How Fast Food Affects Memory and Cognitive Ability?

Processed food is bad for the brain

Fast food is not just a calorie bomb – it also contains many ingredients that, rather than providing valuable nourishment for the body, actually weaken it. Processed food is not the healthiest dietary choice, and many people don’t realise the impact it has on their bodies. Every organ suffers from excessive fast food consumption – from the heart and liver to the grey matter in the brain.

The brain is particularly sensitive to what we eat. It can give subtle hints indicating it is not receiving adequate fuel (in the form of food). Unfortunately, these are quite easily ignored. Fatigue, trouble concentrating, impaired ability to learn, and difficulty seeing how things connect? Not everyone will link these symptoms to a poor diet, and that’s a mistake.

Scientists are increasingly talking about the link between what we call the Western diet (processed, laden with fast food) and accelerated brain aging, impaired learning, concentration, and cognitive abilities. Discover which ingredients have the most negative impact on brain function and health.

Memory-deteriorating trans fatty acids

Trans fatty acids are undoubtedly the worst type of fat to eat. You should aim to limit their consumption to an absolute minimum. According to WHO recommendations, the maximum content of trans fatty acid isomers in your daily diet should not exceed 1% of your total energy intake. Trans fatty acids eaten in excess contribute to atherosclerosis, are carcinogenic, and negatively affect the brain.

Researchers at the University of California, San Diego, analysed the diets of more than a thousand volunteers and tested their memory capabilities. They demonstrated that an increased intake of trans fatty acids is associated with impaired memory. This relationship was observed across different age groups, but it was most pronounced in young adults.

How do trans fats damage the brain? They negatively affect neuronal metabolism and increase oxidative stress on the brain and the entire nervous system. Trans fats increase the presence of oxygen radicals, which destabilise neurons, including their DNA, proteins, and other fats within these cells. In consequence, the neurons die. The cells of the hippocampus are the most sensitive to oxygen free radicals. This brain structure is responsible, among other things, for memory and memorising.

Other studies link consumption of trans fatty acids to increased irritability, mood swings, and even higher levels of aggression.

Trans fatty acids are primarily ingested through processed foods:

• hard margarine and products containing hard margarine;
• pastries: cakes, biscuits, cookies, crackers, ‘butter rolls’;
• fried foods: french fries, nuggets, burgers – especially deep-fried foods prepared using commercial frying oil;
• filled chocolates, spreads, candy bars;
• chips, crackers, popcorn (especially ‘buttered’ popcorn).

Most trans fatty acids consumed, as much as 40%, come from pastries – cakes, cookies, doughnuts, sweet buns... These products are rarely classified as fast food, but when we look at their ingredients, they certainly fit the bill. Store-bought pastries are particularly high in trans fatty acids: ready-made puff pastry, filled croissants, shortbread, and ‘butter buns’. These products, while seemingly innocuous at first glance, don’t appear greasy but are packed with unhealthy trans fatty acids. They should definitely be avoided.

Sugar + fat: an addictive combination

The combination of sugar and fat is particularly appealing to the brain. The human body is evolutionarily wired to prefer calorie-dense flavours and combinations. However, with processed foods, this preference does not translate into real nutritional value. Products high in both fats and carbohydrates are instinctively ‘liked’ and can lead to increased appetite and overeating, which significantly hinders intuitive eating. Examples of foods rich in fat and sugar:

• chips (carbohydrates from potatoes, fat from frying);
• chocolate and chocolate products (cocoa fat and sugar);
• pizza (carbohydrates from white flour, fat from cheese and toppings);
• ice cream (fat from cream and a significant amount of sugar);
• cookies and pastries (butter or margarine as a source of fat, white flour as a source of carbohydrates, added sugar);
• whipped cream, other creams (milk fat and added sugar).

It is worth noting that few single foods in nature are high in both simple carbohydrates and fat.

Upon contact with saliva, the combination of sugar and fat (often enhanced by the addition of salt) stimulates receptors that send signals to the brain, prompting the release of dopamine, known as the pleasure hormone. This might seem innocuous, but a dopamine rush encourages the body to repeat the activity regardless of the consequences. It reinforces the pattern and sparks a desire to repeat the action that triggered the neurotransmitter release. Dopamine is also released when smoking cigarettes, scrolling through social media, or shopping. According to experts, it plays a key role in the development of addictions. Consequently, you can become truly hooked on highly processed foods.

Eating foods high in simple sugars and fats can increase dopamine concentration by up to 200% compared to baseline levels. According to one theory of addiction, the faster a substance affects the brain, the greater its addictive potential. Processed foods and fast foods are quickly digested and have an almost immediate effect on the brain. So it is not an exaggeration to say that processed foods exploit biological mechanisms to make us eat more and, as a result, become addicted.

Fast food and other processed foods have a broad impact on the brain. They aggravate inflammation, increase the risk of atherosclerosis blocking efficient blood flow to organs. As a result, cognitive abilities decline. The brain simply ages more rapidly.

Brain fog from sugar and insulin spikes

Processed foods and fast foods are high in simple sugars that are quickly released into the bloodstream, causing ‘glucose spikes’ and ‘insulin spikes’. This leads to elevated glucose levels over the long term. Glucose is the primary source of energy for all cells, and the brain requires the most glucose to operate.

All brain functions, such as thinking, memorising, and learning, are glucose-dependent. However, this does not mean that more glucose is better for the brain. Maintaining a relatively constant blood glucose level is optimal. Both elevated glucose levels (hyperglycaemia) and excessively low glucose levels (hypoglycaemia) are detrimental to the brain.

The effects? Inattentiveness, impaired concentration and cognitive functions, and the characteristic ‘brain fog’ that manifests as literally ‘clouded’ brain function: forgetfulness, confusion, difficulties focusing on tasks, or even on one’s own thoughts.

The body’s natural mechanisms, such as the release of the hormones insulin and glucagon, are responsible for maintaining the right glucose levels in the blood and cells. Glucose levels are also strongly influenced by diet.

Avoiding fast foods, defined as processed foods with a high glycaemic index and low in fibre and protein, is one way to stabilise blood glucose and insulin levels. First and foremost, high-carbohydrate and low-nutrient foods such as confectionery, sweets, candy bars, cookies, pastries, sugary drinks, sugary breakfast cereals, and white bread should be excluded from the diet.

Deficiency of fibre, a valuable component for the gut-brain axis

Processed and fast foods provide little dietary fibre, which is crucial for gut health and the gut microbiota. Everyone should consume at least 25 grams of fibre per day, but our diet often contains much less.

There is a unique direct connection between the brain and the gut. A diverse gut microbiota supports proper brain function, the adequate release of neurotransmitters, a good mood, and effective rest.

Read more: The gut is your second brain: How does the microbiome affect your well-being??

Fibre deficiency in the diet leads to:

• A depletion of the gut microbiota, which can negatively impact mental wellbeing.
• Aggravated inflammation, which can contribute to problems with memory, concentration, and overall wellbeing.
• A greater risk of sugar spikes after a meal, which can make it harder to concentrate and cause fatigue.
• Disruption in neurotransmitter production that can exacerbate anxiety disorders, worsen mood, and affect overall wellbeing.

Excess salt reduces the oxygen supply to the brain

Fast foods and processed foods are extremely high in salt. The daily salt requirement is no more than 5-6 grams, but Poles exceed this amount by up to three times! The most common culprit is processed food, which contains significant amounts of ‘invisible’ added salt. On average, one hamburger contains about 2 grams of salt, a slice of pizza provides about 1.8 grams, and a pack of chips more than 2 grams. A single fast food meal can cause you to exceed your daily salt intake.

Too much salt in the diet can cause hypertension and heart disease. However, few people realise how excess salt affects the brain. In the long term, it can even lead to cognitive impairment, strokes, or cerebrovascular disease.

One possible mechanism behind the negative effects of excess salt on the brain is the impact of sodium (the main component of salt) on the regulation of vascular tone. Salt reduces blood flow to the brain by constricting blood vessels. This adverse effect leads to hypertension in the long term, but it also instantly reduces the oxygen supply to the brain, affecting its overall performance.

Excess salt in the diet can also cause headaches and even alter the release of neurotransmitters, directly affecting the mood and cognitive function. Too much salt also has a negative impact on the intestines and the immune system, both of which are directly linked to the nervous system.

How to strike a balance?

Processed fast food often provides short-term pleasure, but you don’t necessarily have to give it up altogether. Forcing yourself to avoid a certain type of food at all costs can negatively affect your mood more than the unhealthy product itself. It is extremely important to find the right balance and maintain a good relationship with food.

In a healthy diet, there is room for every product group. Even fast foods can be included in a balanced menu, provided we approach them in the right way. Here are some tips to help you develop your own system and make sensible choices regarding processed foods, rather than making them the core of your diet.

1. Consider healthier alternatives

Healthier options are more and more common on restaurant menus. You don’t have to miss out on going out with friends or decline a lunch invitation to have a nutritious meal. For instance, you can opt for halloumi cheese instead of breaded pork chops or greasy meat. Choose non-breaded options, and if you’re in the mood for something meaty, go for poultry. You can also find many healthier versions of fast food meals in the vegetarian and vegan sections of the menu. While not perfect, these options provide more fibre, vegetables, and fewer saturated fatty acids.

2. Move away from the ‘all-or-nothing’ approach

Don’t let a Friday pizza night or a serving of fries derail all the healthy habits you’ve adopted. Allow flexibility in your diet by following the 80/20 rule. Aim for 80% of your food to be nutritious and balanced, while the remaining 20% can be enjoyed for pure pleasure. Increasing the amount of typical recreational foods in your diet may slow down your progress (if that’s your goal), but it can also help you develop sustainable healthy eating habits.

3. Ask yourself: ‘Do I really feel like it?’

Avoid reaching for fast foods out of habit. Treat them as recreational products. Choose high-quality foods that will provide genuine pleasure or satisfy a specific craving. Don’t opt for low-nutritional foods just because they are readily available. Remember that when a product is on promotion or is available as an ‘extra value meal’, it still doesn’t mean you need to order it. If you’re indulging in a ‘recreational’ product, choose the smallest portion that will bring you enjoyment.

Get a sugar-free drink

If you’re ordering a beverage to accompany your main course or snack, choose something that won’t add extra sugar. A meal eaten ‘out on the town’ is likely to be loaded with easily digestible carbohydrates anyway. Don’t add any more sugar and calories to help control the glucose spike and lower the risk of drowsiness and feeling unwell after the meal. Opt for still or sparkling water, a ‘zero calorie’ drink, or sugar-free tea, for example.

4. Eat something healthy too

If you have a strong craving for a specific less healthy product, go for it, but ensure that the other components of the meal (or subsequent meals) align with the guidelines of a healthy diet.

How to do it in practice? Here are a few suggestions:

• Choose a salad as an accompaniment to your fast food meal, preferably as an appetiser.
• Put a healthy snack, such as crudités, next to your bowl of chips.
• Add chocolate to your oatmeal or millet porridge.
• Wash down your sweet bun with a glass of kefir to boost your protein intake.

The antioxidants from the vegetables will help neutralise inflammation caused by trans fatty acids, while the addition of protein will help manage glucose and insulin spikes after a high-carbohydrate meal.

5. Find true moderation and discover your own balance

Don’t justify ordering unhealthy takeouts several times a week with the idea of maintaining a ‘healthy balance.’ Consider whether you are realistically adhering to the 20/80 rule, or if the 20% of ‘recreational,’ less nutritious foods have inadvertently become 30% or 40%.

There is no single correct way to incorporate recreational foods into your menu. Some people might find that very small portions eaten almost every day work for them, while others may prefer having one recreational meal away from home each week or making exceptions for special occasions such as birthdays or holidays.

_References:

• _{Guo Y., Zhu X., Zeng M., Qi L., Tang X., Wang D., Zhang M., Xie Y., Li H., Yang X., Chen D., A diet high in sugar and fat influences neurotransmitter metabolism and then affects brain function by altering the gut microbiota. Transl Psychiatry, 2021 May 27;11(1):328, doi: 10.1038/s41398-021-01443-2, PMID: 34045460, PMCID: PMC8160265.}
• _{Golomb B. A., Bui A. K., A Fat to Forget: Trans Fat Consumption and Memory, PLoS One, 2015 Jun 17;10(6):e0128129, doi: 10.1371/journal.pone.0128129, PMID: 26083739, PMCID: PMC4470692.}
• _{Chianese R., Coccurello R., Viggiano A., Scafuro M., Fiore M., Coppola G., Operto F. F., Fasano S., Laye S., Pierantoni R., Meccariello R., Impact of Dietary Fats on Brain Functions. Curr Neuropharmacol, 2018;16(7):1059-1085, doi: 10.2174/1570159X15666171017102547, PMID: 29046155, PMCID: PMC6120115.}
• _{Hu L., Zhu S., Peng X., Li K., Peng W., Zhong Y., Kang C., Cao X., Liu Z., Zhao B., High Salt Elicits Brain Inflammation and Cognitive Dysfunction, Accompanied by Alternations in the Gut Microbiota and Decreased SCFA Production, J Alzheimers Dis, 2020;77(2):629-640, doi: 10.3233/JAD-200035, PMID: 32741809.}
• _{Giles C., Takechi R., Mellett N. A., Meikle P. J., Dhaliwal S., Mamo J. C., The Effects of Long-Term Saturated Fat Enriched Diets on the Brain Lipidome, PLoS One, 2016 Dec 1;11(12):e0166964, doi: 10.1371/journal.pone.0166964, PMID: 27907021, PMCID: PMC5132325.}