There is special concern about deficiency during pregnancy, when vitamin B6 needs are higher, as it may cause water retention and the nausea and vomiting of morning sickness and has been correlated with a higher incidence of common problems of later pregnancy, such as toxemia (preeclampsia, high blood pressure, edema, and hyper-reflexes) and eclampsia (those same symptoms plus seizures). B6 deficiency in later pregnancy can be associated with birthing difficulties. There is also an increased likelihood of diabetic and blood sugar problems in pregnancy when vitamin B6 is deficient.
Overall, vitamin B6 deficiency can cause a variety of nervous symptoms, skin problems, and amino acid/protein metabolic abnormalities. These can lead to the more common expressions--headache, dizziness, inability to concentrate, irritability and epileptic-type activity, labile depression, and weakness. Water retention is common. Nausea, vomiting, and dry skin, especially extensive dandruff and a cracked sore mouth and tongue are also more likely with vitamin B6 deficiency.
Requirements: Vitamin B6 intake, though based on many factors, is determined primarily
by protein intake, because it is so important to protein metabolism. The RDA for adults is a minimum of 2 mg. of B6 per 100 grams of protein consumed. In children, it ranges from 0.6-1.2 mg. per 100 grams of protein.
However, the need for vitamin B6 increases in a variety of situations. During pregnancy and lactation and with birth control pill or estrogen use, higher levels are required. For those who eat a high-sugar or processed-food diet or a high-protein diet, requirements for B6 are greater and deficiencies or depletion are more common. When there is impairment of the digestive system, cardiac failure, or radiation use, or even just the aging process, needs for vitamin B6 are increased.
Drugs that influence needs for B6 are oral contraceptives, isoniazid (for tuberculosis), hydralazine (for high blood pressure), amphetamines, reserpine (for high blood pressure), and some antibiotics. More B6 is utilized with an increased intake of the amino acid methionine. Adequate magnesium in the body is important to the functions of vitamin B6.
A safe, basic intake for vitamin B6 is probably 10-15 mg. per day, though much higher daily amounts are easily tolerated. B6 should also be taken along with other B vitamins to prevent metabolic imbalance. For therapeutic purposes, amounts between 50-100 mg. (this is the quantity pyridoxal-5-phosphate usually comes in) are most common, and up to 200-500 mg. per day in time-release forms is used for some conditions, such as premenstrual problems and depression. With the current questions about neurologic side effects associated with megadoses of vitamin B6, particularly as pyridoxine hydrochloride, I suggest limiting regular daily intake to 500 mg. daily or 1,000 mg. for a short course of treatment, such as one to two weeks; also, take some additional magnesium, 200-300 mg, which may help reduce any neurologic concerns.