Unexpectedly Intriguing!
14 August 2008

Could the disparity between the life expectancies of the black and white population of the United States be largely accounted for by the greater incidence of Vitamin D deficiency within the black population? And would addressing this vitamin deficiency in the black population erase the gap in racial life expectancies?

We would hypothesize that the answer to both questions is yes, and we would caution that it's not quite as simple as it sounds.

To understand why, we'll take a closer look at Vitamin D's role in the human body, how it applies to the chronic diseases that disproportionately affect the black population of the U.S., and how the greater incidence of the deficiency among the black population would appear to account for the unusual features we've observed in the percentage of survivors of the black population for each 100,000 born alive. We'll also explain why the steps the U.S. government has instituted in mandating the fortification of dairy products with Vitamin D would appear to be largely ineffective for the adult African American population and ultimately discuss how the deficiency can be addressed more effectively.

Background Information on Vitamin D

The Role of Vitamin D in Human Physiology

The primary role of Vitamin D in the body is to help regulate the level of calcium in the bloodstream. It does this by facilitating the absorption of calcium from dietary sources in the digestive system and by promoting normal bone growth and mineralization. As the tuberculosis study we've previously cited demonstrates, Vitamin D also plays a key role in facilitating the production of cathelicidin, an antimicrobial peptide that play a vital role in the immune system's ability to resist infectious diseases.

Where Vitamin D May Be Obtained

Vitamin D may be obtained from two key sources. The first is from natural sunlight exposure, where ultraviolet rays (UV-B) penetrate into the skin and is synthesized through natural biochemical reactions. The second is from foods or dietary supplements that either contain or have been fortified with Vitamin D. Like Vitamin B, there are several different kinds of Vitamin D. Sunlight exposure creates Vitamin D3, while many food supplements contain Vitamin D2 or D3. The most recommended form for dietary supplementation is Vitamin D3.

How Much Vitamin D Do People Need?

For adults between the ages of 19 and 50 years old, the U.S. Food Nutrition Board recommends a daily Vitamin D intake from food or dietary supplements of 200 IU (International Units), which is equivalent to 5 mcg (micrograms). The American Academy of Pediatrics will be publishing new guidelines for Vitamin D intake this fall, which will recommend that infants, children and adolescents should receive 400 IU (or 10 mcg) This same level is recommended by the Food Nutrition Board for people Age 51-70 years old. People over the age of 70 are recommended to take in 600 IU (or 15 mcg).

These levels are recommended as the level of ultraviolet light exposure that individuals receive on their skin from direct sunlight is difficult to anticipate and varies by prevailing weather conditions and geographic latitude, with people living in northern latitudes especially disadvantaged. Other factors, such as clothing, sunblock application and the amount of melanin skin pigmentation by individual also negatively affect the level of Vitamin D production from UV-B exposure.

It is possible to overdose on Vitamin D dietary supplements. Ingesting more than 2000 IU (50 mcg) a day on a sustained basis may produce a toxic effect, initially indicated by nausea, but possibly leading to kidney damage, kidney stones, muscle weakness or excessive bleeding. Higher amounts may be taken without negative impact for limited periods of time.

How Vitamin D Deficiency Contributes to Shorter Lifespans

With higher levels of melanin in their skin, which absorbs high quantities of the UV-B radiation that stimulates natural Vitamin D production, the black population of the United States is much more likely than the white population to suffer the effects of Vitamin D deficiency, as well as the very closely related conditions associated with calcium levels, which Vitamin D regulates within the body.

In the table below, we've outlined the chronic diseases and health conditions that disproportionately affect the black population, above and beyond those already well-linked to Vitamin D or calcium deficiency, and linked to research supporting the connection if one has been established.

Chronic Diseases Linked with Incidence of Vitamin D Deficiency
Category Chronic Disease or Condition Linked to Vitamin D Deficency?
Infant Mortality Premature Birth/Pre-eclampsia Yes
Low Birth Weight Yes
Heart Disease Cardiovascular Disease Yes
Cancer Breast Cancer Yes
Lung Cancer No
Colorectal Cancer Yes
Cerebrovascular Disease Hypertension Yes
Atherosclerosis Potentially
Infectious Diseases and Conditions HIV/AIDS No
Tuberculosis Yes
Septicemia Unknown
Kidney Disease Yes
Negative Health Contributors Overweight and Obesity Yes
Diabetes Yes

We observe that the increased incidence of Vitamin D deficiency among African Americans would appear to contribute to the increased incidence of the chronic conditions that negatively affects the health the black population of the United States, which in turn shortens their longevity with respect to that of the white population.

Accounting for Disparities Between Black and White Life Expectancy

Now that we've identified the chronic diseases that act to disproportionately shorten the lives of the black population of the United States and confirmed that a deficiency of Vitamin D is a major contributing factor to nearly all of them, let's look again at our chart showing the difference in the percentage of survivors of every 100,000 born between the white and black population of the United States as we begin to hypothesize on why the disparities between races exists:

Difference in Percentage of Survivors by Age, Out of Each 100,000 Born Alive by Race in U.S., 2004

The grand hypothesis we're going to offer is that a deficiency of Vitamin D within the black population accounts for nearly all of the difference observed between the black and white population. Let's take a closer look to see how that might work:

  1. We see that the difference in the percentage of survivors begins immediately in the first year of life. With black mothers far more likely than whites to have a deficiency in Vitamin D, we hypothesize that a large portion of this difference may be attributed to the resulting conditions of pre-eclampsia, which is the leading cause of premature birth, and low birth weight, both of which contribute to the increased rate of infant mortality observed in the black population.

  2. There is little change in the years from 1 to 20 years old between the black and white population of the United States. We hypothesize that this is due to combination of increased exposure to natural sunlight for those in this age range as compared to either infants or adults and the effectiveness of the U.S. government's mandated Vitamin D fortification of dairy products for children. However, as we'll discuss shortly, we believe that the effectiveness of Vitamin D fortification of dairy products becomes ineffective for the black population with the onset of adult maturity.

  3. Once the members of the black population reach adulthood and no longer consume vitamin-fortified dairy products, we hypothesize that the comparatively reduced effectiveness of natural sunlight exposure results in widespread Vitamin D deficiency among the population. As a result, all the chronic conditions for which a deficiency of Vitamin D contributes to the incidence or the severity of these disease begins to claim the lives of the black population in disproportionately large numbers as compared to the white population.

  4. The greater incidence of Vitamin D deficiency among adult African Americans likely also explains why teenage mothers within this group are less likely to give birth to children prematurely or to have low birth weight babies as compared to older mothers. Since Vitamin D is fat-soluable, the teenage mothers, even if they've already stopped consuming dairy products, will have stores upon which their bodies can draw through their pregnancies. Older mothers will have long-since depleted their stores without supplementation through another dietary source.

  5. While higher levels of UV-B absorbing melanin reduces the amount of Vitamin D produced through direct sunlight exposure for the black population, those members of the population living in urban areas are much less likely to have direct sunlight exposure as compared to those who live in suburban or rural areas. We hypothesize that this difference largely accounts for the reduced life expectancy of urban-living blacks.

  6. We should also note that all blacks living in northern latitudes will be similarly negatively affected, as the curvature of the Earth reduces the intensity of the sunlight reaching these regions.

  7. We suspect that a good part of the difference between the native black population of the United States and black immigrants may in part be accounted for by the immigrant black population being more likely to have significantly longer sunlight exposure than the average native-born black, but perhaps comparable to the members of the black population who live in rural areas. Combined with a lower incidence of consumption of tobacco products, this factor likely accounts for much of the foreign-born black immigrants' greater life expectancy.

  8. Meanwhile, the longer lifespans for the members of the black population over the Age of 80 may in part be attributed to where they have primarily lived during the course of their lives, which we would anticipate to coincide with either suburban or rural regions of the United States, and suspect includes a dietary regimen that incorporates Vitamin D.

Why Dairy Doesn't Work For the Adult Black Population

Eastern Africa Cattlemen We promised at the beginning that we'd figure out how to bring cattle herding into the picture, and here it is: the vast majority of the black population of the United States is descended from the peoples of western sub-Saharan Africa and, as a result, become lactose intolerant as they grow into adulthood as their genetic makeup doesn't permit the digestion of dairy products.

Not all peoples of African descent are in that boat. The peoples of eastern Africa do have the ability to digest milk products. The difference between each comes down to a genetic adaptation that takes hundreds of generations to develop that coincides with the practice of cattle herding. The peoples of eastern Africa have a very long history of cattle domestication, beginning anywhere from 3,000 to 7,000 years ago. By contrast, the peoples of western Africa have a much shorter history with herding cattle and haven't developed a similar genetic adaptation.

And that's why the U.S. government's mandated fortification of dairy products with Vitamin D doesn't work for the adult black population! Except perhaps for black immigrants from eastern Africa, which may account for part of the observed greater life expectancy of foreign-born black immigrants to the U.S.

What Would Work Better

Cod Liver Oil Trading Card.  Yum. There are very few foods that naturally contain Vitamin D. The non-fortified dairy product portion of the menu includes items like: cod liver oil, salmon, mackerel, tuna, sardines, margerine, whole eggs, and beef liver. We know - except maybe for salmon, tuna, eggs and margerine, it's hard to look at that list and keep yourself from salivating! (Mmmm, cod liver oil....)

More seriously, there a number of ready-to-eat breakfast cereals are fortified with Vitamin D, which we would recommend be eaten as a dry snack. There are, of course, direct alternatives to dairy products. Of these, our first choice to see if it works would be those dairy products that have been formulated to accommodate those who are lactose intolerant. Other milk-substitutes such as soy milk (are you salivating again?) might work out, but we'll observe that it would work better for women than it would for men.

Meanwhile, there are always Vitamin D tablets. A quick trip to our local supermarket showed a 90-day supply of 400 IU Vitamin D tablets would cost about $4.00 (USD), which means that a year's supply for an individual might be purchased for anywhere from $12-$20 (USD) taking into account competition between stores, sale vs. non-sale prices, availability, etc.

All in all, a super-cheap way to potentially, and quite literally, add years to your life.

The trick would be to find what you wouldn't mind eating or consuming on a regular basis and go with it. Sooner or later, food producers will introduce improved, better tasting products that can meet the specific dietary needs of the black population.


Often, the toughest questions to answer are those that ask "why this, but why not this?"

Throughout this series of posts, that's been our challenge. Why do African Americans have higher infant mortality than whites, but then have a nearly equivalent todder-child-teenager mortality rates? Why do blacks then have a higher adult mortality rate, but then substantially lesser mortality for those over the age of 80 than the white population of the United States? Why do urban blacks, who have significantly greater access to health care facilities than their rural peers, have much lower life expectancies? Why are black teenage mothers less likely than older mothers to give birth either prematurely or to low birth weight babies, the leading cause of infant mortality? Why do black immigrants who statistics indicate would live much shorter lives in their native countries live longer than native-born African Americans if they immigrate to the U.S.?

To answer these questions, we asked and answered several of our own. What health conditions account for the disproportionate mortality of African Americans compared to whites at every stage of life? What factor or factors contribute to these disproportionate outcomes that might also answer "why this, but not this?"

That's how we came to this final post in this series, in which we've presented a single, unifying explanation that potentially accounts for what we observe in all the data we have and leads to our seemingly simple solution. In doing all this, we've linked to cutting edge medical research and breaking news covering some of the latest findings in genetic anthropology, spanning several millenniums of human history in the process.

And we have to note, it might not pan out as we see it. That's where we're at today, awaiting the results of scientific studies and research that confirms or rejects what we've hypothesized.

But we have to admit, it would be pretty cool if we turn out to be right!

All the Posts in the Series

For reference, here are all of the posts in the series:

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.

Update 18 August 2008: Added conclusion and reference links for series!

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