The Dietary Reference Intakes set an Adequate Intake for total fiber of 25 g a day for women aged 19 to 50 and 38 g for men of the same ages. Measured against those, the 13.5 g in a 1 cup serving of lentils is 54% of the first and 36% of the second. US food labels use a single Daily Value of 28 g instead, which puts this serving at 48%.
Calorie for calorie, the figure is 4.4 g of fiber per 100 kcal (this serving is 307 kcal). Among the 114 legumes & beans with USDA energy data here that is 43rd, and 183rd across all 957. The intakes above were derived from 14 g of fiber per 1,000 kcal, or 1.4 g per 100 kcal, so this food sits above the ratio a whole day of eating is meant to reach.
Getting all 25 g from lentils alone would take 2 servings, and 38 g would take 3. Most days reach the target through several different sources.
Dietary fiber and energy in Lentils for 100 g and the USDA household portions
Portion
Grams
Fiber
kcal
100 g
100
7.3 g
166
1 cup - this page's serving
185
13.5 g
307
Gram weights come from the household measures on the USDA record; fiber and energy for each portion are its per-100 g values scaled to that weight.
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