The great D-bate

Recent public health campaigns have alerted Canadians of the dangers of prolonged sun exposure, warning that ultraviolet rays (UV) can damage our skin, causing premature aging, moles or, in the worst cases, skin cancer. It all seems cruel irony to those of us who spend winters cooped up indoors. When the warm weather finally arrives, we’re told not to go out in the sun.

So we dutifully put on a hat, slap on the sunscreen and generally try to avoid the blazing sun. A summer tan or sunburn – once a sign of a robust and outdoorsy lifestyle – is now regarded as irresponsible and reckless behaviour.

But now there’s good news for sun worshippers. Science may have finally seen the light – the sunlight, that is. Some researchers are now suggesting that as long as we practise moderation, we can go out in the sun for short periods. In fact, recent studies show that avoiding the sun may not be such a good idea after all. This notion has created quite a rift in the scientific community, generating fierce debate on the relative pros and cons of spending time in the sun.

The sunshine vitamin

There’s nargument that spending too much time exposed to the sun’s ultraviolet rays is a dangerous habit. What’s causing controversy in the scientific community is the notion that by completely avoiding the sun, we’re also missing out on an important nutrient — vitamin D.

When the direct UVB rays of the summer sun hits our skin, it instigates production of vitamin D. The liver and kidneys help convert this vitamin D into an active hormone. We’ve long known that vitamin D is crucially important to our health. It helps our bodies absorb calcium, which builds stronger bones, helping us avoid the late-life scourge of bone-damaging osteoporosis.

But now there’s a mounting body of evidence that shows that vitamin D may also protect us against other maladies. Dr. Michael Holick, a professor of medicine and dermatology and director of the Bone Health Clinic Boston University school of medicine, is a leading proponent of this theory. In his book The UV Advantage, Holik argues that recent studies show vitamin D may provide us with an “immunity” against such varied diseases as breast, colon or prostate cancer, heart disease, rheumatoid arthritis, multiple sclerosis and diabetes. As well, sunlight may benefit our lung health and protect against depression.

“Can you imagine what would happen if one of the drug companies came out with a single pill that reduced the risk of cancer, heart attack, stroke, osteoporosis, PMS, seasonal affective disorders and various autoimmune diseases?” writes Holick. “Well, guess what? Such a drug exists.” The drug he’s referring to is the sun, and Holick and other researchers argue that, by avoiding it in summer months, we’re losing out on its remarkable benefits.

Holick and his colleagues in the pro-sun camp base these claims on a growing number of studies that found that people who lived in sunlight-deprived northern climes suffered a higher incidence of the above-mentioned diseases compared to those who lived in sunny climates. He feels this is because people living in sunny regions also have been found to have higher vitamin D levels. He’s joined by Dr. Edward Giovannucci, a Harvard professor, who just completed a study showing that men who had higher vitamin D counts had a 40 per cent lower risk of colorectal cancer.

These claims are still subject to controversy and will remain so until clinical trials can prove them beyond a shadow of a doubt. Surprisingly, Holick was fired from his job as professor of dermatology at Boston College for publishing his book. Defending this decision, Dr. Barbara Gilchrist, chair of the department of dermatology, told the The Times Online that Holick’s book was “an embarrassment for this institution and for him” and called his research “professionally irresponsible” and “potentially dangerous.”

Still, the impact of his and other findings has stirred health officials on both sides of the border to begin taking a new look at the role vitamin D plays in our overall health. This past March in Toronto, the Canadian Cancer Society held the North American Conference on UV, Vitamin D and Health, which gathered leading vitamin D experts to share their knowledge and come up with new guidelines regarding sun exposure and the amount of vitamin D we need to realize its health benefits.

The D in your diet

Right now, most nutritionists recommend we take in 400 IU (international units) of vitamin D each day. This level was decided upon decades ago as the amount needed to avoid childhood rickets. With new findings in place on the benefits of vitamin D, most experts now agree we need much more – perhaps up to 1,000 IU a day – if we are to obtain any health benefits. And these levels may be even higher for older people, who need the nutrient to maintain good bone health.

The problem with adding more vitamin D to our diet is that the nutrient doesn’t occur naturally in most foods, with fatty fish (cod liver oil anyone?) being the exception. Other foods – milk, egg yolks, some cereal grain bars and margarine – are fortified with vitamin D, but nutritionists suggest they don’t contain enough to get our counts to a sufficiently high level.

“Current dietary practices indicate that the U.S. population does not consume sufficient vitamin D to meet all their needs. And regional studies in Canada show similar findings,” says Mona Calvo, a nutritional scientist for the U.S. Food and Drug Administration. She points out an interesting exception: “Even in winter, studies show that Japanese women maintain adequate vitamin D levels, mostly because they consume fish four times a week,” she says. However, Calvo concludes that without sunlight or a fish-heavy diet, Canadians will become vitamin D-deficient during our long winter months.

Supplements and salons

Supplements are another way to increase your vitamin D levels. However, there are few vitamin D supplements on the market, and those that do exist are usually found in multivitamins, which contain at most 400 IU, less than half of what experts feel we need on a daily basis.

And recently, organizations representing tanning salons have been touting sunlamps as another means of increasing vitamin D intake. An oft-quoted study suggests that people who used tanning beds have a 90 per cent higher amount of vitamin D circulating in their bodies than people who didn’t get artificial tans. Plus, the tanning industry likes to promote its newer “low pressure lamps,” which emit radiation that has the same properties of “natural sunlight,” thereby stimulating vitamin D production.

However, few people have the time or inclination to visit a tanning booth to stoke their vitamin D levels. As well, unless used with caution, sunlamps can cause just as much damage to the skin as the sun. And recently, Calgary-based Fabutan, which owns 150 salons in Canada, was asked by the Federal Competition Bureau to stop using the health benefits of vitamin D to promote indoor tanning.

The sun solution

So, unless we’re taking supplements, eating a diet composed mainly of fatty fish, such as salmon, tuna, herring and sardines, or become regulars at the local tanning salon, it appears the sun must act as our major source of vitamin D.

There are two problems inherent in this. The first is that for the body to manufacture sufficient levels of vitamin D, the sun must be high in the sky and blasting down its UVB rays. Unfortunately, this only happens during the summer months in most parts of Canada.

Moreover, the sun’s UVB rays must hit extensive parts of your body, neck, arms, legs and back. If not, your skin won’t absorb sufficient sunlight to initiate vitamin D absorption. “I’ve seen farmers who spend their whole time out in the sun who are vitamin D-deficient.” says Dr. Bruce Hollis, professor of pediatrics, biochemistry and molecular biology at the Medical University of South Carolina, who spoke at the March conference.

The second problem concerns the application of sunscreen. Those who take UV warnings seriously and cover up with sunscreen to avoid the risk of skin damage, are actually impeding the body’s ability to manufacture vitamin D. Just 15 minutes of unprotected exposure in the sun (no sunscreen, hats or long sleeves) can generate as much 20,000 IU of vitamin D. However, Holick’s own studies suggest that by wearing sunscreen with an SPF factor of 15, you’re blocking production by up to 97 per cent.

There’s also the wild card of different skin types. Those with fair skin who burn easily may find 15 minutes in the summer sun too much whereas those with darker, easily tanning skin may find it not enough. Moreover, it takes blacks far longer to absorb the same amount of sunlight as it would lighter-skinned people. And age is another factor, as our ability to synthesize vitamin D from the sun decreases as we age.

And there’s the conundrum. Sunlight is both good and bad for you. The right amount of sunshine on the skin instigates the production of healthy vitamin D, possibly protecting you from a raft of diseases. Too much sun exposure, however, may damage your skin or cause skin cancer.

Holick’s book tries to solve the “How much sun is too much?” question with a bewildering set of maps and charts that show when and how long you should go out in the sun, depending on your skin type and the latitude where you live. Though his advice seems overly confusing, it ultimately boils down to the premise that you need about five minutes of unprotected exposure to the sun three times a week.

While Holick’s theory on the sun remains hotly contested, we do know there isn’t a problem with increasing the amount of vitamin D in your diet. Even if its wide-ranging health benefits haven’t been proven, increasing your intake of vitamin D will improve your bone strength. So, for those over 50, Osteoporosis Canada suggests you take up to 800 IU a day, or about twice the current recommendation. Talk to your doctor or a dietitian about ways of introducing more into your diet.

But as far as gardening, golfing or basking in the glorious summer sun without sunscreen, unfortunately, that’s going to have to wait for the experts to rule. The Canadian Cancer Society is currently hammering out new guidelines on vitamin D and the right amount of sun exposure, which should be out sometime in June. Until those new standards are published, health officials are suggesting that we continue to avoid the sun and use sunscreen and a hat as much as possible.

Vitamin D in food
Food Serving Vitamin D (IU)
Milk 1 cup 100
Fortified rice 1 cup 100
Soy beverage 1 cup 100
Fortified margarine 2 tsp 56
Salmon, canned, pink 3 oz 520
Tuna, canned, light 3 oz 200

Vitamin D in food (cont.)
Food Serving Vitamin D (IU)
Herring 3 oz 900
Sardines 3 oz 250

Source: BC Health Guide