You may have seen the recent article in The New York Times that reported on a study linking highly processed foods to cognitive decline and dementia. The study, published in the American Journal of Clinical Nutrition, followed more than 2,000 older adults for 10 years and found that those who ate the most ultra-processed foods had a higher risk of developing Alzheimer's disease and other forms of dementia.
But what exactly are ultra-processed foods and how do they affect our brain health? According to the NOVA classification system, ultra-processed foods are those that undergo multiple industrial processes and contain additives, preservatives, artificial flavors, colors, sweeteners, and other substances that are not normally used in cooking. Examples of ultra-processed foods include soft drinks, candy, chips, frozen meals (but not all), instant noodles, breakfast cereals, and many packaged snacks.
Ultra-processed foods are detrimental to our brain health for several reasons. First, they are often high in sugar, refined carbohydrates, and unhealthy fats, which can cause inflammation, oxidative stress, insulin resistance, and dyslipidemia. These metabolic disturbances can impair the blood flow and nutrient delivery to the brain, as well as damage the neurons and synapses that are essential for memory and cognition.
Second, ultra-processed foods are low in fiber, antioxidants, phytochemicals, and other beneficial nutrients that support the brain's structure and function. For instance, fiber helps regulate blood sugar levels and feeds the gut microbiome, which produces neurotransmitters and modulates inflammation. Antioxidants and phytochemicals protect the brain from oxidative stress and modulate gene expression. Other nutrients such as omega-3 fatty acids, choline, B vitamins, magnesium, zinc, and iron are involved in various aspects of brain development, neurotransmission, neurogenesis, and neuroprotection.
Third, ultra-processed foods can disrupt the gut-brain axis, which is the bidirectional communication between the gastrointestinal tract and the central nervous system (read more on that here). The gut-brain axis influences our mood, cognition, behavior, and immune system. Ultra-processed foods can alter the composition and function of the gut microbiota, increase intestinal permeability (leaky gut), and trigger systemic inflammation. These changes can affect the production and signaling of neurotransmitters such as serotonin and dopamine, as well as activate the hypothalamic-pituitary-adrenal (HPA) axis and increase cortisol levels. Chronic stress and inflammation can impair synaptic plasticity and neurogenesis in the hippocampus, a brain region involved in learning and memory.
The bottom line is that ultra-processed foods offer no health benefit. They can increase our risk of cognitive decline and dementia by affecting multiple pathways that are crucial for optimal brain function. To protect our brain health and prevent cognitive impairment as we age, we should limit or avoid ultra-processed foods and instead choose whole foods that are rich in nutrients and phytochemicals that support our brain health. Some examples of brain-friendly foods include berries, leafy greens, nuts, seeds, fatty fish, eggs, legumes and fermented foods. A safe bet is to follow the principles of the Mediterranean diet (find out more here).
Our foods are high in fiber, antioxidants, phytochemicals and so much more.