Page 32 - Summer 2017 Journal

population” (emphasis added).8
With such wide laboratory reference ranges, what can we say with
reasonable confidence about the level of 25(OH)D in the blood needed to optimize PTH and calcium absorption, and more importantly, to optimize overall health? Do higher levels reduce other health risks or improve problems such as cancer, autoimmune disease, heart disease or any other chronic condition? Do the benefits of higher levels outweigh any potential adverse effects? Are there potential limitations or problems with testing? Can blood levels of 25(OH)D be translated into rule-of-thumb supplementation guidelines? Is there a better way to evaluate our levels or should we even routinely test at all?
Before I offer answers to these compelling questions, we are wise to consider the practices of the healthy pre-industrial populations Dr. Price visited, populations that neither had knowledge of “vitamin D” (or any isolated vitamin) nor the “benefit” of blood testing.
PRE-INDUSTRIAL POPULATIONS
How did pre-industrial populations obtain vitamin D? While the
discovery and isolation of vitamins in the early 20th century is considered a milestone in our understanding of nutrition and health, humans have survived and thrived without the knowledge of which foods contained which vitamins. The populations studied by Price took great care to emphasize the consumption of foods that are now recognized as excel- lent sources of all the fat-soluble vitamins, including vitamin D: deep yellow butter, seafood including fish eggs, organ meats, insects and animal blood.9 In addition, routine sun exposure during the activities of
daily life resulted in significant skin vitamin D synthesis. The modern practice of hours spent “sunbathing” did not exist (see sidebar on page 33).
There are challenges in obtaining adequate amounts of vitamin D from sun exposure and diet alone. Today individuals are often geneti- cally “mismatched” to the climate where they live. (Genetic adaptations require many succes- sive generations.) There is a marked reduction in cutaneous vitamin D biosynthesis in northern latitudes during the winter months, and virtu- ally none above 40 degrees.10 Darker-pigmented individuals can require five to ten times the duration of sun exposure to produce the same amount of vitamin D as lighter-pigmented per- sons. With the need to cover the skin during cold weather, it is not unexpected that vitamin D levels can plummet during the winter, made worse by limited summer sun exposure, which can lead to year-round low vitamin D levels.
Contemporary habits of applying and reapplying sunscreens (SPF 8 or greater) can significantly reduce skin vitamin D synthesis. Showering shortly after outdoor activities, and swimming in chlorinated pools may also reduce
D2 vs. D3?
Some doctors prescribe vitamin D2, others recommend an over-the-counter supplement that contains vitamin D3. What is the difference? Vitamin D2 is the plant form, ergosterol, found in foods like mushrooms. Vitamin D3 is the animal form, cholecalciferol, made in our skin but also available from animal fats. The pharmacokinetic properties of vitamins D2 and D3 differ, with more consistent and higher serum concentrations of 25(OH)D after vitamin D3 supplementation. Clinicians are advised to recommend vitamin D3 supplementation at intervals of four months or less. Longer intervals between doses of vitamin D2 will result in large fluctuations of serum 25(OH)D concentrations (due to more rapid metabolic degradation via 24-hydroxlation and a lesser affinity to the vitamin D-binding protein1), therefore the dosing interval with vitamin D2 is should not exceed fourteen days. The term “calciferol” on a preparation refers to vitamin D2 and “cholecalciferol” to vitamin D3.
While the use of vitamin D3 is generally preferred, a 2013 JAMA study found that many of the over-the-counter vitamin D3 supplements on the market do not contain the amount the label indicates, with the authors more concerned about the fact that they provided too little rather than too much D3. In any case, only trusted sources should be used if vitamin D is supplemented in isolation.
If your choice for a vitamin D source is a fermented cod liver oil, keep in mind that all natural cod liver oils contain an array of different metabolites derived from vitamin D3, with a diverse array of biological activities. While magnetic resonance analysis seems to indicate the presence of vitamin D2, it is likely a mixture of these metabolites. Furthermore, the benefits of natural cod liver oil are often realized without a marked rise in serum 25(OH)D. Masterjohn cautions that this blood test is not only being overused as an indicator of vitamin D nutritional status, but is “being used in an overly simplistic manner.”4
1. Zerwekh JE. Blood biomarkers of vitamin D status. Am J Clin Nutr. 2008;87:1087S-91S.
2. American Geriatrics Society Workgroup on Vitamin D Supplementation for Older Adults. Am Geriatr 2014; 62:147–152.
3. http://www.webmd.com/vitamins-and-supplements/news/20130211/vitamin-d-supplements-is-what-you-see-what-you-get#1
4. https://www.westonaprice.org/health-topics/cod-liver-oil/vitamin-d-in-cod-liver-oil/.
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Wise Traditions
SUMMER 2017