Beyond Four Fruits: Could Seasonal Eating Be a Missing Piece of Colorectal Cancer Prevention?

Beyond Four Fruits: Could Seasonal Eating Be a Missing Piece of Colorectal Cancer Prevention?

By Chef Chuck Hayworth | Real Medical Meals™

When headlines identify four fruits associated with lower colorectal cancer risk, we tend to turn the findings into a shopping list: apples, citrus, watermelon, and kiwi.

As a chef and cancer survivor, I see another question worth asking:

Could part of the benefit belong to a changing pattern of seasonal foods, rather than a handful of fruits eaten repeatedly throughout the year?

My hypothesis is that rotating seasonal, locally available ingredients may contribute to long-term health by encouraging dietary variety and changing the foods available to our gut microbes. International research supports parts of that idea. Whether seasonality and local origin independently reduce cancer risk remains unanswered.

What the four-fruit research actually found

A 2023 research review combined 24 observational studies involving approximately 1.07 million participants. Higher versus lower consumption was associated with lower colorectal cancer odds:

|Fruit or category|Lower odds associated with higher intake|
|-----------------|---------------------------------------:|
|Citrus           |9%                                      |
|Apples           |25%                                     |
|Watermelon       |26%                                     |
|Kiwi             |13%                                     |

The review appeared in the World Journal of Gastroenterology on May 7, 2023. Researchers searched literature through August 2022; the included papers were published between 1996 and 2017. These were separate studies with different observation periods.

Although available through NIH’s PubMed Central archive, this was not an NIH-run trial.

Important weaknesses included observational designs, inconsistent dietary measurements, and potential confounding. Watermelon and kiwi each relied on only two studies. Citrus showed no statistically significant association in the prospective cohort subgroup. Seasonal rotation was not tested. These associations cannot establish that eating a particular fruit prevents cancer. (pmc.ncbi.nlm.nih.gov)

My hypothesis: the changing plate deserves attention

A person who enjoys strawberries in spring, watermelon in summer, and apples in autumn follows a different eating pattern from someone repeating the same fruit bowl every month.

An annual average can obscure that distinction.

I want to know whether those changing patterns matter: the variety of ingredients, their combinations, what they replace, and how the gut responds over time.

Local agriculture offers a practical framework for that rotation. However, “local,” “seasonal,” and “diverse” describe different things. We need evidence that separates their effects.

Europe: dietary biodiversity was associated with fewer gastrointestinal cancers

One of the strongest supporting studies comes from nine European countries.

Published in 2024, it followed 450,111 adults for a median of 14.1 years, during which 10,705 developed gastrointestinal cancers.

Participants with the highest dietary species richness had a 23% lower gastrointestinal cancer hazard than those with the lowest richness. Researchers also found inverse associations involving colorectal cancer.

Species richness counted different biological species across foods and drinks, including animal foods. This was broader than fruit variety, and it did not establish seasonal rotation or local sourcing as the explanation. (portal.research.lu.se)

For my hypothesis, the finding makes biodiversity worth investigating. It cannot tell us whether the same diversity spread seasonally would outperform a consistent year-round selection.

Denmark: familiar regional foods can form a healthy pattern

A Danish study published in 2013 examined a healthy Nordic food pattern featuring fish, cabbage, rye bread, oatmeal, apples, pears, and root vegetables.

The cohort initially enrolled 57,053 adults and recorded 1,025 colorectal cancers over approximately 13 years. Women with the strongest adherence had 35% lower colorectal cancer incidence than those with poor adherence. The adjusted association in men was not statistically significant.

Diet was assessed at baseline, and other lifestyle differences could still influence the findings. Local sourcing and seasonal rotation were not isolated. (cambridge.org)

What interests me is the possibility of building a health-supporting menu around a region’s own ingredients. A Carolina kitchen has its own seasonal vocabulary to explore.

Tanzania and the United States: the gut changes with the seasons

In research published in Science in 2017, scientists examined 350 stool samples collected over more than a year from Hadza hunter-gatherers in Tanzania. Their gut microbial communities showed recurring seasonal changes, with some microbes becoming undetectable and later returning. The study did not measure cancer prevention. (pubmed.ncbi.nlm.nih.gov)

A 2014 American study sampled the same 60 Hutterite adults during summer and winter. Their communal farms supplied fresh seasonal produce, with preserved, canned, and frozen harvests used during winter. Researchers observed consistent seasonal microbiome differences across six colonies.

Again, cancer diagnoses were not an outcome. The findings demonstrate biological responsiveness, not that seasonal microbial changes are necessarily protective. (pmc.ncbi.nlm.nih.gov)

These studies give my hypothesis a biological foundation worth examining. They leave the cancer question open.

South Africa and the United States: changing meals can change colon biology

A 2015 dietary exchange study provided African Americans with a high-fiber, low-fat African-style diet and rural Africans with a higher-fat, lower-fiber Western-style diet for two weeks.

Researchers observed reciprocal changes in microbial metabolism and colon-tissue markers relevant to cancer risk. The African-style diet increased fiber fermentation and butyrate production in the American participants.

This intervention measured biological markers over two weeks, rather than cancer diagnoses over years. It also changed multiple dietary components without testing seasonality. (nature.com)

It helps explain why I focus on the complete meal pattern. It does not identify a particular local ingredient as the protective factor.

The evidence also challenges us

An honest hypothesis must accommodate findings that complicate it.

A British study published in 2000 followed 3,389 adults from 1984/85 to 1991/92. More frequent winter salad-vegetable consumption was associated with lower cancer odds in men. Maintaining consumption from summer into winter also showed an association at the threshold of statistical significance; fruit findings were weaker.

That suggests maintaining produce intake through winter deserves attention. It does not demonstrate that rotating local harvests provides additional protection. (cambridge.org)

Regional-diet evidence is mixed, too. A Swedish study of 45,222 women found no significant association between a healthy Nordic food index and colorectal cancer. (aacrjournals.org)

How I bring the hypothesis into my kitchen

Through Real Medical Meals and CL5 Longevity Cuisine, I use seasonal menus as a practical way to introduce variety:

|Season|Examples for Souteastern US:
|Spring|Strawberries, tender greens, asparagus, peas                     
|Summer|Berries, peaches, watermelon, squash                             
|Autumn|Apples, pears, muscadines, cabbage                               
|Winter|Root vegetables, winter greens, stored apples, preserved harvests

These are culinary examples, not ingredients proven to prevent cancer individually.

My approach includes preserving the harvest and adapting meals to the person’s medical needs. The goal is a varied, workable eating pattern throughout the year.

The question I want science to answer

Does seasonal rotation offer protection beyond total produce intake, fiber, dietary diversity, and other lifestyle factors? Does local origin add anything independently?

Answering that requires repeated dietary measurements, sourcing information, and long-term cancer outcomes. Changes in gut bacteria alone cannot prove fewer future diagnoses.

My hypothesis is that the changing seasonal plate may be an overlooked part of the story. International evidence gives us reasons to investigate it. Establishing its independent effect on colorectal cancer risk is the next scientific step.

Works cited

1. Wu ZY, et al. (2023). Different types of fruit intake and colorectal cancer risk: A meta-analysis of observational studies. World Journal of Gastroenterology.

2. Huybrechts I, et al. (2024). Food biodiversity and gastrointestinal cancer risk in nine European countries. European Journal of Cancer.

3. Kyrø C, et al. (2013). Healthy Nordic food index and colorectal cancer incidence. British Journal of Nutrition.

4. Smits SA, et al. (2017). Seasonal cycling in the gut microbiome of the Hadza hunter-gatherers of Tanzania. Science.

5. Davenport ER, et al. (2014). Seasonal variation in human gut microbiome composition. PLOS ONE.

6. O’Keefe SJD, et al. (2015). Fat, fibre and cancer risk in African Americans and rural Africans. Nature Communications.

7. Cox BD, et al. (2000). Seasonal consumption of salad vegetables and fresh fruit in relation to cardiovascular disease and cancer. Public Health Nutrition.

8. Roswall N, et al. (2015). No association between a healthy Nordic food index and colorectal cancer in a Swedish cohort. Cancer Epidemiology, Biomarkers & Prevention.