Niacin intake in the United States is generous in comparison with the Estimated Average Requirement (EAR). For example, the median intake by adult women is 17 to 20 mg of niacin (Appendixes G and H) in comparison with an EAR of 11 mg of niacin equivalents (NEs). (Survey data are reported as preformed niacin; no addition has been made for the conversion of tryptophan to niacin.) For all life stage and gender groups it appears that almost all individuals’ usual niacin intakes would exceed the EAR if intake was expressed in NEs and thus the contribution of tryptophan was included. Intakes of niacin in two Canadian provinces are reported in NEs and are well above the EAR for all life stage and gender groups (Appendix I).
The Boston Nutritional Status Survey (Appendix F) indicates that this relatively advantaged group of people over age 60 has a median niacin intake of 21 mg/day for men and 17 mg/day for women, again, significantly above the EARs for adult men and women.
Information from the Boston Nutritional Status Survey on the use of niacin supplements by a free-living elderly population is given in Appendix F. For those taking supplements, the fiftieth percentile of supplemental niacin intake was 20 mg for men and 30 mg for women. In the 1986 National Health Interview Survey, 26 percent of all adults reported use of supplements containing niacin (Moss et al., 1989). Supplements containing up to about 400 mg of niacin are available without a prescription.
There is no evidence of adverse effects from the consumption of naturally occurring niacin in foods. Therefore, this review is limited to evidence concerning intake of niacin as a supplement, food fortificant, or pharmacological agent.