Presented by: Erika Connor, RD, CSO
Dietitian, Cancer Supportive Care Program
Stanford Hospital and Clinics
September 22, 2011
For people diagnosed with cancer, one of the first places they turn to is the Internet. But when it comes to advice on what to eat, and what foods, vitamins, and supplements are helpful or harmful to cancer progression, the barrage of information can be overwhelming and contradictory.
“There are lots of grey areas because there are always new studies coming out and we are always learning new things that can challenge what you read and what people tell you,” said Erika Connor, RD, CSO, an oncology dietitian at the Stanford Cancer Center, who spoke at a presentation sponsored by Cancer Supportive Care and the Stanford Health Library.
Connor’s expertise is especially important because nutrition for cancer patients can sometimes seem contrary to conventional wisdom. Patients often need to focus on weight gain and have to deal with food restrictions as well as loss of interest in food and inability to keep food down. Many look to nutritional supplements to complement their diet during treatment.
“As dietitians we help patients navigate the many health claims made about food and supplements, herbs, or other remedies available to complement their diet while maintaining safety,” she said. “My first question to patients taking supplements is, ‘Does your doctor know?’ I try to not take anything away unless I know something is not safe. It’s important to look at the big picture. Food can be a friend or a foe. People with cancer want control of their life, and nutrition is one thing you can control.”
Almost 45 percent of cancer cases could be prevented with a high-fiber, plant-based diet, she said. Avoid processed foods and additives, and increase your intake of fluids and whole foods. Use color as a dietary guideline to include healthful foods like broccollini, pomegranates, blueberries, and carrots.
Connor advises everyone to try to reduce intake of red meat and alcohol, stay active, and keep the weight down. She provided guidance on several of the most common dietary quandaries:
All cells use glucose for energy and will make it from protein or fat if it’s not available in the diet. That means you cannot starve cancer cells by limiting sugar intake without affecting the healthy cells in your body as well. However, Connor said, there’s a tremendous difference between the natural sugars found in fruit, nuts, and grains, and the “hidden” sugar in sweetening substitutes. When it comes to added sweeteners, she sees no difference between table sugar and honey, agave, and corn syrup in regard to their effect on body weight and insulin.
“I look at them as the same. All are equal in calories and none are really better than another,” she said. “The more important question is how much are you using? The more sugar you use, the more of a craving you create. It’s important to make your body work for its energy source.”
She advises to focus on eating fresh, whole food and limit processed foods of any kind to help your palate adapt to less sweet food. Consume no more than 6 tsp (100 calories) from added sugar for women daily and no more than 9 tsp (150 calories) for men.
Read labels to be aware of hidden sugars: Plain yogurt has about 100 calories and 7 grams of carbohydrates; flavored versions have 140 calories and 20 grams of carbohydrates—almost 3 teaspoons of added sugar. She also suggests sticking to fruit rather than fruit drinks to avoid added sugar.
Many cancers—including head and neck, esophageal, breast, colorectal, and possibly liver—have been linked to alcohol intake. While some studies say the antioxidants found in alcohol may slow some types of tumor growth and reduce cancer risk, Connor said that in reality drinking increases cancer risk and can abet weight gain, which is a proven and significant risk.
“In terms of cancer, there is no safe level of alcohol,” she said.
Some studies suggest a close link between ovarian cancer and whole-fat milk, particularly in women with low levels of a galactose enzyme called GALT. Though not common, a GALT test is available, and women with low GALT levels may want to limit their dairy intake. Even low-fat and skim dairy caused an increase in ovarian cancer in these women, Connor said. Prostate cancer has been linked to calcium intake from both food and supplements in several studies. On the other hand, calcium may protect against colon cancer.
Most people should aim for between 100-1200 mg of calcium a day. Take in only two-three servings of dairy a day for healthful calcium and vitamin intake. People with prostate or ovarian cancer should look to non-dairy foods that are rich in calcium, such as sardines with bones, figs, fortified orange juice, and dark leafy greens like kale and bok choy. Yogurt is preferable to milk.
More than 18 ounces of red meat (including pork and lamb) or processed meat (such as deli meat, bacon, and ham) a week has been shown to increase colorectal cancer risk. One study showed that people who ate 3.5 ounces of red meat a day increased their risk of colorectal cancer by 17 percent. Those who ate 3.5 ounces of processed meat a day increased their risk by 36 percent.
Risk is compounded when meat is cooked on the grill, which introduces cancer-causing compounds. Charred vegetables do not have the same negative effects as charred meat, chicken, or fish, Connor added.
Focus on adding more vegetables to your diet, she said. If you do like to grill, try to precook the meat, marinate for at least 30 minutes, trim off the fat, and use low grilling heat.
Coffee and Caffeine
There’s little evidence that caffeine promotes cancer. In fact, coffee is actually a rich source of antioxidants and phytochemicals, and may lower the risk of colorectal, bladder, pancreatic, prostate, and esophageal cancers. One study showed that caffeine may reduce the odds of developing breast cancer. Another found that heavy coffee drinkers have a lower risk of prostate cancer.
Most people can handle two to four cups (300 mg) of coffee a day. Levels of caffeine vary from 120 mg in a cup of black tea to 35 mg in green tea and 75 mg in espresso, and even decaffeinated drinks have enough caffeine to provide some benefit. But be aware that caffeine can be addictive, Connor said, and can induce headaches and insomnia. “Moderation is key,” she added.
Antioxidants may protect cells from damage caused by unstable molecules known as free radicals, including cancer. However studies are contradictory and the benefits of antioxidants remain very controversial. In fact, antioxidants’ affect on free radicals could actually interfere with cancer therapies, Connor said.
Studies have shown antioxidants counteract some of cancer therapy’s side effects; others show they serve to protect tumor cells. Two large clinical trials showed beta carotene increased lung cancer in smokers.
Connor advises patients to avoid antioxidants in general during cancer treatment. “Eat blueberries, but not antioxidant supplements,” she said.
Despite Linus Pauling’s pivotal research in the 1970s that found large doses of supplemental Vitamin C improved cancer outcomes, new studies have shown that, although Vitamin C plays an important role in the immune system, it does not appear to improve longevity or outcome. However Vitamin C from food may reduce incidence of mouth, stomach, lung, and other cancers. Vitamin C supplements appear to have no effect.
Connor suggests you eat food high in Vitamin C throughout the day since your body cannot absorb more than 200 mg a day. Foods high in Vitamin C include orange juice, whole oranges, strawberries, cooked broccoli, red pepper, and guava.
Soy and Isoflavones
Stick to soy foods like tofu, soynuts, tempeh, and soy milk rather than processed soy products. “Eat real food and stay away from processed foods in general,” Connor said. “Look at the ingredient list: If it says concentrated soy protein, don’t bother with it.”
Despite concerns about the estrogen found in soy products, she said that new research shows that soy is not associated with increased risk for breast cancer. “If you are a breast cancer survivor, don’t add extra soy to your diet, but you don’t need to avoid it completely either,” she said.
About the Speaker
Erika Connor, RD, CSO, an oncology dietitian at the Stanford Cancer Center, provides nutritional guidance for patients dealing with side effects of radiation and chemotherapy. Her services are offered free to cancer patients by appointment through the Cancer Supportive Care Program: Sessions can be arranged by calling 650-498-6000.
For questions about the Cancer Supportive Care Program, call 650-723-4268 or 650-725-9456.
For More Information:
Stanford Cancer Center
National Institutes of Health
Center for Complementary and Alternative Medicine
Office of Dietary Supplements
American Cancer Society