Eating 90 g of wholegrains daily linked to lower breast cancer risk

By Dr. Liji Thomas, MDReviewed by Lauren HardakerJun 24 2026

Women who met Nordic wholegrain recommendations for years were less likely to develop breast cancer, while the study revealed that not all wholegrain foods may influence cancer risk in the same way. 

Study: Long-term wholegrain intake in line with the Nordic Nutrition Recommendations 2023 and risk of breast cancer in a population-based cohort of women. Image credit: marilyn barbone/Shutterstock.com

According to a recent study published in the European Journal of Nutrition, women with long-term wholegrain intake of at least 90 g of wholegrains per day, in line with the 2023 Nordic Nutrition Recommendations, had a lower risk of breast cancer than women with much lower wholegrain intake. The findings also suggest that risk associations differ with the type of wholegrain foods consumed.

Nordic wholegrain targets tested against breast cancer

Breast cancer is the most common cancer among women worldwide. It is closely tied to hormonal exposure, especially to exogenous and endogenous estrogen and progesterone. Some scientists hypothesize that diets rich in fiber may bind estrogen in the colon, thereby reducing its reabsorption. This would reduce its levels in the circulation.

This hypothesis is supported by studies reporting a reduced risk of breast cancer in women with high fiber intake. Wholegrains are rich in dietary fiber, but previous studies have provided inconsistent findings on the link between wholegrain intake and breast cancer. This may be due in part to the wide differences in the types of grains consumed across populations, and to the presence of bioactive and anti-carcinogenic compounds within the same type of wholegrain derived from different sources.

Despite this lack of strong evidence, the NNR2023 guidelines recommend consuming 90 g or more of wholegrains per day for health. The current study sought to estimate how adherence to the most recent Nordic Nutrition Recommendations (NNR2023) guidelines on wholegrain intake correlated with breast cancer risk, and more particularly, the intake of specific wholegrain foods such as oats, wheat, and rye.

Compare breast cancer risk across wholegrain intake levels 

The researchers examined data from 36,479 women aged 48–83 years who participated in the Swedish Mammography Cohort. Dietary intake was assessed using food-frequency questionnaires completed in 1997, which served as the baseline. A repeat questionnaire was completed in 2009 by 25,259 of the surviving participants. This provided estimates of long-term wholegrain consumption.

The researchers grouped participants according to how closely they met the NNR2023 wholegrain recommendation: low (<45 g/day), partial adherence (45 to <90 g/day), and full adherence (≥90 g/day).

Participants were followed for an average of 16.5 years, during which 1,979 women were newly diagnosed with breast cancer. At baseline, the mean participant age was 62 years, and 81% were post-menopausal. In comparison, those who developed breast cancer were slightly younger at baseline, 61 years old on average.

The researchers looked for associations between various levels of wholegrain intake and breast cancer risk, adjusting for lifestyle and medical history factors. These included age, body mass index, smoking, physical activity, alcohol intake, dietary quality, menstrual and reproductive history, hormone therapy use, and family history of breast cancer.

Women with long-term full NNR2023 adherence were somewhat more likely to have healthy lifestyles. Crispbread accounted for most of the wholegrain intake across all categories.

Higher wholegrain intake associated with lower breast cancer risk

Women with long-term full adherence were 22% less likely to be diagnosed with breast cancer than those in the low-adherence category. No clear reduction in risk was observed among women with intermediate wholegrain intake.

No significant associations were observed for either hormone receptor-positive or hormone receptor-negative tumors, although there were trends towards lower risk in hormone receptor-positive tumors. Further analyses based on baseline data alone supported the observed association.

Individual wholegrain foods showed differing patterns

Comparing specific wholegrain foods, no single food was clearly linked to total breast cancer risk. However, moderate breakfast cereal consumption was linked to a lower risk, with high consumption suggesting a possible lower risk, although the association was not consistently statistically significant across models. High crispbread consumption was associated with a higher risk of hormone receptor-negative breast cancer in the multivariable-adjusted models.

The authors suggest these differences may reflect variations in fiber composition, bioactive compounds, food processing, or contaminants such as acrylamide in some products, although these possibilities require further study.

Grain-specific compounds may shape cancer associations

Researchers proposed several ways wholegrains might influence breast cancer risk. Their fiber content may help reduce circulating estrogen levels, while effects on gut microbes and inflammation could also play a role.

Higher wholegrain intake has been associated with lower levels of pro-inflammatory mediators such as C-reactive protein and Interleukin-6, as well as improvements in gut microbiota composition that promote the production of immunoregulatory short-chain fatty acids (SCFAs). These SCFAs may help suppress inflammatory processes involved in cancer development. Wholegrains also contain bioactive compounds, including β-glucans found in oats, which have demonstrated antiproliferative and antimutagenic properties.

Conversely, crispbread, although made from wholegrain, may contain acrylamide, which the International Agency for Research on Cancer (IARC) classifies as a probable human carcinogen. As such, it represents a major source of this chemical in the Swedish diet, and previous studies suggest a possible link with hormone receptor-negative breast cancer.

The researchers also highlighted that different grains, including oats, wheat, and rye, vary considerably in their fiber composition and phytochemical content. These differences may help explain why associations with breast cancer risk vary across wholegrain products. The findings further suggest that treating all wholegrain foods as a single category could obscure important differences between specific grain types and products.

Strengths and limitations

The study's strengths include its large population-based cohort and large sample of breast cancer cases, repeated dietary assessments over time using standardized, well-validated questionnaires, long follow-up, near-complete cancer ascertainment through national registries, and adjustment for many lifestyle and breast cancer risk factors.

However, the study was observational and cannot establish causality. Dietary intake was self-reported using food-frequency questionnaires, which may introduce misclassification error. Residual confounding from unmeasured factors, including genetic influences, also cannot be excluded.

Future research should explore the advantages of reporting wholegrain intake rather than that of wholegrain products, while accounting for regional differences in wholegrain foods. It should also consider how best to include wholegrain intake across a wide variety of foods, including those with relatively small proportions of wholegrain.

Meeting Nordic wholegrain goals linked to lower breast cancer risk 

Long-term consumption of at least 90 g of wholegrains per day in line with the Nordic recommendation was associated with a lower risk of breast cancer in this cohort of Swedish women. The findings also suggest that different wholegrain foods may have distinct relationships with breast cancer risk, especially the hormone-receptor subtypes.

This emphasizes the need for further research into how specific grains and food products influence cancer development. The results further indicate that future studies should carefully consider differences among wholegrain foods rather than treating all wholegrain products as a single category.

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