Sucrose raises brain serotonin significantly more than starch in rat study

[JCastro]

The rats who ate 50g/kg sucrose for 2 weeks had significantly higher hippocampal serotonin and a more potent response to the serotonergic drug fenfluramine, all compared to rats who ate 50g/kg starch for 2 weeks. The starch group had longer-lasting serotoninergic effects, but the sucrose group had more intense acute serotonin spikes.

Effects of dietary sucrose on hippocampal serotonin release: a microdialysis study in the freely-moving rat

The effects of dietary supplementation with either sucrose or starch (50 g/kg regular food for 2 weeks) on central 5-hydroxytryptamine (5HT; serotonin) release were investigated in freely-moving rats. It has been suggested that the amount of transmitter that serotoninergic neurons release might be altered by food intake. We monitored the effects of sucrose and starch on concentrations of extracellular 5HT, its metabolite 5-hydroxyindoleacetic acid (5HIAA), gamma-aminobutyric acid (GABA) and dopamine in the hippocampus, using in vivo microdialysis. The major finding was that baseline levels of extracellular hippocampal 5HT in rats with ad libitum access to food supplemented with sucrose were significantly higher compared with the starch control group. We then verified that sucrose supplementation affected the potency of S(+)fenfluramine to increase hippocampal 5HT levels. In both groups of rats, acute intraperitoneal injection (1 mg/kg) of this anorectic drug induced a response curve of the extracellular hippocampal 5HT levels, with a shape that corresponded with earlier data for different brain areas often using up to 10-fold higher doses of S(+)fenfluramine. Nevertheless, we showed that throughout the experiment the absolute values of the sucrose response curve remained higher than in the starch group. On the other hand, S(+)fenfluramine exerted longer lasting effects in the starch group, as compared with the sucrose group. Significant decreases in levels of extracellular hippocampal 5HIAA levels following S(+)fenfluramine administration were simultaneously observed. A practical implication of the present findings is that dietary sucrose may bias the results of studies investigating brain serotoninergic mechanisms and the effects of (anorectic) drugs interacting with 5HT systems in the hippocampus.

Full paper: https://sci-hub.se/10.1079/bjn2001360

 

[Limon9]

The rats who ate 50g/kg sucrose for 2 weeks had significantly higher hippocampal serotonin and a more potent response to the serotonergic drug fenfluramine, all compared to rats who ate 50g/kg starch for 2 weeks. The starch group had longer-lasting serotoninergic effects, but the sucrose group had more intense acute serotonin spikes.

Effects of dietary sucrose on hippocampal serotonin release: a microdialysis study in the freely-moving rat



Full paper: https://sci-hub.se/10.1079/bjn2001360

Interesting idea, but the study design and conditions are uselessly basic. Two of the basic concepts in tryptophan kinetics research (they do acknowledge this) are that (1) tryptophan uptake into the brain, and the subsqeuent brain serotonin synthesis, correlate almost perfectly (r=0.9) with the plasma ratio of total tryptophan to five other large-neutral amino acids (tyrosine, valine, phenylalanine, leucine, isoleucine) which compete for uptake and (2) this ratio is increased more than any other meal composition by ingesting pure carbohydrate, with the subsequent insulin spike lowering the concentration of free amino acids while a large amount of tryptophan remains albumin-bound. Their explanation is that the starch takes longer to digest, producing a weaker and more sustained serotonergic effect. This is true, and it also implies that starch is more prone to fermentation (naturally they did not measure 5-HT, aka enteramine, anywhere else but the brain, which besides persorption was one of the contentions made by Dr. Peat against starches).

This should be a concern for anyone pounding white sugar or cola, but both potatoes and fruit - the whole-food equivalents of starch and sucrose - contain a considerable amount of protein. Unfortunately, there were no control groups given protein-containing wheat flour or powdered berries, or even a water which contained an appropriate amount of insulin-sparing potassium and a mixture of those 5 LNAA. You would expect the refined food groups to have higher hippocampal 5-HT in both categories. John Fernstrom and Richard Wurtman in various of their papers have shown how meal protein composition affects this ratio, and consistently find that "balanced" meals, containing around 5-20% of a protein like casein or gelatin, don't pathologically increase this ratio even with a background of pure dextrose feeding.

In Peat-World, some people do eat lots of white sugar and cola, while others prefer to have fruit and cheese, fruit and milk, sometimes dissolving collagen in their drinks. The results you've shared should only be considered problematic for the first group, as well as for people who abuse whey powder or for some reason consume separated egg whites.

"Combining milk and cheese with fruits adds to the antistress effect. The additional sugar and potassium and other minerals allow the milk protein to be used more efficiently, by moderating the secretion of cortisol, and helping to inhibit the secretion of PTH."

- Milk in context: allergies, ecology, and some myths. Peat, Raymond F.

[1] Choi S, Disilvio B, Fernstrom MH, Fernstrom JD. Meal ingestion, amino acids and brain neurotransmitters: effects of dietary protein source on serotonin and catecholamine synthesis rates. Physiol Behav. 2009 Aug 4;98(1-2):156-62

[2] Yokogoshi H, Wurtman RJ. Meal composition and plasma amino acid ratios: effect of various proteins or carbohydrates, and of various protein concentrations. Metabolism. 1986 Sep;35(9):837-42.

 

[Risingfire]

"regular food/starch vs regular food/sucrose"

That could mean anything

 

[NewACC]

Крысы, которые ели 50 г/кг сахарозы в течение 2 недель, имели значительно более высокий уровень серотонина в гиппокампе и более сильную реакцию на серотонинергический препарат фенфлурамин, по сравнению с крысами, которые ели 50 г/кг крахмала в течение 2 недель. Группа крахмала имела более продолжительные серотонинергические эффекты, но группа сахарозы имела более интенсивные острые всплески серотонина.

Влияние пищевой сахарозы на высвобождение серотонина в гиппокампе: исследование микродиализа на свободно движущихся крысах



Полный документ: Sci-Hub | Effects of dietary sucrose on hippocampal serotonin release: a microdialysis study in the freely-moving rat. British Journal of Nutrition, 86(02), 151 | 10.1079/bjn2001360

I saw this your message for a long time, but decided to comment only now. And it would be redundant to say that the isolated intake of 550g of sucrose for a typical person, without any protein, could never be recommended. Any possible similar amount of carbohydrates derived from fruit, such as banana or orange, would be accompanied by at least 60g of protein and it is a VERY well known fact that isolated carbohydrates, especially fast ones, increase the transport and bioavailability of tryptophan very powerfully, when this effect is easily prevented by additional 3% of protein. It's just that this study is so ridiculously out of context and unrealistic that it's hard to adequately interpret its results.