By Amy Norton
Scientists found that when they added the compounds -- called advanced glycation end products (AGEs) -- to the lifelong diets of laboratory mice, the animals developed greater amounts of beta-amyloid in the brain. Beta-amyloid is the protein that makes up the brain "plaques" seen in people with Alzheimer's disease.
What's more, mice fed these compounds developed more problems with movement and memory as they aged compared to mice that spent their lives dining on chow that produced low levels of these chemicals.
AGEs are naturally present in small amounts in the human body, said senior researcher Dr. Helen Vlassara, of the Mount Sinai School of Medicine in New York City. But you also ingest the compounds through food -- particularly animal products prepared at a high heat.
That includes fried, grilled or broiled meats, and dairy products that are pasteurized or sterilized.
"We ingest these toxins in huge amounts over a lifetime," Vlassara said.
The problem with that, she explained, is that accumulating AGEs can promote chronic inflammation in the body. And that type of persistent, low-level inflammation is implicated in many disease processes, including Alzheimer's.
The new findings, reported Feb. 24 in the Proceedings of the National Academy of Sciences, suggest that a diet high in these compounds is unhealthy for mouse brains.
The investigators found that people with higher blood levels of a particular AGE tended to show a bigger dip in mental acuity over nine months.
However, another Alzheimer's researcher said much more work is needed to clarify how these compounds might affect the human brain.
"We need larger, well-controlled studies to identify a strict correlation between dietary AGEs and cognitive [mental] decline," said Dr. Jeremy Koppel, a geriatric psychiatrist and scientist at the Feinstein Institute for Medical Research in Manhasset, N.Y.
"Well-controlled" means that researchers would have to account for many other factors in people's mental function -- such as education, overall health and lifestyle habits. Koppel said studies should also use "more elaborate" tests of memory and other mental abilities, and not only the short screening tool used in this study.
For now, he said, "The take-away is that a diet enriched in these compounds seems to do bad things in mice."
Vlassara agreed that more human studies are needed. But she said people don't have to wait to make dietary changes -- especially since cutting down on foods high in these compounds, and eating more plant-based foods, generally are considered healthy moves.
"You don't have to become a vegetarian," Vlassara said. "But pay attention to what you eat and how you prepare it."
Since these chemicals are churned out when food is cooked at a high and dry heat, Vlassara said people can try using "less heat and more water" when they cook -- through methods such as poaching, braising and steaming.
No one knows whether swapping cooking techniques will curb the risk of Alzheimer's. And Koppel cautioned that findings from mice cannot simply be applied to humans. It's not clear, for example, how high a person's intake of AGEs would have to be to match what the lab mice ate.
Still, Vlassara said, many people are interested in potential ways to slow or prevent mental decline as they age. Aiming for a healthier diet, she said, "is an easy step you can make on your own."
In the United States, more than 5 million people have Alzheimer's disease. That number could balloon to nearly 16 million by 2050 as the elderly population grows, according to the Alzheimer's Association. There is no proven way to prevent it, but studies have suggested that some of the same problems that damage the heart -- such as high blood pressure, high cholesterol and diabetes -- may also boost the risk of Alzheimer's.