What genetic variation influences the risk of vitamin C deficiency?

Vitamin C, also known as ascorbic acid, is an essential nutrient with a diverse range of functions, including the production of collagen (an essential component of connective tissues and important for wound healing), the synthesis of neurotransmitters (chemical messengers in the brain), stimulation of immune function, and the absorption of non-heme iron. Vitamin C also acts as an antioxidant. This water-soluble vitamin is found in high levels in citrus fruits, broccoli, berries and tomatoes. 

To absorb vitamin C into our cells, we need protein transporters on the cell surface. The SLC23A1 gene encodes one of these transporters, called solute carrier family 23 member 1. A relatively rare genetic variant (rs33972313 A) in this gene is linked to an increased risk of vitamin C deficiency. 

Early signs of vitamin C deficiency include a general feeling of unease or discomfort without an identifiable cause (malaise) and lethargy.  Long-term vitamin C deficiency leads to scurvy. Symptoms of scurvy include inflamed and bleeding gums, nosebleeds, dry hair and skin, decreased wound healing rate and lowered immunity.