August 24, 2004

Vitamin D

Amanda Schaffer writes in Slate about how a surprisingly large number of people who live her in the northlands far from the equator need more vitamin D. I am very surprised that this is controversial. When we Cro-Magnon types came out of Africa 60,000-100,000 years ago, none of us were white. Now practically all of us the bulk of whose ancestors stopped for long in northern Europe or northern China are remarkably pale indeed. I have heard no reason advanced for this other than that melanin in your skin blocks some vitamin D creation. If true, then there must have been a hell of a lot of selection pressure for low-melanin skin, which replies a hell of a large health cost to blocking even a small amount of sun-mediated vitamin D creation:

Essential Nutrient - Why vitamin D deficiency may be a hidden epidemic. By Amanda Schaffer: You may have heard about recent scuffles between prominent dermatologists and experts on vitamin D, a crucial vitamin obtained in part by exposure to UV light. In a front-page story this April titled "BU Advocate of Sunlight Draws Ire," the Boston Globe reported on the brouhaha surrounding Dr. Michael Holick, whose recent book, The UV Advantage, touts the health benefits of moderate sun exposure and downplays the threat of skin cancer. (Dr. Holick, perhaps the most prominent vitamin D researcher in the country, was forced to resign from the dermatology department at Boston University's medical school in February, though he retains his appointment in medicine.) The Globe piece—and a recent article in the New York Times—also noted that Dr. Holick's work is partly funded, and actively promoted, by the Indoor Tanning Association, an industry group with obvious financial interests. It's easy to see why the conflict has escalated and why many in the public are confused about the basic issues underlying this debate.

What exactly are the health benefits of vitamin D? How much does a person need? And why is the issue so often framed in terms of sun exposure—can't you just drink fortified milk or take a multivitamin?

Let's start with the basics: Vitamin D is a fat-soluble substance (that is, it dissolves in and can be stored by fat deposits in the body). It is present in salmon, mackerel, sardines, and cod liver oil; fortified foods including milk, breakfast cereals, and some juices; and vitamin supplements. It can also be synthesized in the skin during sun exposure. Vitamin D (in its active form, which is created after several modifications by the body) functions as a classic steroid hormone, which means it binds to nuclear receptors in various tissues to influence the expression of genes, thereby affecting a range of processes, especially the regulation of calcium.

It has long been known that vitamin D is crucial for healthy bones. The presence of vitamin D in the small intestine aids in the absorption of dietary calcium—people with vitamin D deficiency are able to absorb only a third to half as much calcium as those with sufficient levels—and calcium is vital to the hardness of bone. The two diseases traditionally associated with severe vitamin D deficiency—rickets in children and osteomalacia in adults—are characterized by deformation or softening of bone. And chronic vitamin D deficiency is strongly linked to osteoporosis, a disease defined by loss of bone density and associated with increased risk of fractures.

The common assumption has been that with the fortification of milk, instituted in the United States in the 1930s, and casual exposure to sunshine, most people get all the vitamin D they need. But a small resurgence of rickets in the last few years, particularly among African-American children, has caught the health-care community off guard. As studies have probed the issue, it has become clear that vitamin D deficiency (usually defined as blood levels of less than 15 ng/mL [or nanograms/milliliter]) and insufficiency (less than 20 ng/mL,) are far more widespread than researchers had expected. The elderly, who often receive little sun, are at particular risk, as are African Americans and other dark-skinned people, since skin pigmentation, which protects against damage by UV rays, also interferes with vitamin D production. (Those with dark skin need to spend more time in the sun to produce the same amount of vitamin D.) Infants who are exclusively breast-fed are also at high risk since breast milk, for all its virtues, contains almost none of this vitamin.

Perhaps the biggest surprise, though, has been the prevalence of vitamin D deficiency among women of child-bearing age—particularly African-American women—and among healthy children and adolescents. Dr. Catherine Gordon, an adolescent-health specialist at Children's Hospital in Boston and an expert on vitamin D, told me that calling it a "hidden epidemic" would not be an overstatement. While severe cases early in life result in rickets, less-pronounced deficiencies may slip under the radar because they do not cause noticeable symptoms. Gordon and other doctors worry that for children and adolescents, insufficient vitamin D can prevent proper bone development and increase the risk of disorders such as osteoporosis later in life.

Vitamin D deficiency can easily go undetected in adults as well. In one study, published in 2003 in the Mayo Clinic Proceedings, researchers in Minneapolis tested vitamin D levels in patients suffering from chronic, non-specific, musculoskeletal pain: 93 percent of them turned out to be vitamin D deficient—a condition very likely (though not conclusively) related to their symptoms. And of the East Africans, African Americans, and Hispanics in the study, 100 percent were vitamin D deficient. As a result, the authors argue, all patients with such pain should have their vitamin D levels tested because osteomalacia may turn out to be the underlying cause.

But vitamin D's benefits may go beyond the protection of bone and muscle. There is new research to suggest that vitamin D may also guard against an array of diseases, including colon, breast, and prostate cancers....

Posted by DeLong at August 24, 2004 04:25 PM | TrackBack
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July 20, 2004

A Dermatologist Who's Not Afraid to Sit on the Beach
By GINA KOLATA - New York Times

Dr. A. Bernard Ackerman, a dermatologist, spends much of his time diagnosing the potentially deadly cancer melanoma and other skin diseases.

But when he returned from a recent trip to Israel, he was, well, deeply tanned.

Burnished brown, in fact.

Dr. Ackerman did not use sunscreen on his trip. He did not give any thought to the hundreds of moles that speckle his body. He did not even put a hat on his bald head.

Other dermatologists may worry about getting melanoma from exposure to ultraviolet rays. But Dr. Ackerman, 67, a renowned expert in the field and the emeritus director of the Ackerman Academy of Dermatopathology in New York, said the link between melanoma and sun exposure was "not proven."

He has scrutinized, one by one, the widely held precepts about melanoma and the sun, and found the evidence wanting. "The field is just replete with nonsense," he said.

For example, it is commonly assumed that painful or blistering sunburns early in life set the stage for the skin cancer later on. But while some studies show a small association, Dr. Ackerman says, others show none. And even studies that do show an effect disagree on when the danger period for sunburns is supposed to be.

Taken as a whole, Dr. Ackerman argues, the research is inconsistent and fails to make the case.

Common wisdom also has it that sunscreens protect against melanoma. But Dr. Ackerman points to a recent editorial in the journal Archives of Dermatology concluding that there was no evidence to support that idea.

Finally, many people assert that the more intense a person's sun exposure, the greater the risk of melanoma.

For example, Dr. Darrell S. Rigel, a New York dermatologist, points out that the incidence of melanoma increases as distance to the equator decreases. Dr. Rigel, a past president of the American Academy of Dermatology and the lead editor of "Cancer of the Skin," a major textbook in the field, cites this as a compelling reason to conclude that sun exposure causes the skin cancer.

But it is not compelling to Dr. Ackerman. Epidemiological data on melanoma, he says, are imprecise and inaccurate. In searching for the causes of other cancers, he argues, epidemiological data have led researchers astray, and by their nature they cannot demonstrate cause and effect.

Stay out of the sun, Dr. Ackerman advises, but do it to avoid premature aging of the skin. If you are very fair, avoiding sunlight will also help prevent squamous cell carcinoma, a less dangerous cancer. But it would be a mistake, he says, to assume that avoiding sunlight or using sunscreens will offer protection from melanoma.

Posted by: anne at August 24, 2004 05:02 PM

Dr. Ackerman has been enamored of the skin and its diseases since his earliest days as a resident at Columbia. Studying dermatology, to him, was like taking courses in art history. "If you know a certain artist you can recognize him again," he said. "So it is with lesions in the skin. A lesion is like a painting or a piece of sculpture."

He has spent most of his career in academia and has published 625 research papers. His list of honors and awards includes this year's the Master Award, given to one person a year by the American Academy of Dermatology.

In 1999 he started his own academy, supported by AmeriPath, a company that owns pathology laboratories. "I had nothing to sell - I was always in university life," Dr. Ackerman said. "If you'll excuse the expression and not think I'm a tart, they bought me."

His academy, he says, is now the world's largest training center for dermatopathology. Dr. Ackerman, who is paid a flat salary, and his six associates examine more than 100,000 specimens and have done more than 4,000 consultations each year. Dr. Ackerman continues to teach and write, and also to ask for data and question his field's conventional wisdom.

Challenging the link between sun and melanoma is part of this pattern.

Dr. Ackerman even questions whether the "epidemic" of melanoma proclaimed by many dermatologists exists. The definition of the cancer, he says, has changed over time, leading doctors to diagnose, remove and cure cancerous growths that once would not have been called melanoma.

"The criteria today, clinically and histopathologically, are diametrically different from those 30 years ago," he said. In medical school, he continued, "we were taught that melanoma is a big, black, fungating tumor that kills. Who would have believed then that you can recognize melanoma for what it is when it is small and flat and the size of the fingernail on your pinky? You would have said they were insane."

Anyone who argues that sun exposure causes melanoma, Dr. Ackerman says, needs to explain why blacks and Asians get melanoma almost exclusively on skin that is not exposed to sunlight: the palms, soles, nails and mucous membranes. Even in whites, the most common melanoma sites - the leg in women, the trunk in men - are hardly the most sun-exposed body parts.

It is not a popular argument. Dr. Rigel, reached by telephone in Hawaii, where he was vacationing, said it was perverse of Dr. Ackerman to pick the data apart.

Melanoma, Dr. Rigel said, can occur "where the sun doesn't shine." But that is because sunlight suppresses immune cells in the skin's surface that ordinarily hold cancer at bay, he said.

He himself stays pale, even in Hawaii, that land of intense sunlight.

Posted by: anne at August 24, 2004 05:05 PM

Block that closing tag!

Posted by: HTML at August 24, 2004 05:06 PM

Vitamins D and A both have a toxic dose, so let's not get overenthusiastic.

Posted by: zizka / John Emerson at August 24, 2004 05:56 PM

First, I found out that margarine is actually worse for you than butter.

Now they say the yucky gloopy sunscreen I slathered on all my life did me no good.

I wonder what other pieces of medical conventional wisdom will be overturned in my lifetime.

Posted by: Angelica at August 24, 2004 06:28 PM

Now test that hypothesis against other data, e.g. Tasmanian aborigines who were isolated at comparable southern latitudes for a comparable period of time. Or the denizens of the equatorial parts of South America and the East Indies, who didn't revert to darkness even when there was an admixture of earlier, darker, populations (though there was less pressure there).

Posted by: P.M.Lawrence at August 24, 2004 06:30 PM

from the "93%" study - here - http://health.allrefer.com/news/index.php?ID=5032 -
"We were stunned to find no Vitamin D at all in five patients who had been told their pain was 'all in their head.'"

Z: "Vitamins D and A both have a toxic dose, so let's not get overenthusiastic" -

Can't OD on D from sun, BTW, AFAIK.

Posted by: anna at August 24, 2004 06:47 PM

Brad DeLong writes:
>
> When we Cro-Magnon types came out of Africa 60,000-
> 100,000 years ago, none of us were white.

And if both this and the fact that are deficient in vitamin D are both true, I think it shows that the evolution of hominids was, yet again, a way trickier process than some would have imagined.

So our closest relatives are chimpanzees. Chimps are pretty hairy, but their skin is quite light in color. This makes sense if there is a tension between the vitamin D production from sunlight needed given a chimp-like diet and the ill effects of UV radiation, especially if you have light colored skin. At some point since our divergence with chimps, but apparently quite long ago, we lost almost all of our body hair. It is known that this caused our lice to scramble around a bit to find appropriate niches (hairy heads, and, later, clothing). Presumably, this also set up a tremendous pressure towards darker skin, in the absence of hair and protective clothes (which didn't become a cultural fad until far later than you might think).

But I think the real puzzle out there isn't skin color, but why the heck we lost all that perfectly good hair in the first place? Are there any good and direct selective pressure arguments for that? I guess my first response, whenever I hear a beautiful but just-so explanation for a human trait, is whether the idea has any bearing on what I think is the big hairy mystery of hominid evolution.

Posted by: Jonathan King at August 24, 2004 08:04 PM


But I think the real puzzle out there isn't skin color, but why the heck we lost all that perfectly good hair in the first place? Are there any good and direct selective pressure arguments for that? I guess my first response, whenever I hear a beautiful but just-so explanation for a human trait, is whether the idea has any bearing on what I think is the big hairy mystery of hominid evolution.


Look up "aquatic ape hypothesis" which is sufficiently neat and wraps up enough loose ends that you pretty much hope it turns out to be true.

As for suntans; I have no comments on the issue of cancer. I can however state that it's pretty obvious to anyone with eyes and a brain that too much sun (and too much is pretty damn little) will age skin very very fast. If you WANT to live fast and imagine that there's no life after 30, go right ahead and tan. But if you don't want to look like you're 60 at age 40, you'll avoid sunlight as best you can. Remember evolution had no real interest in what happens to you after about 40 anyway. You might be best off getting your vitamin D through your milk.

Posted by: Maynard Handley at August 24, 2004 08:38 PM

Maynard Handley writes:
>
> Look up "aquatic ape hypothesis" which is sufficiently neat and
> wraps up enough loose ends that you pretty much hope it
> turns out to be true.

Uh...or not. I can't say I know of any serious academic types who have had anything nice to say about this theory for quite some time. I've got to get some lecture stuff together now, but have a look at this page and the links therein:

http://www.aquaticape.org/

Now, to be fair, human hairlessness has *not* been a slam-dunk for any hominid evolutionary theory out there, except to the extent that the theorizers have gotten slammed.

Posted by: Jonathan King at August 24, 2004 08:52 PM

Oh brother....

By the Third Law of Thermodynamics, everything in the Universe is morphing gradually to chaos, (ex. see Iraq) and the Entire Universe has been expanding at a uniformly increasing rate since Big Bang, some 100,000,000,000,000 years ago, more or less.

Since the Entire Universe is expanding, has been expanding, will always be expanding, we surmise that our solar system was once much smaller, and our sun along with it and the very earth itself.

It follows thereby dinosaur fossils have been expanding for some 144 to 65 million years, and that those reptilian forebears were originally no larger than the small gecko lizard of today. Fossils just grew with the Universal expansion.

Tyrannosaurus Mini-me

Our increased need for Vit-D has nothing to do with imaginary theories, ontogeny-recapitulates-philogenyian journeys out of Africa, or any of that tripe, but the simple fact that humankind are much, much enlarged from Cro Magnan days, and hence have a larger need for all vitamins.

Look what an expanding waistline can turn into!
Golly gee, those waddling backsides in the mall!
They're gonna need Vitamin D's by the gallonful!

Posted by: Tante Aime at August 24, 2004 09:11 PM

Several studies of the vitamin D in milk have found considerable variation. There is little or no regulatory testing of the vitamin D content of milk, so it's unwise to depend on that. And in northern latitudes in the winter, exposure to the relatively weak sun produces little vitamin D.

Posted by: BayMike at August 24, 2004 10:05 PM

Moderation, moderation, moderation.

Did I mention moderation?

Ignore the hype and just live a balanced life, dammit. People near the equator are dark because they can't avoid an excess of sunlight. Those near the poles are white because they can't avoid a deficiency. In the meantime, poor Angelica is confused because she was sucked into valuing conventional wisdom over common sense.

Posted by: Dragonchild at August 24, 2004 10:19 PM

let me put in a word for Actinic-keratosis, which does exist, how common is this among us whites? And why is New Zealand now touted as the melanoma capital of the World? since the hole in the ozone layer, over the south pole got so big.

Posted by: big al at August 25, 2004 03:11 AM

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"Now, to be fair, human hairlessness has *not* been a slam-dunk for any hominid evolutionary theory out there, except to the extent that the theorizers have gotten slammed."

Uh, how about *sweat*? Running around on the African savannah with your skin covered with a thick layer of fur might not be a problem if you're an ambush predator like the big cats, but it *is* a problem when you're the world's most endurant long-distance hunter. Extremely fit hominids (the only sort that would have been around 1.2 million years ago) can cover up to 100 miles in a *single* day if need be, i.e, as much as wolves or better; I recall a NZ woman named Maureen Metcalfe doing just that a year or two ago. If humans could use panting to lose heat, that would be one thing, but we can't, which leaves no alternative to losing the fur.


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Posted by: Abiola Lapite at August 25, 2004 04:27 AM

First of all, hormones bind to molecular receptors, not nuclear. Second of all, the toxic amounts of Vitamin D and Vitamin A are controversial at best. Straight retinoid A MAY be toxic at over 25000 IU for long periods of time, but beta carotenes have very low toxicity. The toxic dose for D is so high as to be laughable. Most adults over 50 probably should take 4 times the RDA of D (400 IU) to be on the healthy side.

Posted by: i ain't telling at August 25, 2004 05:21 AM

Hairlessness can be a consequence of other changes with no inherent benefit of its own.

Specifically, Homo Sapiens can generally be described as neotenic, that is having the characteristics of the juvenile.

The more upright gait, curiosity, and the relatively ease of learning are all things more prevalence in juvenile apes.

So is less body hair.

If neoteny is controlled with a relatively small number of genes, then hairless might result through an economy of genetics.

It's kind of like nipples on men.

Having them there, but not activating them turns out to be an elegant way of allocating genetic resources.

Posted by: Matthew Saroff at August 25, 2004 06:17 AM

There are people who think that if one unit of vitamins is good, ten is better. These people do sometimes have problems with A and D. Also, you should put polar bear liver on your list of foods to eat in small quantities, if at all.

Posted by: zizka / John Emerson at August 25, 2004 07:03 AM

First of all, hormones bind to molecular receptors, not nuclear.

What? Receptors in the (cell) nucleus, dude.

Posted by: cerebrocrat at August 25, 2004 08:43 AM

If you want to see what sun does to your skin, compare the face of your significant other with his/her backside. This works better the older you are :)

Posted by: Roger Sweeny at August 25, 2004 01:29 PM

The sun may provide vitamin D, but it destroys folic acid. There is a balance here. According to a Scientific American article (05/2003 Skin Deep) a few years back, the conflicting demands for vitamin D and folic acid have led to a situation in which women are generally a few percentage points paler than men with nearly identical genetics (e.g. sisters and brothers).

Posted by: Kaleberg at August 25, 2004 03:05 PM