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Plasma vitamin C and mortality: the seasons are changing
  1. Marleen Antonetta Helena Lentjes
  1. Correspondence to Dr Marleen Antonetta Helena Lentjes, Department of Public Health and Primary Care, EPIC-Norfolk Study, University of Cambridge, Cambridge CB1 8RN, UK; marleen.lentjes{at}phpc.cam.ac.uk

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The supply and consumption of micronutrients is not uniform throughout the year due to the provision and storage of foods, for example, fruits and vegetables as a source of vitamin C. The extent to which this seasonal variation occurs is different between high-income versus low-income countries and between urban versus rural regions, and in case of vitamin C, reflected in lower plasma ascorbic acid concentrations when the harvest approaches. Graphing food balance sheet data, the amount of fruit and vegetables consumed has changed over time (see figure 1). These ecological data have limitations regarding the within country variation,1 but secular patterns may be observed. In China, contrary to the other continents, fruit and vegetable supply appears to have greatly increased since the mid-80s (although extensive modelling estimates more modest increments1). Despite this, overall consumption in the reported study remains low and greatly season dependent up to 2000, as verified with a biomarker.

Figure 1

Fruit and vegetable consumption derived from food balance data for China, Europe, North America, South America, Australia and Africa between 1960 and 2013 (website: our world in data).

The study reported here by Wang et al is the observational cohort continuation of the general population-based Linxian Nutrition Intervention Trial (LNIT, 1985–1991), testing four combinations of up to twofold RNI-dosed micronutrients in supplement form on mortality, especially gastric cancer.2 This trial showed that those who received beta-carotene, selenium and vitamin E—but not vitamin C—had a 9% reduction in overall mortality (RR: 0.91; 95% CI 0.84 to 0.99) in this suboptimally nourished rural population. The cohort results are based on plasma vitamin C only derived from data collections in winter 1999 and spring 2000 (half at each time point, figure 2), with causes …

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