Western diets high in fat and sugar can lead to bowel disease and cancer, Irish study reveals

Review reveals how different diets can alter significantly the composition and functionality of gut microbes

The study found that a Mediterranean diet, high in fruits and vegetables, is effective in managing conditions such as cardiovascular disease, IBD and type 2 diabetes.

Western diets pose a greater risk of Inflammatory Bowel Disease (IBD) and colorectal cancer, according to an Irish-led review of what people eat around the world.

The study of six prevalent diets has examined how what we consume impacts our gut microbiome — the community of micro-organisms that live in our intestines — and how the shifting balance of its composition influences our overall health.

The review was conducted by APC Microbiome Ireland (APC), a Science Foundation Ireland Research Centre at University College Cork (UCC), and Teagasc. It is published in the journal Nature Reviews Microbiology.

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The study, led by Prof Catherine Stanton — an APC principal investigator and senior principal research officer at Teagasc, examined Mediterranean, high-fibre, plant-based, high-protein, ketogenic and western diets.

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The review reveals how different diets alter significantly the composition and functionality of the gut microbiome, highlighting the production of essential molecules during metabolism such as short-chain fatty acids.

It underscores the detrimental effects of the western diet, characterised by high fat and sugar intake, compared to the benefits of diets rich in plant-based and high-fibre foods.

By contrast, it finds that a Mediterranean diet, high in fruits and vegetables, is effective in managing conditions such as cardiovascular disease, IBD and type 2 diabetes.

“Our review highlights the profound impact of different diets on the gut microbiome. This understanding is crucial for developing dietary recommendations that promote health and prevent disease. It’s fascinating to see how dietary choices can influence the balance of microorganisms in our gut and their metabolic functions,” said Prof Stanton.

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The review offers valuable insights for the food industry and healthcare professionals, guiding them in making informed decisions about diet and health. The detailed analysis of how different diets affect the microbiome provides a foundation for developing targeted nutritional therapies and improving public health outcomes.

“This review is a significant milestone in microbiome research. It provides a detailed look at how dietary patterns shape the gut microbiome and underscores the potential for diet-based interventions in clinical practice. It provides tangible data on how the microbiome is intrinsically relevant to creating health benefits for society,” said Prof Paul Ross, director of APC Microbiome Ireland and co-director of UCC Futures Microbiome and Health.

The review also emphasises the need for exhaustive studies to better understand the causal relationships between individuals, their diet, and micro-organisms. This understanding is vital for advancing precision nutrition and developing microbiome-based therapies tailored to individual health needs.

Ronan McGreevy

Ronan McGreevy

Ronan McGreevy is a news reporter with The Irish Times