If I had to limit my advice on healthier living to just one tip, it would be simply to learn how to breathe correctly.

To be clear, I worry as much about the impact of the Internet as anyone else. I worry about shortening attention spans, the physical cost of sedentary "surfing" and the potential for coarsening discourse as millions of web pages compete for attention by appealing to our base instincts.

Low levels of vitamin D in the population as a whole suggest that most people need to take a vitamin D supplement. This may be especially true for seniors, as the ability to synthesize vitamin D in the skin declines with age.

In my experience, the more people have, the less likely they are to be contented. Indeed, there is abundant evidence that depression is a 'disease of affluence', a disorder of modern life in the industrialized world.

When people are told to "eat many small meals," what they may actually hear is "eat all the time," making them likely to respond with some degree of compulsive overeating. It's no coincidence, I think, that obesity rates began rising rapidly in the 1980s more or less in tandem with this widespread endorsement of more frequent meals.

Limit or eliminate late-night computer and television viewing. A computer or TV screen may seem much dimmer than a light bulb, but these screens often fill your field of vision, mimicking the effects of a room filled with light.

The more people have, the less content they seem to be. In America, the cultural expectation that we're to be happy all the time and our children are to be happy all the time is toxic, and I think that really gets in the way of emotional well-being.