These are two aspects of the same problem. Here is a simple case. We come across a highly irritable man and want to find out why he is so. Investigations reveal vitamin A deficiency. Again, there has to be 90 to 110 mg of sugar for every 100 cubic centimeters of body volume.
Slight deficiency causes emotional disorders.
The man becomes ill-tempered and in extreme cases can even become a murderer. Modem science has proved that ill-temper and the murderous tendency are caused by a deficiency of sugar, niacin and certain vitamins. Chemical deficiency can cause depression. Similarly, one of the causes of fear is vitamin B deficiency. A lot of research is being carried on these days on the properties of a chemical called tryptaphane which produces serotonin.