The research on the links between digestion, mood, health, and even the way you think has been exploding in recent years. And it's no longer possible to ignore the intimate relationship between the gut and the brain.
Scientists used to think that the only way that the gut talked to the brain was through the release of hormones stimulated by nutrients in your gut and "which entered the bloodstream minutes to hours after eating, eventually exerting their effects on the brain." They were partly right. That tryptophan in your turkey dinner is notorious for its transformation into serotonin, the brain chemical that makes you feel sleepy."
But we now know that the brain also perceives cues from the gut more quickly. The message from the gut to the brain is relayed in 100 ms via the vagus nerve and the neurotransmitter glutamate. That's faster than the blink of an eye!
The gut and brain talk to each other all the time. And this communication is bi-directional. This is good news because it means there is an additional way to improve brain health: Through the gut.
Here are three brand new research studies that look at the relationship between the gut and cognitive and psychological health.
Glutathione levels in the brain affect our level of motivation
"The brain is often subjected to excessive oxidative stress from its neurometabolic processes—and the question for the researchers was whether antioxidant levels in the nucleus accumbens, a key brain region, can affect motivation." "The scientists looked at the brain’s most important antioxidant, a protein called glutathione (GSH), and its relationship to motivation."
Using an imaging technique called a proton magnetic resonance spectroscopy, the scientists found that higher GSH levels "in the nucleus accumbens correlated with better and steady performance in the motivation tasks" in both rats and humans.
Higher glutathione (GSH) levels can increase our motivation to do hard things
But this was a correlational finding, and correlation does not mean causation. To investigate whether GSH levels directly affected motivation, the rats were given a GSH blocker. "The rats now showed less motivation, as seen in a poorer performance in effort-based, reward-incentivized tests." "When the researchers gave rats a nutritional intervention with the GSH precursor N-acetylcysteine (NAC)—which increased GSH levels in the nucleus accumbens—the animals performed better.
This study showed that higher GSH levels can increase our motivation to do hard things. NAC, a GSH precursor, can be synthesized from the cysteine contained in high-protein foods such as meat, chicken, and fish. "Other sources with lower content are eggs, whole-grain foods such as breads and cereals, and some vegetables such as broccoli, onions, and legumes."
There is a bidirectional link between depression and inflammatory bowel disease.
People diagnosed with inflammatory bowel disease (IBD) are "nine times as likely to develop depression as the general population, and people with depression are more than two times as likely to develop IBD."
The scientists tracked patients from Taiwan's National Health Insurance Research Database with either IBD or depression for 11 years and compared the onset of IBD or depression with a control group without these conditions.
Dietary changes may relieve depression
The gut-brain axis is a "scientifically established connection between the gut and the central nervous system, which consists of the brain and spinal cord." In addition, "inflammation of the brain, which we already know plays a role in depression, may be linked to the inflammation of the gastrointestinal tract, a hallmark of IBD."
There are dietary changes you can make that will relieve depressive symptoms and may even place depression in remission. These dietary changes include eating a whole foods diet and eliminating sugar and processed foods. In 2017, Jacka and colleagues had participants switch from a junk food to a Mediterranean diet. After 12 weeks on the diet, most participants were able to reduce their depressive symptoms and 1/3 were in remission from their depression.
Ultraprocessed foods are linked to premature death
Researchers from Brazil have found that about "10.5% of all premature deaths and 21.8% of all deaths from preventable noncommunicable diseases [such as diabetes, cardiovascular disease, and cancer] in adults" could be attributed to the consumption of ultraprocessed foods. Ultraprocessed foods are "ready-to-eat-or-heat industrial formulations that are made with ingredients extracted from foods, and that contain little or no whole foods, or synthesized in laboratories."
Brazil consumes far less ultraprocessed foods than high income countries, such as the United States, Canada, the UK, and Australia, yet these numbers are staggering.
A whole foods diet may prolong your life
This is another compelling reason to switch to a whole foods diet: It may prolong your life!
A whole foods diet, with a particular focus on animal protein, can increase your motivation to do hard things, may relieve depression, and may even prolong your life.
Jacka, F., O’Neil, A., Opie, R., Itsiopoulos, C., Cotton, S., Mohebbi, M., … Berk, M. (2017). A randomised controlled trial of dietary improvement for adults with major depression (the “SMILES” trial). BMC Medicine, 15(1), 23. doi:10.1186/s12916-017-0791-y
Kaelberer M.M., Buchanan K.L., Klein M.E., et al. (2018). A gut-brain neural circuit for nutrient sensory transduction. Science. 2018 Sep 21;361(6408). doi: 10.1126/science.aat5236.
Nilson, E.A.F., Ferrari, G., Louzada, M.L.C., et al. (2022). Premature deaths attributable to the consumption of ultraprocessed foods in Brazil. American Journal of Preventive Medicine, November 7, 2022. DOI:https://doi.org/10.1016/j.amepre.2022.08.013
Zalachoras, I., Ramo Fernandez, E., Hollis, F., Trovo, L, et al. (2022). Glutathione in the nucleus accumbens regulates motivation to exert reward-incentivized effort. bioRxiv 2022.02.14.480343; doi: https://doi.org/10.1101/2022.02.14.480343
Zhang, B, Wang, H-H.E., Bai, Y-M., et al. (2022). Bidirectional association between inflammatory bowel disease and depression among patients and their unaffected siblings. Journal of Gastroenterology and Hepatology, 37, 1307-1315.
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