We’ve been discussing how inflammation impacts your risk for arthritis, cancer, and heart disease, but most people don’t consider the impact on your brain.
Most recently, you may have heard reports of how COVID19 survivors suffer “brain fog” and memory loss after recovering from the virus. Experts suggest this may be related to inflammation.
High levels of pro-inflammatory cytokines and the need for mechanical ventilation (life support) in severe cases of COVID may contribute to cognitive decline. The direct, negative impact on the immune system in addition to prior neurologic deficits may also raise the risk of neurological disease. Some patients experience ICU psychosis, which may also be a factor.1 Studies are ongoing to investigate the long-term neurologic consequences of COVID.
A retrospective study in China of 200 subjects also indicated neurologic impairment in a subset of patients including impaired consciousness and acute stroke. Researchers believe infection and the impact of COVID on blood clotting may raise the risk of stroke. One study suggests stroke is 8 times more likely to occur in COVID patients than those that have had the flu. 2, 3
Inflammation and depression
COVID aside, inflammation can impact your brain in other negative ways. Inflammation, particularly as it relates to the gut microbiome, may also impact the risk of depression. Research suggests alterations in gut bacteria impact the secretion of microbial lipopolysaccharides (fat and sugar compounds) that target a gut inflammatory response. 4
Pro-inflammatory chemicals trigger the vagal nerve. This then affects a part of the brain known as the hypothalamic-pituitary-adrenal axis which may initiate symptoms of depression. Authors of the study advise a healthy diet and lifestyle, reduced exposure to pesticides, reduction in medication use that impacts the gut microbiome, and potential use of pre and probiotics. 4
A Western-style diet has been associated with inflammation and may contribute to the risk of depression. A study exploring the relationships between a 9-year dietary pattern and depressive symptoms found a typical Tuscan diet containing high amounts of vegetables, olive oil, grains, fruit, fish, and moderate in wine and red and processed meat might be protective against depressive symptoms 5.
Depressive symptoms were closely related to adolescent dietary patterns containing more red meat, processed meat, bakery items, sugar drinks, and refined carbohydrates, which tend to be more pro-inflammatory. These foods tend to alter gut flora in a negative way. 6
The brain-gut connection
Fiber may be the key to better brain health. A systematic review and meta-analysis of over 60 studies including nearly 3,000 subjects compared high fiber to low fiber diets. The researchers note that different types of fiber may impact the type and number of bacteria produced such as short-chain fatty acids (SCFA). Short-chain fatty acids are important as they regulate the release of chemicals in the body that reduce inflammation. 7
In addition to high fiber foods, Mediterranean diet patterns which include fish, olive oil, fresh fruits, and vegetables have been linked with lower rates of depression. Antioxidants and isoflavonoids found in green tea and green leafy vegetables, respectively have been negatively linked with depression and symptoms of depression. 8
As mentioned above, the use of pre and probiotics may be of some benefit in reducing the risk of depression. A systematic review of pre and probiotics was published in the Journal of Neuroscience behavior in 2019 and found that in 34 controlled clinical control studies examining the impact of prebiotics and probiotics on depression and anxiety, prebiotics didn’t have an impact on depression when compared to placebo. Probiotics offered small, but significant effects on depression, though the authors suggest more randomized clinical trials are needed. 9
On your plate
If you’re concerned with any inflammation-related diseases (including brain health), below are tips on what to add to your meals.
- Include fish at least twice per week. It’s much lower in fat and saturated fat than meat and the American Heart Association gives it their stamp of approval.
- Add more beans and pulses to your diet. These are inexpensive, versatile, and full of fiber to keep your microbiome strong.
- Sneak seasonal fruit into your oats, yogurt, snacks, and salads. Apples, pears, and citrus fruit are in season and high in phytochemicals. Frozen berries are great, too.
- Cut back on refined sugar, processed and red meat, fast food, and sweetened beverages. While it’s easy to give in to cravings during times of stress, these foods may make the bummer cycle worse. Garbage in = garbage out.
- Discuss probiotics with your health care provider to decide if they’re appropriate for you. There are several different strains and can be expensive.
- Keep up your whole grain intake. Start your day with rolled oats or whole-grain toast. Choose brown rice over white rice. Try out quinoa, bulger, and farro. Think “whole grains for brains”.
Lisa Andrews, MEd, RD, LD
- Heneka MT, Golenbock D, Latz E, Morgan D, Brown R. Immediate and long-term consequences of COVID-19 infections for the development of the neurological disease. Alzheimer's Res Ther. 2020 Jun 4;12(1):69.
- Ng Kee Kwong KC, Mehta PR, Shukla G, Mehta AR. COVID-19, SARS, and MERS: A neurological perspective. J Clin Neurosci. 2020 Jul;77:13-16.
- 3. Alexander E. Merkler, MD1; Neal S. Parikh, MD, MS1; Saad Mir, MD1; Ajay Gupta, MD, MS1,2; Hooman Kamel, MD, MS1,3; Eaton Lin, MD2; Joshua Lantos, MD2; Edward J. Schenck, MD4; Parag Goyal, MD5; Samuel S. Bruce, MD, MA1; Joshua Kahan, MBBS, PhD1; Kelsey N. Lansdale, BA1; Natalie M. LeMoss, BS1; Santosh B. Murthy, MD, MPH1; Philip E. Stieg, PhD, MD6; Matthew E. Fink, MD1; Costantino Iadecola, MD1; Alan Z. Segal, MD1; Marika Cusick, MS7; Thomas R. Campion Jr, PhD, MS7; Ivan Diaz, PhD7; Cenai Zhang, MS1; Babak B. Navi, MD, MS1 Risk of Ischemic Stroke in Patients With Coronavirus Disease 2019 (COVID-19) vs Patients With Influenza. JAMA Neurol. Published online July 2, 2020.
- Simkin DR. Microbiome and Mental Health, Specifically as It Relates to Adolescents. Curr Psychiatry Rep. 2019 Sep 2;21(9):93.
- Vermeulen, E.; Stronks, K.; Visser, M.; Brouwer, I.A.; Snijder, M.B.; Mocking, R.J.T.; Schene, A.H.; Nicolaou, M. Dietary pattern derived by reduced rank regression and depressive symptoms in a multi-ethnic population: The HELIUS study. Eur. J. Clin. Nutr.2017, 71, 987
- Molendijk, M.; Molero, P.; Sánchez-Pedreño, F.O.; Van der Does, W.; Martínez-González, M.A. Diet quality and depression risk: A systematic review and dose-response meta-analysis of prospective studies. J. Affect. Disord.2017, 226, 346.
- So D, Whelan K, Rossi M, Morrison M, Holtmann G, Kelly JT, Shanahan ER, Staudacher HM, Campbell KL. Dietary fiber intervention on gut microbiota composition in healthy adults: a systematic review and meta-analysis. Am J Clin Nutr. 2018 Jun 1;107(6):965-983.
- Huang Q, Liu H, Suzuki K, Ma S, Liu C. Linking What We Eat to Our Mood: A Review of Diet, Dietary Antioxidants, and Depression. Antioxidants (Basel). 2019 Sep 5;8(9):376.
- Liu RT, Walsh RFL, Sheehan AE. Prebiotics and probiotics for depression and anxiety: A systematic review and meta-analysis of controlled clinical trials. Neurosci Biobehav Rev. 2019 Jul;102:13-23.