Dr. Fumio Watanabe of Japan’s Kochi Women’s University studied the effects of microwaving milk. Heating samples for six minutes killed as much vitamin B12 as 35 minutes of boiling. In some cases 30-40% was lost.

When Japanese researchers tested for the effects of microwave cooking on vitamin B12 in foods they discovered that just six minutes heating turned 30-40% of the B12 it contained into an inert (dead) form. Beef, pork and pasteurised milk were tested. Microwaved milk was also compared to boiled milk (container in boiling water bath). While heating the milk up to 100 degrees C, microwaving caused greater B12 loss than boiling. The longer the milk was boiled or microwaved the greater the loss but by six minutes microwaving or 30 minutes boiling (far more than required to heat milk for drinking but equivalent to using milk in food processing or cooking) the B12 loss was the same.