Ask the nutritionist: Nutrition can vary among varieties of lettuce
Q: I've heard that lettuce varieties have different nutritional value and some aren't worth eating. Is that true?
A: Yes. And no. There are many types of lettuce, and it's hard to go wrong with any of them. All are loaded with water and they have some fiber, which reduces the risk of colorectal cancer. The popular iceberg lettuce makes a crunchy salad and includes some vitamin K, folate, and beta-carotene, which converts to vitamin A.
Other types of lettuce provide even more vitamins and phytonutrients.
A cup of Boston or bibb lettuce provides more than six times as much beta-carotene as iceberg, and dark green or red leaf lettuce contains even more — about the same amount that's in half a small carrot. These lettuces are also high in lutein, another carotenoid that links to eye health. One cup of romaine gives you more than 80 percent of the recommended amount of vitamin A and more than half of vitamin K. Romaine also contains the B vitamin folate that helps maintain healthy DNA and may play a role in protecting against cancer.
You may also have seen the mixture of field greens called mesclun. Some mixes include mainly mild-flavored greens such as baby oak leaf and romaine, while other blends contain more peppery flavored greens, such as arugula and mustard. In general, nutrients in these greens are similar to that of romaine or leaf lettuce: high in beta-carotene and folate.
Whatever type of lettuce you choose as your salad base or in your sandwiches, all are less than 10 calories a cup and can help keep you full without many calories. By mixing up your lettuce choices, you'll keep your salads interesting and pack in a variety of vitamins and other cancer protective compounds.
Q: Is it true that pomegranates help prevent prostate cancer?
A: Research showing possible effects of pomegranates and pomegranate juice against prostate cancer is underway, but results are tentative. The majority of research comes from cell and animal studies, with few cancer-specific studies in people.
Pomegranates have a high amount of polyphenols, a group of compounds that have shown antioxidant and anti-inflammatory effects in lab studies. One polyphenol — punicalagin — is unique to pomegranates. During digestion, our body produces urolithins from punicalagin and related polyphenols. In laboratory studies, these urolithins have decreased prostate cancer cell growth and its ability to spread.
Human studies have shown that pomegranate juice or extract can raise blood levels of antioxidant compounds, although people vary in their response. Two small intervention studies found that drinking one to three cups of pomegranate juice or equivalent in extract daily significantly slowed the rise of PSA levels in men with early stage prostate cancer. No studies have found effects in men with advanced prostate cancer.
The high polyphenol content of pomegranates and laboratory-based anti-cancer effects show exciting potential, but we're far from having a basis to recommend pomegranates for prostate cancer protection. Nevertheless, while we wait for more research, there are many nutrition and taste reasons to enjoy pomegranate juice and the arils — the red seed pods inside the fruit. Mix the arils in salads, hot or cold cereal, yogurt, smoothies, rice and many other foods.
• The American Institute for Cancer Research is the cancer charity that fosters research on the relationship of nutrition, physical activity and weight management to cancer risk, interprets the scientific literature and educates the public about the results. AICR has published two landmark reports that interpret the accumulated research in the field, and is committed to a process of continuous review. AICR is a member of the World Cancer Research Fund International.