Of all places to do a study on sunshine and health, the United Kingdom has produced a ground-breaking paper proving that vitamin-D supplement therapy has been based on a fallacy: that the human body doesn't distinguish between vitamin D2 from plants and vitamin D3 from animal sources.
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It does, according to the study, which was done on adult women. The scientists didn't check men and children, at least yet.
Vitamin-D deficiency is common, even in sunny Israel. Our skin cells produce vitamin D when exposed to sunlight, but even in Israel, people do not generally sunbathe enough to produce the amounts they need. (Exposing the elbow in the car window won't cut it.)
People living in less sunny areas, and vegans who eschew eggs, fish and dairy are particularly vulnerable to developing deficiency. Severe deficiency can lead to bone brittleness, skeletal deformity and even asthma and cognitive impairment.
If sufficiently alarmed by our bloodwork, some of us take supplements. Also, the vitamin is routinely added to some breakfast cereals, dairy products and other foods.
Until now, manufacturers had no reason to distinguish between D2 (plant origin) and D3 (animal origin).
But in 335 South Asian and white European women fed fortified juice and cookies over two consecutive winters, vitamin D3 of animal origin proved twice as effective in raising levels of the vitamin in the body than D2 or plant origin.
When the placebo really doesn't work
The women had been divided into five groups: one got placebo, the second got juice containing vitamin D2, the third got juice with D3, the fourth group got a cookie with D2 and the fifth group got cookie with D3.
Make no mistake, the plant-based vitamin D2 was helpful, but the animal-sourced vitamin D3 was doubly helpful.
Those given D2 saw an increase of 33 percent and 34 percent over the course of the 12-week intervention, the scientists report.
Vitamin D levels in women who received vitamin D3 by juice or biscuit rose 75 percent and 74 percent respectively.
In the placebo group, vitamin D levels dropped 25 percent over the same period.
In short, health guidelines stating that the two forms of vitamin D are equivalent, are wrong, they conclude.
Even in sun-soaked Israel
In the UK, more than 20 percent of people have low levels of vitamin D, says Public Health England. There is no parallel statistic for Israel, a situation the Health Ministry is working to rectify.
"The Health Ministry is aware of the deficiency of vitamin D in parts of the population," ministry spokesman Eyal Basson told Haaretz. "However, it is important to understand that studies based on lab tests taken from patients are sometimes skewed, because these are testees suspected of being deficient to begin with." The ministry has asked for and received data on vitamin D deficiency from Israel's health care funds, which it's still working on.
In fact, Israel has no uniform standard for a satisfactory lab result for vitamin D, the ministry points out. There too, rectification is pending: A ministry commission on foodstuff fortification, with external experts and international consultants, is writing up its action recommendations, the ministry says.
Crucially, it urges people alarmed at the reports not to "take drastic measures", i.e., rush to gobble supplements or fish oil: surplus vitamin D is not a good thing either: calcium buildup and nausea are the least of the problems that hypervitaminosis D can cause.
Happily for Israelis, local manufacturers that Haaretz checked all used the D3 form.
Osem stated on behalf of its parent company Nestle that breakfast cereals with fortification contain D3. Dairy company Strauss, which fortifies Gamadim puddings for children and also Yotvata chocolate milk, also uses D3. Strauss spokesman Gil Messing adds that the company stays on top of scientific nutritional research for the sake of product development.
Supplement makers in Israel that Haaretz checked also use D3, such as CTS of Kiryat Malakhi, which sells it as oral drops, and Tevacall, which is marketing an oral spray of D3 (you spray a metered dose into your mouth instead of swallowing a capsule) and others. Tiptipot Vitamin D explains on its website that the Health Ministry recommends babies from birth to a year get 400 international units of vitamin D3 a day (and says each of its drops contains 200).
Foreign manufacturers available in Israel such as Solgar also make D3 options. Also, by regulation, all 1%-fat milk in Israel is fortified with D3, as the Health Ministry helpfully pointed out.
Manufacturers who use D2 apparently can't use cost as an excuse. "I've previously been told that D2 & D3 cost the same to purchase (i.e., as ingredients for food products)," lead author Dr Laura Tripkovic from the University of Surrey told Haaretz. "So it's unlikely to affect cost if food manufacturers switch to D3."
"Our findings show that vitamin D3 is twice as effective as D2 in raising vitamin D levels in the body, which turns current thinking about the two types of vitamin D on its head," Tripkovic stated. "Those who consume D3 through fish, eggs or vitamin D3 containing supplements are twice as more likely to raise their vitamin D status than when consuming vitamin D2 rich foods such as mushrooms, vitamin D2 fortified bread or vitamin D2 containing supplements."