Olestra
Olestra is
a fat substitute that has the properties of a fat in flavor and texture, but is
indigestible-hence a fake fat. It does not add any calories as a normal fat would.
Olestra is part fatty acids from cottonseed or soybean oils and part sucrose
rather than glycerol in triglycerides. The six to eight fatty acids are bonded
to the hydroxyl or alcohol groups on the sucrose using an ester synthesis
reaction. This makes for a rather large molecule that looks like an octopus
with many arms. Olestra cannot be digested by enzymes which hydrolysis the
sucrose or the triglycerides. Since the enzymes cannot break down the olestra,
it travels through the intestines undigested and unabsorbed. In 1996, the FDA
approved the use of olestra in potato chips, tortilla chips, crackers and fried
snacks, as it is the only heat stable fat substitute for fried foods. There
have been some reports of adverse reactions in the intestines including
diarrhea and cramps, indicating that it may act as a laxative in some people. Since
olestra is such a large nonpolar molecule, it may dissolve or combine with some
of the fat soluble vitamins such as A, D, E, and K, and carotenoids. As a
result, the FDA now these vitamins must be added to any products containing
olestra.
Olestra has
an extraordinary avidity for certain fat-soluble substances, far exceeding what
one would expect based on the fat substitute's proportion of the diet.
Olestra's removal from the body of fat-soluble nutrients is linked directly to
the additives being a non-absorbable lipid-like substance.
In Procter
& Gamble's two eight-week clinical studies, the lowest level tested -- 8
gm/day (equivalent to 16 olestra-containing potato chips) — caused dramatic
depletion of fat-soluble vitamins within two weeks. Procter & Gamble also
measured total serum carotenoids, alpha-carotene, beta-carotene, lutein, and
lycopene. Olestra caused significant declines in all carotenoids monitored.
Total serum carotenoids declined sharply by the fourteenth day of olestra
consumption and was down by 50% to 60% by the end of the studies. A dosage of
32 gm/day of olestra reduced total serum carotenoids by 70% over the eight
weeks.
Feeding
olestra with one or more meals, as was done in the several clinical studies,
results in the greatest depletion of carotenoids. While that might seem to be a
worst-case scenario, many people would, indeed, consume olestra-containing
foods with meals. In fact, Procter & Gamble's petition states that
mealtimes constitute the great majority (79%) of the occasions during which
consumers eat "savory snacks." Also, since the frequency of
consumption of snacks would likely increase if olestra snacks were available,
interaction between nourishing foods and olestra at meals would be likely to
increase, resulting in lower serum levels of fat-soluble carotenoids and other
phytochemicals. There would also be more opportunities for olestra to reduce
the absorption of beta-carotene and fat-soluble vitamins that people ingest in
dietary supplements and fortified foods.
Olestra's
depletion of carotenoids is of great concern, because a growing body of
evidence indicates that they may confer important health benefits. The
physiological activities of fat-soluble plant nutrients are just now being
elucidated. For instance, in a recent case-control study, lutein (along with
zeaxanthin) was strongly associated with a lower risk of macular degeneration,
the most common cause of blindness in the elderly (J.A.M.A. 272: 1413 (1994)).
That observation is buttressed by the fact that lutein and zeaxanthin form the
yellow pigment in the macula (the central part of the retina). In three
clinical studies, 3 gm/day of sucrose polyester or 8 gm/day of olestra reduced
lutein levels by 20% to 40%.
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