Vitamin B-6 is the master vitamin in the processing of amino acids--the building blocks of all proteins and some hormones. Vitamin B-6 helps to make and take apart many amino acids and is also needed to make serotonin, melatonin, and dopamine. Vitamin B-6 also aids in the formation of several neurotransmitters and is therefore an essential nutrient in the regulation of mental processes and possibly mood. To some extent, vitamin B-6 lowers homosistine levels, a substance that has been linked to heart disease, stroke, osteoporosis, and Alzheimer's disease. A link between vitamin B-6 deficiency and carpal tunnel syndrome has been reported in some, but not all, research. You can find vitamin B-6 in potatoes, bananas, raisin bran cereal, lentils, liver, turkey, and tuna are all good sources of vitamin B-6. Vitamin B6 deficiencies, although very rare, cause impaired immunity, skin lesions, and mental confusion. A marginal deficiency sometimes occurs in alcoholics, patients with kidney failure, and women using oral contraceptives. Many nutrionally oriented doctors believe that most diets do not provide otimal amounts of this vitamin. Pregnant and lactating women should not take more than 100 mg of vitamin B-6 a day. No one should take more than 500 mg. per day.