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Saturday, January 12, 2008

Adding Vitamin D to a Nondairy Diet

One of the more interesting points I learned while researching Milk Is Not for Every Body: Living with Lactose Intolerance is that many scientists believe that lactose tolerance evolved because northern Europeans no longer were able to expose their bare skin regularly to the sun.

The reasoning is that sun exposure makes vitamin D. That vitamin aids in calcium absorption, which goes to making strong bones. Lack of sun exposure, therefore, leads to vitamin deficiency diseases of the bones like rickets and osteomalacia. (Quick technical note: vitamins are defined as vital substances only available in food. So if the body can directly make vitamin D, then perhaps it isn't really a vitamin. But if you can only get it from food... Definitions can drive you crazy.)

Anyway, those who could drink milk could gain calcium, which would help counter the effects of the loss of vitamin D. And there is some evidence, although it is disputed, that the presence of lactase in an adult improves calcium absorption when lactose is ingested. The result was genetic pressure to favor adult lactose producers as descendents of those few who naturally had the mutation that allowed them to never stop making lactose.

All this is still true today. Many older adults in the U.S. and in other northern latitudes do not get very much sun exposure on their bare skin for long months of the year if at all. Most calcium supplements today come with a variety that contains vitamin D.

And all milk in the U.S. is fortified with vitamin D, which makes dairy products an excellent nutritional source in multiple ways.

What if you don't eat or drink dairy and still want vitamin D from food sources rather than supplements?

The U.S. National Institutes of Health has an Office of Dietary Supplements. Who knew? It has a webpage that is a Vitamin D Fact Sheet full of information. Unless you want to go in directly for cod liver oil, the best sources of vitamin are fish like salmon and mackerel. Even canned tuna fish and sardines are good sources.

Some foods besides milk are also fortified with vitamin D. Certain soy milks, fruit juices, even breakfast cereals have good amounts of vitamin D.

Here's a good account of food sources from dietitians Carrie Cassens and Teresa Smith at the Sauk Valley newspaper site.

Note the warning that they give not to exceed 2000 IU of vitamin D a day. By comparison a capsule supplement often has 400 IU a day.

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TedHutchinson said...

It is not strictly true that milk is an excellent source of Vitamin D. Whenever studies have been done on fortified milk most samples contain less than half the stated amount.
Even if fortified milk did contain 100iu of Vit D, no one can consume 40glasses of it daily. Wild salmon is a good source but that only averages 400iu portion and nice as it is one portion daily is the most anyone could manage so diet can only provide at most 10% of your daily Vitamin D requirement.

Your 400iu tablet can only raise status by 7-12nmol/l. See The urgent need to recommend a vitamin D intake that is effective
Risk Assessment Vitamin D proposes 10,000iu/daily as the safe upper limit.
Not enough vitamin D Health consequences for Canadians is a medical review for Canadian doctors that says "the oral dose of vitamin D3 to attain and maintain 25(OH)D levels >80 nmol/L is 2200 IU/d if baseline levels are 20 to 40 nmol/L"

Steve Carper said...

If a glass of milk contains 100 IU of vitamin D, then one need drink only 4 glasses - not 40 - to get the recommended amount. When one includes other sources of dairy in the diet, this amount isn't far-fetched. You don't need or want 4000 IU of vitamin D a day. That would be hazardous to your health.

My intent was to give information about using a variety of food sources to reach that 400 IU goal. A diet rich in seafoods and fortified foods, including but not restricted to dairy, would probably achieve this goal without straining the normal American diet.

It would be helpful if you gave proper citations.

Here are the articles you mention.

The urgent need to recommend an intake of vitamin D that is effective, by Reinhold Vieth et al. American Journal of Clinical Nutrition, Vol. 85, No. 3, 649-650, March 2007

Not enough vitamin D:
Health consequences for Canadians, by Gerry Schwalfenberg.
Canadian Family Physician Vol. 53, No. 5, May 2007, pp.841-854

The first is not a journal article, but a letter of comment on an article.

Hypovitaminosis D in British adults at age 45 y: nationwide cohort study of dietary and lifestyle predictors, by Elina Hyppönen and Chris Power. American Journal of Clinical Nutrition, Vol. 85, No. 3, 860-868, March 2007

All the articles do agree that most people in the UK and Canada do not get enough vitamin D and this is putting their health at risk. No one source of vitamin D is used sufficiently. Public health measures always wind up with the same recommendations: use as wide a variety of sources as possible to get the needed nutrient to those who need it because no one route will work.

If you can have dairy and will use dairy, then it is a fine source of vitamin D. If you can't or won't, there are a variety of other methods you can use.

That was the message in my original post, and I see no reason to change it now.