IntrOductIOnImportance of Vitamin B12 in the production of DNA and RNA is been well established. Deficiency of Vitamin B12 causes macrocytic anaemia, peripheral neuropathy, dementia, weight loss, neural tube birth defects and various other adverse health effects. Recently increased prevalence of Vitamin B12 deficiency is been identified in various studies across different parts of India [1][2][3]. Easy availability of diagnostic facility to identify B12 deficient individuals, who were otherwise unidentified earlier as well as increased awareness among public causing voluntary testing of B12 levels may be some of the reasons for recently increased prevalence. Pure vegetarian diet lacking in milk or dairy product is one of the most commonly identified risk factors for development of Vitamin B12 deficiency, yet there is possibility that some newly developing but unidentified risk factors to be responsible for its recently increasing prevalence.Along with life style changes, changes have kept on occurring in people's dietary habits and type of drinking water over period of time; there is a possibility that some of these changes may be associated with recently increasing Vitamin B12 deficiency. One of the frequently questioned such factors is use of drinking water processed by Reverse Osmosis (RO) technology. With population growth and exploitation of available water sources causing scarcity of safe drinking water, mainly in developing countries, public based RO plants and home based RO units are being increasingly used. RO system very effectively removes dissolved solids as well as many microorganisms making water palatable and relatively safe to use [4][5][6]. With increased use of RO processed demineralised water, many adverse health effects are also been increasing identified. Increased cardiovascular morbidity and mortality is now been well established due to use of demineralised water low in calcium

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