Patients with vitamin D3 (25(OH)D) blood levels of 86 nmol/L (the top end of what is currently considered a ‘healthy level’) absorbed 65% more calcium from their food and drink than subjects with D3 levels of 50 nmol/L (the bottom end of ‘healthy’). The scientists suggested that the bottom end of ‘healthy’ was currently set too low.

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Ed.- (i) Although 50 nmol/L is generally the accepted bottom end of the normal range, [1] more recent research suggests that parathyroid hormone (PTH) levels [2,3] and calcium absorption [4] are not optimised until serum D3 levels reach approximately 80 nmol/L, just below the average serum levels achieved in the group who received D3 supplementation at the beginning of the above study. Thus, at least one vitamin D expert has argued that serum D3 values less than 80 nmol/L should be considered deficient, [5] while another suggests that a healthy serum 25(OH)D value should be considered to be between 75 nmol/L and 125 nmol/L. [6] Studies investigating the level of vitamin D intake which would be required by adults living in temperate latitudes to achieve such a range of levels suggest a daily vitamin D3 supplement of between 800 and 1,000 IU. [7,8]

Current US ‘adequate D3 intakes’ are: anyone under the age of 51, including pregnant and breastfeeding women - 200IU; anyone aged 51 to 70 - 400IU; anyone over the age of 70 - 600IU.

So, raising blood vitamin D levels by either exposing skin or eyes to sunlight or consuming more vitamin D3 in food supplements might reduce, even eliminate, the need for calcium supplementation.

(ii) Current US recommended upper intakes: infants 0-12 months - 1,000 IU, children 1-18 years and adults 19 years and older - 2000 IU.

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