Expert Advice

Ask the Joslin Dietitian

Q. What does an eating plan for a pregnant woman look like?

A. Interestingly, it looks similar to a healthy eating plan for an adult woman who isn't pregnant, just with more calories and special attention to certain vitamins and minerals. During pregnancy women should eat plenty of fresh fruits and vegetables, whole grain products, lean meats or meat substitutes and lowfat dairy foods. Foods with little nutritional value, such as sweets and fats, should be consumed sparingly. You should also drink plenty of fluids, although avoid drinking alcohol, and limit caffeinated beverages. During the second and third trimesters of pregnancy your body and the baby's body are growing so you need about 300 more calories and about 10 extra grams of protein each day. In addition, you need additional iron, calcium, zinc, folic acid and B6 for your baby's growth.

Because it is important to get enough folic acid in the months before you conceive, your diet should contain plenty of foods with naturally occurring folate, such as orange juice, green leafy vegetables, beans, peanuts, broccoli, asparagus, peas and lentils. To make sure you meet your vitamin and mineral needs, your health care provider will likely prescribe a prenatal multivitamin. Protein, calorie and calcium requirements can easily be met from food sources. By having three servings from the milk group, four servings from the vegetable group, two to three servings from the fruit group, two to three servings from the meat or meat substitutes group, and seven to nine servings from the bread/grain group, you will be on your way to a nutritionally healthy pregnancy.

These recommendations are for healthy adult women. Teenagers and women with special needs should contact their provider or a registered dietitian for specific advice.

The following Web sites provide additional information on pregnancy and nutrition:

• USDA Food and Nutrition Information Center Lifecycle Nutrition: http://healthymeals.nal.usda.gov
• U.S. Centers for Disease Control and Prevention (CDC): www.cdc.gov/ncbddd/bd/abc.htm

Q. I finished chemotherapy for estrogen receptor positive (ER-positive) breast cancer this past April. I take tamoxifen and have been advised by my doctor to avoid foods that contain estrogen. Although avoiding all estrogens in foods is probably impossible, I would still like to know what are some common foods with high amounts of estrogen or phytoestrogens, such as soy, flax and wild yams, that I should avoid?

A. You are certainly on the right track. The goal for people who have had breast cancer and/or are taking tamoxifen is to avoid a diet high in phytoestrogens, but not to avoid all sources, as more than 300 foods have been found to contain some level of these substances. Depending on the source (both food or supplement) and its preparation, the phytoestrogen content of similar products can vary widely. Phytoestrogens are naturally-occurring substances found in plants that can either mimic the actions of estrogen in the body or work against the body's estrogen. Because phytoestrogens can cause tissue growth, women who have had breast cancer are cautioned against ingesting large amounts of these compounds. Additionally, studies have found that genistein, a type of phytoestrogen, prevented the tumor suppressive action of tamoxifen.

There are three classes of phyoestrogens:

• Isoflavonoids, found in legumes, with soybeans being the major dietary source of this compound.
• Lignans, found in cereal bran, beans, fruits and vegetables, with flaxseed having the highest amount.
• Coumestan, found in peas, pinto and lima beans, with alfalfa and clover sprouts having the highest amounts.

Wild yam, by the way, is not related to sweet potatoes or yams that we often eat in the United States. The root of the wild yam is used to make supplements that some women take to treat menopausal symptoms or osteoporosis, but there's no evidence that it's effective. Always talk to your health care provider before taking any supplement. You should definitely avoid taking phytoestrogen-based supplements, such as soy isoflavones or black cohosh. Also, reduce your intake of soy products (e.g., tofu, miso, tempeh, soymilk), flaxseed, alfalfa and clover to keep your phytoestrogen intake close to the United States average, which is considered quite low.

More information on diet and cancer prevention and therapy can be found at:

• American Institute of Cancer Research: www.aicr.org
• American Cancer Society: www.cancer.org

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