Increase Vit D RDA’s Say Scientists

On July the 28th 2010 the Journal Experimental Biology and Medicine published an article looking at the levels of Vitamin D in the general population and made recommendations concerning the RDA levels needed to limit osteomalacia in adults and rickets in children.[1] This they say is because scientists and nutritionists from many countries agree that at present about half of elderly North Americans and Western Europeans and probably also of the rest of the world are not receiving enough vitamin D to maintain healthy bone. This is nothing new to this web site or indeed the thousands of people that have been following this story for the last 10 years.

The paper goes on to say that over the past decade there has been a  dramatic increase in the understanding of the many biological actions that result from vitamin D acting through its daughter steroid  hormone, 1α,25-dihydroxyvitamin D3 [1α,25(OH)2D3] in collaboration with its cognate vitamin D receptor (VDR). In other words Vitamin D does more than support bone health.

Evidence has accumulated that beside intestine and bone, there are five additional physiological systems where the Vitamin D Receptor with 1α,25(OH)2D generates biological responses.
These include the

  1. Immune system (both the innate and adaptive),
  2. Pancreas and metabolic homeostasis,
  3. Heart-cardiovascular,
  4. Muscle and brain systems
  5. as well as the control of the cell cycle, and thus of the disease process of  cancer

It does this by acting through the Vitamin D Receptor, 1α,25(OH)2D3  to produce a  wide array of favourable biological effects that collectively are projected to contribute to the improvement of human health. Responsible medicine and Nutritional Therapy demands that worldwide vitamin D nutritional guidelines should reflect current scientific knowledge about vitamin D’s spectrum of activities. Thus, worldwide vitamin D nutritional policy is now at a crossroads. This paper presents several proposed policy changes with regard to the amount of vitamin D daily intake that if implemented will maximise vitamin D’s contribution to reducing the frequency of many diseases, which would then increase the quality and longevity of life and significantly reduce the cost of medical care worldwide.

Contribution of Vitamin D to good health. The three columns on the right side, respectively, indicate the following: Physiological systems (the six physiological systems that the essential nutrient vitamin D3 supports by its metabolism to 25(OH)D3 and 1α,25(OH)2D3; biological responses (examples of biological responses generated by 1α,25(OH)2D3 in the six physiological systems); and vitamin D-deficient related diseases (identifies for each system some of the disease states that are associated with an inadequate vitamin D nutritional status)

Comment

The paper reinforces an up to date acceptance of the very issue I have been describing for a number of years; Vit D can really only be maintained at an optimal level in humans by increased exposure to sunlight or UVB – yet this is contraindicated because of increased UVB related risks, lack of sunshine, social restraints etc.

There is NO sufficient naturally vitamin D-rich food available to correct the world wide insufficiency either, therefore the only options are direct supplementation with vitamin D3 or indirect via food fortification. This also needs to be undertaken on an ongoing basis, so compliance and ease of delivery inevitably become important factors. I have found that a liquid form of Vitamin D is best tolerated and adhered to, as well as a winter holiday in the sun!

Current RDA levels are inadequate and in many cases even these are not being reached. In the absence of blood tests – and it is recommended that prior to significant supplementation >2000iu per day of VitD3 per day for months, that a blood test is arranged the doses below are recommended as meeting current scientific opinion.

Doses in the region of 5000iu per day for an adult during the winter months is regarded as safe, but for clinical purposes we suggest a periodic 25(OH)D test.

Vitamin D Dose Recommendations
Age Dose
Under 5 years of age 35iu per pound of weight (0.453Kg)
Age 5-10 2500iu per day
Adults 5000iu per day
Pregnant women 5000iu per day
CautionThere is no easy way to determine if you are above the recommended levels. The ONLY way to qualify this is to test your blood. As a result you may need 4-5 x the above dose to achieve optimal levels.

Nutritional status levels for Vitamin D as determined by circulating levels of 25(OH)D

Serum 25(OH)D
ng/mL nmol/L Nutritional description Reference
<5 <12 Severe Vitamin D deficiency [2]
<10 <25 Vitamin D deficiency [3]
10-20 25-50 Vitamin D insufficiency [2]
10-30 25-75 Vitamin D insufficiency [2]
>20 >50 Vitamin D sufficiency [2]
>30 >75 Vitamin D sufficiency [4],[5]
100-150 250-375 Possible toxicity [6],[7],[8],[9]

References

[1] Norman AW, & Bouillon R (2010). Vitamin D nutritional policy needs a vision for the future. Experimental biology and medicine (Maywood, N.J.) PMID: 20667908

[2] Food and Nutrition Board. Dietary Reference Intakes for Calcium, Magnesium, Phosphorus, Vitamin D and Fluoride. Washington DC: National Academy Press, Institute of Medicine, 1997:250-87

[3] Need AG. Bone resorption markers in vitamin D insufficiency. Clin Chim Acta. 2006 Jun;368(1-2):48-52. Epub 2006 Feb 9. Review. View Abstract

[4] Vieth R, Bischoff-Ferrari H, Boucher BJ, Dawson-Hughes B, Garland CF, Heaney RP, Holick MF, Hollis BW, Lamberg-Allardt C, McGrath JJ, Norman AW, Scragg R, Whiting SJ, Willett WC, Zittermann A. The urgent need to recommend an intake of vitamin D that is effective. Am J Clin Nutr 2007;85:649–50  View Full Paper

[5] Heaney RP. The case for improving vitamin D status. J Steroid Biochem Mol Biol 2007;103:635–41 View Abstract

[6] Barger-Lux MJ, Heaney RP. Effects of above average summer sun exposure on serum 25-hydroxyvitamin D and calcium absorption. J Clin Endocrinol Metab 2002;87:4952–6 View Abstract

[7] Better OS, Shabtai M, Kedar S, Melamud A, Berenheim J, Chaimovitz C. Increased incidence of nephrolithiasis in lifeguards in Israel. In: Massry SG, Ritz E, Jaihresi G, eds. Phosphate and Minerals in Health and Disease.New York: Plenum Publishers, 1980:467–72

[8] Haddad JG, Chyu KJ. Competitive protein-binding radioassay for 25-hydroxycholecalciferol. J Clin Endocrinol Metab 1971;33:992–5  View Abstract

[9] Jacobus CH, Holick MF, Shao Q, Chen TC, Holm IA, Kolodny JM, Fuleihan GE, Seely EW. Hypervitaminosis D associated with drinking milk. N Engl J Med 1992;326:1173–7 View Abstract

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