# Ketogenic Diet Shows Mixed Cancer Risk in Mice, MIT Study Finds

> A new study by Massachusetts Institute of Technology researchers indicates that while ketogenic diets may protect against colon cancer, they could increase the risk of cancer in the small intestine in genetically predisposed mice.

By PrimaryBrief newsroom · Published 2026-10-20T21:39:27.647520Z
Canonical: https://primarybrief.com/article/ketogenic-diet-shows-mixed-cancer-risk-in-mice-mit-study-finds-4b87dc9a

Massachusetts Institute of Technology (MIT) researchers have found that a ketogenic diet produced opposite effects on cancer risk in different parts of the digestive tract in mice. The study, published in Nature, revealed that a high-fat, low-carbohydrate ketogenic diet accelerated tumor growth in the small intestine of mice predisposed to cancer, while simultaneously suppressing tumor formation in the colon [1][9][10]. This finding challenges previously generalized views on the diet's anti-cancer properties [1].

This nuanced understanding of how ketogenic diets impact gastrointestinal health is important for individuals considering such diets, as it suggests that effects can vary significantly depending on the specific organ within the digestive system. The research indicates that what might be beneficial for one tissue could be detrimental for another, urging caution against broad generalizations about the diet's health impacts [11][12][17].

## What the records show

The study, published in Nature on July 15, 2026, details experimental results from mice genetically predisposed to developing intestinal tumors [6][11][18]. Researchers fed these mice one of three diets: a ketogenic diet, a standard control diet, or a high-fat, high-calorie diet designed to induce obesity [10]. The unexpected results showed that the ketogenic diet increased small-intestinal stem cell activity and accelerated tumorigenesis in the small intestine [7]. The increased risk was attributed to the way intestinal stem cells processed the diet's high levels of fat, rather than the production of ketone bodies, which are a hallmark of ketogenic diets [9][13][15]. This fat-burning activity caused cells to multiply more rapidly, potentially increasing the chance of cancerous changes [13]. Conversely, the same ketogenic diet reduced tumor formation in the colon [9][10]. The study specifies that these are findings from a mouse study and not a clinical study on humans [19]. Previous research, including a Nature study from 2022, had reported that ketogenic diets reduced colon tumor formation [18].

## The timeline

Research regarding the ketogenic diet's impact on cancer has been ongoing. A previous Nature study in 2022 indicated that the diet could reduce colon tumor formation [18]. The new findings, published in Nature on July 15, 2026, specifically detail the differential effects on the small intestine and colon [11][18]. The study's findings became public through various reports in the following months, including articles on July 16, 2026 [10], July 21, 2026 [18], and October 5, 2026 [9][12].

## What changed and for whom

This research introduces a critical nuance to the understanding of ketogenic diets, challenging previously generalized views on their anti-cancer properties [1]. While some research indicated potential protection against colon cancer, the new findings suggest an increased risk for cancer in the small intestine [1]. This means that the impact of a ketogenic diet is not uniform across the digestive system, and its effects are tissue-specific [1]. For patients with conditions like familial adenomatous polyposis (FAP), who frequently develop intestinal polyps, understanding these nuanced impacts is particularly relevant [8].

## What the researchers have said publicly

Omer Yilmaz, director of the MIT Stem Cell Initiative, associate professor of biology at MIT, and a member of MIT's Koch Institute for Integrative Cancer Research, is the senior author of the study [11][12]. Yilmaz stated, "I think the message here is that we need to be very careful in generalizing the effects that these diets can have, because what might be beneficial for one tissue may be detrimental for another tissue" [11][12][17]. He emphasized that "Ketogenic diets have distinct effects on different tissues even within the gastrointestinal tract" [12]. MIT postdoctoral researchers Jessica Shay and Fangtao Chi are lead authors of the paper [11][12][18].

## What we could not confirm

We could not confirm if there are ongoing human clinical trials to validate these findings from mouse models. We also could not confirm the specific dietary recommendations or changes that might arise from these findings for human ketogenic diet practitioners.

## Evidence cited
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6. (August 14 2026) Epub 2026 Jul 15. Authors. Jessica E S Shay , Fangtao Chi , Constantine N Tzouanas 1 5 6 7 , Shixun Han , Xiao Zhang , ... (nih.gov) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQGRs5gMh8gId9trcNHlxPSdvokQXzPFhY_0AhWSrOGk47XHiAeUPRN4IanDRDDfJ1canL3Bj_OmWYGAVw1lbiK43acBGjKD2EdHb53Shb5caaEgDLiRVe9fwdUOx81w-2y6Xs-z
7. Logg på. Søk · Hjem · Nytt · Lister. 4. august. 1385-Ketogenic diet mediates intestinal tumorigenesis. Paper Talk. 22 min. This research explores how a ketogenic diet (KD) influences intestinal tumor growth, specifically within the small intestine of mice predisposed to cancer. The study reveals that while a KD increases small-intestinal stem cell activity and accelerates tumorigenesis, these effects are driven by the oxidation of dietary fats rather than the production of ketone bodies. Through (apple.com) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQHAuh7ukaEEjdY12Rtn5vpsOqTBthrC7LP5timIkV4E-geWNev91sipdLooFrpGaAu3zb8RWbRTV8QcbKeMitNDJxdynZVNlAJjARL2iWBpUT-4CzawlyDGG-Cs3NiW4UpQOdw3-GRwrRTZxS6RC8zFPgWSjbFpez59LPYvDPKDD_pCWCfJjVydl7_lh0-wijUQVeAHwJGoqlRqfgZ2XQtWHkdlKt9HX7eAMvT-b9E7oSbWLvirxP4V
8. (June 07 2025) Abstract. Diet composition shapes tissue function and disease risk by modulating nutrient availability, metabolic state, and cellular dynamics. In the gastrointestinal tract, obesogenic high-fat diets enhance intestinal stem cell activity and tumorigenesis. However, the impact of ketogenic diets (KD), which contain even higher lipid content but induce ketogenesis, remains poorly understood. This is particularly relevant for patients with familial adenomatous polyposis (FAP), who f (biorxiv.org) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFLpgJEUXlKlePK1PlEwxj8JUAsc6Pi5H0ts1_9S269tUrE2Bfx_o-_mLUw4O7F03WQbF63lBHtymwULBO_Pizq8AK1LsSO2JcXXbIDvPpsQwLX4ynAKVDb2DM_SwA-vYgoOqq-VZ0gTUrqmqDmYw2kK2usRzs9
9. (October 05 2026) The keto diet may raise small intestinal cancer risk, MIT researchers warn. A new Nature study found that cancer-prone mice on a ketogenic diet developed more small intestinal tumors — not because of ketone bodies, but because of how intestinal stem cells burn dietary fat. Surprisingly, the same diet reduced tumor formation in the colon, revealing starkly opposite effects within the same digestive tract. (curie.md) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQE7oXsqhkrnqVbsc2HoiroOZ_tvR2SXrRlG5a6e2pIaft9BbuB04fsXugj7xrCN1jNtpgy729n8hfw_tWYq7-cIxDrMUXNFbdbzyeuqVwrOaazA4_cWs2_x
10. (July 16 2026) ... . To find out, the researchers fed mice genetically predisposed to developing intestinal tumors one of three diets: a ketogenic diet, a standard control diet, or a high-fat, high-calorie diet commonly used to induce obesity. The results were unexpected. "Surprisingly, neither increasing nor eliminating ketone production altered intestinal tumor growth," co-first author and MIT molecular biologist Fangtao Chi told ScienceAlert. "Instead, we found that its tumor-promoting effect (sciencealert.com) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQEtaPstt53JjCcQHB5kvrsMhYxNcwShx1XfM3U6cqXH2J93P2xr56Fz5Q12IbegKYsaoKGV9HIUN_Lfm6curQvFsOTwgSyrBIlPQZn2vVhCjApWwldodA52KdcwDJekyGfAkyaeJ7Qd0uJVy3aok158sCNuTkQR2feJrVC56vvESySnmuWqXmh8gJcIKKLORrCz-NbOQt5zW9cJssSj3Waveg==
11. (July 15 2026) While some research has shown that the diet may protect against the development of colon cancer, a new study by MIT researchers suggests that in the small intestine, a ketogenic diet may increase the risk of cancer. (mit.edu) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQE8i8VzLMg1CbX-bDOWJc4_VjSqeqjr_1-AW6UGP2IaDTrl5_9GdQw8ClSvQuZFF76Kh9v1LRnrr_Qpn8l7kPRYSVdFn7Xks1CWHqKUDoN7KqvLsroDCvpfoTdBilMRcqiM2qT1QgZMbAwkaAWcLyFOZzXZVL0eCcN0W6ginV_Ct12CHmf3IEySnmuWqXmh8gJcIKKLORrCz-NbOQt5zW9cJssSj3Waveg==
12. (October 05 2026) A ketogenic diet increased small-intestinal tumors in cancer-prone mice while reducing tumors in the colon, revealing a strikingly different response within neighboring parts of the gut. Researchers traced the increased risk not to ketones, but to the way intestinal stem cells processed the diet's high levels of fat. That fat-burning activity pushed the cells to multiply more rapidly, potentially raising the chance of cancerous changes. (sciencedaily.com) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQEOj9yoBHC_JfTWS1CXdUAHj7u0UpzKNqAWktcD6YZ1r1lzhFTdQw6RyhdeISYHVw9CVyG-NhUOEAJiG1epSnINRB-Ymjagx_4YFXOKQGvCj2W94hZqd1bCrYqaYqmgc89PLC6clFATI032l0nGtGorvcHa4AOWEIL4
13. (July 29 2026) Researchers traced the increased risk not to ketones, but to the way intestinal stem cells processed the diet's high levels of fat. That fat-burning activity pushed the cells to multiply more rapidly, potentially raising the chance of cancerous changes. https://www.nature.com/ … (instagram.com) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQGYNtr-0cBhdCpwOJ76niHOhe6FmxuPD9k7Wlq-B7bwoEjwdc55lCXpk450EWgqjzxtjsJ7-Zv3f4qaxU6NIpMGWHuW49SuUxUEM-prhhCV6_TriZlOf0m-5pPmHv5aYh1Cmkw=
14. (October 07 2026) A new study from MIT finds that a ketogenic diet increases small intestine tumor risk in genetically predisposed mice, contrasting with prior research suggesting anti-tumor effects, especially in the colon. Most related studies report protective or neutral effects of ketogenic diets on cancer, so these new results highlight important tissue-specific risks not previously recognized. While prior animal studies generally observed anti-tumor effects of ketogenic diets, particularly (consensus.app) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFpA-vTgriLhJ8PCBQ0BYhbcH1bpR0hXh1tdTy0t2Jz7_U5wPlYnV1vnZxy2OnDqd0baOZEj4Zziei-b99DMbiMLL1jXCxtyakNXu61Dc_gBSprK1hY3ImZdl7G2Wy5IpwTvt5Twso0VUfNPazFAyFizsnuwF6a7BFkahnAYJVBzXflas-qiiR9fAXZACHLhGb58EXD5nPU3iLY5hCripfroUcUSprpEpF7mUWlvmcubJKKYgixFHKPA6ngaarZE9h2GP8n7khGNRaVwmg6gA-_
15. (July 17 2026) Dietary regimens have become increasingly common, whether to prevent disease, avoid worsening existing health conditions, or simply for aesthetic reasons. Among the wide variety of dietary approaches, one has gained particular attention because it is characterized by a very low intake of carbohydrates and a high proportion of fats: the keto, or ketogenic, diet. The goal of this diet is to reduce the availability of glucose in the body, causing it to rely on other sources, such as  (williamscancerinstitute.com) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFOIq0p-VZrkuJSQYpoF70VIt8JsHZmT_uCfJ2tJf_b54EYSKBXn756rxPH1DcAqH8kbPtfTglO2ivN2lgaMx4fvCkv9cMIu89yiBcUTgf-4Rq4SBMEmu1fzs52BSdBmZknNiLVIC_cZSrmuU0opTG2y3vFAJicKWPKN9RMjCTFxmY3UpErL4QAYfaD9kUjImm9h-bBMw=
16. (July 22 2026) Ketogenic, or “keto”, diets were initially designed to help treat epilepsy but have risen in popularity as a strategy for weight-loss. However, new research indicates that keto diets may increase the risk of cancer in the small intestine, and illustrates that this is “surprisingly” due to dietary fat, rather than an increase in ketones. Subscribe to Cancer Research updates for FREE and get: Daily Breaking Science News; Tailored newsletters; Exclusive eBooks, infographics and onlin (technologynetworks.com) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFAUoe7SJ5i23EqC_90lEL1Q-4X4EjKdhnTYsM5qijqsZIc75l7-o2jnKluOrEHrKcU8zsOa1uZ_qoe8GbuFKWwTK4g66IgAoisFPcyRhkE7u233_O5r34e6AIqOTkS7KsEH3mp2YH-Y-9PjIzwrF9OiZT9xIXp55QnhcHVf4IeUHAZKnWyDS8yWT0CRNo9vwOV3SOWxuFvBFb6aGg0pDSoNPYqiIm5_bf1PbHtZ2NBqxcD8L0H
17. (October 14 2026) Keto diet leads to small intestine cancer in mice A ketogenic diet may protect against colon cancer, but new research from Massachusetts Institute of Technology (MIT) found the opposite effect in the small intestine. Feeding mice genetically predisposed to intestinal cancer a ketogenic diet led to as many, or even more, tumours than a diet that causes obesity – despite the mice not gaining weight. The team found that this was driven by increased cell proliferation caused by how (facebook.com) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQGpEKPKKXYji0A9K24AKew1P94-84ARO0NvANCS2x6oSlpWD2xwcnMH8kazzeO75PnGDEt0vVHTpUkFuv5TshT7dsI66pp0cUHTd1Yh7xfcFyt7d_oMlb8Q16q6Zrce7UyW--JLDHfxrr9yrQRZi_a5oqNlWI3J1jLOEZJ_SYJ9JKdwTlam9mnuQZP9lbHNy6r9h5ev4OqCShPvMjlCXuo18wEHNNVCD6kMa6rYewqK6klbJ5ugqEia_kcy-6-TcPEwQ2chkWEpTLE9ybFhZ-ec=
18. (July 21 2026) As reported in the earlier Nature study from 2022, the ketogenic diet reduced colon tumor formation. Yet the new experiments suggest that ketone bodies were not directly responsible for that protection either. “Given how much attention has been paid to ketone bodies like BHB, both as a commercial health trend and in recent high-profile studies suggesting BHB suppresses colon cancer, we fully expected them to be the direct drivers. Instead, our experiments in genetically engineered (scitechdaily.com) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQE4PzucIkltTRIeURubnts-sf7FmSoIgn_qRrJcRABeoAZSw11rYtMMjRdZI8TRkhLIjcPQf4yBMhXwC51swfsfu_AFJ-HWYCJE7zcN0jfrFZBeW1AZt4VJwwFqbW_F8EWKe-7tR5GQ_KdbZNkn3NEKdPc5wLBtVqxt0o2rn8M=
19. (October 11 2026) Nature published a new study examining, at a mechanistic level, the relationship between a popular eating pattern, the ketogenic diet, and intestinal tumor formation. The finding has two layers, and the second is more interesting than the first: First: In mice that spontaneously develop intestinal adenomas (benign polyps with the potential to become cancerous), a ketogenic diet increased tumor burden and shortened survival. Second — and the real surprise: The effect was not cau (drozdogan.com) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQHIJ_V9icLyB6Uu5q4SWnMZHW7535oRdzcvp-HmeFxlO-nv9BPi7Hg_-y6TPsmAAOTeiOTjieKr5I6CWd7R1NGwTencMDV3arKb5k2eq-AYrmft95ksP1dXtHbahTqSwhh738BKJJtDZ_NKL28ASAm7fiAn7srVcSMXDIVjm5QxeQ9fs76Htogy0QNbBrYdMfeDzUOxQGDy7N5Mc6uf8W2tdJtvSjNM2uLoy5oe-ec=
20. When mice in the lab are on low-carb diets, like the "keto" diet many people follow, the liver makes a ketone that slows the growth of colorectal cancer. The Challenge. Research has shown that certain types of diets are known to increase the risk of developing colorectal cancer. These include diets high in red meat and processed meats (like deli meat, hot dogs, bacon) as well as diets high in sugar or alcohol. But little is known about diets that may help prevent, or even treat, colorectal cance (cancer.org) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQFTD_Hobpxc_gHH16jacHoNKjNOMxu_nLNvO4h-Brd4S--TzkYRDhWWc8cEf3fq6LtUib_8izBCtJZQj7dKNAYmsU1X31D1hkRWWJOTLZTsO6atkBnXrJGlz-RySxWX4gQS5avcqPg5tPPVQcb_TbZ0WkEVgJY3Pe6ZRcqBF8dGGOI45P2vyLxeslFi37mfeCu9xc7lRGtI9mX-aLKz5gIiHXGZOzbG0f-9MIlc48yUGA2b2BUKugUSmvPHgYNyR_eneqiCE0SMqsBrA2xUqk4sB_ziD1k3OzlWYuqGw3E7InlffLOY0aM=
21. (February 20 2025) Importantly, stearate-producing members were enriched in ketogenic conditions, whereas consumers were depleted and supplementation of stearic acid reduced tumor burden in vivo. Results. KD leads to reduced colonic tumor burden and immune inflammatory response in CRC. To study the relevance of the gut … (nih.gov) — https://vertexaisearch.cloud.google.com/grounding-api-redirect/AUZIYQERIzXz-oAv9KJ83b1KkMb6p2UU6NFpgLshIQrv-k4oeQRbL-rTcOu_YxDXYsTAoOu2yssp3MANHf7h3fVdlG-8Dhbp69NWsGW55K25QQ6PQa-oHIkEw2ODkTq7dyWG9gxZHzCFbXtMpzmXvWjm