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TABLE 6-1 Experimental Human Studies of Niacin Intake and Urine N1-methylnicotinamide Excretion

Reference

Subjects

Regimen

NE Intake Calculated to Result in N1-methylnicotinamide Excretion of 1.0 mg/d, Mean ± SD (CV%)a

Goldsmith et al., 1952

5 females, 25–54 y

Four fed a corn-based diet low in niacin and trp (7.7 mg of NEs) and one fed a wheat-based diet (9.5 mg of NEs) for up to 135 d. Supplemented with N1-methylnicotinamide or trp.b

12.6 ± 3.0 (23%) or ≈6.8 mg of NEs/1,000 kcal

Goldsmith et al., 1955

3 females, 26–60 y

Fed wheat-based diet low in niacin and trp (8.3 mg of NEs) for up to 80 d. Supplemented with N1-methylnicotinamide.

10.9 ± 0.9 (8%) or ≈5.8 mg of NEs/1,000 kcal

Horwitt et al., 1956

14 male mental patients, 30–65 y

Fed three ordinary food diets low in niacin and trp in a series of studies for up to 87 wk. Supplemented with N1-methylnicotinamide or trp to provide 9–12 mg/d of NEs.

11.5 ± 4.5 (39%) or ≈4.9 mg of NEs/1,000 kcal

Jacob et al., 1989

7 males, 23–39 y

Gelatin-based diet of ordinary foods fed over 11 wk with varying ratios of trp and N1-methylnicotinamide to provide 6 or 10 mg/d of NEs (and varying leucine).

11.3 ± 4.6 (41%) or ≈4.4 mg of NEs/1,000 kcal

Average of the four studies, two with females and two with males, on low-niacin diets (6–12 mg/d of NEs) for 4–24 wk

11.6 ± 3.9 (34%) or ≈4.8 mg of NEs/1,000 kcal

a NE = niacin equivalent (1 NE = 1 mg niacin = 60 mg tryptophan); SD = standard deviation; CV = coefficient of variation.

b trp = tryptophan.



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