Whites have higher 25(OH)D than every other racial group, and the conventional explanation is that light skin evolved to allow sufficient vitamin D synthesis far away from the equator. In episode 24, I explain why these differences may relate to genetics of vitamin D metabolism that have nothing to do with skin color and may reflect a lower average need for 25(OH)D rather than a lower average ability to get enough. But “average” is the key word and when it comes to using this information on a practical level we need to look beyond racial categories and treat each person as an individual.
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Show Notes for Episode 24
In this episode, you’ll find all of the following and more (these times refer to the podcast, and they may be different in the YouTube video):
- 0:06.37 Should I offer online nutrition classes?
- 0:09.49 This will start off sounding like it's about racial groups, but it's really about individuals.
- 0:10:34 Blacks in America have lower 25 (OH)D than whites.
- 0:12:52 The conventional hypothesis explains this as dark skin being poorly adapted to these latitudes.
- 0:13:17 Genetic evidence suggests light skin began evolving long after the migration from Africa.
- 0:18:39 Aggregate global 25(OH)D data do not support the conventional hypothesis.
- 0:20:05 Caucasians have higher average 25 (OH)D than non-Caucasians at every latitude; Caucasians have higher average 25 (OH)D at temperate latitudes than non-Caucasians have at equatorial latitudes.
- 0:22: 32 Blacks in America have higher bone mineral content than whites.
- 0:26:19 Calcitriol dominance favors getting calcium from our food, while PTH dominance favors getting calcium from our bones.
- 0:27:59 Genetic variation in the 1-hydoxylase can account for the difference in 25(OH)D between blacks and whites in America, but this has nothing to do with skin color or racial groups in the way we have socially defined them.
- 0:35:02 Calcium intake could influence how the genetic variation translates into 25(OH)D.
- 0:37:14 This does not affect white 25 (OH)D, and it could be related to calcium intake; ancestral calcium intake could have mediated selective pressure on the relevant genes.
- 0:38:32 Blacks in the United States have higher average calcitriol and a higher average calcitriol-to-PTH ratio than whites.
- 0:39:38 Similar differences between Inuit and Danes: lower 25(OH)D, higher calcitriol, and lower PTH; a traditional diet raises 25(OH)D, raises calcitriol further, and suppresses PTH further.
- 0:41:22 Asians have lower 25 (OH)D than whites in Hawaii.
- 0 42:44 The references ranges may in effect be applying average white requirements to drive recommendations for everyone.
- 0:43:49 The Maasai and Hadza have higher 25 (OH)D, but this may be due to higher calcium intakes, and/or higher ancestral calcium intakes that influenced their genetics.
- 0:48:24 Non-whites are probably adapted to lower 25 (OH)D than whites on average, but it is individual genetics rather than racial groups that are relevant.
- 0:52:59 25 (OH)D + calcitriol can be summed for a biological activity index.
- 0: 54:09 PTH should be in the lower half of the reference range.
- 0: 56:20 Magnesium deficiency could confound the PTH measurement, but it probably has to be extreme.
Links Related to Episode 24
Vitamin D: More Is Not Better, by Chris Kresser
Mastering Nutrition Episode 9: Balancing Calcium and Phosphorus in the Diet, and the Importance of Measuring Parathyroid Hormone (PTH)
An Ancestral Perspective on Vitamin D Status Part 1: Problems With the “Naked Ape” Hypothesis of Optimal Serum 25(OH)D
An Ancestral Perspective on Vitamin D Status Part 2: Why Low 25(OH)D Could Indicate a Deficiency of Calcium Instead of Vitamin D
The Scientific Approach of Weston Price, Part 2: Problems with Comparing Different “Racial Stocks,” with Inuit Adaptations in Vitamin D Metabolism as an Example
References Related to Episode 24
Vitamin D status and calcium metabolism in adolescent black and white girls on a range of controlled calcium intakes. [PubMed]
Global patterns of diversity and selection in human tyrosinase gene. [PubMed]
A Genetic Mechanism for Convergent Skin Lightening during Recent Human Evolution. [PubMed]
Rethinking the dispersal of Homo sapiens out of Africa. [PubMed]
Global vitamin D levels in relation to age, gender, skin pigmentation and latitude: an ecologic meta-regression analysis. [PubMed]
Influence of Secondary Hyperparathyroidism Induced by Low Dietary Calcium, Vitamin D Deficiency, and Renal Failure on Circulating Rat PTH Molecular Forms. [PubMed]
Common variation in vitamin D pathway genes predicts circulating 25-hydroxyvitamin D Levels among African Americans. [PubMed]
Americans are not meeting current calcium recommendations. [PubMed]
Dietary Influence on Calcitropic Hormones and Adiposity in Caucasian and African American Postmenopausal Women Assessed by Structural Equation Modeling (SEM). [PubMed]
Vitamin D insufficiency in Greenlanders on a westernized fare: ethnic differences in calcitropic hormones between Greenlanders and Danes. [PubMed]
Low vitamin D status despite abundant sun exposure. [PubMed]
Traditionally living populations in East Africa have a mean serum 25-hydroxyvitamin D concentration of 115 nmol/l. [PubMed]
Determinants of parathyroid hormone response to vitamin D supplementation: a systematic review and meta-analysis of randomised controlled trials. [PubMed]