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TalkingNutrition

Providing perspectives on recent research into vitamins and nutritionals

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Benefits of Fruit and Vegetables: Researchers Claim it’s all about Vitamin C

By Michael McBurney

Rarely does one read a scientific paper with the potential of transforming a field of study. Most research studies ferret out details of a pathway or process. In terms of road construction, research is more often ‘ filling potholes’ to streamline travel than redesigning roads and changing the distance and time required to get from point A to B. Today’s main citation is a landscape change.

Based on data from tens of thousands of people, Kobylecki and colleague write that elevate plasma vitamin C levels may be as important as reducing triglycerides when it comes to change risk of heart disease and mortality. Cardiologists and members of the American Heart Association, are you listening?

The study will probably be ignored by the media. After all, the FDA has approved health claims for fruit and vegetables for cancer and coronary heart disease years ago. Everyone knows we should eat more fruit and vegetables. It isn’t surprising that plasma vitamin C concentrations increase as self-reported fruit and vegetable intake increases (Supplemental Figure 6).

Because the researchers stratified individuals by polymorphisms in the sodium-dependent vitamin C transporter (SLC23A1), they found some individuals (GG genotype) had 25% higher vitamin C concentrations than others (AA genotype). These concentration difference were not exclusively dependent upon self-reported fruit and vegetable intake. The discrepancy was so profound that the authors conclude that high vitamin C concentrations may account for the beneficial effects associated with eating more fruit and vegetables. In other words, health isn’t dictated by our food group choices as much as by our nutritional status.

While other risk factors, e.g. blood pressure and body weight, may obscure relationships with cardiac outcomes, genetics and dietary intake interact to affect health.

Having higher vitamin C concentrations is beneficial. It certainly isn’t in the best public health interest of societies or individuals to have 6% of the population 6 years and over being vitamin C deficient (<11.4 µmol/L). The relative risk of coronary heart disease and stroke decreases 26% with increasing blood vitamin C concentrations (Singh et al 1995; Nyyssonen et al 1997, Simon et al 1998).

For those who didn’t inherit the more efficient vitamin C transporter (and who really knows without genetic testing), the reality is that even more vitamin C has to be ingested to achieve the same plasma concentrations. Don’t forget vitamin C!

Main Citation

Koblyecki CJ, Afzal S, Smith GD, Nordestagaard BG. Genetically high plasma vitamin C, intake of fruit and vegetables, and risk of ischemic heart disease and all-cause mortality : a Mendelian randomization study. 2015 Am J Clin Nutr doi: 10.3945/ajcn.114.104497

Other Citations

Timpson NJ, Forouhi NG, Brion M-J, Harbord RM, Cook DG, Johnson P, McConnachie A, Morris RW, Rodriguez S, Luan J, Ebrahim S, Padmanabhan S, Watt G,  Bruckdorfer KR, Wareham NJ, Whincup PH, Chanock S, Sattar N, Lawlor DA, Smith GD. Genetic variation at the SLC23A1 locus is associated with circulating concentrations of L-ascorbic acid (vitamin C): evidence from 5 independent studies with >15,000 participants. 2010 Am J Clin Nutr doi: 10.3945/ajcn.2010.29438

Wade KH, Forouhi NG, Cook DG, Johnson P, McConnachie A, Morris RW, Rodriguez S, Ye Z, Ebrahim S, Padmanabhan S, Watt G, Bruckdorfer KR, Wareham NJ, Whincup PH, Chanock S, Sattar N, Lawlor DA, Smith GD, Timpson NJ. Variation in the SLC23A1 gene does not influence cardiometabolic outcomes to the extent expected given its association with L-ascorbic acid. 2015 Am J Clin Nutr doi: 10.3945/ajcn.114.092981

Singh RB, Ghosh S, Niaz MA, Singh R, Beegum R, Chibo H, Shoumin Z, Postiglione A. Dietary intake, plasma levels of antioxidant vitamins, and oxidative stress in relation to coronary artery disease in elderly subjects. 1995 Am J Cardiol doi:10.1016/S0002-9149(99)80348-8

Nyyssonen K, Parviainen MT, Salonen R, Tuomilehto J, Salonen JT. Vitamin C deficiency and risk of myocardial infarction: Prospective population study of men from eastern Finland. 1997 Br Med J doi: 10.1136/bmj.314.7082.634

Simon JA, Hudes ES, Browner WS. Serum ascorbic acid and cardiovascular disease prevalence in US adults. 1998 Epidemiol doi: 10.1016/S1047-2797(99)00008-3


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