CHAPTER 1 What Is Vitamin D? Is it a hormone or a vitamin? Somewhere along the equator a ten-year-old girl is growing up with- out the luxuries most of us enjoy on a daily basis. She will never learn how to use a computer, order a pizza to be delivered, or drive a car to the mall for clothes and cosmetics. She spends most of her days playing outside near her farming parents, and soon she will join them in tilling the soil. She will never learn to read or write. She will endure periods of poor nutrition and poverty. And she knows nothing about sunblock and probably never will. Now let''s sail north to the United States or Europe, where another ten-year-old girl leads an immensely different life. She is maturing into a savvy user of electronics, passes the majority of her days indoors at a rigorous school, has access to the best nutrition and all the benefits that modern medicine can provide, and will know what SPF means long before graduating from high school and pursing higher education.

If both girls continue on their separate paths, the equatorial girl will be at least half as likely to get cancer during her lifetime as her northern counterpart. She also will have an 80 percent reduced risk of developing type 1 diabetes in the first thirty years of her life. In fact, barring any freak accident or untreated medical condition, her longevity overall will be 7 percent greater . The northern girl, on the other hand, faces a host of increased health risks throughout her life, from breast and ovarian cancer to depression, obesity, type 2 diabetes, osteoporosis, arthritis, high blood pressure, heart disease, and stroke. She will be more susceptible to upper-respiratory-tract infections, dental cavities and gum disease, and infectious diseases like the flu and tuberculosis. As a group, she and her girlfriends will break their arms 56 percent more often than their peers did just forty years ago. Because she was born in northern latitudes and has lived there for the first ten years of her life, for the rest of her life she has a 100 percent increased risk of developing multiple sclerosis no matter where she chooses to live in the world after age ten. She would likely lose in a jumping contest with her equatorial sister, who can jump higher and with more force.

If she complains of muscle weakness and wide- spread muscle and joint pain later on in adulthood, her doctor will likely diagnose fibromyalgia or chronic fatigue syndrome when tests don''t turn up anything specific. The equatorial girl might never experience such debilitating aches or chronic pain and in fact may develop into a much stronger, leaner, and more fertile woman. If both women become pregnant, the equatorial mom-to-be won''t have to worry as much about serious complications like preeclampsia. And she won''t have trouble giving birth the old-fashioned way. The northern mom-to-be, however, will have a much higher risk of having an unplanned C-section and of giving birth to a child who will suffer from schizophrenia. By the time the northern girl reaches midlife and her later years, chances are good that she''ll have been treated for an internal cancer (breast, colon, ovarian, pancreatic--take your pick) at some point and been prescribed multiple drugs to combat chronic ailments like hypertension, osteoporosis, arthritis, depression, obesity, type 2 diabetes, dementia, Alzheimer''s, and perhaps even insomnia. Because of a significant loss of bone mass, she will be terrified of falling and fracturing a bone, and therefore will have limited some of her favorite outdoor activities, such as tennis, skiing, horseback riding, and golf, significantly cutting back on physical activity. And because she will have lost a considerable amount of muscle strength, her biological age will be much older than she really is.

The equatorial woman not only may outlive her northern counterpart, but she''ll also be less prone to chronic diseases that afflict her northern counterpart. For this reason, the equatorial woman may, overall, enjoy a higher quality of life--even when advanced age sets in. What''s going on here? The answer lies in the difference between these two girls'' exposure to natural sunlight, which is our main source of vita- min D. Obviously, I''ve taken some liberty in letting a few assumptions go. The equatorial girl''s limited access to health care and preventative medicine has its own basket of risks, but let''s focus for a moment just on the difference in exposure to sunlight and the conclusions that can be drawn from that single fact. Let''s also assume that these girls grow up to exhibit vastly different levels of vitamin D in their systems, which is not a stretch given the documented records of vitamin D deficiency patterns across the globe. If I were to test each of these girls'' vitamin D levels, I would not be surprised to find the northern girl''s levels terribly low as compared to her equatorial counterpart. And that difference means everything.

The sun is as vital to your health and well-being as food, shelter, water, and oxygen. I''m going to prove it to you through a comprehensive exploration of vitamin D. What does vitamin D have to do with aging and disease? More than we ever imagined. Our Most Common Health Challenge When I tell people that vitamin D deficiency is our most common health challenge globally, the response I get is pretty much the same in wealthy, developed nations: "Well, that can''t happen to me or anyone else in my country; besides, we have great health care." And when I remind people that the best way to ensure healthy levels of vitamin D is through sensible sun exposure two to three times a week, a common thread is heard in the response, which is along the lines of, "You can''t be serious. The sun is the demon of cancer and aging. No way am I going to consider sunlight as medicine. It''s just not possible.

" The statistics proving otherwise speak volumes, and you''re going to hear about them throughout this book. Increasing numbers of studies are confirming the link between vitamin D and optimal health, and attitudes are beginning to shift. Researchers have long known that the "sunshine vitamin" boosts bone strength by encouraging the body to absorb calcium, but only recently have we begun to see just how far- reaching vitamin D is in maintaining the health of every system and cell in the body''s intricate machinery. Vitamin D may be as vital to your heart and brain health, for example, as it is to your bone health. As noted in the introduction, increasing the amount of vitamin D in the body can prevent or help treat a remarkable number of ailments, from high blood pressure to back pain, from diabetes to arthritis, from upper-respiratory- tract infections to infectious diseases, and from fibromyalgia to cancer. It also seems to improve fertility, weight control, and memory. The evidence is clear: just as we require a little fat and salt for survival, we need the sun in moderation, too. I''ll add to that the following fact, which will be fully explored in chapter 8: there is essentially no substantiated scientific evidence to suggest that moderate sun exposure significantly increases risks of benign skin cancers or, and more importantly, the most deadly form of skin cancer, melanoma.

In fact, if you were unfortunately to develop melanoma, you would be more likely to survive it if you had adequate sun exposure as a child and young adult. And if you had adequate sun exposure as a child, you would have a 40 percent reduced risk of developing lymphoma as a young adult. In the past five years alone there has been a breakthrough in our understanding of why sun exposure benefits health in so many ways, something that was not fully comprehended until now. This breakthrough has forced people to take a closer look at the value of sun exposure. I am proud to say that I have been at the forefront of this research. Groundbreaking new research has linked a wide array of disorders that afflict up to two hundred million Americans to a single common factor--vitamin D deficiency or insufficiency, the most common medical condition in the world with sometimes devastating, if not fatal, consequences. And the research keeps coming from various labs around the world investigating vitamin D. As I write this, doctors at the University of Pennsylvania have revealed that vitamin D can prevent or forestall the irreversible decline in respiratory function over time that leaves many asthmatics even more vulnerable when they suffer an asthma attack.

At the same time, scientists at the Moores Cancer Center at the University of California at San Diego have raised the possibility that low vitamin D may be the root cause of cancer. No doubt we will continue to see remarkable studies emerge, and you''ll be reading about some of the more fascinating and profound studies in the upcoming chapters. It''s no wonder that this vitamin made Time magazine''s list of the top ten medical breakthroughs of 2007. So if you can dramatically decrease your risk of illness and age-related disease and live a healthier, happier life-- without its costing you a penny--wouldn''t you want to do that? Centuries of Problem Solving When you put the vitamin D story into the perspective of human history, it begins with the Industrial Revolution. As the revolution began to sweep across northern Europe in the mid-seventeenth century, doctors reported seeing a new disease that afflicted young children with a constellation of physical signs and symptoms, notably deformities of the skeleton, such as bowed legs, misshapen pelvis, enlarged head, prominent knobby projection.