aNDF estimated by multiplying analyzed cellulose by 2.5.
bNDF estimated by adding 10 to analyzed ADF.
cNDF estimated by multiplying analyzed crude fiber by 2.
dWeighting coefficient based on proportions of plant foods in stomach.
eWeighting coefficient based on time spent in feeding on each food item.
fWeighting coefficient based on calculated mass of each food item eaten.
values of 17.7%, 13.4%, and 1.9% for glucose, fructose, and sucrose, respectively (Matthews et al., 1987). Galactose, trioses, and tetroses also were known to be present but were unmeasured. Assuming that the unmeasured sugars were present in low concentrations, failure to consider them should produce only a minimal error in the estimate of total sugar concentrations. Total carbohydrate (including the water-soluble sugars) concentration was reported to be 90.2%, and fiber concentration 5.3% (Watt and Merrill, 1963). Because the latter figure was determined with the Weende crude-fiber procedure, it is probably too low; and because the total carbohydrate value was determined by difference from 100% after analysis of moisture, crude protein, ether extract, crude fiber, and ash, it is probably too high. Nevertheless, the domesticated fig is appreciably lower in fiber and higher in nonstructural carbohydrates than the wild figs consumed by free-ranging primates.
SIGNIFICANCE OF FIBER
Among primate species, acceptable concentrations of fiber in the diet and the ability to digest it tend to be highest in Colobinae (with pregastric fermentation similar to that in ruminants). Human diets are generally low in fiber and elevated levels may decrease fat and protein digestibility, although apparent digestibility of TDF has been shown to range from 67 to 82% (Baer et al., 1997). Certain fibers have a high cation-exchange capacity and may influence mineral metabolism by reducing absorption of iron, calcium, copper, and zinc (Schneeman, 1990). That is not to say that fiber in the diet is an entirely adverse factor. In humans, dietary fiber is useful in managing obesity (Burley and Blundell, 1990; Rytigg et al., 1990). Some fiber appears to lower plasma lipid and cholesterol (Anderson et al, 1990; Sugano et al., 1990), modulate the postprandial glycemic and insulinemic response (Trowell, 1990; Wolever, 1990), and improve large bowel function (Stephan, 1985) in humans. Soluble fiber that undergoes fermentation may contribute little to laxation (Stephen and Cummings, 1980; Southgate and Englyst, 1985), and insoluble fibers of cereal brans are more effective than fiber in domestic fruits and vegetables for increasing fecal bulk (Stephen, 1985). However, fine grinding of cereal brans may greatly reduce this laxation effect (Brodribb and Groves, 1978; Floch and Fuchs, 1978; Wrick et al., 1983; Van Soest, 1994). The risk of diverticular disease (Painter, 1985) and colon cancer (Hill and Fernandez, 1990; Lanza, 1990) in humans may be reduced by increased fiber intake from fruits and vegetables, but the data are not conclusive (Schatzkin et al., 2000). It is difficult to separate the effects of fruit and vegetable fiber from other potentially beneficial components of these foods or from the decrease in relative intake of other foods that may have components that increase disease risk (Gallaher and Schneeman, 1996).
Whether fiber in the diet of nonhuman primates promotes the health benefits proposed for humans has not been sufficiently studied. It has been shown that some fiber or fiber sources may be associated with increases, decreases, or no change (depending on fiber type) in serum lipid and cholesterol concentrations and the incidence of atherosclerosis and colonic mucosal damage in rhesus (Macaca mulatta) and vervet or green (Chlorocebus aethiops) monkeys (Heine et al., 1984; Kritchevsky et al., 1986,