Researchers followed over 84,000 people, mostly Black and low-income Americans, to see if eating a healthier diet could reduce their chances of getting cancer. They looked at three different ways to measure diet quality and tracked cancer cases over many years. The results were surprising: eating better didn’t seem to make a big difference in preventing most cancers. However, for some groups, a healthier diet did appear to lower the risk of colorectal and prostate cancer deaths. This study highlights that we need more research on how diet affects cancer risk in different communities.

The Quick Take

  • What they studied: Whether eating a healthier diet (measured three different ways) could help prevent cancer or reduce cancer deaths in a large group of people.
  • Who participated: 84,507 adults from the Southern United States, with a focus on Black individuals and people with lower incomes. Researchers followed these people for many years, tracking what they ate and whether they developed cancer.
  • Key finding: Eating a healthier diet showed little to no connection with preventing most cancers. However, among White participants, following a healthy eating pattern (called DASH) was linked to fewer deaths from colorectal cancer and prostate cancer.
  • What it means for you: While eating well is still important for overall health, this study suggests that diet alone may not be as powerful at preventing cancer as previously thought. Other factors like genetics, environment, and healthcare access may play bigger roles. This doesn’t mean you should ignore diet—just that cancer prevention is complicated.

The Research Details

This was a long-term follow-up study where researchers tracked the same group of people over many years. At the beginning, participants answered detailed questions about what they ate. Researchers then calculated three different diet quality scores for each person based on their answers. Over time, they recorded who developed cancer and who died from cancer, and compared these outcomes to each person’s diet quality scores.

The three diet quality measures were: DASH (a diet recommended for heart health), EDIP (a diet pattern that measures inflammation-causing foods), and EDIH (a diet pattern that measures foods affecting blood sugar control). Researchers used statistical methods to determine if people with higher diet quality scores had fewer cancers or cancer deaths than those with lower scores.

This study is important because most previous research on diet and cancer has focused on white, higher-income populations. By studying a large group of Black Americans and low-income people, researchers could see if diet affects cancer risk differently in these communities. Understanding these differences is crucial for creating health advice that works for everyone.

This study has several strengths: it followed a very large number of people (over 84,000), tracked them for many years, and focused on understudied populations. However, the study relied on people remembering what they ate, which isn’t always accurate. Also, the researchers could only measure diet at one point in time, not how eating habits changed over the years. The study shows associations (connections) but cannot prove that diet directly causes cancer risk changes.

What the Results Show

The main finding was surprising: eating a healthier diet showed almost no connection with preventing cancer in this population overall. When researchers looked at all cancers combined, colorectal cancer, prostate cancer, and breast cancer separately, the diet quality scores didn’t strongly predict who would get cancer.

However, there was one notable exception: among White participants in the study, people who followed the DASH diet pattern had about 21% fewer deaths from colorectal cancer and 44% fewer deaths from prostate cancer compared to those who didn’t follow this pattern as closely. This suggests the diet may help more with surviving cancer rather than preventing it.

The researchers also measured inflammation markers in blood samples (substances that indicate inflammation in the body). They expected that healthier diets would reduce these markers, but they found little to no connection between diet quality scores and these inflammation markers.

The study found that diet quality was generally better (meaning people ate healthier) among women compared to men, and among White participants compared to Black participants. This difference is important because it suggests that access to healthy foods or knowledge about healthy eating may not be equal across different groups. The study also showed that the three different diet quality measures didn’t strongly correlate with each other, meaning they may be measuring different aspects of diet.

Previous studies have suggested that diet quality is important for cancer prevention, but most of those studies focused on white, higher-income populations. This study challenges those findings by showing that in a predominantly low-income, Black population, diet quality measures showed weaker connections to cancer risk. This doesn’t mean diet doesn’t matter, but it suggests that other factors—like access to healthcare, environmental exposures, stress, and genetics—may play larger roles in cancer risk than diet alone.

This study has several important limitations. First, researchers only measured diet once at the beginning of the study, but people’s eating habits change over time. Second, people had to remember what they ate, which isn’t always accurate. Third, the study couldn’t prove that diet causes changes in cancer risk—only that certain patterns were associated with cancer outcomes. Fourth, the study population was mostly from the Southern United States, so results may not apply to other regions. Finally, the study couldn’t account for all factors that affect cancer risk, such as exposure to environmental toxins or access to cancer screening.

The Bottom Line

Based on this research, eating a healthy diet is still recommended for overall health and may help with cancer survival, but it appears to be less powerful at preventing cancer than previously thought. A healthy diet should include plenty of vegetables, fruits, whole grains, and lean proteins. However, cancer prevention likely requires a multi-faceted approach including regular exercise, avoiding smoking, limiting alcohol, maintaining a healthy weight, and getting recommended cancer screenings. (Confidence level: Moderate—this finding challenges previous assumptions, so more research is needed.)

Everyone should care about this research, especially people from Black and low-income communities who have historically been underrepresented in nutrition research. Healthcare providers should use this information to avoid oversimplifying cancer prevention as just a diet issue. Policymakers should recognize that addressing cancer disparities requires looking beyond individual diet choices to systemic factors like food access and healthcare quality.

If diet does help prevent cancer, the benefits would likely take years or decades to appear, since cancer develops slowly. This study followed people for many years and still found weak connections, suggesting that if diet helps, the effect is modest and takes a long time to show up.

Want to Apply This Research?

  • Track daily servings of vegetables, fruits, whole grains, and lean proteins using the DASH diet framework (aiming for 5+ servings of produce daily). Record weekly and compare to baseline to identify trends over 8-12 weeks.
  • Start by adding one extra serving of vegetables or fruits to one meal per day, then gradually increase. Use the app to log meals and receive reminders about healthy eating patterns, while also tracking other cancer prevention behaviors like exercise and sleep.
  • Monitor diet quality monthly using a simple scoring system within the app. Combine this with tracking other health factors (exercise, weight, stress levels) to understand how multiple lifestyle factors work together for health. Share results with your healthcare provider to discuss personalized cancer prevention strategies.

This research suggests that diet quality alone has a weak connection to cancer prevention in low-income and Black populations, though it may help with cancer survival. Diet is just one factor affecting cancer risk—genetics, environmental exposure, healthcare access, and screening also matter significantly. This study should not be interpreted as meaning diet doesn’t matter for health. Always consult with your healthcare provider about personalized cancer prevention strategies, especially if you have a family history of cancer or other risk factors. This information is for educational purposes and should not replace professional medical advice.