Does Eating Too Much Wheat Flour Cause Colorectal Cancer? Checking the Link Between Wheat and Cancer Against Studies and Government Data
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You may have heard that “eating too much bread and noodles gives you colorectal cancer,” or that “cancer increased once Japanese people started eating wheat.”
Colorectal cancer is the most common cancer in Japan. About 154,000 people were newly diagnosed with colorectal cancer in 2023, and about 54,000 people died of it in 2024, the second-highest number of deaths after lung cancer (National Cancer Center Japan, cancer statistics).
This article checks the following against studies and government data.
- Does the link to colorectal cancer differ between wheat flour (refined white flour) and whole-grain flour, which is milled with the bran?
- What about cancers other than colorectal (stomach, esophagus, pancreas, liver, breast, uterine body, and so on)?
- What about gluten itself, burnt bread (acrylamide), and ultra-processed foods?
- Does cancer increase in proportion to how much wheat people eat?
Conclusion
- Lumping everything together as “wheat” gives the wrong answer. Studies look separately at whole grains (whole-grain flour and so on) and refined grains (white wheat flour, white rice, and so on)
- Whole grains show a consistent result: people who eat more have less colorectal cancer. Each 90 g per day increase goes with about 17% lower risk, and the World Cancer Research Fund (WCRF) judges that they “probably lower the risk”
- The link between refined grains (white wheat flour) and colorectal cancer is unclear. WCRF’s judgment is “limited, no conclusion.” There are reports of more colorectal cancer in people who eat a lot of white bread, but the number of studies is small and the results are not consistent
- For cancers other than colorectal, there are reports that people who eat more refined grains have more stomach cancer (mainly case-control studies). In the National Cancer Center Japan’s evaluation as well, grains and stomach cancer are rated “possible (raises risk).” On the other hand, whole grains mostly show results on the “lower” side for stomach, esophageal, pancreatic, and liver cancers, and diets that raise blood sugar easily (high glycemic load) are judged to “probably raise” the risk of endometrial cancer
- In people without celiac disease, no link was seen between gluten intake and digestive cancers (three large US follow-up studies, about 200,000 people)
- There is no evidence that cancer rises in proportion to the amount of wheat eaten. Wheat per person in Japan has stayed roughly constant (31 to 33 kg) for 50 years since fiscal 1975, but over that time colorectal cancer mortality rose and then fell, and stomach cancer mortality dropped to less than one-fifth
- If you eat wheat, replacing part of the white flour with whole-grain flour is the choice that fits the study results
Terms: wheat, wheat flour, whole-grain flour
A wheat kernel consists of the outer skin (bran), the part that becomes the sprout (germ), and the inside (endosperm).
| What remains | Examples | |
|---|---|---|
| Whole grains | All of the bran, germ, and endosperm | Whole-grain flour, whole-grain bread, brown rice, oatmeal |
| Refined grains | Bran and germ removed, endosperm only | White wheat flour (soft and bread flour), white bread, udon, white rice |
Bran and germ are rich in dietary fiber, vitamins, and minerals. Refining greatly reduces them.
One more thing to note: the “refined grains” in studies often include sweets and processed foods such as cake, doughnuts, cookies, and pizza (Gaesser 2020). It is hard for studies to separate whether “white flour is bad” or whether “a diet with many sweets and processed foods is bad.”
Colorectal cancer: what studies show
Whole grains: the more, the lower the risk
| Study | Subjects | Result |
|---|---|---|
| Aune et al. (2011, BMJ) | 6 follow-up studies, about 770,000 people (7,941 colorectal cancers) | For every 90 g per day (3 servings) increase in whole grains, colorectal cancer was 17% lower (relative risk 0.83) |
| WCRF evaluation (2017 update) | 6 follow-up studies (8,320 cases) | Likewise 17% lower per 90 g per day. Judgment: “probably lowers the risk” |
| UK Biobank (Bradbury et al., 2020) | About 476,000 people in the UK, followed for an average of 5.7 years | People with the highest fiber intake from bread and cereal had 14% less colorectal cancer than those with the lowest |
Possible reasons include short-chain fatty acids (such as butyrate) formed when gut bacteria break down dietary fiber, and shorter transit time of stool through the intestine.
Refined grains (white wheat flour): unclear
| Study | Result |
|---|---|
| WCRF evaluation | “Cereals and their products” and “glycemic load” and colorectal cancer: “limited, no conclusion” |
| Gaesser (2020, summary of meta-analyses) | People who ate the most refined grains had 27% more colon cancer (relative risk 1.27), but no difference for colorectal cancer overall. The underlying follow-up studies were only three |
| Gaesser et al. (2024, meta-analysis of bread) | No link between amount of bread and colorectal cancer (hazard ratio 1.03). Limited to white bread and low-fiber bread, cancer was 21% higher, but there were only three studies and the authors say it “should be viewed with caution” |
For white bread, there are reports of “22% more colorectal cancer in those who ate the most” in UK Biobank, and “slightly more with more” in the European EPIC study (as introduced by Gaesser 2024). However, people who eat a lot of white bread are also people who do not eat whole-grain bread. It has not been possible to distinguish whether “white bread increased it” or whether “not enough whole grain” was the cause.
Note The bread meta-analysis by Gaesser and colleagues (2024) was funded by the Grain Foods Foundation in the US. In their 2020 paper as well, the author states that he serves as a scientific advisor to the Foundation, a wheat industry association, and a flour milling company.
How easily blood sugar rises (glycemic index)
White wheat flour raises blood sugar more easily than whole-grain flour. One theory is that high blood sugar and insulin help cancer grow.
| Study | Result |
|---|---|
| Aune et al. (2012) | 14 follow-up studies. No link between colorectal cancer and carbohydrate amount, glycemic index (GI), or glycemic load (GL) |
| Turati et al. (2019) | 19 studies. People with the highest GI had 20% more colorectal cancer. No difference for GL (a value that also multiplies by amount) |
The results are not consistent, and WCRF also says “no conclusion” for colorectal cancer.
Studies of Japanese people
| Study | Subjects | Result |
|---|---|---|
| JPHC Study (Abe et al., 2014) | About 74,000 people in Japan, followed for an average of 11 years | None of rice, bread, noodles, or cereal had a clear link to colorectal cancer |
| JPHC Study (Cai et al., 2022) | About 90,000 people followed for 17 years | People on a diet with fewer carbohydrates and more animal foods such as meat tended to have more cancer overall, colorectal cancer, and rectal cancer |
The national evaluation
In the National Cancer Center Japan’s “Evaluation List of Cancer Risk and Preventive Factors” (May 2026 version), for colorectal cancer:
- Grains: insufficient data
- Dietary fiber: possible (lowers risk)
- Processed meat and red meat: possible in women (raises risk)
- Smoking and drinking: convincing (raises risk); obesity: probable (raises risk); physical activity: probable (lowers risk of colon cancer)
The Center explains that many foods and nutrients end up with “insufficient data” because, among other reasons, Japanese diets vary little.
Cancers other than colorectal
Summary by site
| Cancer | Whole grains | Refined grains, white bread, how easily blood sugar rises |
|---|---|---|
| Stomach | 13 to 39% lower in people who eat more (mainly case-control studies; follow-up studies alone show no clear difference) | 36% higher in people who eat more refined grains (18 case-control studies). The National Cancer Center Japan’s evaluation also rates grains and stomach cancer as “possible (raises risk)” |
| Esophagus | About 46% lower in people who eat more (6 studies) | No notable reports |
| Pancreas | 24 to 30% lower in people who eat more (mainly case-control studies) | No link with GI or GL (Turati 2019) |
| Liver | 8% lower per 16 g per day (5 follow-up studies) | No conclusion |
| Breast | 16% lower in people who eat more, but no difference in follow-up studies alone | One report of “slightly more” with white bread (2% per 2 servings a week). No link for grains overall |
| Uterine body | ― | WCRF judges that diets that raise blood sugar easily (high GL) “probably raise the risk”. However, some recent meta-analyses show no significant difference |
| Prostate | ― | No link with white bread (US study) |
(Whole grains: Zhang 2020, Gaesser 2020, Watling 2024, Xiao 2018. Refined grains and white bread: Gaesser 2020, Kim 2025, Gaesser 2024, Kazemi 2021. GI and GL: Turati 2019, Choi 2012)
The “possible for grains” rating for stomach cancer is an evaluation by the National Cancer Center Japan based on Japanese studies from 1975 to 2007. The biggest cause of stomach cancer is Helicobacter pylori (convincing), and salt and salt-preserved foods are also rated “probable.” From the evaluation list, it is not clear whether the grain rating is due to rice or wheat, or whether it was separated from dietary salt.
What about gluten itself?
Does gluten, the protein in wheat, increase cancer?
| Study | Subjects | Result |
|---|---|---|
| Wang et al. (2022) | About 206,000 US people without celiac disease (three follow-up studies, about 4.8 million person-years in total) | No difference in digestive cancers between the highest and lowest gluten intake groups (hazard ratio 0.94). No link for any cancer of the mouth, esophagus, stomach, small intestine, colon and rectum, pancreas, gallbladder, or liver |
The authors say that “it is unlikely that avoiding gluten in the general population will prevent digestive cancers.”
For people with celiac disease, in which gluten causes inflammation of the small intestine, the story is different.
| Study | Subjects | Result |
|---|---|---|
| Lebwohl et al. (2022) | 47,241 people with celiac disease in Sweden | Cancer overall was higher within one year of diagnosis but showed no difference afterward. Blood cancers, lymphoid cancers, and hepatobiliary and pancreatic cancers remained higher |
| Ludvigsson et al. (2026) | About 200,000 people with celiac disease in the US | Blood cancers (such as non-Hodgkin lymphoma) were higher. No difference for solid cancers overall |
| Lasa et al. (2018) | 3 colonoscopy studies in people with celiac disease | Colorectal adenomas (polyps) were not increased |
People diagnosed with celiac disease follow a gluten-free diet on a doctor’s instructions.
Burnt bread: acrylamide
Baking bread or cookies produces a substance called acrylamide. The International Agency for Research on Cancer (IARC) classifies it as “probably carcinogenic to humans (Group 2A).”
However, summing up the studies of dietary acrylamide and cancer in people:
- Filippini et al. (2022): 16 follow-up studies, about 1.15 million people. No link with any cancer site examined (except gynecologic cancers)
- Pelucchi et al. (2015): 32 studies. No link, apart from a borderline difference on the “higher” side for kidney cancer
The author of the bread meta-analysis (Gaesser 2024) also discusses that burnt bread in ordinary amounts has little effect on cancer.
Ultra-processed foods
“Ultra-processed foods” such as sweet buns, instant foods, processed meat, and soft drinks use a lot of wheat flour.
- Wang et al. (2022, BMJ): about 200,000 people in the US. Among men with the highest ultra-processed food intake, colorectal cancer was 29% higher. No difference overall in women. The items strongly linked in men were processed meat and fish products and sweetened drinks
- Jiang et al. (2026, meta-analysis): 9 follow-up studies, digestive cancers 12% higher. Especially linked were ultra-processed meat and protein products
Here too, the links to processed meat and sweetened drinks stand out more than the link to wheat flour itself.
Check: does cancer rise in proportion to how much wheat people eat?
“Rising in proportion” can be checked from two directions.
1. Studies that followed the same people: does more mean more?
| What was examined | Relationship with amount |
|---|---|
| Amount of gluten (Wang 2022) | Even when split into five levels, there is no trend of more with more (digestive cancers) |
| Amount of refined grains (meta-analysis introduced in Gaesser 2020) | For every 90 g per day, death from all cancers was 6% lower (only two studies) |
| Amount of white bread (UK Biobank) | Slightly more colorectal cancer with more (10% per standard deviation). Mostly this one study |
| Amount of whole grains (Aune 2011) | Less colorectal cancer with more (17% per 90 g per day) |
Looking at “wheat” as a whole, we found no result showing cancer rising in proportion to the amount. Results in the “more” direction are limited to things like “white bread” and “refined grains and stomach cancer,” and the number of studies is small.
2. Trends across Japan: did cancer rise when wheat rose?
We lined up wheat per person in Japan (MAFF “Food Balance Sheet”) with age-adjusted incidence and mortality of colorectal cancer (National Cancer Center Japan). An age-adjusted rate removes the effect of population aging so that years can be compared.
| Fiscal year | Wheat (kg per person per year) | Colorectal cancer mortality (nationwide) | Colorectal cancer incidence (3 prefectures) | Stomach cancer mortality (nationwide) |
|---|---|---|---|---|
| 1960 | 25.8 | 8.8 | ― | 73.1 |
| 1975 | 31.5 | 13.2 | ― | 56.9 |
| 1985 | 31.7 | 16.0 | 34.0 | 40.8 |
| 1995 | 32.8 | 18.5 | 51.8 | 29.8 |
| 2005 | 31.7 | 17.2 | 49.8 | 21.2 |
| 2015 | 32.8 | 16.1 | 56.0 | 14.8 |
| 2024 | 32.3 | 15.4 | 55.7 (2023) | 9.7 |
(Per 100,000 people, age-adjusted to the 1985 model population. Incidence uses the three prefectures of Yamagata, Fukui, and Nagasaki, for which long-term data are available. The national cancer registry began in 2016, and the way cases are registered changed)
What we can see from this:
- Wheat increased only until the 1960s and early 1970s (25.8 kg to 31.5 kg). For the 50 years from fiscal 1975 it has been roughly constant at 31 to 33 kg
- During those 50 years, colorectal cancer mortality rose to 18.7 in 1996, then fell to 15.4 in 2024 (about 18% below the peak). With no change in the amount of wheat, it rose and then fell
- Stomach cancer mortality fell to less than one-fifth over the same period. This also moved independently of the amount of wheat
- Comparing year-to-year “increases and decreases,” changes in wheat and changes in colorectal cancer mortality are hardly linked (correlation coefficient 0.15, 1961 to 2024)
If you calculate the correlation over the whole of 1960 to 2024, wheat and colorectal cancer mortality look “linked” (correlation coefficient 0.77). This is because both rose at the same time in the 1960s and early 1970s. In that period, meat roughly doubled (9.2 kg in fiscal 1965 to 17.9 kg in fiscal 1975), milk and dairy products rose about 1.4 times, and rice fell. From fiscal 1965 to fiscal 2025, meat is about 3.7 times, milk and dairy products about 2.4 times, and rice less than half. Because many things changed together over the same period, simply lining up national figures cannot decide which one raised cancer.
Note Comparing trends across a whole country is called an “ecological study,” and it does not look at what each individual ate and whether they got cancer. The comparison here checks whether the theory that “cancer rose as wheat rose” fits; it does not prove that wheat is unrelated to cancer.
Summary of the check
- Neither in studies that followed the same people nor in national trends do we see cancer rising in proportion to the amount of wheat
- However, results split by whole-grain or white flour. Eating few whole grains is linked to colorectal cancer risk
If you eat wheat flour: domestic whole-grain flour
The choice that fits the study results is not “quit wheat” but replacing part of the white flour with whole-grain flour. Baking with whole-grain flour alone changes the rise and texture. At first, mixing it into your usual bread flour or soft flour is one way to go.
It is known that whole-grain flour from imported wheat tends to retain more of the pesticides in the bran than white flour does (for details, see the article on gluten and spelt wheat). Here we introduce two whole-grain flours made only from domestic wheat.
| Whole-grain bread flour | Spelt wheat whole-grain flour | |
|---|---|---|
| Name | Kinoshita Flour Milling “ブラウワー和の全粒粉” (Brauer Wa no Zenryuko) | Kubo-san’s naturally grown spelt flour, whole grain, 1 kg (久保さんの自然栽培スペルト小麦粉 全粒粉 1kg) |
| Ingredient | Wheat (from Kagawa Prefecture) | Spelt wheat (from Wakayama Prefecture) |
| Dietary fiber (per 100 g) | 8.7 g (estimated) | ― |
| How it is grown (per the seller) | Not stated | No pesticides, herbicides, or chemical fertilizers |
| Size and price (tax included) | 1 kg x 3 bags 2,354 yen / 250 g x 3 bags 820 yen (shipping extra) | 1,944 yen + 800 yen shipping |
| How it arrives | Regular shipping | Made to order. Orders received by each month’s deadline are milled and shipped once a month |
| Best-before | 8 months from manufacture | 4 months after manufacture |
| Buy | See on Rakuten (木下製粉) PR See on Amazon.co.jp PR See on Yahoo! Shopping PR |
See on Rakuten (たまな商店) PR |
(Checked on the Rakuten Ichiba sales pages on September 29, 2026. Prices and shipping may change)
- Kinoshita Flour Milling is a flour milling company in Sakaide, Kagawa Prefecture, and its Rakuten Ichiba shop also operates under the company’s name (sold by Farina Corporation)
- Spelt wheat does not have less gluten than ordinary wheat (the article on gluten and spelt wheat)
- After opening, store it sealed according to the bag’s instructions and use it up soon
Note Switching to whole-grain flour does not mean you can prevent cancer. Most of the studies introduced here are observational studies of “what kind of diet people with more cancer had.” What is considered “convincing” for preventing colorectal cancer includes not smoking and cutting back on alcohol. After age 40, get colorectal cancer screening (fecal occult blood test). People with celiac disease or wheat allergy cannot eat wheat.
Summary
- “Eating too much wheat flour causes colorectal cancer” cannot be asserted from the studies. The link between white wheat flour (refined grains) and colorectal cancer is “no conclusion”
- What is clear is the opposite direction: people who eat more whole grains have less colorectal cancer
- For cancers other than colorectal, there are reports on the “more” side for refined grains and stomach cancer, and for diets that raise blood sugar easily and endometrial cancer
- The amount of wheat Japanese people eat has been roughly constant for 50 years and does not move in step with the rise and fall of cancer
- If you eat wheat, replacing part of the white flour with whole-grain flour is the choice that fits the studies
Sources
- National Cancer Center Japan, Institute for Cancer Control, “Evaluation List of Cancer Risk and Preventive Factors” ver.20260526 https://epi.ncc.go.jp/can_prev/outcome/index.html
- National Cancer Center Japan, Cancer Information Service, “Cancer Statistics” tables (national cancer deaths 1958–2024, national cancer incidence 1975–2015, three-prefecture cancer incidence 1985–2023, national cancer registry 2016–2023) https://ganjoho.jp/reg_stat/statistics/data/dl/index.html
- MAFF, “Food Balance Sheet,” long-term series by item (wheat, fiscal 2024 final figures), “Food Balance Sheet for fiscal 2025 (estimate)” https://www.maff.go.jp/j/tokei/kouhyou/zyukyu/
- World Cancer Research Fund / AICR, “Diet, nutrition, physical activity and colorectal cancer” (CUP, 2017 revision) https://www.wcrf.org/
- Aune D et al. (2011) BMJ. https://pubmed.ncbi.nlm.nih.gov/22074852/
- Aune D et al. (2012) Cancer Causes Control. https://pubmed.ncbi.nlm.nih.gov/22418776/
- Gaesser GA (2019) Adv Nutr. https://pubmed.ncbi.nlm.nih.gov/30947337/
- Gaesser GA (2020) Nutrients. https://pubmed.ncbi.nlm.nih.gov/33297391/
- Gaesser GA et al. (2024) Curr Dev Nutr. https://pubmed.ncbi.nlm.nih.gov/39668947/
- Bradbury KE et al. (2020) Int J Epidemiol. https://pubmed.ncbi.nlm.nih.gov/30993317/
- Turati F et al. (2019) Nutrients. https://pubmed.ncbi.nlm.nih.gov/31581675/
- Choi Y et al. (2012) Br J Nutr. https://pubmed.ncbi.nlm.nih.gov/23167978/
- Abe SK et al. (2014) Br J Cancer. https://pubmed.ncbi.nlm.nih.gov/24384682/
- Cai H et al. (2022) Cancer Sci. https://pubmed.ncbi.nlm.nih.gov/34821435/
- Zhang et al. (2020) Nutr J. https://pubmed.ncbi.nlm.nih.gov/32493399/
- Kim et al. (2025) J Gastric Cancer.
- Kazemi A et al. (2021) Adv Nutr. https://pubmed.ncbi.nlm.nih.gov/33271590/ https://pubmed.ncbi.nlm.nih.gov/40200873/
- Watling CZ et al. (2024) Hepatology. https://pubmed.ncbi.nlm.nih.gov/38441973/
- Xiao Y et al. (2018) Nutr J. https://pubmed.ncbi.nlm.nih.gov/30241536/
- Wang L et al. (2022) Clin Gastroenterol Hepatol (gluten). https://pubmed.ncbi.nlm.nih.gov/34800737/
- Lebwohl B et al. (2022) Clin Gastroenterol Hepatol (celiac disease, 47,241 people). https://pubmed.ncbi.nlm.nih.gov/34033925/
- Ludvigsson JF et al. (2026) Lancet Reg Health Am (celiac disease and dermatitis herpetiformis). https://pubmed.ncbi.nlm.nih.gov/42256615/
- Lasa JS et al. (2018) Rev Gastroenterol Mex. https://pubmed.ncbi.nlm.nih.gov/29422261/
- Filippini T et al. (2022) Front Nutr. https://pubmed.ncbi.nlm.nih.gov/35548558/
- Pelucchi C et al. (2015) Ann Oncol. https://pubmed.ncbi.nlm.nih.gov/25403648/
- Wang L et al. (2022) BMJ (ultra-processed foods). https://pubmed.ncbi.nlm.nih.gov/38752573/
- Jiang et al. (2026) Front Nutr. https://pubmed.ncbi.nlm.nih.gov/42528625/
- Rakuten Ichiba sales pages for Kinoshita Flour Milling “ブラウワー和の全粒粉” and Tamana Shoten “久保さんの自然栽培スペルト小麦粉” (checked September 29, 2026)
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