Secret 39: Get Your Daily Dose of Sunshine

The sun can kill, but without our sun life on Earth would not exist. Sunshine is another great example of the importance of moderation. Sunshine affects our health and well-being, and is used by the body to produce an important hormone: Vitamin D: You may know that Vitamin D is also called the 'sunshine vitamin'. Vitamin D can be obtained through diet, especially fatty fish such as salmon (100 g. of cooked salmon provide about 350 IU Vit. D), tuna, eel, mackerel and sardines, but ten to twenty minutes of exposure to sunlight for people with skin that burns easily (or three to six times more if you have darker skin) will allow your body to produce enough Vit. D to cover your needs. Simply put, cholesterol in the skin, when exposed to sunshine, forms Vit D. To be more precise 7-dehydrocholesterol, present in mammalian skin, when stimulated by UVB rays (270 nm to 300 nm wavelength) changes into a Vit. D precursor. During long, dark winter days you may wish to add dietary sources of Vit. D such as eggs (a mid-size egg provides 20 IU) or, better yet, cod liver oil (one tablespoon = 1360 IU).

a Vitamin D feast

Beare claims that adequate levels of Vit. D protect against 'cancer, TB, osteoporosis, multiple sclerosis and hypertension. So why not simply supplement with mega doses of Vit. D to stave off these undesirable conditions? Studies on Vit. D supplementation have so far been inconclusive and contentious. Also, Vit. D is fat-soluble, and excessive amounts of Vit. D are not excreted like water-soluble vitamins such as C but are stored in the body and can be toxic. So how much Vit. D does a healthy body need? The health departments of different countries recommend different levels of dietary Vit. D.  But they do seem to agree that the upper acceptable limit of Vit. D supplementation is 4000 IU. Beare is more conservative. She urges half this amount or no more than 2000 I.Us per day for adults. First symptoms of Vit. D overexposure are nausea, vomiting and constipation. Long-term intake of excessive Vit. D leads to irreversible kidney damage. Note that if you supplement Vit. D, your body will still be manufacturing this hormone when you expose your skin to UVB. Can you overdose on Vitamin D if you stay in the sun too long? No. You will increase your possibility of developing skin cancer, but the body will destroy any excess sun-produced Vit. D once equilibrium had been reached. And, as stated above, this happens within ten to twenty minutes in light-skinned humans. Also note that sunscreen with levels as low as SPF 8 will block out more than 90% of UVB rays and thus prevent Vit. D formation. Make sure you use a sunscreen that:
i. does not contain unnecessary toxic chemicals (see http://www.ewg.org/skindeep/ for one possible classification system)
ii. also blocks UVA (UVB changes skin cholesterol to Vit. D, and Vit. D can protect the skin from precancerous changes, but if your sunscreen blocks UVB and not UVA, you are left with very little protection!)

If you are not a fan of sunscreen just stay in the shade and cover up. Or enjoy the sun when it is closer to the horizon.

Enjoy the sun setting over the Pacific

When the sun is high in the sky use an umbrella. Umbrellas are more effective than caps and hats at protecting you from the sun and can make a nice accessory to compliment your attire....

Low levels of Vit. D, on the other hand, cause rickets and may exacerbate multiple sclerosis. 

So what roles does Vit. D play in your health? First and foremost, as a hormone it regulates the concentration of calcium and phosphate in your blood. This affects bone growth and development. Vit. D also modulates cell growth, reduces inflammation and increases glutathione levels. Glutathione is an important antioxidant and is a critical element in iron metabolism. 

In Western countries milk, orange juice and cereal are often supplemented with Vitamin D. One way milk is enhanced with Vit. D is by exposing it to UVB radiation.  This procedure is also used to increase Vit. D levels in mushrooms.

But back to sunshine. Beare states that all five long-living populations live in sunny climates. Some of the benefits of sunshine include:

• improved mood: melatonin is built up during dark, winter months and may lead to SAD or seasonal affective disorder. Sunshine inhibits the formation of melatonin.
• better sleep-wake cycles or circadian rhythms: one of the constituents of sunshine is blue light (wavelength 460 nm to 480 nm) and blue light suppresses melatonin. Melatonin is also called 'the hormone of the darkness' and increases sleepiness. 
• Vit. D production

So get your ten to twenty minutes of sunshine in the morning or late afternoon, use a sunscreen with UVA protection at lunch, and enjoy some salmon or mackerel!