By Anne Chiavacci, R.D., M.S., M.A.
Brigham and Women's Hospital
For generations our parents have said, "An apple a day keeps the
away." Compelling scientific research during the last several
suggests that they may be right. The simple message, "Eat 5 to 10
servings of fruits and vegetables daily" has been shown to pack a
powerful payoff for disease prevention.
In two large Harvard-based studies of about 110,000 people, those
averaged 8 or more servings of fruits and vegetables a day were 30%
likely to have a heart attack or stroke than those who ate less than
What Counts as a Serving?
One serving equals
1 cup leafy greens, berries or melon chunks
½ cup other fruits and vegetables
1 medium fruit/vegetable (such as apple, orange or tomato)
What's So Unique About Fruits and Vegetables?
Fruits, vegetables, whole grains and spices are the sole source of
phytonutrients. (Phyto is the Greek word for plant.) These are
compounds that give plants their color, flavor, smell and texture.
Phytonutrients are the immune system of a plant. They protect plants
from disease and they can protect you too!
There are as many as 2,000 known phytonutrients. Just one serving of
vegetable or fruit may possess more than 100 different types.
Let's look at phytonutrient families and their role in health
Broccoli, cabbage, cauliflower, Brussels sprouts, bok choy, dark
Cruciferous vegetables contain phytonutrients that may prevent
and interfere with the growth of cancer cells.
Indole-3-Carbinol (I3C), (converted to diindolylmethane in the
stimulates the liver to transform the tumor-promoting forms of
to the weaker and safer form, thus decreasing risk of breast and
cervical cancer. Test-tube and animal studies have shown I3C to
interfere with prostate cancer cell growth, and it also may be
against growth of tumors of the lung and colon. I3C is effective in
treating precancerous cervical dysplasia.
I3C and another phytonutrient found in cruciferous vegetables,
sulforaphane, help the liver "detoxify." This means that they turn
the cleaning agents in the liver, called enzymes, to change harmful,
cancer-causing chemicals to forms that the body can get rid of.
Berries, cherries, red and purple grapes, currants, pomegranates,
walnuts, apples with skin, citrus, red onions, tomatoes, bell
red wine, grape juice
Researchers are interested in ellagic acid as a potential
cancer-fighting agent. Most of the studies to date have been done in
test tubes and animals. Ellagic acid interferes with steps that
cancer cells to keep multiplying. It also causes apoptosis, which is
cancer cell death. Ellagic acid also stimulates the detoxification
enzymes in the liver.
Glucarate neutralizes several cancer-causing compounds such as
heterocyclic amines, which form when cooking animal protein at high
temperatures. It also may play a role in estrogen-related cancer.
Glucarate blocks the enzyme that allows estrogen to be reabsorbed
the blood from the bile in the digestive tract.
Flavonoids resveratrol and quercetin may provide protection against
heart disease by decreasing inflammation, hindering the clumping of
platelets, and protecting cholesterol from being changed to unsafe
Anthocyanins interfere with the enzyme in the liver that makes
cholesterol. These flavonoids also have antitumor actions.
Among flavonoid-rich foods, apple consumption appears to be
with decreased risk of diabetes in a Harvard-based study of 40,000
women. Those who consumed at least one apple a day showed a
28% reduced risk of type 2 diabetes compared with those who did not
Red, green, yellow and orange vegetables and fruits, such as
carrots, sweet potato, squash, broccoli, dark leafy greens,
corn, peppers, mango, guava, apricots, peaches, cantaloupe,
red grapefruit, oranges, tangerines
Beta-carotene is a familiar carotenoid to many, yet it is only one
more than 600 compounds in the carotenoid family that have been
discovered to date. Alpha-carotene, cryptoxanthin, lycopene, lutein
zeaxanthin also have notable health benefits.
Carotenoids have been linked with prevention of colon, prostate,
and lung cancer. Two large Harvard studies of more than 124,000
showed a 32% reduction in risk of lung cancer for those who consumed
variety of carotenoid-rich foods. However, carotenoid supplements in
pill form have not demonstrated the same protective benefits. In
two studies found beta-carotene supplements to be associated with
risk of lung cancer and death in smokers.
The Women's Healthy Eating and Living (WHEL) study evaluated the
concentration of total carotenoids in the blood of more than 1,500
who had completed treatment for early-stage breast cancer. Women
the highest carotenoid concentration had a 43% reduction in risk of
cancer recurrence compared with those who had the lowest level of
Lutein and zeaxanthin are the two primary carotenoid pigments in the
eyes that protect the macula and retina from photo damage. Studies
suggest that approximately 10 milligrams of dietary lutein daily may
reduce the risk of developing age-related macular degeneration and
cataracts. One cup of cooked kale or spinach has three to four times
this recommended dose!
D-limonene, limonin and nomilin are among about 40 limonoids found
the peel, membranes, seeds, flesh and juice of citrus fruits. These
powerful compounds have anticancer activity and turn on the liver's
detoxification processes to rid the body of cancer-causing agents.
The Bottom Line
Distinctive health benefits are often related to the intensity of
of the plant. Most phytonutrients are not lost in cooking because
Aim to consume a complete color spectrum of fruits and vegetables
Make it your goal to eat at least two servings by noon each day.
your thinking to create a meal around vegetables and fruits and fill
half your plate with color. Savor the skins and add orange and lemon
zest to breads, casseroles and desserts.
In this case, more is better! Be mindful that medicine is in your
Anne Chiavacci, R.D., M.S., M.A., is a senior nutritionist at
and Women's Hospital and Dana-Farber Cancer Institute. She received
Bachelor of Science in nutrition from the University of
Amherst and her Master of Science in nutrition at Tufts University.
Chiavacci completed her dietetic internship at Frances Stern
Center, New England Medical Center in Boston. She has a Master of
in counseling from the Biblical Theological Seminary in Hatfield, Pa.