Most kids in northern latitudes don't get enough vitamin D in winter
Improvements to diet and increased awareness are considerations for closing the vitamin D gap when the sun can’t do the job.
Web URL: Read the story on MedicalXpress here
FAB RESEARCH COMMENT:
This controlled clinical trial found that much higher doses of Vitamin D than the standard 'recommended daily allowance' (RDA) were needed to eliminate Vitamin D deficiencies in children living in the Boston area, in the northern US.Before supplementation, 40% of children showed Vitamin D deficiency (defined as blood levels below 30 ng/mL). This was entirely expected from previous research (owing to the lack of bright sunshine at that latitude in the long winter months) - as was the finding that children with darker skin, and those with obesity, were particularly likely to be Vitamin D deficient.
Vitamin D deficiency has numerous negative effects on health, including weak bones and teeth, impaired immunity, and sub-optimal development and function of almost every organ and system - including the brain.
Very importantly, this dose-ranging trial found that supplementation with 2000 IU per day of Vitamin D (i.e. 50 mcg/day) was needed to eliminate deficiencies.
This dose is over three times the current US (and EU) RDA of 600 IU for children and adults of working age - and five time the UK's daily recommendation of just 400 IU (10 mcg) per day.
The UK's distance from the equator is similar to Boston's - so no Vitamin D can be made from sunlight there either between October to March. But unlike the US (or most other developed countries at northern latitudes) the UK has no public health policy of fortifiying any basic foodstuffs with Vitamin D, so deficiencies are widespread.
Importantly, the 2000 IU /day dosage of Vitamin D shown to be most efficient in eliminating deficiencies in northern US children is only half of the Upper Safe Level.
This dose also matches the 1500-2000 IU recommended by the Endocrine society in 2011 to achieve blood levels needed just for optimal bone health and strength.
UPDATE 2024:
A recent narrative review has summarised more recent evidence supporting 2000 IU / day of Vitamin D3 as a safe and appropriate RDA for the general adult population. See:
For details of the research trial reported in the news article below, see:
For more information on findings from clinical trials of Vitamin D supplementation (in children or adults), see:
And for more information on Vitamin D in children, and in relation to ADHD, autism and related developmental conditions, please see:
24 October 2017 - MedicalXpress
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Living in northern latitudes such as New England means not only shorter days and less sunlight during the winter, but also far less vitamin D, the "sunshine" vitamin. And adequate vitamin D intake, which is crucial to bone health, can be difficult for children in particular to achieve through food alone.
In a new study, researchers from the Friedman School of Nutrition Science and Policy at Tufts and colleagues conducted a clinical trial administering three supplemental doses of vitamin D in Boston area schoolchildren who were vitamin D deficient or at risk for deficiency. They found that bringing the majority of participants safely to sufficiency took a dose that was more than three times the recommended daily allowance for vitamin D for children.
The study, published online last month in the Journal of Clinical Endocrinology & Metabolism and led by Jennifer Sacheck, associate professor of nutrition at the Friedman School, sought to determine whether the current recommended daily allowance (RDA) was enough to raise blood levels to nutrient sufficiency in children in northern latitudes, especially across the winter months when blood levels tend to fall.
The randomized double-blind clinical trial investigated the effect of three supplemental doses of vitamin D3 - the current RDA of 600, as well as 1000 or 2000 IU per day - administered over six months in more than 600 schoolchildren ages 8 to 15 in the greater Boston area.
In previous work with urban schoolchildren around Boston, the researchers found that upwards of 90 percent of the children they were studying were vitamin D deficient, prompting them to question what was needed to increase levels to sufficiency.
Deficiency is also reported to be more common among those with obesity, darker skin pigmentation, and/or living in the northern portion of the United States.
At the start of the study, 40 percent of the children were either vitamin D deficient or severely deficient (blood levels 30 ng/mL).
While all three doses raised serum vitamin D levels and virtually eliminated severe deficiency by the end of the six months, it took a dose of 2000 IU per day to move the majority of children out of deficiency and to see the greatest number of children attain sufficiency. The vitamin D upper limit for children nine years and older is 4000 IU per day.
The researchers also noted that children with obesity and Asian children responded less to supplementation, while African-American children, who started at the lowest levels, responded the most.
"Food is the best source for valuable nutrients, but obtaining even just the RDA of vitamin D from food alone would take the equivalent of six eight-ounce glasses of fortified milk," said Sacheck. "Improvements to diet and increased awareness are considerations for closing the vitamin D gap when the sun can't do the job."
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