Impact of sugar on the body, brain, and behavior

Estava curioso para saber quais as últimas pesquisas, ou melhor, o apanhado de pesquisas, que valida o que sabemos sobre o efeito do açúcar no corpo. Tenho picos de sugar craving e este é um dos pontos que a auto-análise sozinha não funciona. É preciso cavar mais a fundo na fisiologia do próprio corpo.

Recortes

Sugar typically refers to a category of simple carbohydrates that includes monosaccharides like fructose and glucose, and disaccharides, like sucrose and lactose, which have different effects on the body and brain.

Sucrose, or table sugar, is a disaccharide made up of one-part glucose and one-part fructose.

Because most added sugar consumption comes from sucrose or HFCS, we typically consume both fructose and glucose together. However, research on the individual monosaccharides, fructose and glucose, has revealed large differences in how they affect the body.

Most of the glucose in the blood stream is not stored in the liver but rather, through the action of insulin, quickly passes through to muscle, adipose, and other peripheral tissues where it can immediately be used as energy. Fructose, on the other hand, is a less direct source of energy. Independent of insulin, the liver converts fructose to glucose, lactate, and/or fatty acids before passing it to the blood stream where it can be oxidized in other tissues for energy

Glucose from the bloodstream is the main source of energy for the brain

In contrast, fructose cannot directly supply the brain with energy as it crosses the blood brain barrier to a much lesser degree than glucose

There are two principal rewarding aspects of sugar consumption: nutrition and taste. Rodent studies have indicated that these two aspects are distinct and dissociable and may follow different neural pathways

While the nutritive reward of sugar in mice causes DA release primarily in the dorsal striatum, the sweetness reward is concentrated in the ventral striatum

This suggests that DRD2 in the NAc are essential both for regulating peripheral glucose levels as well as the reinforcement/reward learning of glucose consumption, which explains why dysregulation of this system may lead to overeating.

Just as fructose and glucose have different metabolic pathways, they have different hedonic effects on the brain and behavior.

Sugar consumption alone will not lead to weight gain or obesity--even rats exhibiting addictive behavior towards sugar do not gain weight. The same is true for fat--rats given intermittent access to fat will binge on it, but will not gain significant weight. However, like sugar, fat also increases food palatability, which can lead to hyperphagia.

While fat or sugar alone may not induce weight gain, together they do. Highly processed foods, which are often over-consumed, tend to contain both fat and added sugar (e.g. ice cream, pizza, etc).

Unlike sugars, which can be absorbed in the upper half of the GI tract, certain complex carbohydrates are not digestible by human enzymes and must be broken down by microbes in the large intestine (,,,,). Gut microbes produce short chain fatty acids (SCFAs) as a byproduct of the fermentation of these complex carbohydrates. The primary SCFAs produced are acetate, propionate, and butyrate, which can be used by the body as an energy source. Complex carbohydrates are more filling than sugars because SCFAs can increase the release of hormones and peptides from enteroendocrine cells that result in increased satiety, thus reducing food seeking behavior

Sugar is a highly palatable food that triggers our reward systems due to both caloric input and taste. Taken in excess, sugar can trigger these reward systems too strongly, inducing compulsive eating. The nutritive and taste reward centered in the striatum and the homeostatic signaling from the hypothalamus become less effective at communicating with each other to signal satiety. Added fructose is especially disruptive because it is not immediately available as an energy source for the brain, providing a sweet taste without the accompanying beneficial and timely nutritive input. The following dysregulation of eating behavior in many ways parallels the compulsive consumption of drugs in addiction.

When we examine glucose and fructose separately, added fructose is associated with many more health risks than glucose. Fructose can increase food-seeking and lead to fat production and storage. It may also be related to neurodegenerative inflammatory disease like diabetes and Alzheimer’s. As an alternative to sugar, complex carbohydrates in fruits, vegetables, legumes and fiber-rich grains are fermented by gut microbes, producing SCFAs, which may counterbalance the inflammatory effects of sugar.

The combination of sugar and fat is especially potent for triggering food overconsumption and weight gain. While each alone will not cause weight gain, sugar and fat together are highly palatable and can induce weight gain and obesity.

Wanderley Caloni, 2022-03-15 19:54:43 -0300

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