Ultra-processed foods linked to higher risk of death in long-term study

BMJMay 8 2024

Higher consumption of most ultra-processed foods is linked to a slightly higher risk of death, with ready-to-eat meat, poultry, and seafood based products, sugary drinks, dairy based desserts, and highly processed breakfast foods showing the strongest associations, finds a 30-year US study in The BMJ today.

The researchers say not all ultra-processed food products should be universally restricted, but that their 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.

Mounting evidence links ultra-processed foods to higher risks of obesity, heart disease, diabetes and bowel cancer, but few long term studies have examined links to all cause and cause specific deaths, especially due to cancer.

To address this knowledge gap, researchers tracked the long-term health of 74,563 female registered nurses from 11 US states in the Nurses' Health Study (1984-2018) and 39,501 male health professionals from all 50 US states in the Health Professionals Follow-up Study (1986-2018) with no history of cancer, cardiovascular diseases, or diabetes at study enrolment.

Every two years participants provided information on their health and lifestyle habits, and every four years they completed a detailed food questionnaire. Overall dietary quality was also assessed using the Alternative Healthy Eating Index-2010 (AHEI) score.

During an average 34-year follow-up period, the researchers identified 48,193 deaths, including 13,557 deaths due to cancer, 11,416 deaths due to cardiovascular diseases, 3926 deaths due to respiratory diseases, and 6343 deaths due to neurodegenerative diseases.

Compared with participants in the lowest quarter of ultra-processed food intake (average 3 servings per day), those in the highest quarter (average 7 servings per day) had a 4% higher risk of total deaths and a 9% higher risk of other deaths, including an 8% higher risk of neurodegenerative deaths.

No associations were found for deaths due to cardiovascular diseases, cancer, or respiratory diseases.

In absolute numbers, the rate of death from any cause among participants in the lowest and highest quarter of ultra-processed food intake was 1472 and 1536 per 100,000 person years, respectively.

The association between ultra-processed food intake and death varied across specific food groups, with meat, poultry, and seafood based ready-to-eat products showing the strongest and most consistent associations, followed by sugar sweetened and artificially sweetened beverages, dairy based desserts, and ultra-processed breakfast food. 

And the association was less pronounced after overall dietary quality was taken into account, suggesting that dietary quality has a stronger influence on long term health than ultra-processed food consumption, note the authors.

This is an observational study, so no firm conclusions can be drawn about cause and effect, and the authors point out that the ultra-processed food classification system does not capture the full complexity of food processing, leading to potential misclassification. In addition, participants were health professionals and predominantly white, limiting the generalizability of the findings.

However, this was a large study with long follow-up, using detailed, validated, and repeated measurements, and results were similar after further analyses, providing greater confidence in the conclusions.

The researchers stress that not all ultra-processed food products should be universally restricted and say oversimplification when formulating dietary recommendations should be avoided. 

But they conclude: "The findings provide support for limiting consumption of certain types of ultra-processed food for long term health," adding that "future studies are warranted to improve the classification of ultra-processed foods and confirm our findings in other populations."

In a linked editorial, researchers in New Zealand point out that recommendations to avoid ultra-processed food may also give the impression that foods that are not ultra-processed, such as red meat, can be frequently consumed.

They argue that debate about the ultra-processed concept must not delay food policies that improve health, such as restrictions on marketing unhealthy foods to children, warning labels on nutritionally poor food products, and taxes on sugary drinks.

"Our focus should be on advocating for greater global adoption of these and more ambitious interventions and increasing safeguards to prevent policies from being influenced by multinational food companies with vested interests that do not align with public health or environmental goals," they conclude.