Sugar May Promote Dementia, German Medical Societies Say

On the occasion of World Brain Day (22 July 2024), the German Society for Neurology (DGN) and the German Brain Foundation have highlighted that excess sugar can harm the brain. Current results from the Global Burden of Diseases study show that stroke and dementia are among the top 10 causes of death. A healthy and active lifestyle with sufficient exercise and sleep, as well as avoiding harmful substances such as alcohol, nicotine or excess sugar, protect the brain.

“Of course, it’s the dose that makes the poison, because the brain, which is the body’s powerhouse, needs glucose to function,” said Dr. Frank Erbguth, president of the German Brain Foundation, in a press release from the DGN and the German Brain Foundation. “However, with a permanent increase in blood sugar levels due to too many and too large meals and constant snacking, we overload the system and fuel the development of neurological diseases, especially dementia and stroke.”

In 2021/2022, sugar consumption per capita was 33.2 kg, almost double the recommended amount. The German Nutrition Society recommends that sugar should not account for more than 10% of energy consumed. With a target of 2,000 kilocalories, this corresponds to 50 g per day, or 18 kg per year. This total includes not only added sugar, but also naturally occurring sugar, such as in fruit, honey or fruit juices.

What is the mechanism?

High blood sugar levels damage the blood vessels in the brain and promote deposits on the vessel walls, reducing blood flow and nutrient supply to brain cells. This process can lead to various limitations, as well as vascular dementia.

In Germany, around 250,000 people are diagnosed with dementia each year, of which 15 to 25 percent suffer from vascular dementia. This proportion represents between 40,000 and 60,000 new cases each year.

In addition, glycosaminoglycans, which are complex sugar molecules, can directly impair cognition. They affect the functioning of synapses between nerve cells and, therefore, neuronal plasticity. Experimental data presented at the 2023 meeting of the American Chemical Society demonstrated this phenomenon.

Twenty years ago, a study showed that a diet high in fat and sugar disrupts neuronal plasticity and can impair hippocampal function in the long term. A recent meta-analysis confirms these results: although mental performance improves 2 to 12 hours after sugar consumption, prolonged sugar consumption can permanently damage cognitive functions.

Diabetes mellitus can indirectly cause brain damage. Since the 1990s, it has been known that patients with type 2 diabetes have a significantly higher risk of dementia. It is also suspected that glucose metabolism is disrupted in neurons, contributing to the development of Alzheimer’s disease. Insulin also plays a role in the formation of Alzheimer’s plaques.

The Max Planck Institute for Metabolism Research demonstrated last year that regular consumption of foods high in sugar and fat can change the brain. This leads to an increased craving for foods high in sugar and fat, which in turn promotes the development of obesity and type 2 diabetes.

Reduce sugar consumption

DGN and the German Brain Foundation recommend limiting sugar consumption. This process is often difficult, because even a small dose of sugar can trigger signals from the gut to the brain via the vagus nerve, causing a strong craving for sugar. “This could be the reason why some people quickly eat an entire chocolate bar after eating only one,” says Erbguth. In addition, the “feel-good hormone” dopamine is released in the brain when sugar is consumed, leading to a craving for more sugar.

“It makes sense to break this cycle by avoiding sugar as much as possible,” said Dr. Peter Berlit, secretary general and spokesman of the DGN. “The effort is worth it, because 40 percent of all dementia cases and 90 percent of all strokes are preventable, many of which are linked to industrial sugar,” said Berlit. The DGN and the German Brain Foundation support the call for a tax on particularly sugary drinks. They also point out that foods such as yoghurt or ketchup contain sugar and that alcohol can also significantly increase blood sugar levels.

This story was translated from German edition of Medscape using multiple editorial tools, including AI, in the process. Human editors reviewed this content before publication.

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