Women with diets high in vegetables were more than 50% less likely to have long-lasting HPV infections, which also meant they might be less likely to develop cervical cancer, according a report in the journal Cancer Epidemiology, Biomarkers & Prevention (Vol. 11, No. 9: 876-884).

Researcher Rebecca L. Sedjo, MSPH, and colleagues from the University of Arizona found that both high vegetable intake and higher levels of cis-lycopene in the blood were less likely to be linked to persistent HPV infections.

An infection in the cervix with some strains of HPV is thought to be necessary in the development of most, if not all, cases of cervical cancer, said the authors. HPV is commonly spread through sexual contact.

But only a very small percentage of women infected with HPV will go on to develop the cervical changes that could lead to cancer. Most HPV infections seem to go away on their own after a short time. Persistent (long-term) infections, however, are more likely to lead to cervical changes.

Researchers aren’t sure why some women are more at risk for persistent HPV infection, and therefore cervical cancer. But a few risk factors have been identified, including smoking, other sexually transmitted diseases (STDs), and possibly oral contraceptives (birth control pills).

The role of diet in cervical cancer has also come under study in recent years, with several studies finding potential links to certain nutrients, or lack of them, in the diet.

Sedjo wanted to find whether levels of vitamin A and related nutrients in the diet or in the blood affected HPV persistence.

The study looked at more than 200 women who had tested positive for HPV in the Young Women’s Health Study. The women were tested for HPV infection at a first visit to a health clinic, and then again three and nine months later. At the three-month visit the women also answered a set of questions about their diet and had a blood sample drawn to determine nutrient levels.

The women were considered to have persistent HPV infections if they tested positive on two visits in a row.

The researchers found that a diet high in certain nutrients that come from vegetables raises levels of those nutrients in a woman's blood. This may shorten the length of cervical infection with the human papillomavirus (HPV), which may lower a woman’s risk of developing cervical cancer.

The researchers found that women who ate diets high in vegetables were more than 50% less likely to have persistent HPV infection, although no specific nutrient stood out as decreasing risk. Juices and fruits did not appear to be as protective.

When the researchers looked at the blood levels of vitamin A and carotenoids (nutrients related to vitamin A, such as beta carotene), they saw that women with the highest cis-lycopene levels also had more than a 50% decreased risk.

Lycopene is a nutrient responsible for giving some vegetables and fruits, such as tomatoes, pink grapefruit, and watermelon, their reddish color. It has been linked to a lower risk of prostate cancer among men in some studies. Scientists believe it may act as an antioxidant. (Cis-lycopene is a form of lycopene.)

The researchers stressed that although the study suggested a link, more investigation is needed. "These associations need to be assessed in larger…studies that include longer follow-up periods that include multiple measures of nutrient status and HPV status," they concluded.

Diets high in fruits and vegetables have been linked to lower rates of several kinds of cancer, as well as other serious diseases. The exact nutrients responsible for these effects are unknown, but are now being studied.

Until such relationships are better defined, all women can benefit from eating at least five servings of vegetables and fruits each day, as outlined in the American Cancer Society's nutrition guidelines.