They were also asked about their consumption of nuts and legumes, including peanut butter, peanuts, walnuts, other nuts, string beans, beans, peas, soy milk and tofu.
More than 11,000 cases of dementia were identified during the follow-up period.
Processed meat twice a week raises risk by 14%
Consuming two servings of processed red meat each week appeared to raise the risk of dementia by 14 per cent, compared with consumption of about three servings a month, according to the study abstract, which has been presented to the Alzheimer’s Association International Conference in the US.
The researchers also assessed the language, executive function and processing of more than 17,000 people involved in the study. They also analysed their ability to recall and understand words and sentences, also known as verbal memory.
They found that replacing one daily serving of processed red meat with a daily serving of nuts, beans or tofu every day may lower the risk of dementia by 23 per cent, with 20 per cent lower odds of cognitive decline.
There was no significant link found between unprocessed red meat – such as steak and lamb chops – and dementia risk.
Previously, studies have suggested that processed meat fuels heart disease, with growing evidence that what is bad for the heart is bad for the brain.
The new study could not prove any causal link between the foods consumed and the risk of dementia, but scientists said the preservatives and salt in such foods might be fuelling the risks.
Researchers said that, until now, study results had been mixed on the relationship between cognitive decline and meat consumption, prompting them to take a closer look at how eating different amounts of both processed and unprocessed meats affects cognitive risk and function.
‘A significant risk factor’
Lead researcher Yuhan Li, who conducted the study while a graduate student at the Harvard TH Chan School of Public Health in Boston, said: “By studying people over a long period of time, we found that eating processed red meat could be a significant risk factor for dementia.”
Li, now at Brigham and Women’s Hospital in Boston, said: “Dietary guidelines could include recommendations limiting it to promote brain health.
“Processed red meat has also been shown to raise the risk of cancer, heart disease and diabetes. It may affect the brain because it has high levels of harmful substances such as nitrites (preservatives) and sodium.”
Heather Snyder, vice-president of medical and scientific relations at the Alzheimer’s Association, said: “Prevention of Alzheimer’s disease and all other dementia is a major focus, and the Alzheimer’s Association has long encouraged eating a healthier diet – including foods that are less processed – because they’ve been associated with lower the risk of cognitive decline. This large, long-term study provides a specific example of one way to eat healthier.”
Dr Hilda Mulrooney, reader in nutrition and health at London Metropolitan University, said the study was a “large and long-term” piece of work which found “significant association between both processed red meat and red meat consumption and risk of cognitive decline”.
The nature of the study meant a causal relationship could not be demonstrated but she said the findings had “biological plausibility”.
“The findings align with recommendations to replace meat with protein-rich alternatives such as beans and nuts for sustainability reasons.
“The UK healthy eating guidelines already recommend reducing meat and processed meat consumption and focusing more on non-meat protein sources for health and sustainability reasons – although this study can’t prove cause and effect, its findings are in line with that.”
