Ăn thịt siêu chế biến có nguy cơ tử vong sớm cao hơn

Ăn thịt siêu chế biến có nguy cơ tử vong sớm cao hơn

Một nghiên cứu của Harvard trong hơn 30 năm đã cho thấy ăn thịt siêu chế biến có liên quan đến việc tăng nguy cơ tử vong sớm.

Scientists tracked more than 114,000 adults in one of the most extensive studies into the long-term consequences of modern diets.

The highest risks were associated with the most processed meats such as sausages and ham. Regular consumers of such products had a 13 per cent higher chance of dying over the 34 years tracked.

Diets high in sugary and artificially sweetened drinks had a 9 per cent increased risk, the study found.

Overall, those eating diets with a high proportion of packaged goods and snacks were found to have a 4 per cent higher risk of death over the period.

Such foods have already been linked with obesity, heart disease, diabetes and bowel cancer.

However, few studies have tracked participants for such a long time, or examined overall deaths.

The Harvard study also went further than previous research in teasing out the potential impact of different types of ultra-processed foods.

Dairy desserts – such as cheesecake or fromage frais – were linked to a 6 per cent increased risk, while breads and breakfast cereals were linked to a four per cent increase.

Study tracked participants for 34 years

In the major study, researchers tracked the long-term health of 74,563 female nurses and 39,501 male health professionals between 1984 and 2018.

Female participants were aged between 30 and 55 at the start of the research, while men were between 40 and 75.

Every two years participants provided information on their health and lifestyle habits, with detailed food questionnaires completed every four years.

In the years that followed, researchers identified 48,193 deaths from cancer, cardiovascular, respiratory and neurodegenerative diseases.

Diets were analysed and split into four groups.

Overall, those with the highest intake of ultra-processed foods – an average of seven servings daily – had a four per cent higher risk than those in the lowest group, which consumed an average of three daily servings.

The strongest links were found between meat, poultry and seafood ready-to-eat products, such as sausages, ham, hot dogs, convenience meals and processed snacks. These were followed by sugary and artificially sweetened soft drinks and then by dairy-based desserts.

The findings “provide support for limiting consumption of certain types of ultra-processed food for long-term health”.

“Our findings suggest that meat/poultry/seafood-based ready-to-eat products and sugar-sweetened and artificially sweetened beverages are major factors contributing to the harmful influence of ultra-processed foods on mortality,” researchers from Harvard’s Departments of Epidemiology and Nutrition concluded.

They said the findings “provide support for limiting consumption of certain types of ultra-processed food for long-term health”.

Ultra-processed foods include packaged baked goods and snacks, fizzy drinks, sugary cereals, and ready-to-eat or heat products.

They often contain colours, emulsifiers, flavours and other additives and are typically high in energy, added sugar, saturated fat, and salt, but lack vitamins and fibre.

However, there is no clear definition, with arguments about whether some products, such as wholemeal bread, should be categorised as ultra-processed.

In the Harvard study, wholegrain foods were not counted as ultra-processed, with researchers saying they were excluded because of their established benefits in lowering mortality.

The study was observational, meaning no firm conclusions could be drawn about cause and effect.

The research also found the association was less pronounced after overall dietary quality was taken into account.

Mixed reaction to study results

Dr Duane Mellor, a dietitian and spokesperson for the British Dietetic Association, said the findings were interesting and in line with other studies highlighting the risks of processed meats and sugary and artificially sweetened drinks.

However, he said the findings suggested the overall health of the diet was most important.

Dr Mellor said: “It is also noticeable that those who consumed most ultra-processed foods tended to eat few vegetables, fruit, legumes and whole grain. This appeared to suggest that it might not be as simple as that those who ate more ultra-processed foods were more likely to die earlier – it is quite possible that these foods might displace healthier foods from the diet.”

Professor Christine Williams, Emeritus Professor Human Nutrition, University of Reading, said the approach taken by researchers was more “nuanced” than many studies attempting to establish the risks of processed foods in separating out different categories.

She said: “This new UPF study comes from the Harvard group – the leading group worldwide in the area of nutritional epidemiology. This large study includes men and women followed up for cause of death for over 34 years with baseline information dating back to 1984 and 1986. They examined the relationship between UPF consumption levels and risk of mortality (all diseases) as well as mortality from specific causes (cancer, cardiovascular, respiratory, neurodegenerative and other causes).

“The study showed a modest association with high UPF consumption on the outcome category ‘All deaths’, which were 4 per cent higher in the high UPF group.”

However, Professor Sir David Spiegelhalter, Emeritus Professor of Statistics, University of Cambridge, said such an association was “weak”.

He said it was “surprising” that researchers’ conclusions focused on the risks from processing given their acknowledgement that overall dietary quality had the greatest impact.

It comes after research found that people following a personalised nutrition program that avoids ultra-processed foods lost more weight and saw improvements in blood sugar control, compared with those following standard health guidelines.

This research – published in the journal Nature Medicine – tracked adults following Zoe, a program that provides food recommendations after testing an individual’s gut bacteria and response to fats and sugars, encouraging a diet rich in plants and avoiding ultra-processed foods.

The randomised 18-week control trial involving 347 adults in the US found those put on the program lost an average of 2.5 kilograms more than those following generalised government advice.

Tests showed significant improvements in blood sugar control, more “good” gut bacteria, and improved mood and sleep among those following the program, founded by Professor Tim Spector.

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