Animal studies have shown that a high fructose intake can lead to insulin resistance in the brain, as well as a reduction in brain function, memory, learning and the formation of brain neurons (6, 7). One study in rats found that a diet high in sugar increased brain inflammation and impaired memory. Additionally, rats that consumed a diet consisting of 11% HFCS were worse than those whose diets consisted of 11% regular sugar (8)
High-fructose corn syrup (HFCS) may be especially harmful, causing brain inflammation and impairing memory and learning.
Research has shown that just a single meal with a high glycemic load can impair memory in both children and adults (10). This effect on memory may be due to inflammation of the hippocampus, a part of the brain that affects some aspects of memory, as well as responsiveness to hunger and fullness cues (10).
One study looked at elderly people who consumed more than 58% of their daily calories in the form of carbohydrates. The study found they had almost double the risk of mild mental impairment and dementia (12). Another study found that children aged six to seven who consumed diets high in refined carbs also scored lower on nonverbal intelligence (13). However, this study could not determine whether consuming refined carbs caused these lower scores, or simply whether the two factors were related.
In animal studies, rats fed a high-fat, high-sugar diet for eight months showed impaired learning ability and negative changes to brain plasticity. Another study found that rats fed a high-calorie diet experienced disruptions to the blood-brain barrier (30, 31, 32). The blood-brain barrier is a membrane between the brain and blood supply for the rest of the body. It helps protect the brain by preventing some substances from entering.
One of the ways processed foods may negatively impact the brain is by reducing the production of a molecule called brain-derived neurotrophic factor (BDNF) (10, 33). This molecule is found in various parts of the brain, including the hippocampus, and it’s important for long-term memory, learning and the growth of new neurons. Therefore, any reduction can have negative impacts on these functions (33).
aspartame is made of phenylalanine, methanol and aspartic acid (35). Phenylalanine can cross the blood-brain barrier and might disrupt the production of neurotransmitters. Additionally, aspartame is a chemical stressor and may increase the brain’s vulnerability to oxidative stress (35, 36).
One study looked at the effects of a high-aspartame diet. Participants consumed about 11 mg of aspartame for every pound of their body weight (25 mg per kg) for eight days. By the end of the study, they were more irritable, had a higher rate of depression and performed worse on mental tests (37).
Another study found people who consumed artificially sweetened soft drinks had an increased risk of stroke and dementia, though the exact type of sweetener was not specified (38).
A study of repeated aspartame intake in mice found that it impaired memory and increased oxidative stress in the brain. Another found that long-term intake led to an imbalance in antioxidant status in the brain (39, 40). Interestingly mice and rats are reportedly 60 times less sensitive to phenylalanine than humans (35, 41).
A number of papers have reported that aspartame has no adverse effects (42).
When consumed in moderation, alcohol can be an enjoyable addition to a nice meal. Chronic alcohol use results in a reduction in brain volume, metabolic changes and disruption of neurotransmitters, which are chemicals the brain uses to communicate (43).
However, moderate alcohol consumption may have beneficial effects, including improved heart health and a reduced risk of diabetes. These beneficial effects have been particularly noted in moderate wine consumption of one glass per day (51, 52, 53).
Written by Elise Mandl, BSc, APD on January 28, 2018
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