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AI Vinik and DJ Jenkins
Department of Internal Medicine, University of Michigan,
Ann Arbor.
Current evidence suggests that high-fiber
diets, especially of the soluble variety,
and soluble fiber
supplements may offer some improvement in carbohydrate
metabolism, lower total cholesterol and low-density lipoprotein
(LDL) cholesterol, and have other beneficial effects in patients
with non-insulin-dependent diabetes mellitus
(NIDDM). Diets enriched with wheat bran and guar gum
induce 10-20% reductions in serum cholesterol and LDL
in both normo- and hypercholesterolemic subjects and have
the ability to blunt the hypertriglyceridemic effects of diets
high in carbohydrate and low in fiber.
In insulin-dependent diabetes mellitus (IDDM)
the situation is less clear, but a decrement of the circadian
glucose profile has been shown. Americans, in general, consume
too little fiber. With the need to
restrict fat and reduce protein, an increase in carbohydrates
is mandatory. A practical goal would be to establish the
present level of fiber intake (15-30 g/day)
and to gradually increase it. An intake of up to 40
g of fiber per day or 25 g/1000 kcal of food
intake appears beneficial; in many individuals on weight-reducing
diets higher levels may be unacceptable because of
gastrointestinal side effects. The level of maximum
benefit has not been determined. Fiber supplementation
appears beneficial only if given with a diet comprising
approximately half of the calories as carbohydrate.
Foods should be selected with moderate to high amounts
of dietary fiber from a wide variety of choices
to include both soluble and insoluble
types of fiber. Insufficient data are available
on the long-term safety of high-fiber supplements.
People at risk for deficiencies, such as postmenopausal
women, the elderly, or growing children, may require
supplements of calcium and trace minerals. People with
upper gastrointestinal dysfunction are at risk of bezoar formation
and cautioned against a diet high in fiber
of the leafy vegetable type. Careful attention must
be paid to insulin dose because hypoglycemia can result if
there is a radical change in fiber intake
and insulin dose is not reduced appropriately. Care
must be exercised in the use of "novel" fibers,
including the wood celluloses, because little is known of
their safety and efficacy.
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