Fiber, although not considered a macronutrient, has a RDA of 25 – 38 gm/ day again according to the National Academy of Sciences Institute of Medicine’s Food and Nutrition Board and is only available from plants. And we know that the most healthful diet is one that is high in fiber and low rapidly digested carbohydrates. This regimen is referred to as a low-glycemic diet because it helps keep our blood glucose at optimum levels. Wild fruits and vegetables are the original low-glycemic foods.
It is estimated that 97% of Americans do not consume the recommended minimum amount of fiber.
Shown below are a few example foods and their fiber density, expressed as grams of fiber per total grams of dry weight of food substance.
Generalizing, fruit and vegetables are significant sources of fiber, but beans and cruciferous vegetables are best and starch and grains much less so.
 Robinson, J. (2013). Eating on the wild side: The missing link to optimum health (pp. 4-5).
 Moshfegh, A., & Goldman, J. (2005). What We Eat in America, NHANES 2001-2002: Usual Nutrient Intakes from Food Compared to Dietary Reference Intakes. U.S. Department of Agriculture, Agricultural Research Service.