The intricate relationship between the brain and body is a subject of increasing scientific interest. It's becoming clear that what we eat profoundly impacts not just our physical health, but also our cognitive function, mood, and overall well-being. The "Brain-Body Diet" emphasizes this interconnectedness, exploring how dietary choices can either support or undermine the health of both the brain and the body.
The Interdependence of Brain and Body
The brain, as the control center of the body, influences every aspect of our health, daily functions, and relationships. As Maria Shriver and Dr. Sara Gottfried highlight, the brain is the ultimate output center for all efforts of the body. There is an interdependent relationship between the brain and the body, mutually dependent and mutually supporting. If one system falters, the other is inevitably affected. You can’t have a healthy brain if your body is out of whack, and you can’t have a healthy body if your brain is out of whack.
Many individuals, particularly women, experience symptoms like foggy thinking, anxiety, depression, addictive tendencies, forgetfulness, overwhelm, and exhaustion. These seemingly brain-related problems can often be linked to underlying issues in the body, such as inflammation.
The Role of Inflammation
Inflammation, often stemming from the stresses and environmental toxins of modern life, plays a significant role in this brain-body connection. As Dr. Gottfried notes, inflammation acts as an ugly low-level burn that’s quietly robbing you of brain cells and the connections between them, making you fat, tired, and dim. This inflammation can manifest in various ways, with symptoms appearing first in the gut, then the brain, or vice versa.
Common gut symptoms include gas, bloating, loose stool, gluten and dairy sensitivity, acid reflux, and difficulty losing weight. Additional indicators of inflammation include feeling swollen or puffy, brain fog, anxiety, moodiness, and early memory loss (short-term memory first), which usually can be traced back to the gut.
Read also: The Keto-Brain Fog Link
Brain Trash: A Serious Threat
A particularly harmful form of inflammation is "brain trash," an invisible toxic brain damage caused by environmental toxins like bisphenol A, alcohol, lead, and mercury. Brain trash is the insidious damage to our gray matter, which usually occurs below the radar. One type of brain trash is amyloid beta, a toxin that accumulates in the brain that is believed to be involved in the development of Alzheimer’s Disease.
The body attempts to clear this toxin using an enzyme called insulin-degrading enzyme, which is also responsible for processing insulin. However, this enzyme can’t do both jobs at once. If the enzyme is busy breaking down insulin because your blood sugar is too high -thereby cranking out the insulin to try to drive the blood glucose into cells-your insulin-degrading enzyme won’t be free to break down amyloid beta.
The body has its own natural ability to fight toxins that build up in the body. However, when the body is constantly trying to defend itself against the daily onslaught of stresses and environmental toxins of modern life, these toxin fighters are overwhelmed. It might be from poor DNA-repairing genes and habits (e.g., drinking too much alcohol), marginal stress-coping tendencies, and poor toxin elimination.
Fueling the Brain: The Importance of Diet
The brain, constantly "on" and working hard 24/7, requires a steady supply of fuel from the foods we eat. Like an expensive car, your brain functions best when it gets only premium fuel. Unfortunately, just like an expensive car, your brain can be damaged if you ingest anything other than premium fuel. If substances from "low-premium" fuel (such as what you get from processed or refined foods) get to the brain, it has little ability to get rid of them.
Diets high in refined sugars, for example, are harmful to the brain. In addition to worsening your body's regulation of insulin, they also promote inflammation and oxidative stress. If your brain is deprived of good-quality nutrition, or if free radicals or damaging inflammatory cells are circulating within the brain's enclosed space, further contributing to brain tissue injury, consequences are to be expected.
Read also: The science behind the Grain Brain Diet.
The Gut-Brain Axis: A Two-Way Street
The gut-brain axis highlights the bidirectional communication between the digestive system and the brain. As Arpana “Annie” Gupta, PhD, co-director of the Goodman-Luskin Microbiome Center at UCLA, explains, “Animal and human studies show us that the brain and gut microbiome are intimately connected. When most people think about mental health, they only think about the brain, but there is bi-directional communication between the gut and brain. I tell people the gut and the brain are like BFFs. The brain and the gut are in constant communication with each other.”
This complex relationship involves several key channels:
- The vagus nerve: This nerve acts as a communication highway between the brain and gut.
- Gut microbes: These microbes produce chemicals and metabolites that circulate in the blood to the brain.
- Immune system: Gut microbes play an important role in inflammation and the immune system by controlling what is circulated in the body and what is excreted from the body.
- Endocrine cells: These cells produce hormones, neuropeptides, and neurotransmitters.
Serotonin Production in the Gut
Notably, neurotransmitters like serotonin are not only produced in the brain, but are also produced by gut cells. “Serotonin is one of those neurotransmitters that is associated with mental health, and it’s produced by good bacteria. Up to 95% of serotonin is produced in the gut, so, we have to eat healthy foods to increase the presence of these good bacteria,” Dr. Gupta said. Serotonin is a neurotransmitter that helps regulate sleep and appetite, mediate moods, and inhibit pain. Since about 95% of your serotonin is produced in your gastrointestinal tract, and your gastrointestinal tract is lined with a hundred million nerve cells, or neurons, it makes sense that the inner workings of your digestive system don't just help you digest food, but also guide your emotions. What's more, the function of these neurons - and the production of neurotransmitters like serotonin - is highly influenced by the billions of "good" bacteria that make up your intestinal microbiome. These bacteria play an essential role in your health.
The Enteric Nervous System: The "Second Brain"
The enteric nervous system (ENS) is referred to as our body’s “second brain” or “gut brain,” and facilitates gastrointestinal function. The ENS also sends signals to the brain that trigger changes in our mood, emotions and cognitive function. The gut-brain system involves two-way communication between the central and enteric nervous system and links emotional and cognitive centers of the brain with peripheral intestinal functions. So when you’re nervous and experience “butterflies” in your stomach, there’s more actually going on than just the sensation that the term suggests.
Shelby Yaceczko, RD, a registered dietitian in the UCLA Vatche & Tamar Manoukian Division of Digestive Diseases, emphasizes the role of nutrients: “We’re starting to recognize more that the nutrients we get from healthy foods and beverages can enable us to think more clearly and feel better. When somebody’s diet is rich with things like antioxidants, phytonutrients and fiber, we know that person is going to get a variety of different vitamins and minerals that support anti-inflammatory properties of the body. Those properties are then going to beneficially alter the neurotransmitters, which in turn affects mood and cognition.”
Read also: Nutrition and Brain Tumors
Foods to Support the Gut-Brain Axis
To optimize the gut-brain interaction, increasing your intake of probiotic and prebiotic foods is essential.
Probiotic Foods
Probiotic foods introduce beneficial bacteria into the gut. Natalie Gavi, RD, a registered dietitian with the UCLA Steve Tisch BrainSPORT Program, recommends the following probiotic foods and beverages:
- Yogurt
- Sauerkraut
- Kefir
- Miso
- Tempeh
- Kombucha
- Kimchi
The fresher, the better, Gavi said. “It’s important to get foods like this from the refrigerated section of the grocery store so their beneficial bacteria remain intact and have not been destroyed, as they are when the food is canned or processed.”
Prebiotic Foods
Prebiotic foods, on the other hand, feed the good bacteria in probiotic foods. Gavi advises that probiotic foods are most effective when the diet also includes prebiotic-rich foods, which serve to feed the good bacteria in probiotic foods. Good sources of prebiotics include:
- Asparagus
- Apples
- Jerusalem artichokes
- Bananas
- Oats
- Onions
- Garlic
- Leek
The Downside of Processed Foods
Processed foods can have undesirable effects on the brain. “There are studies that show the connection between highly processed foods and depression and anxiety,” Gavi said. “However, I’m always cautious when telling people to limit or restrict certain foods. That can add to their stress, which can lead to binge eating and also affect the gut microbiome.”
Even so, there are certain types of foods that have been clearly linked to depression. These include what are known as ultra-processed foods, or UPFs. UPFs consist of carbonated drinks, sweet or savory packaged snacks, processed meats, candy, and fried fast food. Enjoying such food occasionally won’t have a negative impact on your mental health or mood, as long as you’re following a healthy dietary pattern, said Gavi.
Traditional Diets vs. Western Diets
Studies have compared "traditional" diets, like the Mediterranean diet and the traditional Japanese diet, to a typical "Western" diet and have shown that the risk of depression is 25% to 35% lower in those who eat a traditional diet. Scientists account for this difference because these traditional diets tend to be high in vegetables, fruits, unprocessed grains, and fish and seafood, and to contain only modest amounts of lean meats and dairy. They are also void of processed and refined foods and sugars, which are staples of the "Western" dietary pattern.
Practical Steps for a Brain-Body Diet
- Pay attention to how food makes you feel: Start paying attention to how eating different foods makes you feel - not just in the moment, but the next day.
- Try a "clean" diet: Try eating a "clean" diet for two to three weeks - that means cutting out all processed foods and sugar. See how you feel.
- Incorporate probiotic and prebiotic foods: Increase your intake of yogurt, sauerkraut, kefir, miso, tempeh, kombucha, kimchi, asparagus, apples, Jerusalem artichokes, bananas, oats, onions, garlic, and leeks.
- Limit processed foods: Reduce your consumption of carbonated drinks, sweet or savory packaged snacks, processed meats, candy, and fried fast food.
The Evolutionary Perspective
Over thousands of years, diet, in conjunction with other aspects of daily living, such as exercise, has had a crucial role in shaping cognitive capacity and brain evolution. Advances in molecular biology have revealed the ability of food-derived signals to influence energy metabolism and synaptic plasticity and, thus, mediate the effects of food on cognitive function, which is likely to have been crucial for the evolution of the modern brain.
Dietary consumption of omega-3 fatty acids is one of the best-studied interactions between food and brain evolution. Docosahexaenoic acid (DHA) is the most abundant omega-3 fatty acid in cell membranes in the brain; however, the human body is not efficient at synthesizing DHA, so we are largely dependent on dietary DHA. It has been proposed that access to DHA during hominid evolution had a key role in increasing the brain/body-mass ratio (also known as encephalization). The fact that DHA is an important brain constituent supports the hypothesis that a shore-based diet high in DHA was indispensable for hominid encephalization. Indeed, archeological evidence shows that early hominids adapted to consuming fish and thus gained access to DHA before extensive encephalization occurred.
Gut Hormones and Cognitive Function
The ingestion of foods triggers the release of hormones or peptides, such as insulin and glucagon-like peptide 1 (GLP1), into the circulation; these substances can then reach centers such as the hypothalamus and the hippocampus and activate signal-transduction pathways that promote synaptic activity and contribute to learning and memory. In turn, the lack of food that is signaled by an empty stomach can elicit the release of ghrelin, which can also support synaptic plasticity and cognitive function. Chemical messages derived from adipose tissue through leptin can activate specific receptors in the hippocampus and the hypothalamus, and influence learning and memory. Insulin-like growth factor 1 (IGF1) is produced by the liver and by skeletal muscle in response to signals derived from metabolism and exercise. IGF1 can signal to neurons in the hypothalamus and the hippocampus, with resulting effects on learning and memory performance.
Vagal Nerve Stimulation (VNS)
Vagal afferents from the gastrointestinal tract are critical for monitoring various aspects of digestion, such as the release of enzymes and food absorption. Based on observations that the application of VNS to patients with epilepsy was associated with improved mood, VNS was perceived as a potential treatment for depression. In humans, VNS failed to produce improvements in depression patients who participated in a short-term open trial (lasting 10 weeks); however, in a longer-term study (lasting 12 months), VNS produced beneficial effects that were sustained after 2 years.