skin did not evolve solely to resist the power of the sunshine—your skin is also the conduit through which your body uses the sun’s radiation to create the vitamin D you need for your very survival. Plus, you have an entire DNA-repair system made up of enzymes whose job is to repair damaged DNA and replace it with healthy new material. My colleagues and I are doing research to determine if the skin’s DNA repair program is enhanced when it is exposed to moderate sunlight, and I suspect that it is. All this is to say that your body is designed to accommodate the effects of sunshine. To suggest that sunshine is necessarily harmful to your skin is to underestimate the human species’ ability to adapt to its environment.
Antisun activists argue that to differentiate between the causes of nonmelanoma skin cancer and the causes of melanoma is to confuse the issue—
they maintain that you need to avoid all sunshine and become a sunphobe. This ignores the fact that some sun exposure is necessary to survive and be healthy.
The amount of sun exposure that causes the potentially deadly melanoma—an amount that results in a sunburn—should be stringently avoided, but the moderate, regular sun exposure, which is your main source of vitamin D and which is associated with the rarely deadly and easily treated nonmelanoma skin cancer, should not be forsaken. If it is, you increase your risk of developing a variety of more serious and deadly diseases.
Some people enjoy being in the sun and using indoor-tanning facilities so much that they will risk nonmelanoma skin cancer in favor of all the potential benefits of sun exposure. Others may choose to get only the minimum amount of UVB exposure necessary to build and maintain vitamin D levels. These are choices only you can make. However, we know a couple of things for sure.
Subjecting yourself to unlimited amounts of UVB is potentially harmful. But denying yourself any and all UVB can lead to serious health problems if you are not taking enough vitamin D from dietary and supplemental sources to satisfy your body’s requirement for vitamin D.
The Holick Solution for Sensible Sun is a guide to how much sun exposure you need to maintain appropriate vitamin D levels. Here’s how it works. You estimate how long it would take for you to get a mild sunburn (when your skin gets pink—this amount of exposure is known as 1 MED), then two to three times a week, you expose 25 percent of your body (e.g., arms and legs) for 25 percent to 50 percent of that time. In other words, if it would take thirty minutes for your skin to get pink in the sunshine (as it would for me at noon on a Cape Cod beach in the summertime), then two to three times a week, spend eight to fifteen minutes in the sun before putting on SPF30 sunscreen.
Use these guidelines if you choose to visit a tanning salon, too, but do not exceed 50 percent of the manufacturer’s maximum recommended time of exposure.
CHAPTER 9
Step 2: Bone Up on Calcium
The dynamic duo of calcium and vitamin D can sustain your life
Virtually everyone can recite the milk industry’s campaign slogan: It does a body good. Much of this goodness no doubt hinges on the calcium content of milk. Calcium is the most abundant mineral in the human body, with over 99 percent of the amount present being found in the bones and teeth. For the growth and maintenance of healthy bones it is essential that we have sufficient calcium intake; we are at risk of developing bone diseases such as osteoporosis when calcium leaching is not balanced by dietary ingestion. But calcium is not only important for the skeleton; it also has a role to play in nerve function, blood clotting, muscle health, and other areas.
And, like an orphan child without a parent to guide it properly, calcium cannot work properly in the body without the help of vitamin D. Calcium and vitamin D share a special relationship that plays into everything about you, from your ability to build and maintain bone strength to your neuromuscular faculties and brain power. I’ve already touched upon these ideas in earlier chapters, but here I’ll explore more about this calcium-vitamin D connection and encourage you to pay attention to your calcium intake as much as your vitamin D intake.
It is also well recognized that vitamin D aids in the absorption of calcium as well as phosphate.