below are some (of many) sources that suggest that too little calcium can affect your vitamin B12 levels. According to "Vegans deficient in three nutrients - meat eaters in seven" and other sources, calcium is one of the most important nutrients vegans should pay attention to. (It's not difficult to get enough calcium, but you need to know where to find it).

Vegans are known to have lower B12 levels than non-vegans, and to me, it doesn't look like there is one cause for the low B-12 levels among vegans, but many. Could lack of calcium be a more important part of the vegan/B12 issue than most people think?

From http://www.livingwithms.co.uk/ms/nutrit.html :
"B12 needs to be combined with Calcium for proper absorption"

From http://foodsupplements.homestead.com/B12.html :
" B-12 METHYLCOBALAMIN 1000 mcg 1 or 2 a day. Methylcobalamin is the preferred type. Cyanocobalamin must be converted to methyl or adenosyl cobalamin by the body. Required for fat and carbohydrate metabolism and formation of blood cells . Deficiency results in mental confusion ,anemia , homocystenia, brain damage, tinnitus ,asthma , and depression . B-12 deficiency leads to heart risk. ( Science News 2-16-02 ) May benefit multiple sclerosis patients. Deficiency is widespread in people over sixty years of age. Blood test to determine B-12 level is recommended. Alcohol, estrogen, oral contraceptives, sleeping pills interfere with utilization. Natural sources are liver, beef, pork, eggs, milk, and cheese , except where soil is deficient in cobalt . ( 19 ) Needs calcium for absorption. Microwave cooking destroys B-12."

From http://www.chinatown-online.com/cons.../nutrition.htm
"B12 Depleting Factors: Alcohol, coffee, tobacco, calcium deficiency."

From http://www.noni-juice-distributor.us...t_glossary.htm :
"Calcium (as calcium phosphate): the bodyÍs most abundant mineral. Every cell needs calcium to survive. Calcium is necessary for body synthesis of B12 and uses vitamin D for absorption. It works with phosphorus to build sound teeth and bones, with magnesium for cardiovascular health and skeletal strength. It helps blood clotting, lowers blood pressure, prevents muscle cramping, maintains nervous system health, controls anxiety and depression, and insures quality rest and sleep."

From http://www.leaflady.org/cancer.htm
About B12: "Utilization assisted by calcium. [...] More effective when taken with B complex and Vitamin C, Lecithin, Potassium, Calcium, and Sodium."

From http://www.unhinderedliving.com/VitaminB12.html
"When taking B12, it is a good idea to also supplement with calcium at the same meal, as calcium assists with absorption. There must also be hydrochloric acid present. A properly functioning thyroid gland also helps with absorption of B12"

Finally, about calcium and tap water: (From http://www.pharo.com/health_and_heal...0_contents.asp )
"Despite assurances from water companies, tap water is full of potentially dangerous chemicals - even, in some areas of Britain, including the highly controversial fluoride, and also probably residues from the contraceptive pill. Heavy metals in the water are believed to prevent the absorption of calcium. Natural water is high in calcium, necessary for strong teeth and bones, although the fizzy sort is also high in sodium (salt), so don't drink it often."