RIBOFLAVIN AND VITAMIN-B-6 INTAKES AND STATUS AND BIOCHEMICAL RESPONSE TO RIBOFLAVIN SUPPLEMENTATION IN FREE-LIVING ELDERLY PEOPLE

Free-living elderly people aged greater than or equal to 65 y were rec ruited to assess riboflavin and vitamin B-6 intakes and status and the effect of riboflavin supplementation on biochemical indicators of the se 2 vitamins. The status of riboflavin (erythro cyte glutathione redu ctase activation coefficient; EGRAC) and vitamin B-6 (plasma pyridoxal -5'-phosphate; PLP) were determined in a total sample of 92 subjects, from whom dietary intake data were obtained by using the diet history method (n = 83). Although dietary intakes of both vitamins were consid ered to be adequate according to current reference values, abnormal EG RAC and plasma PLP values were identified in 49% and 38% of subjects, respectively, with 21% having suboptimal status for both nutrients. A subgroup of subjects from the initial sample (n = 45) was assigned in a double-blind manner to receive either 1.6 or 25 mg riboflavin or pla cebo daily for 12 wk. In those subjects with a baseline EGRAC or plasm a PLP value falling outside the currently accepted threshold value for adequacy, low-dose riboflavin supplementation improved status of the limiting nutrient significantly (P < 0.0001 and P = 0.020 for EGRAC an d plasma PLP responses, respectively). We conclude that a high proport ion of healthy elderly people may have suboptimal status for these nut rients despite apparently adequate dietary intakes. Furthermore, we sh owed that riboflavin supplementation at physiologic doses corrects bio chemical abnormalities of not only EGRAC, but also plasma PLP, confirm ing the biochemical interdependency of these vitamins and suggesting t hat riboflavin is the limiting nutrient.