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 U.S. observational study. The results were published in the journal The BMJ.

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”. 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 causes 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 States in the Nurses’ Health Study (1984-2018) and 39,501 male health professionals from all 50 U.S. 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, 3,926 deaths due to respiratory diseases, and 6,343 deaths due to neurodegenerative diseases.

Compared with participants in the lowest quarter of ultra-processed food intake (average three servings per day), those in the highest quarter (average seven 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 1,472 and 1,536 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. 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.

The safety of intermittent fasting, a popular strategy to lose weight by limiting food intake to certain times, was called into question by a surprise finding from research presented at a medical meeting. 

Limiting mealtimes to a period of just eight hours a day was linked to a 91% increase in risk of death from heart disease in the study, which was released on Monday in Chicago. The American Heart Association published only an abstract, leaving scientists speculating about the details of the study protocol. The study was reviewed by other experts prior to its release, according to the AHA. 

Lifestyle interventions aimed at weight loss have come under scrutiny as a new generation of drugs help people shed pounds. Some doctors questioned the study’s findings, saying they could have been skewed by differences – such as underlying heart health – between the fasting patients and the comparison group, whose members consumed food over a daily period of 12 to 16 hours. 

“Time-restricted eating is popular as a means of reducing calorie intake,” Keith Frayn, emeritus professor of human metabolism at the University of Oxford, said in a statement to the UK Science Media Center. “This work is very important in showing that we need long-term studies on the effects of this practice. But this abstract leaves many questions unanswered.” 

The researchers, led by Victor Zhong of the Shanghai Jiao Tong University School of Medicine, analyzed data from about 20,000 adults included in the US Centers for Disease Control and Prevention’s National Health and Nutrition Examination Survey. 

The study looked at answers to questionnaires along with death data from 2003 through 2019. Because it relied in part on forms that required patients to recall what they ate over two days, scientists said there was room for potential inaccuracies. About half of the patients were men and the mean age was 48. 

It wasn’t clear how long the patients continued the intermittent fasting, though the researchers assumed they kept it up, according to Zhong. 

The fasting patients were more likely to be younger men with a higher BMI and food insecurity, he said by email. They also had a lower prevalence of hypertension, diabetes and cardiovascular disease based on self-reports. “We controlled for all these variables in the analysis, but the positive association between 8-h time-restricted eating and cardiovascular mortality remained,” Zhong said. 

The abstract was presented at the AHA’s Lifestyle Scientific Sessions meeting in Chicago. 

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