vitamins and minerals are classified as antioxidants. An antioxidant is a substance
that reduces cellular damage. Our bodies produce some antioxidants naturally.
Certain foods are also good sources of antioxidants. It’s well accepted
that eating foods rich in antioxidants is a healthful thing to do. The jury
is split on whether or not to use vitamin supplements to further boost antioxidant
intake. Some studies show benefit from supplementing with antioxidant vitamins,
while other studies aren’t so conclusive.
Oxidation is a process by which damage occurs as a result of contact with
oxygen. Oxidation of iron results in rust, as illustrated by a nail that’s
exposed to air. Food spoilage happens, in part, because of exposure to oxygen
in the air. Even though oxygen is essential to humans, we aren’t exempt
from oxidative damage. We won’t rust or spoil; the damage is more discreet.
Oxidation leads to the formation of “free-radicals.” Free radicals
form from normal cellular processes. Environmental hazards can increase free
radical production. Exposure to the sun’s damaging rays, car exhaust,
ozone, cigarette smoke, drugs, poisons, and pesticides can all amplify free
radical production. (It’s not enough to take care of ourselves; we must
take care of our environment!)
Free radicals are unstable molecules that can damage cells and tissues and
can interfere with the immune system. Free radicals are also implicated in heart
disease because they favor plaque formation in the arteries, which can lead
to atherosclerosis. Free radicals are partially to blame for cataract formation,
arthritis, and even the effects of aging.
An antioxidant is a substance that prevents oxidative damage caused by free
radicals. Antioxidants hold promise in preventing and treating diseases like
cancer and heart disease. The benefits that antioxidants play in diabetes are
still unclear and are under study. Certain nutrients have natural antioxidant
qualities. Vitamin C, vitamin E, beta-carotene, and selenium all act as antioxidants
to protect the body from oxidative damage. Fruits and vegetables are naturally
chalk full of antioxidants. To reap the benefits, eat at least 5 servings per
day from a combination of fruits and vegetables. (A serving is approximately
1 small piece, or 1/2 cup. The exchange lists can be used for portioning.) Green
tea also has antioxidant activity.
Tip: Eat at least five servings per day from a combination of fruits and vegetables.
Recommended Dietary Allowance (RDA): The average daily dietary intake level
that’s sufficient to meet the nutrient requirement of nearly all healthy
Adequate Intake (AI): A recommended intake that’s assumed to be adequate
for healthy individuals. This is used when RDAs cannot be determined.
Tolerable Upper Intake Level (UL): The highest level of daily nutrient intake
that’s likely to pose no adverse risks for most people.
Besides acting as an antioxidant, vitamin C has many other useful functions.
Among other things, it’s important for wound healing and fighting infections.
It also facilitates the absorption of iron; so if you take an iron supplement,
eat a food rich in vitamin C at the same time and you’ll absorb the iron
better. Vitamin C is a water-soluble vitamin. Some of the vitamin C in foods
is lost when the foods are cooked. Steaming or rapid cooking in a small amount
of water can help to preserve the vitamin C content of foods. Raw foods contain
the maximum amount of vitamin C.
When most people think of vitamin C, they think of orange juice. Sure, oranges
are a great source of vitamin C, but so are many other foods.
The following foods are all rich in vitamin C:
Greens (cabbage, spinach, collard, turnip, mustard, kale)
Vitamin C Requirements
Recommended Dietary Allowance (RDA) for Vitamin C (in milligrams per day)
Adult women: 75
Pregnant women: 85
Lactating women: 120
Adult men: 90
The Tolerable Upper Intake Level (UL) for all adults is set at 2,000 milligrams
Caution: Supplementation with vitamin C at the upper intake levels may cause
upset stomach and diarrhea.
Vitamin E “Tocopherol”
Vitamin E is a fat-soluble vitamin. This vitamin is not lost by most cooking
methods, except the high heat of deep-frying. The main function of vitamin E
is to serve as an antioxidant. Fruits, vegetables, and grains supply some vitamin
E, but salad oils and margarine supply the most. Vitamin E deficiency is very
The following foods provide vitamin E
Green leafy vegetables
Tip: As you probably noticed, many foods rich in vitamin E happen to be high
in fat. If you’re trying to lose weight, you shouldn’t eat more
fat; instead you may choose to supplement vitamin E.
Vitamin E “Tocopherol” Requirements
Recommended Dietary Allowance (RDA) for Vitamin E (in milligrams per day)
Adult women: 15
Pregnant women: 15
Lactating women: 19
Adult men: 15
The Tolerable Upper Intake Level (UL) for all adults is set at 1,000 milligrams
Tip: Vitamin E is sometimes measured in international units. To convert from
milligrams (mg) to international units (IU), multiply by 1.5.
For example: 15 mg = 22 IU, and 19 mg = 28 IU.
Beta-carotene is in the class of nutrients known as carotenoids. There are
more than 600 types of carotenoids. Carotenoids, abundant in fruits and vegetables,
have antioxidant properties. People who consume diets that are high in fruits
and vegetables appear to have less risk for developing certain diseases, including
cancer, stroke, and heart disease. Although eating fruits and vegetables has
been shown to have health benefits, isolating individual carotenoids and taking
them in pill form has not always shown clear-cut health benefits. Supplementation
study results range from positive effects to negative health outcomes. Supplementation
of carotenoids is not a replacement for eating whole foods.
Beta-carotene’s other important role is that it’s converted to
vitamin A in the body. Vitamin A is necessary for vision, healthy skin, fighting
infections, reproduction, and normal growth and development. Beta-carotene is
a fat-soluble nutrient. Cooking doesn’t destroy it. A very large intake
of dietary carotenoids can produce a yellowing of the skin, as avid drinkers
of carrot juice can attest!
The following fruits and vegetables are rich in beta-carotene:
Leafy greens (lettuce and all cooked greens)
Red bell peppers
No RDAs have been set for beta-carotene. Until more supplementation studies
are done to prove safety, carotenoids should be obtained from a healthful intake
of fruits and vegetables and not from a pill, unless under medical supervision.
Selenium is a trace mineral. Selenium works in partnership with vitamin E
prevent oxidative damage. The selenium content of food varies according to
where it was grown, as soil and water selenium concentrations vary. Selenium
deficiency in the United States is very rare.
The following foods are good sources of selenium:
Recommended Dietary Allowance (RDA) for Selenium (in micrograms per day)
Adult women: 55
Pregnant women: 60
Lactating women: 70
Adult men: 55
The Tolerable Upper Intake Level (UL) for all adults is set at 400 micrograms
If you aren’t sure whether you should take a vitamin or mineral supplement,
you may want to contact a registered dietitian. A registered dietitian can evaluate
your diet and your medical history to determine if a supplement could be beneficial.
To find a registered dietitian in your area, call 1-800-366-1655.
SHERRI SHAFER received her BS in Nutrition and Dietetics from the University
of California at Berkeley. She has been a Dietitian at UCSF Medical Center for
10 years. Sherri specializes in medical nutrition therapy counseling for individuals
in adult and pediatric diabetes clinics, and is an Instructor for classes on
diabetes self management for Type 1 and Type 2 diabetes. She has just completed
her first book, Diabetes Type 2 Complete Food Management Program from Prima