Tag Archives: vitamin D

Health, News

Elderly Persons! Your Vitamin D Level Better Be More Than 20 Ng/ml

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This cactus illustrates the best way to get vitamin D: live in Mexico. (Photo: MvB)

Vitamin D! Do you have enough? The numbers have been squishy. At one point, it seemed likely that everyone in the U.S. was suffering from a “deficiency.” But what did that mean, exactly, outside of the non-FDA-regulated claims of vitamin D retailers? A new study says that vitamin D deficiency for people over 65 is 20 nanograms/milliliter of 25(OH)D in your blood. Fall below that for too long, and bad things tend to happen.

University of Washington researchers went looking for a bright statistical line to see how levels of vitamin D circulating in the blood correlated with the risk of a major medical event. “Major” in this case meaning: heart attack, hip fracture, cancer diagnosis, or death. (We can all agree that death is as major an event as it gets.)

Their sample was drawn from a study of 1,621 Caucasian adults that was intended to ferret out risk factors for (and progressive stages of) heart disease in people age 65 and over. They had an eleven-year timeline of 25-hydroxy-vitamin D levels–in short, 25(OH)D–to look at. (One glaring limitation here is that the original study included no one of color, and while the jury is still out, there’s some concern that melanin-protected skin can cut down on vitamin D production, just as SPF 8 does.)

Today, their findings appeared in the Annals of Internal Medicine: “Serum 25-Hydroxyvitamin D Concentration and Risk for Major Clinical Disease Events in a Community-Based Population of Older Adults.”

Luckily UW News is there to put results into English for you: “[T]he researchers concluded that the risk of these disease events rose when the concentration of 25(OH)D fell below 20 ng/milliliter or 50 nmol/liter.”

The first thing to note is that as Dr. Ian de Boer, assistant professor of medicine in the Division of Nephrology, points out, this is mostly in line with the threshold level suggested by the Institute of Medicine. Here’s the NIH on IOM recommendations: “Practically all people are sufficient at levels ≥50 nmol/L (≥20 ng/mL); the committee stated that 50 nmol/L is the serum 25(OH)D level that covers the needs of 97.5% of the population.”

Daily supplements of 600 t0 800 IU of vitamin D3 should do the trick, if you’re not getting much vitamin D from anywhere else. (The Institute of Medicine, by the way, does not recommend exceeding 4,000 IU per day of vitamin D3 for adults.) A separate study on vitamin D dose response in post-menopausal women found that “response was curvilinear and tended to plateau at approximately 112 nmol/L in patients receiving more than 3200 IU/d of vitamin D3. The RDA of vitamin D3 to achieve a 25 (OH)Dlevel greater than 50 nmol/L was 800 IU/d.”

The second thing suggested by the study is that vitamin D levels are best understood in terms seasonal snapshots: Typically, you will top off the tank in summer, thanks to exposure to the sun. If it’s not replenished, that vitamin D bank balance gets drawn down all through next spring, so that you may be lower on vitamin D in March than October, even though the amount of sun is about the same. You might think you’d increase supplements most in winter and taper off in spring, but this study indicates otherwise.

Health, News, Science

Hutch Studies: “No strong evidence that multivitamins decrease your cancer risk”

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This looks healthy. (Photo: Slightlynorth, from our Flickr pool)

What can’t dietary supplements do? They prevent cancer, lengthen the life of your joints, and stave off Alzheimer’s. Or at least that’s what it may say on the label. Americans are still a trusting people, and CNN reports that about half of us take some kind of dietary supplement, together spending about a quarter of a trillion dollars annually.

So why is the Fred Hutchinson Cancer Research Center reporting that “In general, there’s no strong evidence that taking a multivitamin increases or decreases your cancer risk”?

You remember that little disclaimer you see a lot on bottles: “This statement has not been evaluated by the FDA”? That’s thanks to legislation that President Clinton signed into law in 1994, allowing companies to market supplements on their recognizance, as it were. When it comes to mixing up existing, approved ingredients, anything goes, and pretty much any claim goes, so long as that little statement is appended.

Companies need prove the safety only of a “new” ingredient, although, as the FDA notes, “manufacturers and distributors are responsible for determining if a dietary ingredient is ‘new’,” in the first place. (As for efficacy, without casting aspersions on company-funded studies, it’s clear that if their conclusions were completely reliable, no one in the world would be suffering from anything.)

The U.S. Food and Drug Administration is mainly concerned that supplements not poison you–and their regulatory authority at this point comes to bear only after you’ve been harmed. In essence, it’s all supplemental fun and games until someone loses an eye. Luckily, you’re protected somewhat by the invisible hand of the market, which dictates that killing off or disabling a lifelong customer base is a terrible idea.

Still, for many in our health-insurance-less age, dietary supplements are the next best thing to medicine. The Hutch’s Dr. Emily White argues that when it comes to cancer prevention, that’s not necessarily so. Fruits and vegetables are, pills and caplets aren’t.

White “spent several years tracking how 38 different supplements impact the health of more than 75,000 study participants,” reports the Hutch. She couldn’t find any cancer prevention from multivitamins. (A 2009 study by the Hutch’s Dr. Marian Neuhouser included “161,000 women and found that taking multivitamins did not affect the likelihood of contracting cancer or cardiovascular disease.”)

It’s a bit like whack-a-supplement, but the Hutch researchers have previously found that neither Vitamin E nor selenium seem to prevent prostate cancer. (Scratch beta carotene and retinyl palmate, as well.) Calcium and vitamin D have no discernible impact on colorectal cancer.

Fish oil is still in the running, but Dr. White’s bottom-line assessment is this: Rather than poring over supplement fine print, “You should be shopping in the produce section instead.” Whatever it is in food that’s good for us, it’s mostly in the food. (NB: If you have a known vitamin deficiency, especially because of a food-related allergy, taking a supplement is a good idea. But without a deficiency, caveat emptor.)

News, Science

Finally, a Medical Reason to Sunbathe Nearly Nude All Summer

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Madison Park’s beach is a prime source of Seattle’s vitamin D intake.

Good news from the New York Times: “Given appropriate sun exposure in summer, it is possible to meet the body’s yearlong need for vitamin D.” Didn’t know you could store up the D like a battery, did you? (Fun fact: it’s actually a steroid hormone, not a true vitamin–if you get enough sun you don’t need another source.)

The consulting physician on the article, Boston U’s Dr. Michael Holick, suggests you take sun breaks “from 10 a.m. to 3 p.m. two or three times a week for 5 to 10 minutes.” Put sunscreen only on your face, and–think Lady Gaga–maximize your skin exposure.

What’s the big idea? Nutritionists have discovered that we aren’t getting nearly the amount of vitamin D that we need. While a serious vitamin D deficiency has long been known to cause rickets, it’s becoming more evident that chronic low levels of vitamin D can have serious health impacts as well.

Besides documented effects on bone health, Holick references studies that show a lack of vitamin D impacting multiple sclerosis, arthritis, type I diabetes, and immune response in general. Locally, the Fred Hutchinson Cancer Research Center has been researching vitamin D intake and colorectal cancer and breast cancer rates, and have also found that diet, geography, and lifestyle aren’t good predictors of individual vitamin D levels; a blood test is the best way to be sure.

Here’s the FHCRC line on vitamin D, what it does, how much you need, and how to get it.

While a blood serum level of 40 nanograms per milliliter of 25-hydroxyvitamin D is optimal–and easy to maintain if you’re outdoors frequently in sunshine–Holick says U.S. “Caucasians average 18 to 22 nanograms and African-Americans average 13 to 15 nanograms.”

Again, with sun, it’s easy. Holick says 15 to 20 minutes in the summer noonday sun can deliver the “equivalent to taking 20,000 IU of vitamin D orally.” (Yes, there’s a book.) If you start feeling droopy in winter, besides D3 supplements (1,000 to 2,000 IU day is the new, higher recommended intake), you can also feast on salmon regularly (360 IU per serving) or, better yet, halibut (510). Scroll down to see the food-derived vitamin D chart here.

One bonus of the sunbathing method is that your body knows when it’s manufactured enough D; if you’re increasing D levels via supplements, you can reach toxic levels. They’re very high, and not easy to get to, but some people do think that if x of a vitamin is good, 10x must be terrific. Constipation and nausea is nature’s way of correcting their math.