The fiber fix for lower cancer risk
29 Jan 2026
By Ronald
Allan M. Ponteres, MD, MBAH
Dietary fiber remains a key nutritional factor in decreasing the risk of several cancers, with strong evidence supporting that both soluble and insoluble fiber contribute to this protective effect through distinct biological mechanisms. Studies demonstrate that fiber’s benefits arise from its ability to modulate the gut microbiome, reduce inflammation, and improve bowel motility, thereby decreasing mucosal exposure to carcinogens. In the Philippines, colorectal cancer is the third most common cancer with 20,736 new cases in 2022, while breast cancer is the leading cancer among Filipino women, accounting for 33,079 new cases (GLOBOCAN, 2022), highlighting the need for preventive strategies, particularly nutrition‑focused interventions. As cancer incidence continues to rise locally, promoting a fiber‑rich diet offers a practical, public health approach to reducing cancer burden in the country.
Fiber-fortified protection
Dietary fiber includes nondigestible carbohydrates and lignin found naturally in plant-sourced foods. It supports health by improving digestion and lowering cardiometabolic risk. Most adults are advised to consume about 25–38 grams of fiber per day. This corresponds to the guideline of approximately 14 grams per 1,000 kilocalories, based on evidence linking higher fiber intake with reduced disease risk (Korczak & Slavin, 2020). Fiber is generally recommended for better gut health and chronic disease prevention, but it should be used cautiously (or avoided) in conditions such as bowel obstruction, severe motility disorders, or active flares of gastrointestinal disease, where high‑fiber intake can worsen symptoms (Ioniță‑Mîndrican et al., 2022).
Dietary fiber exists primarily as soluble and insoluble forms, each offering distinct health benefits. Soluble fiber, found in foods like oats, legumes, apples, and citrus fruits, is readily fermented by gut bacteria and contributes to metabolic and immune benefits, while insoluble fiber from whole grains, nuts, seeds, and vegetables helps regulate bowel movements and supports gut homeostasis. (Alahmari, 2024; Baky et al., 2022)
Soluble fiber is broken down by gut bacteria into short‑chain fatty acids (SCFAs), including butyrate. These SCFAs help strengthen the immune system and maintain healthy epithelial cells in the colon. They may also play a role in preventing malignant transformation, contributing to fiber’s protective effects against cancer (Mann et al., 2024).
Insoluble fiber helps add bulk to stool and increases overall stool mass. This promotes faster movement through the intestines, reducing the time harmful substances remain in contact with the gut lining. As a result, it helps lower mucosal exposure to potential carcinogens, supporting colorectal cancer prevention (Dreher, 2017).
Bulk evidence
Colorectal cancer: A recent systematic review and meta‑analysis found that both soluble and insoluble fiber play a meaningful role in lowering colorectal cancer risk. The analysis included data from over 241,000 participants, providing strong evidence across diverse populations. Researchers observed that people who consumed the highest amounts of dietary fiber consistently showed lower rates of colorectal cancer compared with those who consumed the least. These protective effects were seen across different types of fiber, suggesting a broad benefit rather than one limited to a single source. Overall, the findings reinforce the important role of dietary fiber as a protective factor against colorectal cancer (Arayici et al., 2021).
Breast cancer: A 2024 case‑control study involving 962 women, 464 with breast cancer and 498 healthy controls, found that women who consumed more total dietary fiber had noticeably lower odds of developing breast cancer. The protective effect was especially clear for insoluble fiber and fiber from fruits and vegetables. In this study, women with and without breast cancer consumed an average of 33.1 ± 15.3 g/day and 34.2 ± 16.5 g/day of fiber, respectively. These results suggest that increasing fiber intake from whole plant foods may meaningfully reduce breast cancer risk (Zademohammadi et al., 2024). Large systematic reviews show that women who eat more dietary fiber have an 8–10% lower risk of developing breast cancer. This benefit is seen with total fiber intake, as well as soluble fiber and, to a lesser extent, insoluble fiber. These findings suggest that even modest increases in daily fiber consumption can contribute to meaningful reductions in breast cancer risk (Farvid et al., 2020).
Pancreatic cancer: A meta‑analysis found that higher dietary fiber intake was linked to a lower risk of pancreatic cancer. The analysis included 3,287 patients across one cohort and thirteen case‑control studies, giving strong support to this association. A related dose‑response analysis showed that each additional 10 grams of fiber per day was associated with about a 12% reduction in pancreatic cancer risk, highlighting a meaningful protective effect. Overall, these findings suggest that increasing daily fiber intake may offer important benefits in lowering pancreatic cancer risk (Wang et al., 2015; Mao et al., 2017).
Other cancers: A 2023 umbrella review evaluated evidence across multiple cancer sites, including breast, endometrial, ovarian, renal, prostate, colorectal, and esophageal cancers. The review analyzed 11 meta‑analyses, each synthesizing data from numerous observational studies, and found probable evidence that higher dietary fiber intake is linked to lower cancer risk across many of these sites. Although the umbrella review did not specify an optimal daily fiber amount, it consistently showed that people with the highest fiber intakes had lower cancer risk than those with the lowest intake (Hu et al., 2023).
Feed the gut
The gut microbiome plays an essential role in how dietary fiber supports health. High fiber intake increases levels of important SCFA‑producing bacteria (e.g. Faecalibacterium prausnitzii and Akkermansia muciniphila) which are linked to better immune function and reduced inflammation, both important for lowering cancer risk. These beneficial microbial changes help create a more favorable environment for the body to respond to cancer treatments. A systematic review found that people who ate more fiber were about 5.8 times more likely to respond well to cancer immunotherapy, compared with those who ate less fiber. Overall, the evidence shows that increasing dietary fiber can meaningfully improve both gut health and the effectiveness of immunotherapy (Somodi et al., 2025).
Dietary fiber has been shown to support the growth of beneficial gut bacteria linked to a lower risk of colorectal cancer. Cross‑sectional microbiome studies demonstrate that people who eat more fiber tend to have higher levels of these protective bacterial taxa, including major fiber‑fermenting species. They also consistently show greater overall microbial diversity, a marker of a healthier and more resilient gut ecosystem (Um et al., 2023).
Research backed, expert led
Although different cancer sites respond differently to dietary fiber and results vary by fiber subtype, the collective evidence supports increasing dietary fiber intake as part of cancer‑preventive nutrition. Research consistently shows that whole grains, fruits, and vegetables contribute to lower risk, particularly for colorectal cancer, where fiber’s protective association is strongest.
In an interview, Dr Carlo Miguel Berba, an internal medicine–oncology specialist, emphasized this point, noting, “Dietary fiber plays a meaningful, though not singular, role in cancer prevention, particularly for colorectal cancer, having been associated with lower colorectal cancer risk in observational studies.” He explained that fiber may help by “improving the gut microbiome in promoting healthier bacteria and reducing inflammation—both resulting in a modest risk reduction.” While evidence for fiber and other cancer types is less definitive, he emphasized that higher fiber intake improves overall health through better cholesterol control, healthier weight maintenance, and reduced excess calorie intake.
Practical guidance aligns with Dr Berba’s recommendations. For example:
• Emphasize whole grains, given their strong link to reduced colorectal cancer risk.
• Increase fruit and vegetable intake, beneficial for both breast and gastrointestinal cancer prevention.
• Aim for about 25–35 g/day of total fiber, which Dr. Berba describes as achievable through “simple, food‑based strategies rather than strict counting.”
He suggests visual meals where “colorful plants cover two‑thirds of the plate”, including fruits, leafy greens, root vegetables, and whole grains, paired with lean proteins such as fish, eggs, tofu, beans, or chicken. Another “pragmatic approach,” he adds, is striving for five servings of fruits and/or vegetables daily. While fiber supplements can help, he cautions that “they generally do not provide the same breadth of benefit as whole foods.”
Dr Berba also acknowledges local challenges: “It is challenging for Filipinos as lower‑fiber, less healthy options are more available, cheaper, and more convenient for day‑to‑day life.” He stresses the value of incremental, sustainable dietary changes, tailored to each patient’s preferences, budget, and lifestyle. “By emphasizing progress rather than perfection,” he notes, healthcare providers can help patients adopt long‑term habits that meaningfully improve health. He further encourages clinicians: “Don’t miss the opportunity to work with our colleagues in nutrition and the allied medical professions for more individualized patient care.”
Together, the scientific literature and expert clinical insights reinforce the same message: increasing dietary fiber is a practical, evidence‑supported strategy for reducing cancer risk and improving overall health.
Rough fight
Dietary fiber is a simple but effective way to help lower the risk of several cancers, thanks to its ability to support gut health, reduce inflammation, and limit the body’s exposure to harmful substances. With colorectal and breast cancer affecting thousands of Filipinos each year, increasing fiber intake is an easy and accessible prevention strategy. Encouraging more whole grains, fruits, vegetables, legumes, and other fiber‑rich foods in everyday meals can make a meaningful difference in long‑term health. And when it comes to cancer prevention, fiber isn’t just rough, it’s the kind of roughage that puts up a real fight.
(Disclaimer: Consult your physician before making any decisions about fiber intake, as recommendations should be tailored to your specific health needs.)
References
Alahmari, L. A. (2024). Dietary fiber influence on overall health, with an emphasis on CVD, diabetes, obesity, colon cancer, and inflammation. Frontiers in Nutrition, 11, 1510564.
Arayici, M. E., Mert‑Ozupek, N., Yalcin, F., Basbinar, Y., & Ellidokuz, H. (2021). Soluble and insoluble dietary fiber consumption and colorectal cancer risk: A systematic review and meta‑analysis. Nutrition and Cancer, 74(7), 2412–2425.
Baky, M. H., Salah, M., Ezzelarab, N., Shao, P., Elshahed, M. S., & Farag, M. A. (2022). Insoluble dietary fibers: structure, metabolism, interactions with the human microbiome, and role in gut homeostasis. Critical Reviews in Food Science and Nutrition, 64(7), 1954–1968.
Dreher, M. L. (2017). Fiber and colorectal cancer. In Dietary Fiber in Health and Disease (pp. 333–365). Springer.
Farvid, M. S., Spence, N. D., Holmes, M. D., & Barnett, J. B. (2020). Fiber consumption and breast cancer incidence: A systematic review and meta‑analysis of prospective studies. Cancer, 126, 3061–3075.
GLOBOCAN. (2022). Philippines fact sheet. International Agency for Research on Cancer.
Hu, J., Wang, J., Li, Y., Xue, K., & Kan, J. (2023). Use of dietary fibers in reducing the risk of several cancer types: An umbrella review. Nutrients, 15(11), 2545.
Ioniță‑Mîndrican, C.-B., Ziani, K., Mititelu, M., Oprea, E., Neacșu, S. M., Moroșan, E., Dumitrescu, D.-E., Roșca, A. C., Drăgănescu, D., & Negrei, C. (2022). Therapeutic benefits and dietary restrictions of fiber intake: A state‑of‑the‑art review. Nutrients, 14(13), 2641.
Korczak, R., & Slavin, J. L. (2020). Definitions, regulations, and new frontiers for dietary fiber and whole grains. Nutrition Reviews, 78(Suppl_1), 6–12.
Mann, E. R., Lam, Y. K., & Uhlig, H. H. (2024). Short‑chain fatty acids: linking diet, the microbiome and immunity. Nature Reviews Immunology, 24(8):577-595
Mao, Q., Lin, Y., Chen, H., Qin, J., Zheng, X., Xu, X., & Xie, L. (2017). Dietary fiber intake is inversely associated with risk of pancreatic cancer: A meta‑analysis. Asia Pacific Journal of Clinical Nutrition, 26(1), 89–96.
Somodi, C., Dora, D., Horváth, M., et al. (2025). Gut microbiome changes and cancer immunotherapy outcomes associated with dietary interventions: A systematic review. Journal of Translational Medicine, 23, 756.
Um, C. Y., Peters, B. A., Choi, H. S., et al. (2023). Grain, gluten, and dietary fiber intake influence gut microbial diversity. Cancer Research Communications, 3(1), 43–53.
Wang, C.‑H., Qiao, C., Wang, R.‑C., & Zhou, W.‑P. (2015). Dietary fiber intake and pancreatic cancer risk: A meta‑analysis of epidemiologic studies. Scientific Reports, 5, 10834.
Zademohammadi, F., Sasanfar, B., Toorang, F., et al. (2024). Dietary soluble, insoluble, and total fiber intake and breast cancer. BMC Public Health, 24, 2560. ______________________
Dietary fiber remains a key nutritional factor in decreasing the risk of several cancers, with strong evidence supporting that both soluble and insoluble fiber contribute to this protective effect through distinct biological mechanisms. Studies demonstrate that fiber’s benefits arise from its ability to modulate the gut microbiome, reduce inflammation, and improve bowel motility, thereby decreasing mucosal exposure to carcinogens. In the Philippines, colorectal cancer is the third most common cancer with 20,736 new cases in 2022, while breast cancer is the leading cancer among Filipino women, accounting for 33,079 new cases (GLOBOCAN, 2022), highlighting the need for preventive strategies, particularly nutrition‑focused interventions. As cancer incidence continues to rise locally, promoting a fiber‑rich diet offers a practical, public health approach to reducing cancer burden in the country.
Fiber-fortified protection
Dietary fiber includes nondigestible carbohydrates and lignin found naturally in plant-sourced foods. It supports health by improving digestion and lowering cardiometabolic risk. Most adults are advised to consume about 25–38 grams of fiber per day. This corresponds to the guideline of approximately 14 grams per 1,000 kilocalories, based on evidence linking higher fiber intake with reduced disease risk (Korczak & Slavin, 2020). Fiber is generally recommended for better gut health and chronic disease prevention, but it should be used cautiously (or avoided) in conditions such as bowel obstruction, severe motility disorders, or active flares of gastrointestinal disease, where high‑fiber intake can worsen symptoms (Ioniță‑Mîndrican et al., 2022).
Dietary fiber exists primarily as soluble and insoluble forms, each offering distinct health benefits. Soluble fiber, found in foods like oats, legumes, apples, and citrus fruits, is readily fermented by gut bacteria and contributes to metabolic and immune benefits, while insoluble fiber from whole grains, nuts, seeds, and vegetables helps regulate bowel movements and supports gut homeostasis. (Alahmari, 2024; Baky et al., 2022)
Soluble fiber is broken down by gut bacteria into short‑chain fatty acids (SCFAs), including butyrate. These SCFAs help strengthen the immune system and maintain healthy epithelial cells in the colon. They may also play a role in preventing malignant transformation, contributing to fiber’s protective effects against cancer (Mann et al., 2024).
Insoluble fiber helps add bulk to stool and increases overall stool mass. This promotes faster movement through the intestines, reducing the time harmful substances remain in contact with the gut lining. As a result, it helps lower mucosal exposure to potential carcinogens, supporting colorectal cancer prevention (Dreher, 2017).
Bulk evidence
Colorectal cancer: A recent systematic review and meta‑analysis found that both soluble and insoluble fiber play a meaningful role in lowering colorectal cancer risk. The analysis included data from over 241,000 participants, providing strong evidence across diverse populations. Researchers observed that people who consumed the highest amounts of dietary fiber consistently showed lower rates of colorectal cancer compared with those who consumed the least. These protective effects were seen across different types of fiber, suggesting a broad benefit rather than one limited to a single source. Overall, the findings reinforce the important role of dietary fiber as a protective factor against colorectal cancer (Arayici et al., 2021).
Breast cancer: A 2024 case‑control study involving 962 women, 464 with breast cancer and 498 healthy controls, found that women who consumed more total dietary fiber had noticeably lower odds of developing breast cancer. The protective effect was especially clear for insoluble fiber and fiber from fruits and vegetables. In this study, women with and without breast cancer consumed an average of 33.1 ± 15.3 g/day and 34.2 ± 16.5 g/day of fiber, respectively. These results suggest that increasing fiber intake from whole plant foods may meaningfully reduce breast cancer risk (Zademohammadi et al., 2024). Large systematic reviews show that women who eat more dietary fiber have an 8–10% lower risk of developing breast cancer. This benefit is seen with total fiber intake, as well as soluble fiber and, to a lesser extent, insoluble fiber. These findings suggest that even modest increases in daily fiber consumption can contribute to meaningful reductions in breast cancer risk (Farvid et al., 2020).
Pancreatic cancer: A meta‑analysis found that higher dietary fiber intake was linked to a lower risk of pancreatic cancer. The analysis included 3,287 patients across one cohort and thirteen case‑control studies, giving strong support to this association. A related dose‑response analysis showed that each additional 10 grams of fiber per day was associated with about a 12% reduction in pancreatic cancer risk, highlighting a meaningful protective effect. Overall, these findings suggest that increasing daily fiber intake may offer important benefits in lowering pancreatic cancer risk (Wang et al., 2015; Mao et al., 2017).
Other cancers: A 2023 umbrella review evaluated evidence across multiple cancer sites, including breast, endometrial, ovarian, renal, prostate, colorectal, and esophageal cancers. The review analyzed 11 meta‑analyses, each synthesizing data from numerous observational studies, and found probable evidence that higher dietary fiber intake is linked to lower cancer risk across many of these sites. Although the umbrella review did not specify an optimal daily fiber amount, it consistently showed that people with the highest fiber intakes had lower cancer risk than those with the lowest intake (Hu et al., 2023).
Feed the gut
The gut microbiome plays an essential role in how dietary fiber supports health. High fiber intake increases levels of important SCFA‑producing bacteria (e.g. Faecalibacterium prausnitzii and Akkermansia muciniphila) which are linked to better immune function and reduced inflammation, both important for lowering cancer risk. These beneficial microbial changes help create a more favorable environment for the body to respond to cancer treatments. A systematic review found that people who ate more fiber were about 5.8 times more likely to respond well to cancer immunotherapy, compared with those who ate less fiber. Overall, the evidence shows that increasing dietary fiber can meaningfully improve both gut health and the effectiveness of immunotherapy (Somodi et al., 2025).
Dietary fiber has been shown to support the growth of beneficial gut bacteria linked to a lower risk of colorectal cancer. Cross‑sectional microbiome studies demonstrate that people who eat more fiber tend to have higher levels of these protective bacterial taxa, including major fiber‑fermenting species. They also consistently show greater overall microbial diversity, a marker of a healthier and more resilient gut ecosystem (Um et al., 2023).
Research backed, expert led
Although different cancer sites respond differently to dietary fiber and results vary by fiber subtype, the collective evidence supports increasing dietary fiber intake as part of cancer‑preventive nutrition. Research consistently shows that whole grains, fruits, and vegetables contribute to lower risk, particularly for colorectal cancer, where fiber’s protective association is strongest.
In an interview, Dr Carlo Miguel Berba, an internal medicine–oncology specialist, emphasized this point, noting, “Dietary fiber plays a meaningful, though not singular, role in cancer prevention, particularly for colorectal cancer, having been associated with lower colorectal cancer risk in observational studies.” He explained that fiber may help by “improving the gut microbiome in promoting healthier bacteria and reducing inflammation—both resulting in a modest risk reduction.” While evidence for fiber and other cancer types is less definitive, he emphasized that higher fiber intake improves overall health through better cholesterol control, healthier weight maintenance, and reduced excess calorie intake.
Practical guidance aligns with Dr Berba’s recommendations. For example:
• Emphasize whole grains, given their strong link to reduced colorectal cancer risk.
• Increase fruit and vegetable intake, beneficial for both breast and gastrointestinal cancer prevention.
• Aim for about 25–35 g/day of total fiber, which Dr. Berba describes as achievable through “simple, food‑based strategies rather than strict counting.”
He suggests visual meals where “colorful plants cover two‑thirds of the plate”, including fruits, leafy greens, root vegetables, and whole grains, paired with lean proteins such as fish, eggs, tofu, beans, or chicken. Another “pragmatic approach,” he adds, is striving for five servings of fruits and/or vegetables daily. While fiber supplements can help, he cautions that “they generally do not provide the same breadth of benefit as whole foods.”
Dr Berba also acknowledges local challenges: “It is challenging for Filipinos as lower‑fiber, less healthy options are more available, cheaper, and more convenient for day‑to‑day life.” He stresses the value of incremental, sustainable dietary changes, tailored to each patient’s preferences, budget, and lifestyle. “By emphasizing progress rather than perfection,” he notes, healthcare providers can help patients adopt long‑term habits that meaningfully improve health. He further encourages clinicians: “Don’t miss the opportunity to work with our colleagues in nutrition and the allied medical professions for more individualized patient care.”
Together, the scientific literature and expert clinical insights reinforce the same message: increasing dietary fiber is a practical, evidence‑supported strategy for reducing cancer risk and improving overall health.
Rough fight
Dietary fiber is a simple but effective way to help lower the risk of several cancers, thanks to its ability to support gut health, reduce inflammation, and limit the body’s exposure to harmful substances. With colorectal and breast cancer affecting thousands of Filipinos each year, increasing fiber intake is an easy and accessible prevention strategy. Encouraging more whole grains, fruits, vegetables, legumes, and other fiber‑rich foods in everyday meals can make a meaningful difference in long‑term health. And when it comes to cancer prevention, fiber isn’t just rough, it’s the kind of roughage that puts up a real fight.
(Disclaimer: Consult your physician before making any decisions about fiber intake, as recommendations should be tailored to your specific health needs.)
References
Alahmari, L. A. (2024). Dietary fiber influence on overall health, with an emphasis on CVD, diabetes, obesity, colon cancer, and inflammation. Frontiers in Nutrition, 11, 1510564.
Arayici, M. E., Mert‑Ozupek, N., Yalcin, F., Basbinar, Y., & Ellidokuz, H. (2021). Soluble and insoluble dietary fiber consumption and colorectal cancer risk: A systematic review and meta‑analysis. Nutrition and Cancer, 74(7), 2412–2425.
Baky, M. H., Salah, M., Ezzelarab, N., Shao, P., Elshahed, M. S., & Farag, M. A. (2022). Insoluble dietary fibers: structure, metabolism, interactions with the human microbiome, and role in gut homeostasis. Critical Reviews in Food Science and Nutrition, 64(7), 1954–1968.
Dreher, M. L. (2017). Fiber and colorectal cancer. In Dietary Fiber in Health and Disease (pp. 333–365). Springer.
Farvid, M. S., Spence, N. D., Holmes, M. D., & Barnett, J. B. (2020). Fiber consumption and breast cancer incidence: A systematic review and meta‑analysis of prospective studies. Cancer, 126, 3061–3075.
GLOBOCAN. (2022). Philippines fact sheet. International Agency for Research on Cancer.
Hu, J., Wang, J., Li, Y., Xue, K., & Kan, J. (2023). Use of dietary fibers in reducing the risk of several cancer types: An umbrella review. Nutrients, 15(11), 2545.
Ioniță‑Mîndrican, C.-B., Ziani, K., Mititelu, M., Oprea, E., Neacșu, S. M., Moroșan, E., Dumitrescu, D.-E., Roșca, A. C., Drăgănescu, D., & Negrei, C. (2022). Therapeutic benefits and dietary restrictions of fiber intake: A state‑of‑the‑art review. Nutrients, 14(13), 2641.
Korczak, R., & Slavin, J. L. (2020). Definitions, regulations, and new frontiers for dietary fiber and whole grains. Nutrition Reviews, 78(Suppl_1), 6–12.
Mann, E. R., Lam, Y. K., & Uhlig, H. H. (2024). Short‑chain fatty acids: linking diet, the microbiome and immunity. Nature Reviews Immunology, 24(8):577-595
Mao, Q., Lin, Y., Chen, H., Qin, J., Zheng, X., Xu, X., & Xie, L. (2017). Dietary fiber intake is inversely associated with risk of pancreatic cancer: A meta‑analysis. Asia Pacific Journal of Clinical Nutrition, 26(1), 89–96.
Somodi, C., Dora, D., Horváth, M., et al. (2025). Gut microbiome changes and cancer immunotherapy outcomes associated with dietary interventions: A systematic review. Journal of Translational Medicine, 23, 756.
Um, C. Y., Peters, B. A., Choi, H. S., et al. (2023). Grain, gluten, and dietary fiber intake influence gut microbial diversity. Cancer Research Communications, 3(1), 43–53.
Wang, C.‑H., Qiao, C., Wang, R.‑C., & Zhou, W.‑P. (2015). Dietary fiber intake and pancreatic cancer risk: A meta‑analysis of epidemiologic studies. Scientific Reports, 5, 10834.
Zademohammadi, F., Sasanfar, B., Toorang, F., et al. (2024). Dietary soluble, insoluble, and total fiber intake and breast cancer. BMC Public Health, 24, 2560. ______________________