The cancer diet debate: Is cutting meat really protecting you?

Liver Doc questions a new study linking vegetarian diets to lower cancer risk, pointing to conflicting evidence and gaps in how such research is interpreted.

In Short

• The analysis reported lower overall cancer rates among vegetarians and vegans
• Dr Cyriac Abby Philips said the conclusions rely on limited studies
• Researchers cannot easily separate diet from lifestyle, screening and healthcare access

A new meta-analysis has reignited the debate: does cutting out meat actually lower cancer risk?

The study, which pooled data from multiple long-term cohort studies, reported that vegetarians have a 13% lower risk of overall cancer, while vegans show a 23% lower risk, compared to meat-eaters.

The findings are published in the European Journal of Epidemiology.

On paper, the message seems straightforward, that plant-based diets may offer protection.

But not everyone is convinced the story is that simple.

Kerala-based hepatologist Dr. Cyriac Abby Philips, popularly known as the Liver Doc on X, has challenged the interpretation of these findings, arguing that the headline numbers risk being taken out of context.

In a detailed response, he pointed out that the meta-analysis led by Aune et al. draws its conclusions from a relatively small subset of data.

“The summary relative risk for total cancer in vegetarians vs non-vegetarians is based on only four studies,” he wrote, even though the paper itself includes 17 publications overall.

For him, the issue is not the numbers themselves, but what they are assumed to mean.

“These are associations, not proof,” he emphasised.

A LARGER STUDY, A MORE COMPLICATED PICTURE

To make his case, Dr. Philips pointed to a newer and significantly larger pooled analysis published in the British Journal of Cancer. That study tracked 1.8 million people across nine cohorts spanning the UK, US, Taiwan and India, far exceeding the scale of the meta-analysis now doing the rounds.

Its findings complicate the narrative.

According to that analysis, vegans had a 40% higher risk of bowel cancer, while vegetarians showed nearly double the risk of certain oesophageal cancers. In other words, while overall cancer rates may appear lower in some plant-based groups, the risk is not uniformly reduced across all cancer types.

“The ‘lower total cancer’ headline hides important details,” Dr. Philips noted, arguing that focusing only on overall risk can obscure increases in specific, and often deadly, cancers.

THE LIMITS OF OBSERVATIONAL SCIENCE

The main issue is that most nutrition research is observational in nature.

Such studies can identify patterns. For instance, one group tends to have lower cancer rates than another, but they cannot establish direct cause and effect.

People who follow vegetarian or vegan diets often differ from meat-eaters in many other ways, making it difficult to isolate diet as the decisive factor.

Independent reviews, including those by the NutriRECS, have previously concluded that the evidence linking meat consumption to adverse health outcomes is low to very low in certainty.

Genetic studies using Mendelian randomisation, which attempt to get closer to causality, have similarly found no strong link between red or processed meat and most cancers.

WHO ARE WE REALLY COMPARING?

Another point raised by Dr. Philips is that the populations studied are not representative of everyday eating patterns.

Much of the data in the meta-analysis comes from British cohorts and American Seventh-day Adventists - a group known for healthier lifestyles overall. They tend to smoke less, drink less alcohol, exercise more and have better access to healthcare.

Even within these groups, meat-eaters often have lower cancer rates than the general population.

“The comparison is not between typical meat-eaters and vegetarians,” he argued. “It is between unusually health-conscious people on both sides.”

This, he suggests, can exaggerate the apparent benefit of avoiding meat.

THE WEIGHT FACTOR

Body weight may be doing more of the heavy lifting than diet labels.

Vegetarians and vegans, on average, tend to have a lower body mass index (BMI), and maintaining a healthy weight is a well-established factor in reducing cancer risk.

Some analyses, including those from large datasets like the UK Biobank, show that once BMI is accounted for, the protective effect of vegetarian diets becomes significantly smaller.

In practical terms, this means similar benefits could be achieved through weight management alone, without necessarily eliminating meat.

SMALL NUMBERS, BIG CONCLUSIONS

There is also the question of scale, particularly when it comes to vegan data.

Despite the large overall sample size, the number of vegans included in these pooled analyses remains relatively small. Dr. Philips pointed out that in a dataset of 1.8 million people, only about 8,800 were vegans, raising concerns about how robust the 23% risk reduction estimate really is.

Add to that a long list of variables that are difficult to fully control, screening behaviour, alcohol use, sleep, supplement intake, income, education, and the picture becomes even more complex.

A DEBATE FAR FROM SETTLED

Taken together, the evidence paints a far less clear-cut picture than the viral headline suggests.

Yes, some studies, including the latest meta-analysis, do show lower overall cancer rates among vegetarians and vegans. But others highlight increased risks for specific cancers, while many underline the role of broader lifestyle factors.

For now, the debate remains open.

What is increasingly clear, however, is that reducing cancer risk is unlikely to hinge on a single dietary choice.

Weight, physical activity, alcohol intake, smoking and access to screening all play a role, often as much, if not more, than whether meat is on the plate.

- Ends