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25.2.3 Other Nutrients
25.2.3.1 Dietary Fiber
Dietary fiber is categorized as either water–soluble or insoluble. While soluble
fibers dissolve or swell in fluid, insoluble fibers do not dissolve or swell in fluids.
These are found in plant (leaves, seeds, fruits, and stems) foods in ample amounts.
Dietary fibers are polysaccharides that are highly branched and cross–linked and
include pectin, gums, cellulose, hemicellulose, and lignin. Lignin, however, is not
composed of carbohydrate units. Humans do not produce the enzymes that can
break down dietary fiber. Unlike starch, dietary fiber does not break down into single sugars. It does not contain any calories, and hence does not supply energy.
Instead, it passes through the gastrointestinal tract undigested, which supports
healthy digestion. Other possible health benefits of dietary fiber include the prevention and management of adult–onset diabetes, certain cancers, coronary heart disease and digestive tract disorders. Soluble fibers like inulin, pectin, and guar gum
are found in apples, barley, legumes, oats, prunes, rye, algae, and some root vegetables, such as onions and potatoes. They help provide texture and consistency to
foods such as jellies (citrus pectin), salad dressings (guar gum) and ice cream (carrageenan). Soluble fibers help delay the absorption of glucose from the bloodstream
and lead to improved sugar tolerance in diabetics; slow the absorption of cholesterol
and help to lower blood cholesterol in coronary heart disease; and provide fullness
and satisfaction when they take up fluid and swell during digestion, which may
benefit weight management. Soluble fibers are more easily accessible to bacterial
enzymes in the large intestine so they can be broken down to a greater extent than
insoluble fibers, but even some breakdown of cellulose and other insoluble fibers
occurs (Gibney et al. 2009; Marcus 2013; Titchenal et al. 2018).
Insoluble fibers include bran, flax, hemicellulose, lignans, nuts, seeds, avocados,
the skin of fruits and vegetables like cauliflower, and whole grain foods. The seeds
and skin of fruits and vegetables are particularly good sources. Cellulose is the most
abundant fiber in plants, making up the cell walls and providing structure. Insoluble
fibers help to increase bulk and soften the stool so it passes quickly through the large
intestine. This feature makes it potentially beneficial in the prevention of digestive
diseases, including colon cancer, diverticulosis and hemorrhoids. Insoluble fibers
also assist in weight management in that they speed the transit time of food in the
intestines. For this reason, they may also be protective against gastro intestinal
diseases.
A third type of dietary fiber is resistant starch (RS) that resists digestion in the
small intestine due to its fibrous outer coat. It can produce the benefits of both
soluble fiber and insoluble fiber. While sugars and starches are absorbed as glucose
through the small intestine and used for short–term energy or stored, resistant starch
passes into the large intestine, where it acts like dietary fiber. Resistant starch may
contain some calories, but it does not raise blood sugar. Legumes, whole grains,
unripe bananas, plantains and raw potatoes contain resistant starch. Resistant starch
K. Sharma et al.
25.2.3 Other Nutrients
25.2.3.1 Dietary Fiber
Dietary fiber is categorized as either water–soluble or insoluble. While soluble
fibers dissolve or swell in fluid, insoluble fibers do not dissolve or swell in fluids.
These are found in plant (leaves, seeds, fruits, and stems) foods in ample amounts.
Dietary fibers are polysaccharides that are highly branched and cross–linked and
include pectin, gums, cellulose, hemicellulose, and lignin. Lignin, however, is not
composed of carbohydrate units. Humans do not produce the enzymes that can
break down dietary fiber. Unlike starch, dietary fiber does not break down into single sugars. It does not contain any calories, and hence does not supply energy.
Instead, it passes through the gastrointestinal tract undigested, which supports
healthy digestion. Other possible health benefits of dietary fiber include the prevention and management of adult–onset diabetes, certain cancers, coronary heart disease and digestive tract disorders. Soluble fibers like inulin, pectin, and guar gum
are found in apples, barley, legumes, oats, prunes, rye, algae, and some root vegetables, such as onions and potatoes. They help provide texture and consistency to
foods such as jellies (citrus pectin), salad dressings (guar gum) and ice cream (carrageenan). Soluble fibers help delay the absorption of glucose from the bloodstream
and lead to improved sugar tolerance in diabetics; slow the absorption of cholesterol
and help to lower blood cholesterol in coronary heart disease; and provide fullness
and satisfaction when they take up fluid and swell during digestion, which may
benefit weight management. Soluble fibers are more easily accessible to bacterial
enzymes in the large intestine so they can be broken down to a greater extent than
insoluble fibers, but even some breakdown of cellulose and other insoluble fibers
occurs (Gibney et al. 2009; Marcus 2013; Titchenal et al. 2018).
Insoluble fibers include bran, flax, hemicellulose, lignans, nuts, seeds, avocados,
the skin of fruits and vegetables like cauliflower, and whole grain foods. The seeds
and skin of fruits and vegetables are particularly good sources. Cellulose is the most
abundant fiber in plants, making up the cell walls and providing structure. Insoluble
fibers help to increase bulk and soften the stool so it passes quickly through the large
intestine. This feature makes it potentially beneficial in the prevention of digestive
diseases, including colon cancer, diverticulosis and hemorrhoids. Insoluble fibers
also assist in weight management in that they speed the transit time of food in the
intestines. For this reason, they may also be protective against gastro intestinal
diseases.
A third type of dietary fiber is resistant starch (RS) that resists digestion in the
small intestine due to its fibrous outer coat. It can produce the benefits of both
soluble fiber and insoluble fiber. While sugars and starches are absorbed as glucose
through the small intestine and used for short–term energy or stored, resistant starch
passes into the large intestine, where it acts like dietary fiber. Resistant starch may
contain some calories, but it does not raise blood sugar. Legumes, whole grains,
unripe bananas, plantains and raw potatoes contain resistant starch. Resistant starch
K. Sharma et al.