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Walter, a reader in Monterey,
Calif., writes: "I appreciated your initial piece on the
subject of fiber (a few weeks ago) and I have some questions
on further details I'd like to know on the subject."
Here are Walter's questions:
Q: I take it the usual person
should eat enough fiber as a daily requirement of 25 to 35
grams. But can one eat too much, and how much is too much? And
if too much is consumed, what are the consequences?
A: Technically, the daily
requirement for fiber is 14 grams for every 1,000 calories
consumed. So a 3-year old may need just 19 grams a day while a
young active man may need 38 grams. Since most people don't go
around calculating how many calories they eat every day, the
general recommendation is 25 grams to 35 grams. Can we eat too
much? No "Upper Tolerable Limit" (the amount of
fiber above which you may have problems) has been set due to
insufficient evidence, according to the Institute of Medicine,
the body of experts who make such decisions. One thing is for
sure: if you suddenly increase your intake of fiber, you may
experience digestive consequences. It's also important to
drink plenty of fluids when you eat more fiber.
Q: Regarding
"soluble" and "insoluble," is either
preferred and what is an appropriate mix? And if one fails on
the mix, what are the consequences?
A: Well, Walter, it looks like
the terms "soluble" and "insoluble" fiber
are on their way out, based on scientific findings that
fiber's health benefits don't seem to have much to do with its
solubility. Instead, fiber's "viscosity" and
"ferment ability" appear to be more meaningful
characteristics, according to a report by the IOM that
proposes new definitions for fiber. What is a good
"mix"? A varied diet of fiber-rich foods (fruits,
vegetables, whole grains) provides viscous fibers and
fermentable fibers that help keep cholesterol, blood sugars
and weight under control.
Q: I've checked some boxes of
cereal and some list both "soluble" and
"insoluble," while others just set forth
"dietary fiber" with no breakdown. Is it soluble or
insoluble, and which?
A: Yes. Dietary fiber can be
listed as such on the food label or designated
"soluble" or "insoluble." But don't worry;
as soon as the definitions of fiber change, the food label
will change, too, and then we'll really be confused.
Q: One site on the Internet
stated, "Soluble fiber is actually found in foods
commonly thought of as starches, though soluble fiber itself
differs from starch as the chemical bonds that join its
individual sugar units cannot be digested by enzymes in the
human GI tract. In other words, soluble fiber has no calories
because it passes through the body intact." All packets
on any type of food I've read that reflect some dietary fiber
seems always to state calories. Could you clarify what this
means?
A: Glad to. Fiber is one
component of starchy foods. The starch contains calories as
carbohydrates. But since fiber is not digested, it does not
provide the body with any calories. For example, a slice of
whole grain bread contains starch and fiber. The calories on
the label come from the starch, not the fiber. That's just one
of the good consequences of fiber.
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