My doctor had me take a blood test for my vitamin D levels, and found them low – so he recommends that I take vitamin D supplements. According to several sources, Vitamin D is supposed to be important in maintaining adequate calcium levels in my bones, so low Vitamin D may also indicate low calcium levels.
However, Mrs. Tracer – who also has low vitamin D levels – just told me that you’re NOT SUPPOSED TO take Vitamin D at the same time that you take Calcium. Calcium supposedly interferes with your ability to absorb vitamin D, so you need to take them at least 4 hours apart.
I’ve been told to take them together. And in fact they market supplements that are specifically labeled Calcium and Vitamin D like Caltrate D-plus so it must be reasonably common to take them together.
Also, the best way to get Vitamin D is a few minutes in the sun; you can produce 10,000 IU in 10 minutes (which exceeds tolerable upper intake levels, although your body stops producing it before it reaches toxic levels). For comparison, recommendations are for 400-800 IU from the diet, depending on age; tolerable upper intake is 4,000 IU for ages 9+ (source).
Calcium should be taken an hour or more apart from fiber supplements and from iron (as already mentioned), but I don’t know of any common recommendation that it be separated from Vit D. My calcium chew package claims that Vit D increases the absorption of Calcium, but it makes no claims about what Calcium does to the absorption of Vit D.
A small subset (like 20%) of people have low acid production in the stomach, and those people will get better absorption of calcium if they take calcium citrate, as opposed to the more popular, cheaper, calcium carbonate. If you take drugs to reduce stomach acid, like Prevacid, omeprazole, Zantac, Prilosec, etc., then you should likewise choose calcium citrate. Calcium carbonate should be taken after a meal or with food*; calcium citrate can be taken any time.
Like most supplements, studies consistently show that you’re better off increasing dietary sources, rather than taking supplement pills, unless otherwise directed by your doctor (that is, unless you’re really, clinically, super low in something.)
Mrs. Tracer is also low in Vitamin D, and may have been told not to take it within 4 hours of taking calcium by her own doctor, or by her allergist or something. I’ll have to ask her, as it seems that this advice may be (and from what y’all tell me, probably is) wrong.
Vitamin D deficiency is turning out to be far more common than we previously thought. It’s possibly because we’ve been so good at getting out the message to use sunscreen, as well as (as you point out) greater time spent indoors, out of sunlight. Obesity also has a direct link with Vit D deficiency, because fat cells alter the metabolism of Vit D; as obesity rises in our population, so does Vit D deficiency. Smoking increases Vit D deficiency. IBS, Crohn’s Disease, Celiac and other diseases of the bowel can lead to Vit D deficiency, as can kidney function which declines with age. Dark skin can make it very hard to get enough Vit D from the sun, and African Americans have higher than average rates of lactose intolerance, so often don’t get Vit. D from fortified milk or milk products.
[Vitamin D insufficiency is highest among people who are elderly, institutionalized, or hospitalized. In the United States, 60% of nursing home residents and 57% of hospitalized patients were found to be vitamin D deficient.
However, vitamin D insufficiency is not restricted to the elderly and hospitalized population; several studies have found a high prevalence of vitamin D deficiency among healthy, young adults. A study determined that nearly two thirds of healthy, young adults in Boston were vitamin D insufficient at the end of winter.
The decreased efficacy of vitamin D production by darker-pigmented skin explains the higher prevalence of vitamin D insufficiency among darker-skinned adults. Dawson-Hughes and colleagues demonstrated that in Boston, 73% of elderly black subjects were vitamin D insufficient, compared with 35% of elderly non-Hispanic whites.
I wouldn’t call the doctor a quack for diagnosing two partners with Vit D deficiency, if their blood levels meet generally accepted guidelines. In fact, since so many of the things that create Vit D deficiencies are related to diet and lifestyle, I’d expect there to be a rather strong correlation between married couples’ Vitamin D status (but I don’t know if anyone’s done a study on that.)
FWIW, I live in South Florida, and drive a convertible. I don’t use sun screen daily - just when I’m going to be out for extended periods of time. After testing my levels, my doctor has me on 2000IU/day Vitamin D.
In many countries, what happens is that the definition of “milk” includes levels of nutrients including liposoluble Vitamins A and D, thus low-fat milk (which loses too much of those two when fat is taken out) gets A and D re-added to go back to original levels; they do not get added to regular milk.
If that is the case, and I did find this article saying that sun exposure doesn’t prevent Vitamin D deficiency, then it would seems as if recommended blood Vitamin D levels are too high; in other words, why is there a global epidemic of Vitamin D deficiency, by some estimates over 75% of the world population (I have no idea what my levels are and don’t see any reason to get it tested; that said, I do get daily sun exposure and drink enough milk to get 100% of the RDA from that alone, much less other foods and a daily (regular, 100% RDA) multivitamin). Presumably, it has to do something with modern lifestyles and diets because nobody was worried about Vitamin D deficiency when people were hunter-gatherers, or even more recently.
But remember that evolution isn’t concerned with *optimal *health. It’s concerned (to anthropomorphize) about “good enough to reproduce”. Aside from rickets, which takes a *very *deficient deficiency that’s been recognized for years, Vit D deficiency related health problems tend to happen after reproductive age. So as far as hunter-gatherers were concerned, you had babies, you got old and you fell and broke bones and died. That’s just how things happened sometimes. They didn’t have a blood test and spreadsheet to tell them why this old guy broke bones and that old guy didn’t. Maybe it was because his spirit was weak, maybe it was a curse, maybe god was punishing him because he was a bastard in a previous life…who knows?
Now, we’d prefer most people live into their 90s and we’d prefer they didn’t break hips along the way. Plus, we’ve identified a host of other medical issues which seem to be linked to Vit D deficiences, some of them at numbers much higher than we used to think of as “deficient”.
So, you’re right - the current recommendations may be “too high” for prehistoric peoples. They may not be “normal” for the human animal. But they’re numbers where we see fewer illnesses and broken bones, so they’re the goal now.
This is true in the summer in temperate climates, but it’s much more difficult to achieve in the winter here in Canada. We can’t get the kind of skin exposure needed, but moreover, even if we could, the sunlight isn’t as intense enough to do as much good.
In the U.S. – at least in California, where I live – vitamin D is usually added to WHOLE milk as well as to lowfat milk. Lowfat milk also gets vitamin A added to it, though, which doesn’t get added to whole milk.
A Nurse Practitioner told me that vitamin D production was the most pronounced in the eyes, not the skin, and recommended that I go out early in the morning and look around at the sunlit landscape (but not directly at the sun).
I’m convinced she’s off her rocker, because this flies in the face of everything we know about how the skin actually produces vitamin D. In the early morning shortly after sunrise, most of the Ultraviolet B coming from the sun is blocked, because the sunlight has to pass through too much air, and it’s UV-B that’s needed to synthesize vitamin D!