There is now a lot of persuasive evidence that people can benefit from increased
intake of antioxidant nutrients. Why is this? Many people have an excess of
potentially damaging molecules called free radicals. This excess load of free
radicals can promote heart disease, diabetes, arthritis, cataracts, and cancer.
Free radicals are a byproduct of oxidation, a chemical reaction inside cells
that fuels bodily processes. Under ideal conditions, our cells consume almost
all free radicals for productive purposes, and special antioxidant enzymes and
dietary nutrients neutralize the remaining 2 to 5 percent. When antioxidants
are in short supply, excess free radicals are free to strip electrons from molecules
in cell walls and genetic material, and to oxidize dietary fats in the blood.
This initiates a rapid chain reaction that yields even more free radicals. In
addition, many of the man made chemicals in our air and water, as well as food
additives and pesticides, produce free radicals.
Most Americans do not eat enough fruits, vegetables, and whole grains, which
are the chief sources of antioxidant nutrients, including vitamins A,
C, and E,
the carotenoids, and selenium,
a trace mineral. Research suggests that such deficiencies can result in premature
aging of tissues, weakened immunity, and increased risk of heart disease, cancer,
and other degenerative diseases.
Antioxidants, Aging,
and Immunity
Antioxidants exert the following protective effects:
Antioxidant nutrients slow aging of cells and body tissues.
Supplemental antioxidants may significantly boost immunity in the elderly.
In one clinical trial, multi-nutrient supplements containing three to four
times the RDA for vitamin E and beta-carotene halved infection rates in people
over 65.
Higher dietary intakes of vitamin C and E may halve the risk of cataracts.
Antioxidants and Heart
Disease
Evidence indicates that elevated cholesterol levels alone do not produce atherosclerosis
(clogged arteries), the primary cause of heart attacks and strokes. Instead, atherosclerosis appears to be initiated by oxidation of the
lipids (fats) that carry cholesterol in the blood. Antioxidant vitamins and
food factors have been shown to inhibit oxidation of blood lipids in the test
tube. The following list is a sample of the evidence in favor of a heart-protective
effect of antioxidants:
A 10-year Harvard Medical School study involving 22,000 male physicians found
that among the participants with a history of heart disease, those who took
50 mg of supplemental beta carotene every other day experienced half as many
heart attacks, strokes, and deaths as those taking a placebo.
Of 120,000 health professionals surveyed in a Harvard University study, those
who took daily vitamin E supplements (100 IU or three times the RDA) for two
years had a 40 percent lower risk of heart attacks and strokes.
The Journal of Clinical Nutrition reported that the most reliable
risk factor for heart disease is a deficiency of vitamin E.
UCLA researchers who analyzed a 10-year federal health survey found that
in comparison with men consuming less than the RDA for vitamin C, those consuming
five times as much (300 mg/day) enjoyed a 42 percent lower risk of death from
heart disease and a 35 percent lower risk of death from all causes.
Antioxidants and Cancer
The anti-cancer effects of antioxidant supplements remain uncertain, because
they have not been tested in long-term clinical studies. But population studies
strongly suggest antioxidant-rich diets are cancer-preventive:
The National Cancer Institute says that most population studies link diets
high in beta-carotene (i.e., fruits and vegetables) to low rates of lung cancer.
UC Berkeley researchers report similar findings concerning vitamin C and cancers
of the mouth, throat, and stomach.
Most relevant studies suggest people in the top 25 percent of vitamin C intake
(380 mg/day, or five times the RDA) have half the cancer risk of those in
the bottom 25 percent.
University of Arizona researchers found that three to six months of daily
beta-carotene supplements reduced pre-cancerous mouth lesions in 70 percent
of subjects.
The American Journal of Epidemiology has reported that vitamin E supplements
reduced the risk of oral cancers by 50 percent. And in an Italian study, selenium
supplements (300 mcg) halted growth of pre-cancerous oral lesions.
Vitamin C
During the 1970's, two-time Nobel Laureate Linus Pauling made expansive health
claims for supplemental vitamin C. At the time, other scientists dismissed his
views. Has anything changed?
More recent evidence seems to vindicate much, if not all, of Dr. Pauling's
enthusiasm for vitamin C. UCLA medical researchers made big news when they found
that people getting the most vitamin C (300 mg/day) have the lowest rates of
heart disease and cancer, and live the longest. (Differences in exercise, diet,
and lifestyle among the 11,000 study participants were taken into account.)
Yet, a 1985 survey of 4,000 Americans indicated that anywhere from one to four
in five were not getting the recommended daily allowance of vitamin C (60 mg)
from their diets. The best food sources are vegetables and citrus fruits, which
offer other essential nutrients, plus health-promoting fiber and phytochemicals.
Cold Comfort. There's ample proof that vitamin C boosts the efficiency of key immune cells. The supplement skeptics at the
Center for Science in the Public Interest who reviewed the evidence concluded
that regular consumption of vitamin C does not prevent colds, but reduces
their duration and severity. One well-designed study found that participants
taking 1,000 mg every day had 19 percent fewer colds, which were 38 percent
shorter in duration.
Vitamin E: A Change
of Heart
For decades, physicians ignored evidence that supplemental vitamin E can provide
impressive preventive health benefits. Now evidence supports and even expands
the early promise of this antioxidant nutrient. Four large scale studies have
examined the effects of dietary vitamin E on risks of developing heart disease
and on deaths from heart disease. While currently there is no proof that supplemental
vitamin E reduces death rates from heart disease, the weight of evidence indicates
that supplemental vitamin E does reduce the risk or severity of heart disease.
As Harvard University researchers concluded in a January, 2000 review of the
evidence, "...studies consistently support an effect of vitamin E supplementation
on reducing risk of coronary heart disease. The evidence suggests that the major
effect, if any, is found at supplemental intake levels at or greater than 100
IU/d [100 IU per day]." Yet, it is very difficult to get even the recommended
daily intake (22 IU) from foods.
Multiple Benefits. Research suggests that vitamin
E offers many other critical benefits:
Multi-nutrient supplements containing three to four times the RDA for vitamin
E and beta-carotene halve infection rates (colds, flu, strep, etc.) in people
over 65. Animal studies consistently confirm such immune-boosting effects.
Vitamin E can prevent and treat many neurological conditions, and several
disorders relating to malabsorption and maldigestion of nutrients, including
gluten sensitivity. (Consult your physician.)
Supplemental vitamin E may reduce muscle fatigue, soreness, inflammation,
and tissue damage following aerobic exercise. Very high doses of supplemental
vitamin E (2,000 IU or 7 times the US RDA) may delay the progression of
symptoms in moderately severe Alzheimer's disease.
Radical Theory. Vitamin E made headlines when
cardiovascular experts announced startling new findings. It was long thought
that dietary cholesterol and fat are the key factors promoting atherosclerosis
(clogged arteries), which is the chief cause of heart attacks and strokes,
but new findings led most researchers to conclude that atherosclerosis develops
only when fatty compounds that transport cholesterol through the bloodstream
become oxidized by unstable free radicals.
Researchers already knew that vitamin E prevents unhealthful blood clots
and improves circulation; now vitamin E has been shown to block oxidation
of blood fats. Together, these facts explain the following:
Dietary deficiency of vitamin E is one of the most reliable risk factors
for predicting development of heart disease.
Of 120,000 health professionals participating in a study, those who took
daily vitamin E supplements containing three times the U.S. government's
RDA (Recommended Daily Allowance) levels over a two-year period cut their
risk of heart attacks and strokes by 40 percent.
Supplemental "E" Thirty percent of
young children do not get the full RDA from their diets, and the average adult
consumes only 30-50 percent of their RDA (10 IU). Many researchers now recommend
400-600 IU per day of supplemental "E" for adults, and up to 200
IU for children aged one to 10. The new RDI's have been set at 22 IU of natural
E, with a maximum safe level of 1,500 IU.
Vitamin E is available in natural (d-alpha tocopherol) and synthetic (dl-alpha
tocopherol) form. There is strong evidence that natural "E" is more
potent than synthetic vitamin E, which is why the Institute of Medicine has
set a higher RDI for the synthetic form (33 IU, maximum safe intake of 1,100
IU).
If you have blood pressure or clotting problems, consult your doctor before
taking vitamin E.
Exciting New Antioxidants
Essential antioxidant nutrients like vitamin C, vitamin E, beta-carotene, and
selenium remain the top priorities of any disease-preventive diet. But research
suggests that additional antioxidants promise even greater preventive power:
Carotenoids are a group of antioxidant, red-yellow plant pigments.
Beta-carotene is the most
famous—but not necessarily the most effective—disease-preventive
carotenoid: lutein and lycopene may reduce the risk of many cancers, including cancers of the prostate, esophagus,
stomach, and pancreas.
Lipoic acid. Lipoic acid (also called alpha lipoic
acid) is a potent, sulfur-based antioxidant, soluble in water and fat—uncommon
attributes that give it the rare ability to duplicate the effects of vitamins
C and E and neutralize many kinds of damaging free radicals. Lipoic acid is
most often prescribed to provide extra antioxidant and metabolic support to
persons with diabetes, cirrhosis, and heart disease-conditions in which free
radical stress plays an important role.
Lipoic acid is also used in AIDS cases, in part because patients often cannot
eat well, and it is essential to the efficient extraction of energy from carbohydrates.
Athletes also use lipoic acid to maximize energy levels, and to help reduce
lactic acid build up in working muscles. The best food sources are liver and
yeast.
Because lipoic acid enhances metabolism of sugars, diabetics should consult
a physician before taking it.
OPCs (oligomeric
proanthocyanidins) or pycnogenols
(pronounced pick-noj-en-awls) are terms used to describe plant-derived complexes
of extremely potent antioxidant compounds. As polyphenol flavonols, OPCs are
closely related to the catechins that make green tea a potent anti-cancer
food. But OPCs have somewhat different properties and are found in grape seeds,
pine bark, and a wide variety of berries. In test tube experiments, OPC complex
displays about 50 times more antioxidant activity than vitamin E, and 20 times
more than vitamin C.
OPCs act alone and in concert with vitamin C to protect and heal connective
tissue-that is, blood vessels, collagen, and cartilage. In Europe, approved
medical uses of OPCs include treatment of varicose veins, venous insufficiency,
and inflammation related to injury or surgery. But based on its known properties,
and its relative scarcity in the modern diet, OPC may be one of the most important
new preventive/therapeutic supplements.
Pycnogenol, alternatively, describes OPCs. The term pycnogenol is also now
trademarked for a proprietary OPC product extracted from pine bark. It is
important to note that pine bark-derived OPC products such as pycnogenol lack
B2-3'O-gallate, the most potent of all OPC antioxidant compounds. In addition,
most of the research into OPCs has employed grape
seed extract—not pine bark extract.
