Vitamin D, produced when skin is exposed to light, is essential for our bodies. Unfortunately, modern lifestyles have minimized our time we spend under the sun. The Sun's Heartbeat explains why a tan isn't as bad as previously thought.


The first scenes in one Sun-tragedy unfolded long before there were written records of any kind. Spurred by events we can only guess at, a human exodus began 50,000 to 70,000 years ago, when our ancestors migrated away from the tropics and the equatorial region's strong sunlight. Immediately, people developed vitamin D deficiencies.

Our bodies make vitamin D when our skin is struck by the Sun's ultraviolet rays. Because UV intensity declines dramatically with lower Sun angles, people in temperate regions, and especially those in even higher latitudes, receive as little as 10 percent of the UV experienced by those near the equator. As our ancestors migrating north developed vitamin D deficiencies, the results were swift and brutal. They were removed from the breeding pool by a cruel Darwinian process: the fetus inside a woman with rickets (a disease resulting from low vitamin D) is unable to emerge from her body, and both die in childbirth.


Within just a few thousand years, natural selection had turned some people's skin white, and they were now able to manufacture ample vitamin D even from the reduced Sun intensity of the higher latitudes. (Dark skin color, called melanin, is a sunblock, needed because naked bodies near the equator can suffer from too much ultraviolet exposure.) In North America and northern Europe, the climate is sufficiently warm that their skin was almost fully exposed for more than half the year, and their bodies stored vitamin D in the muscle and fat. A new balance had been restored.

But starting a century ago, everything changed. First, the United States and Europe went from a mostly outdoors agrarian society to a mostly indoors manufacturing one. Then people started driving around in vehicles surrounded by windows. Glass prevents any vitamin D production because it blocks the Sun's UV. When air-conditioning became widely available starting in the late 1950s and then got cheaper in the 1970s, people stopped keeping their windows open. Fixed- pane units became increasingly popular. The only sunlight that reached us in our homes and workplaces came through UV-stopping glass.

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The last straw was sunblock. It did not even exist until thirty years ago. The initial UV- reducing creams, which cut exposure only in half, were marketed in the 1950s to promote tanning, not totally screen out ultraviolet rays. Then, in the 1980s, a new product came on the market: sunblock. With SPF (sun protection factor) numbers such as 30 and 45, sunblock essentially stops the body's vitamin D production cold. At the same time, people were advised to cover themselves with these lotions throughout the summer months. Even the medical establishment urged hiding from the Sun as a way to counter skin cancer.

The metamorphosis was complete: we had become like the Morlocks in H. G. Wells's book The Time Machine, shielded almost totally from sunlight's UV.


Enter modern vitamin D researchers such as John Cannell, MD, executive director of the Vitamin D Council, a nonprofit educational corporation that believes that "many humans are needlessly suffering and dying from Vitamin D Deficiency." Cannell is no ordinary medical doctor. He's no ordinary researcher either. He is a proselytizer, the first in the theater to shout "Fire!" when the smoke appears, while there's still time to get out. And these days, he's very, very passionate. He believes that human beings have unwittingly transformed themselves into something uniquely and self- destructively unnatural.

"We are the first society of cave people," he lamented to me in 2010. "In the development process of creating the skin, nature never dreamed that we'd deliberately avoid the Sun so thoroughly."


What Cannell and a growing legion of researchers are decrying are the past three decades of newspaper and TV scare stories that have made the public afraid of the Sun. The consequence, they believe, is that our blood's natural vitamin D levels are just a tiny fraction of what nature intended. And this is producing an avalanche of horrible consequences that include vastly increased rates of cancer.

That vitamin D is super-important is no longer in doubt. It has become the new needed supplement, recommended increasingly by family doctors and the popular media alike. The March 2010 Reader's Digest calls vitamins in general "a scam" and urges people to take no daily supplements whatsoever - with the single exception of 1,000 international units (IU) of vitamin D3, the form most recommended as a supplement.


This sudden interest has been sparked by a spate of studies strongly indicating that vitamin D is the most powerful anticancer agent ever known. Robert Heaney, MD, of Creighton University, a vitamin D researcher, points to thirty- two randomized trials, the majority of which were strongly positive. For example, in a big study of women whose average age was sixty-two, subjects who were given a large daily vitamin D supplement enjoyed a whopping 60 percent reduction in all kinds of cancers after just four years of treatment compared to a control group.

The skeptical might well wonder how, when cancer typically takes decades to develop, such a huge drop can be detected after just a few years. Heaney believes it's because vitamin D prevents tiny predetectable tumors from growing or spreading. "That's the kind of cancer I'd want to have - one that never grows," he told me in June 2010.


The Canadian Cancer Society raised its vitamin D intake recommendations to 1,000 IU daily in 2009. But Cannell, Heaney, and others think that even this is still way too low.

"I went to a conference and asked all the researchers what they themselves take daily and give to their families," Heaney said. "The average was 5,500 IU daily. There is certainly no danger in doing this, since toxicity cannot arise in under 30,000 IU a day."


Why is this vitamin D craze happening now? It sounds suspiciously familiar - like the antioxidant craze of the 1990s, when everyone was gobbling vitamin E to guard against "free radicals." Or the Linus Pauling– led vitamin C frenzy of the 1970s. Recent studies have shown that all those vitamins have no effect on mortality whatsoever. Indeed, a multivitamin a day now seems to be no better for your health than gobbling a daily Hostess Twinkie. Perhaps our bodies were not designed to get flooded with vitamins. Or maybe the couple of dozen known minerals and vitamins are only the tip of the health iceberg, and what's important are hundreds, or perhaps thousands, of trace substances of which we are not yet even aware.

Yet it is here, in a discussion of the natural environment in which our bodies were fashioned, that vitamin D makes so much sense. After all, our bodies create it naturally out of the Sun's ultraviolet rays.


Spending just ten minutes in strong sunlight - the kind you get from 11:00 AM to 3:00 PM between April and August - will allow your body to make as much vitamin D as you would get from drinking two hundred glasses of milk. This is astonishing. Asks John Cannell rhetorically, "Why does nature do this so quickly? Nature normally doesn't do this kind of thing."

The implied answer, of course, is that we were designed to have a high and steady level of this vitamin in our bodies. Yet as more and more people are tested, researchers are finding serious vitamin D deficiencies in virtually all of the population of the United States, Canada, and northern Europe. The reason? According to Cannell and the other doctors on the Vitamin D Council, we have been hiding from the Sun for decades.


The results may be even worse than we realize. Many researchers now fear that the explosive increase in autism is a result of pregnant mothers having close to no vitamin D in their bodies and then young babies and infants being similarly shielded from the Sun. The Centers for Disease Control (CDC) says that virtually no infants are getting enough vitamin D. The inadequacy figures, even using the CDC's pre-2011 lower recommendations of what they thought the body should have, was that 90 percent of infants are deficient.

According to Cannell, the highest autism rates occur in areas that have the most clouds and rain, and hence the lowest blood levels of vitamin D. A Swedish study has strongly linked sunlight deprivation with autism. Moreover, blacks, whose vitamin D levels are half those found in whites living at the same latitudes, have twice the autism rates. Conversely, autism is virtually unknown in places such as sunny Somalia, where most people still spend most of their time outdoors. Yet another piece of anecdotal evidence is that autism is one of the very few afflictions that occur at higher rates among the wealthier and more educated - exactly the people most likely to be diligent about sunscreen and more inclined to keep their children indoors.


As we saw in assessing links between earthly events and sunspot fluctuations, it's perilous to assign connections too quickly, and autism in particular is a can of worms. Nonetheless, these early threads should set off alarms: it might be wise for pregnant women and mothers of small children to immediately start exposing themselves and their kids to more sunlight.

When Cannell was in medical school in 1973, he was taught that human breast milk contains little or no vitamin D. "This didn't make sense," he said during a phone conversation with me in 2011. "Why would nature ever deprive a nursing infant of this vital substance?" Then it came to him: "When pregnant women start taking 5,000 international units of vitamin D daily, their milk soon contains enough vitamin D for a breast-feeding baby. So there's the key to how much a woman should naturally be getting every day."


In contrast to all this, and to the great annoyance of physicians and researchers on the Vitamin D Council, the FDA continued to advise only 400 IU of D3 daily as of early 2011. The agency officially regards most vitamin D studies as "incomplete" or "contradictory" and clearly has taken a cautious, go-slow approach.

In November 2010, the National Academy of Sciences' Institute of Medicine issued its first new recommendations about the vitamin since 1997, and many people were disappointed. The institute did boost its recommended daily amounts to 400 IU for infants, 600 IU for most adults, and 800 IU for those over age seventy. It also said there was no harm in taking up to 10,000 IU daily, although it conservatively adopted 4,000 IU as the official recommended upper limit.


According to Cannell, the new recommendations are still "irrelevant dosages." Michael Holick, MD, of Boston University, another vitamin researcher, agreed, saying that he personally takes 3,000 IU daily.

Cannell told me that the National Academy of Sciences report was a "scandal" and that four physicians had disgustedly resigned from the committee that put out the paper. "Commonsense aspects are totally lacking," he said. "For example, they urge infants to get 400 IU daily, but adults just 600 IU. Yet this vitamin is distributed in muscle and fat. The more you weigh, the more you should be getting. It doesn't make sense."


"Listen," he added, "everyone knows that there is an explosion of childhood cases of autism, asthma, and autoimmune disease. It all began when we took our children out of the Sun. Starting twenty-five years ago, a perfect storm of three events has changed how much sunlight children get. First came the scare of childhood sexual predators in the early eighties, then the fear of skin cancer, and finally the Nintendo and video game craze. Nowadays, kids do not play outdoors. Playgrounds are empty. You're a bad mother if you let your child run around. And it's almost a social services offense if your kid gets a sunburn. Never before have children's brains had to develop in the absence of vitamin D."

Since this is not a medical book, I can only pass on the recommendations of those in the forefront of vitamin D research. Their best advice is to go in the Sun regularly without burning. Wear as little clothing as you can. You know how much Sun you can han-dle without turning red. Unless you have a very light complexion and blond or red hair, you should be able to expose yourself safely to ten to twenty minutes of strong sunlight at a time. Lie out in the Sun in shorts for five to ten minutes on each side. The key to UV intensity is Sun height. If your shadow is shorter than you are, your body will produce a good amount of vitamin D.


After experiencing twenty minutes of unprotected midday Sun from May to July, or a full hour or more during March, early April, and late August through October, you can certainly use sunblock. The experts say to buy the kind whose active ingredient is either zinc or titanium oxide. Most other kinds will be absorbed by the skin, then enter the bloodstream and circulate. "You might as well drink the stuff," Cannell says disdainfully.

During the low-Sun winter months, you need to spend much more time sunbathing and probably take a vitamin D supplement. The experts are currently urging 2,000 to 3,000 IU daily.


Why not skip the Sun altogether and just pop the pills year- round? Some doctors, including those responsible for the 2010 National Academy of Sciences report, suggest doing exactly that. They figure that you can have it all - nice, high vitamin D serum levels plus no UV exposure, with its skin cancer risk. But others believe that's a bad idea. "Some of my colleagues think D3 supplements are enough," Cannell says. "But that supposes we know everything. I suspect that we do not know everything. Natural sunlight has to be the preferred route whenever possible."

Everyone should use solar power wisely and not go totally bonkers. There's no need to fry. But whatever extra skin cancer risk we might assume certainly seems to me to be a reasonable price to pay, considering the benefits. It now appears that adequate sunlight- mediated vitamin D might prevent as many as 150,000 cancer deaths a year in the United States alone and also reduce infections, bone problems, and perhaps, though more science is needed, even autism and asthma rates. Of course, on the other side of the balance beam, melanoma causes 8,500 US deaths a year. Every activity from bicycle riding to barroom brawling involves some balancing of risks, and the decision of what trade- offs to make is, of course, yours alone.


Tomorrow is a new day. As the Sun rises, its orange beams will cast magical rays in the morning mist. Is the Sun our enemy or our friend? Will it take our life or save it?

Reprinted with permission from Little, Brown and Company. Top art courtesy of the Orlando Sentinel


Bob Berman is an American astronomer, author, and science popularizer. He is director of the Storm King Observatory in Cornwall, New York, and of the Overlook Observatory in Woodstock, New York, USA. He is an adjunct professor of astronomy at the performing arts college, Marymount Manhattan College.


The Sun's Heartbeat: And Other Stories from the Life of the Star That Powers Our Planet is available from Amazon.com