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TalkingNutrition

Providing perspectives on recent research into vitamins and nutritionals

Possible Concentrations of an Essential Element in the Diet

Stop Wasting Money on Nutrition Interventions in Well-Nourished People

By Michael McBurney

As scientists began studying deficiency diseases, they discovered vitamins, minerals and essential amino acids and fats by fractionating and isolating compounds from foods. Extracts were added back to purified diets. Carefully designed experiments comparing diets (control vs interventions) were used to remedy deficiencies and define nutrient requirements. Adding nutrients to a diet consumed by individuals with suboptimal nutrient status has measurable effects, e.g. increased growth, decreased mortality, etc. The magnitude of the response depends upon the nutritional status of the subjects. Adding nutrients to the diet of individuals with optimal nutrient status doesn’t generally change outcomes unless subjects are exposed to dangerously high intakes.

Low serum 25-hydroxyvitamin D3 levels have been associated with increased risk of diabetes. Gagnon et al, 2011 reported that mean serum 25(OH)D3 concentrations below 58 nmol/L increased the risk of diabetes. In an epidemiological survey of Stockholm participants, Deleskog and colleagues reported that each 10 nmol/L increase in serum 25(OH)D3 concentration was associated with a 25% reduced risk in progression to type 2 diabetes from prediabetes. Seasonally adjusted baseline serum 25(OH)D3 concentrations were ~59 nmol/L. Seasonally adjusted quartiles of <46.2, 46.2-58.0, 58.1-71.0, and >71.0 nmol/L. The odds ratios (OR) were similar in quartiles 3 and 4 (>58 nmol/L).  

Based on observational evidence like this, Sollid and colleagues hypothesized vitamin D supplementation would reduce the risk of diabetes. They designed and executed an intervention (20,000 IU/wk of vitamin D3 vs placebo for 1 year) in 511 individuals with impaired fasting glucose.  The experimental design is good. The execution wasn’t. Why? Because mean baseline serum 25(OH)D3 concentrations were ~60 nmol/L. It cannot be inferred from observational data that increasing vitamin D levels above 60 nmol/L will change diabetes risk. The Institute of Medicine defined ≥ 50 nmol/L  as sufficient. Why do researchers continue to conduct intervention trials in nutritionally-sufficient individuals?

Agencies need to adopt new requirements when funding nutrition interventions. Researchers should  be mandated to define nutrition status criteria and use these cut-points as inclusion/exclusion criteria prior to treatment randomization. Stop wasting money conducting nutrition interventions in individuals with adequate nutrition status.

Main Citation

Sollid ST, Hutchinson MYS, Fuskevag OM, Figenschau Y, Joakimsen RM, Schirmer H, Njolstad I, Svartberg J, Kamycheva E, Jorde R. No effect of high-dose vitamin D supplementation on glycemic status or cardiovascular risk factors in subjects with prediabetes. 2014 Diab Care doi 10.2337/dc14-0218

Other Citations

Gagnon C, Lu ZX, Magliano DJ, Dunstan DW, Shaw JE, Zimmet PZ, Sikaris K, Grantham N, Ebeling PR, Daly RM. Serum 25-hydroxyvitamin D, calcium intake, and risk of type 2 diabetes after 5 years : Results from a national, population-based prospective study (the Australian Diabetes, Obesity and Lifestyle study). 2011 Diab Care doi: 10.2337/cd10-2167

Deleskog A, Hilding A, Brismar K, Hamsten A, Efendic S, Ostenson C-G. Low serum 25-hydroxyvitamin D level predicts progression to type 2 diabetes in individuals with prediabetes but not with normal glucose tolerance. 2012 Diabetologia doi: 10.1007/s00125-012-2529-x


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2comments
The argument that trials should be done in populations with deficiency isvalid enough but is predicated on the assumption that the cut point to define deficiency for a given outcome is known. The IOM committee set the threshold at 50nmol/L for bone related outcomes only and concluded that there was insufficient evidence to suggest levels for other outcomes. In the first half of your piece you state that there is evidence that 25(OH)D<58 increases risk for T2D and then you say that baseline levels were about that…the argument that this is testing irrelevant interventions does not hold weight.
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If you look at the IOM report you'll see that the 50 nmol threshold was for bone health only - not for diabetes. As far as I know there are no agreed upon thresholds for vitamin D deficiency for diabetes so who is to say what constitutes deficiency? Should the threshold be set at 30nmol? 15 nmol? 60 nmol? levels exceeding 100 nmol (which is what we probably evolved at). Until that question is answered it is premature to say that money is wasted through such trials. No offense intended, just telling it like it is.
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