Deficiency of Vitamin C in South Asia

Vitamin C (L-ascorbic acid) is a water soluble vitamin which is an antioxidant and has a wide variety of biological functions for growth and development of the human body. It is essential for maintaining good health. The objective of this review is to share with the scientific community, the status of vitamin C in the South Asian populations compared to other populations in the world. The focus in this review is on populations from Pakistan, India, Thailand, Malaysia, Nepal and Singapore. Mean plasma levels of vitamin C of Indians/South Asians living abroad did not vary much compared to other ethnic groups, however, there was a significant decrease in these levels among those living in Pakistan and India. In general, males, smokers, persons using drugs of abuse, individuals infected with H. pylori or parasitic infections and those with low-HDL cholesterol have lower plasma levels of vitamin C when compared to females, non-smokers and normal healthy subjects free from drugs of abuse and infections (parasitic as well as H. pylori) and having normal levels of HDL cholesterol. In winter, plasma levels of vitamin C are, generally, higher compared to summer. Availability of non-sweet fruits, namely oranges, grape fruit, guava, lime and strawberries in winter could be the reason for that. There is a positive relationship between serum haptoglobin (Hp) levels and serum vitamin C concentrations. Individuals carrying a Hp2-2 phenotype (less stable Hp) have lower levels of vitamin C. The prevalence of vitamin C deficiency (plasma levels < 2 μg/ml) is highest among Indians and people of South Asian origin compared to other races except the Mexican population. Lower intake of fresh fruits and vegetables and over-cooking of food by South Asians might contribute to the high prevalence of vitamin C deficiency in these populations. The high proportion of individuals with low levels of vitamin C in Pakistani, Indian, Malay and Chinese populations compared to most Western populations might explain higher rates of cardiovascular disease and cancer among South Asians.