Mathieu Torck

Vitamin C deficiency: more than just a nutritional disorder

Although vitamin C deficiency and scurvy are generally considered as pure nutritional disorders, only a minority of the vitamin C concentration is determined by food intake. In the presence of transition metals (iron and copper), the antiscorbutic factor shifts from an antioxidant to a pro-oxidant function. Haptoglobin (Hp) is a plasma α-2 glycoprotein characterized by 3 common phenotypes (Hp 1–1, Hp 2–1 and Hp 2–2). Its free hemoglobin (Hb)-binding capacity prevents Hb-driven oxidative damage. When the antioxidant capacity of Hp is insufficient, its role is taken over by hemopexin (heme-binding protein) and by vitamin C (free radical scavenger). The Hp 2–2 phenotype has a lower capacity to inhibit oxidation and vitamin C depletion. In this article, two consequences of this major finding are tackled. The Hp polymorphism is an important non-nutritional modifying factor in the pathogenesis of vitamin C deficiency and scurvy, which may explain the success of long-range human migration by the natural selection of some populations characterized by high Hp 1 allele frequencies. Moreover, we propose tailoring the recommended dietary allowance (RDA) values of vitamin C, taking into consideration the Hp phenotype dependency.

Human plasma protein polymorphisms and the persistence of cultural diversity

Recently, Laitin et al. (1) reported on the roots of cultural diversity. Geographic axis ratios for individual countries help to understand the diversity of language, showing more diversity in north–south oriented countries. We believe that genetic factors related to vitamin requirements also should be taken into account as confounders. Human long distance migration has been limited by availability of vitamin C and D. Biological half-life of vitamins C and D in man is largely determined by genetic polymorphisms of plasma proteins such as haptoglobin (Hp) and vitamin D binding protein (DBP) (2, 3). These polymorphisms are in a state of transient gene equilibrium, proving their major role as a genetic migration driver.