Plant-Based Diet Lowers Risk of Aggressive Prostate Cancer, Study Says

Prostate cancer is the second most common cancer in American men, after skin cancer. In 2021, about 248,500 men were diagnosed with prostate cancer, and about 34,000 men died of the disease.

A new study published in the American Journal of Clinical Nutrition shows that a plant-based diet may blunt severe forms of prostate cancer and lower the risk of death from this disease.

"When looking at plant-based diets, we tend to see less processed options and more of an emphasis on whole foods, including fruits, vegetables, whole grains, nuts/seeds, and legumes," says Julie Balsamo, MS, RDN, a registered dietitian with Nutrition By Julie.

About the Study

For this prospective study, researchers used data from Health Professionals Follow-up Study, which followed 47,239 men over 28 years. Every 4 years, the men in the study filled out food frequency questionnaires to track their dietary habits.

Researchers were looking for associations between plant-based diets and the risk of advanced, lethal, and fatal prostate cancers among men of different ages. The researchers found that eating more plant-based foods was associated with a lower risk of advanced, lethal, and fatal prostate cancer for men aged 65 or younger. The associations were not found in men over age 65.

In men younger than 65, those who ate the most plant-based foods had a statistically significant reduction in risk of advanced prostate cancer, lethal prostate cancer, and death from prostate cancer compared with those eating fewer plant-based foods. In fact, their risk was reduced by more than one-third.

"It is not the least bit surprising that this new study shows a lower risk of prostate cancer linked to a plant-based diet since plant-based foods are filled with fiber, phytochemicals, vitamins, and minerals," says Rayna McCann, MS, RDN, CSO, CDN, a board-certified specialist in oncology nutrition and the founder of Happy Healthy Nutrition, LLC in Long Island, New York.

Why Plant-Based Eating Is Beneficial

A plant-based diet is one that includes mostly foods of plant origin, such as vegetables, fruits, whole grains, beans, lentils, nuts, and seeds. Some plant-based diets are exclusively vegan and contain no animal-based foods, while other people choose mostly plants, but also include smaller amounts of poultry, fish, meat, dairy, or eggs in their eating plan.

Plant-based diets are helpful as cancer-fighters because they contain vitamins, minerals, fiber, and phytochemicals, such as carotenoids, lycopene, indoles, and flavonols, explains Balsamo.

"Lycopene, the bright red pigment found in tomatoes and watermelon also has been shown to be beneficial in terms of protecting against prostate cancer," says Balsamo.

Fruits, vegetables, beans, nuts, seeds, and whole grains also are naturally high in fiber, she adds. Research has shown that a high-fiber diet may reduce hormone levels that could be involved in the progression of prostate cancer. Fiber also helps to remove toxins in our body by keeping the digestive system regular.

"As a general recommendation, aim for at least 25 grams of fiber a day from whole food sources," Balsamo says.

How Dairy Affects Prostate Risk

The American Institute for Cancer Research says that there is limited and suggestive evidence that diets high in dairy products or calcium may increase prostate cancer risk. This information is based on older studies, which found that men who drink two or more cups of whole milk daily had a greater risk of developing advanced prostate cancer.

Studies in more recent years have found this not to be the case. To date, the research on dairy, calcium, and prostate cancer is mixed.

A systematic review on dairy and prostate health from 2020 indicates that there are no formal clinical recommendations regarding the consumption of dairy products for people at risk for prostate cancer or who have a history of prostate cancer. More research is needed to determine the connection.

How to Add More Plants to Your Diet

Eating more plants is a great start, whether you choose to also eat animal-based foods or not. Studies show that the Mediterranean diet, which is mostly plant-based but does include some animal foods, is also associated with a lower risk of prostate cancer progression, because of its anti-inflammatory properties. So, you do not need to be fully vegan to reap the benefits of eating more plants.

"In my professional opinion, the ideal diet for prostate cancer prevention would be primarily plant-based, focusing on fruits, vegetables, nuts and seeds, whole grains, and legumes with a moderate intake of lean proteins, low-fat dairy, and seafood," says Balsamo.  

Fewer than 1% of participants in the prostate cancer study followed a strict vegetarian or vegan diet, but simply eating more plants had positive results. There is no pressure to be totally vegan to see benefits.

"Start your nutrition plan where you're at," says McCann. "Try basing your meals around plant-based foods. Small changes are still changes."

It also might help to think of it as eating a plant-centered diet. McCann indicates some of her clients find this concept less daunting and helps them create meals with their favorite vegetables, beans, and grains.

"If you hate kale, don't eat kale," says McCann. "Find plant-based foods that you enjoy.  It's a lifestyle and the choice is yours!"