Sun
In 2013, 5.6 billion USD were spent on sun protection products. Needless to say, we are a population that fears the sun.
But we quickly overlook all the sun has to offer. Our bodies gain an enormous amount of vitamin D from the sunlight, a vitamin that we truly cannot do without. The sun causes our bodies to synthesize vitamin D, which is necessary for the small intestine to absorb calcium and other minerals. Without sunlight, the only thing we can gather is osteoporosis, arthritis, and malnutrition.
That last one is the key to all degenerative illnesses, such as Alzheimer's, Parkinson's, and even depression.
Now, how can we benefit from the sun without harming ourselves? Going to the beach and lying on the sand in as little clothes as possible for eight hours is not exactly the solution.
Exercise (which is talked about in detail under the 'Exercise' tab above) is a wonderful way to receive sunlight. If you take a walk, ride a bicycle, or swim in an outdoor pool, you will be receiving sunlight. It's a good idea to wear short sleeves and shorts in order to get the maximum effect of the sunlight on your skin.
Caution should always be used at the beach, but this does not mean that you should go in a unitard, a giant hat and sunglasses, and a canvas tent. Allowing your skin some sunlight is absolutely okay at the beach, as long as you don't overdo it and take the necessary precautions.