BCCT/CancerChoices Take: MEAL Study: Effect of Eating Vegetables on Prostate Cancer Progression

This post was originally published on our predecessor site, BCCT.

In January 2020, a reputable journal published the “MEAL Study” which asked men on active surveillance for early stage prostate cancer to increase their vegetable intake.¹Parsons JK, Zahrieh D, Mohler JL, et al. Effect of a behavioral intervention to increase vegetable consumption on cancer progression among men with early-stage prostate cancer: The MEAL randomized clinical trial. JAMA. 2020;323(2):140–148. The men were expected to increase the amount of vegetables they ate to seven servings per day and received dietary counseling by phone. They were followed for two years to track cancer outcomes. 

The authors reached two conclusions: 

1. Men in this situation can increase their vegetable intake and maintain that eating pattern for two years.
2. This intervention did not significantly reduce the risk of prostate cancer progression compared to patients in the control group, who received only a handout with diet recommendations. 

Some critics say that the intervention wasn’t intense enough—there was not a big enough difference between the number of servings of vegetables eaten by men in the control group versus. the intervention group. 

Would a higher level of vegetable consumption make a difference?

Another criticism is that even though the intervention group increased their consumption of vegetables, there’s a good chance that they still didn’t reach the level needed to improve outcomes. The American Cancer Society (ACS) Guidelines on Nutrition and Physical Activity recommend eating at least 2½ cups (five servings) a day of fruits and vegetables.²American Cancer Society. ACS Guidelines on Nutrition and Physical Activity for Cancer Prevention. January 11, 2012. Viewed January 29, 2020. The intervention group—those who ate more vegetables—achieved an average of only two servings a day of the vegetables with the most cancer-fighting properties, and fewer than four servings a day of all vegetables, short of the of the ACS guidelines and far short of the study goal of seven servings a day.

Would a higher level of vegetable consumption make a difference? A clue is found in a breast cancer study which this current study referenced. Participants in that study ate substantially more vegetables (six to eight servings a day) and still did not reduce additional breast cancer events or mortality during a 7.3-year follow-up period.³Pierce JP, Natarajan L, Caan BJ, et al. Influence of a diet very high in vegetables, fruit, and fiber and low in fat on prognosis following treatment for breast cancer: the Women’s Healthy Eating and Living (WHEL) randomized trial. JAMA. 2007;298(3):289–298. However, in the breast cancer study, vegetables with higher cancer-fighting properties were not tracked, so we still don’t know if higher consumption of these vegetables—the broccoli family (brassicas), tomatoes, and dark yellow or orange vegetables high in carotene—would improve cancer outcomes. 

What else could affect outcomes?

Yet other critics say that you also have to look at what else is going on in the diet: Were the study subjects continuing to eat foods that might affect cancer growth and spread? Did they look at the men’s weight and weight loss or gain over the study period? Did they look at levels of physical activity?

The problem with conducting lifestyle intervention studies using the randomized controlled triala study design in which people are randomly assigned to either an experimental group or a control group to compare the outcomes from different treatments; an RCT is considered a strong design for determining a therapy’s effects is that it’s really hard to control for all the behaviors and conditions that people do and have in addition to the change being studied (in this case, increased vegetable intake). Though there are lots of good reasons to eat healthy vegetables, man (and woman) cannot live on vegetables alone. 

It actually is no surprise to BCCTBeyond Conventional Cancer Therapies (predecessor website to CancerChoices)/CancerChoices that a single change in behavior did not show up as making a difference in prostate cancer progression. In fact, we talk about the importance of an integrative approach to reduce the risk that early prostate cancer will progress to the point where treatment is needed.

In studies of those following Dr. Ornish’s program, we see several positive results:

• Slower progression or stable cancer in men with early stage or low-risk prostate cancer 
• Fewer men needing conventionalthe cancer care offered by conventionally trained physicians and most hospitals; examples are chemotherapy, surgery, and radiotherapy treatments
• Significant improvements in weight, abdominal obesity, blood pressure and lipid profiles

Our assessment

BCCTBeyond Conventional Cancer Therapies (predecessor website to CancerChoices)/CancerChoices’s take-away: Don’t put all your eggs in one basket. Consider an integrativein cancer care, a patient-centered approach combining the best of conventional care, self care and evidence-informed complementary care in an integrated plan approach to reduce the risk that your cancer will progress. A good place to start is looking at which of the 7 Lifestyle Practices might need shoring up in your life.

Consider getting support and professional guidance in making lifestyle changes and using an integrative treatment plan.

And, because of broad benefits to health, it’s still a good idea to eat your vegetables!

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