Although many people believe that the primary emphasis of my work is about diet, it’s not. What we eat is important, of course, but what comes out of our mouth may be more important than what goes into it.

Intimacy is healing. Study after study have shown that people who feel lonely, depressed, and isolated are three to 10 times more likely to get sick and die prematurely than those who have strong experiences and networks of connection and community.

In part, this is because people who feel lonely and depressed are more likely to overeat, drink too much, smoke cigarettes, and abuse themselves. As a patient once told me, “I’ve got 20 friends in this package of cigarettes; they’re always there for me, and no one else is. You want me to give up my 20 friends? What are you going to give me instead?” In part, it’s via mechanisms that are not fully understood, but are real.

There has been a radical shift in our social networks during the past 25 years. We all know that this affects the quality of our lives, but it also affects the quantity of our lives — our survival. I don’t know any other factor — including diet and smoking — that has a more powerful effect on our health, well-being, and longevity.

The need for love and intimacy is a fundamental human need, as primal as the need for food, water, and air. Yet because of the breakdown of social networks in the past 25 years, this need often goes unfulfilled.

In business, when you can meet an unmet need that is this primal, even meeting it in a superficial way can create a multi-billion-dollar business, e.g., the chat rooms in AOL when it first came out, or the lounges in Starbucks, or the billion people who are on Facebook, even though these are hardly the most intimate of life experiences.

Trust leads to intimacy, which leads to healing and meaning. We can only be intimate to the degree we can make ourselves vulnerable. But when we open our hearts, we can get hurt. So in the absence of social networks that feel safe — an extended family, a stable neighborhood you’ve lived in for years, a church or synagogue, a job that feels secure — it’s easy to keep our walls and emotional defenses up all the time.

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