The bioavailability of vitamin B₆ from selected foods as measured by urinary 4-pyridoxic acid in men saturated with pyridoxine

Abstract

The bioavailability of vitamin B₆ in four selected foods (bananas, filberts, soybeans and beef) was determined in five men, aged 22 to 25 years, who were saturated with pyridoxine. The study consisted of a five-day adjustment period followed by a 28-day experimental period. All subjects consumed a constant diet containing 1.34 mg of vitamin B₆ from Monday to Friday of each week, and their self-chosen diets on the weekends. During the experimental period the subjects received 5 mg of pyridoxine each day, including weekends, except on the days when loading doses of crystalline pyridoxine and the selected foods were administered. Doses of 2 mg of crystalline pyridoxine or doses of food containing approximately 2 mg of vitamin B₆ were given. The subjects collected daily 24-hr urine specimens. Vitamin B₆ bioavailability was determined by comparing the yield of 4-pyridoxic acid in response to the test food doses to the yield of 4-pyridoxic acid in response to the 2mg of crystalline pyridoxine. Compared to the 100 percent bioavailability of 2mg crystalline pyridoxine, the mean percent bioavailability of vitamin 65 from banana was 131.4 ± 68.2; from filberts, 88.1 ± 13.9; from soybeans, 58.3 ± 24.3; and from beef, 81.5 ± 28.6. Factors affecting bioavailability of vitamin B₆ from these foods are discussed.