Unexpectedly Intriguing!
July 7, 2009

If African-American teenagers are any indication, half of the entire black population of the United States has chronic Vitamin D deficiency. These individuals then make up nearly 3 out of 5, or 57.2%, of all those who have Vitamin D deficiency in the United States.

Here's how we know. Earlier this year, the findings of a study conducted by New York City's Weill Cornell Medical College researchers Sandy Saintonage, Heejung Bang and Linda M. Gerber were published in Pediatrics: Implications of a New Definition of Vitamin D Deficiency in a Multiracial US Adolescent Populatuion: The National Health and Nutrition Examination Survey III in March 2009.

The study sought to determine the extent of Vitamin D deficiency nationally in the United States' population of adolescents given the then proposed increase in the determination threshold of Vitamin D deficiency. At the time of the study, the level of deficiency was defined as an individual's serum 25-hydroxyvitamin D level begin below 11 nanograms per milliliter (ng/mL), which recently has been increased to include serum levels of up to 20 ng/mL as the new standard.

The study used data from the National Health and Nutrition Examination Survey III, which looked at a cross-sectional nationally representative sample of 2955 individuals between the ages of 12 and 19, and which ran in the years from 1988 to 1994, taking into account their sociodemographic characteristics. Doing that, the study's authors found that the incidence of Vitamin D deficiency increased from 2% of the sample population under the old standard to 14%, or 414 out of the sample population of 2,955 with the new, higher standard.

For black teenagers however, the increase in the incidence of Vitamin D deficiency is more significant. Under the old standard, some 11% of the sample population would have been counted as being deficient in Vitamin D under the old standard. Under the new standard, that figure increases to 50% of the sample population.

Since the source data for the study considers those Age 12-19, we extracted the size of the black population within the survey sample by first finding the percentage of blacks within the entire U.S. population. Since the survey ran from 1988 through 1994, we found that value by backing out the birth years of those who would have been 19 years old in 1988, the first year of the survey, and 12 years old in 1994, the final year of the survey. This gave us a range of birth years for the sample population of 1969 through 1982.

Difference in Percentage of Survivors by Age, Out of Every 100,000 Born Live by Race in U.S., 2004 We next utilized the CDC's records of the number of live, registered births in the United States by race for these years. From 1969 through 1982, there were 47,831,224 live births registered in the U.S., of which, 7,654,595 were counted as being black (according to the race of the child before 1980 and the race of the mother after 1980). That works out to be 16.00%. While black mortality is generally higher than than for whites, especially in the first year of life, we've previously found that there's just a 1% difference between those who reach ages between 1 and 20 for the black and white populations, so we used the 16% of the population figure for our calculations.

With that percentage, we can now estimate how many of the sample population of 2,955 were black. Multiplying this figure by 16%, we find that 473 members of the surveyed sample were black. 50% of this figure was counted as having Vitamin D deficiency according to the new standard, which works out to be 236 individuals.

Going back to the sample population, we find that 14% of the 2,955 individuals Age 12-19 were counted as having Vitamin D deficiency, which works out to be 414 individuals. We therefore find that the 236 black individuals with Vitamin D deficiency represent 57.2% of all those with Vitamin D deficiency in the United States.

The study also found that non-Hispanic blacks were 20 times more likely than their non-Hispanic white peers to have Vitamin D deficiency. Dividing 236 by 20 and rounding to the nearest whole number, that means that there were 12 whites counted as having Vitamin D deficiency, or 2.9% of the entire sample population.

The remaining 165 individuals counted as having Vitamin D deficiency represent 40% of those with the condition. The authors' other observations will be unsurprising to long-time Political Calculations readers. Here are a selection of study author Linda Gerber's comments from the Lempert Report on 27 April 2009 (emphasis ours):

"While previous guidelines were based on the prevention of rickets, scientists have found that higher serum levels of vitamin D are necessary to achieve optimal bone mineralization throughout the lifespan," says Dr. Linda Gerber, co-author of the study and Professor of Public Health and Medicine at Cornell.

...

"Generally, milk had been the primary source of dietary vitamin D among children. Among adolescents milk consumption has been replaced by soft drinks, juice, and other beverages that are not fortified with vitamin D. Further, many teens from ethnic populations are lactose intolerant and avoid milk. Though there are other nutritional sources of vitamin D, many teens are eating foods that are low in nutritional value," says Gerber.

Helping overweight teens achieve proper vitamin D levels presents a unique challenge. Vitamin D is fat soluble, so deficiency in this population may be magnified if the vitamin is hiding in body fat, limiting bioavailability. Oral doses approaching the upper limit of 2000 IU/day may be necessary for this group, says Gerber. And appropriate nutrition should be a longer-term goal.

...

"New evidence suggests that vitamin D deficiency may be associated with risk factors for many chronic diseases such as high blood pressure. Therefore, by studying the adolescent population, we may be able to prevent the progression to some of these," she says.

Follow the links below for more of what we've had to say on the topic:

Blacks Living Longer Than Whites

The post that started the whole thing! We were surprised to find that blacks over the age of 80 had longer remaining life expectancies than whites of the same ages in the U.S. We also used the opportunity to ridicule some pretty blatant rent-seeking behavior on the part of researchers seeking funding for their work.

Erasing the Gap in Racial Life Expectancies

We revisited the life expectancy figures between blacks and whites and took a closer look at the underlying data, which allowed us to reject racism as an explanation for what we observed. We also began asking "why this, but not this?" in comparing not just the survivorship of the black and white populations of the United States, but urban vs rural blacks, immigrant vs native-born blacks, and the effect of older vs younger mothers for African American infant mortality.

The Disproportionate Killers

You can't address racial disparities in life expectancies unless you know what chronic health conditions disproportionately affect the black population of the United States compared to other racial or ethic groups.

African Blessings, African Curses

Chronic diseases often have a very strong genetic or heredity component in determining who is vulnerable to them. In this post, we explored the idea that what doesn't kill you either softens you up for what will or makes you more vulnerable to other health hazards in comparing the black population of the United States to sub-Saharan Africans who share much the same genetic anthropology, while also discovering very recent research whose results potentially explain why all peoples of African descent are more vulnerable to the things that disproportionately kill African Americans.

A Seemingly Simple Solution

Does a chronic vitamin deficiency explain why the disparities between black and white life expectancies in the U.S.? We explore this possibility and why it may not as easy to address as you might think on first glance, as well as how individual African Americans might do so successfully.

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