All the students beware! Nibbling sweets and drinking soda during cramming might actually threaten your exams. UCLA scientists found that unhealthy diet hampers the brain functions such as learning and memory. According to their findings, presented in the May edition of Journal of Physiology (1), rats watered with fructose solution were slow in finding the way out of a maze, which they had learnt before the introduction of diet. A mechanism responsible for this relation is connected with insulin receptor signalling and synaptic plasticity in the central nervous system. Fortunately, the researchers found the antidote – omega -3 fatty acids (n-3) minimize the harmful effects of high-sugar diet.

All-pervasive evil fructose

Fructose is a monosaccharide found in many plants like grapes, berries, root vegetables and honey. It is also a component of table sugar – a disaccharide sucrose, where it is bound to glucose. Commercially, fructose is found in two more forms: crystalline fructose and high-fructose corn syrup, a well-known sweetener and preservative. All of them are virtually unavoidable, because besides their natural occurrence in fruit and juice, they are massively added to processed foods in order to enhance palatability. So far it has been observed that excessive fructose intake may cause insulin resistance, obesity, elevated LDL cholesterol and triglycerides (2). All lead to metabolic syndrome, a plague of 21st century. In addition, various studies (3) indicate that the insulin resistance could lead to synaptic function disruptions and result in development of mental diseases like for example Alzheimer’s disease (4). The exact mechanism of this pathology is a subject of the presented study.

Rats on fructose alone – lost in a maze

In course of the discussed experiment animals were fed with ordinary rat chow and trained on a maze for 5 days before the change of diet, at that time all of them presenting the same cognitive status. Rats were randomly assigned to an omega-3 fatty acid diet or omega-3 fatty acid deficient diet, with or without 15% fructose solution as drinking water. After 6 weeks the rats were put in the same maze and tested for their recollection of the exit. The deficiency of omega-3 fatty acid in the diet lead to a significant increase in latency time, which indicates memory impairment. It was additionally worsened by fructose intake. The negative influence of fructose on memory in n-3 deficiency group was neutralized by the n-3 diet. It furthermore proves that dietary polyunsaturated acids deficiency increases the susceptibility for fructose induced changes.

Fatty acids protect the brain from fructose effects

Rats whose diet was enhanced with flaxseed oil (rich in alpha-linolenic acid)and docosahexaenoic acid (DHA) capsule oil managed to maintain their memory even despite the burden of excessive fructose intake. Consequently, the scientists discovered that the lack of dietary n-3 fatty acids elevated molecular parameters of peripheral insulin resistance. This caused improper insulin signalling also in the brain, resulting in a so called brain metabolic syndrome which manifested itself in lowered learning performance in the maze. Diet rich in fructose aggravated the handicap. What could be the underlying mechanism of this relationship? It is known that DHA, one of the major n-3 polyunsaturated fatty acids in the brain, is a component of neuronal membranes of synapses at sites of signal transduction. Therefore, it is crucial for central nervous system development and plasticity. As mammals are unable to produce DHA from precursors, supplementation of DHA in the diet is crucial for maintaining the healthy function of neurons, especially in conditions of metabolic disturbances.

Fish or chips?

The idea of metabolic syndrome refers to all the tissues except for central nervous system. Here we see that the spectrum of pathology spreads further to the brain. Diet high in fructose may be the reason, but also polyunsaturated omega-3 fatty acids deficiency. If 6 weeks was enough to impair rats cognition, then what about our whole life of unhealthy diet? Yet again we are confronted with the modern reality threats. Not only students should be interested. If you cannot restrain yourself from sweets and energy drinks, at least introduce DHA rich products such as salmon, walnuts and flaxseed. Or simply take a daily DHA supplement capsule.

Autor: Natalia Neumann

Źródło:
1.J Physiol. 2012 May 15;590(Pt 10):2485-99. Epub 2012 Apr 2.’Metabolic syndrome’ in the brain: deficiency in omega-3 fatty acid exacerbates dysfunctions in insulin receptor signalling and cognition. Agrawal R, Gomez-Pinilla F.
2.Nutr Metab (Lond). 2005 Feb 21;2(1):5. Fructose, insulin resistance, and metabolic dyslipidemia. Basciano H, Federico L, Adeli K.
3.Am J Manag Care 13, S170–177. Metabolic syndrome and mental illness. Newcomer JW
4.Insulina podawana donosowo powoduje poprawę u pacjentów z chorobą Alzheimera. Natalia Neumann. MedTube Tribune. http://medtube.pl/tribune-pl/2011/10/904/

Want to know more about sugar? Watch on medtube.net “Diabetes: Type 2″