Depression: From the book "This is Your Brain on Food"
The vagus nerve, also known as the “wanderer nerve,” originates in the brain stem and travels all the way to the gut, connecting the gut to the central nervous system. When it reaches the gut, it untangles itself to form little threads that wrap the entire gut in an unruly covering that looks like an intricately knitted sweater. Because the vagus nerve penetrates the gut wall, it plays an essential role in the digestion of food, but its key function is to ensure that nerve signals can travel back and forth between the gut and the brain, carrying vital information
between them. Signals between the gut and brain travel in both directions, making the brain and gut lifelong partners. That is the basis of the gut-brain romance. But what sometimes gets lost in discussions about mental health is a simple truth: the food you eat can have just as profound an effect on your brain as the drugs you take. All it takes is two hours’ worth of psychological stress to completely change the bacteria in your gut. In other words, a tense family Christmas dinner or unusually bad traffic can be enough to upset the balance of your microbiome. The theory is that the ANS and HPA-axis send signaling molecules to gut bacteria when you are stressed, changing bacterial behavior and composition. Food influences your brain directly and indirectly. When food is broken down by the microbiota into fermented and digested materials, its components directly influence neurotransmitters, such as serotonin, dopamine, and GABA, which travel to the brain and change the way you think and feel. When food is broken down, its constituent parts can also pass through the gut wall into the bloodstream, and certain metabolites can act on the brain that way as well. Your gut bacteria may become less diverse as a result of your diet, which may cause the bad bacteria to outgrow the good bacteria, triggering a cascade of negative health effects. Food can also influence the chemical messages these bacteria send from your gut up to your brain along the vagus nerve—signals that can make you feel either depressed and drained or uplifted and energized. Prebiotics are essentially food for helpful bacteria, certain types of fiber that we cannot digest but the good bacteria in our guts can. For probiotics to be effective, it is helpful for them to have prebiotic foods available in the gut to digest. Probiotics break down prebiotics to form short-chain fatty acids that help reduce gut inflammation, block the growth of cancerous cells, and help the growth of healthy cells. Yogurt with active cultures is one of the best sources of probiotics; just avoid fruited yogurts high in added sugars. Other probiotic-rich foods include tempeh, miso, and natto (fermented soybean products); sauerkraut; kefir (soured yogurt); kimchi (Korean pickle); kombucha (a fermented tea drink); buttermilk; and select cheeses such as cheddar, mozzarella, and Gouda. Examples of prebiotic-rich foods include beans and other legumes, oats, bananas, berries, garlic, onions, dandelion greens, asparagus, Jerusalem artichokes, and leeks. While scientific literature backs the long-held notion that feeling down in the dumps can lead you to overindulge in sugary treats, it also suggests the opposite to be true: the more sugar you eat, the more likely you are to be depressed. Why might sugar cause depression? The brain relies on glucose, a type of sugar, from the food we eat in order to survive and to function. Over a twenty-four-hour period, the brain needs only 62 grams of glucose to do its job, an incredible display of energy efficiency considering the brain has at least 100 billion cells. You can easily meet this need through healthy, whole foods. Consuming unhealthy processed foods like baked goods and soda, which are loaded with refined and added sugars, often in the form of high-fructose corn syrup, floods the brain with too much glucose. This “sugar flood” can lead to inflammation in the brain and may ultimately result in depression. Saccharin (Sweet’N Low), aspartame (NutraSweet), sucralose (Splenda), and stevia (Truvia) are just a few of the most popular artificial sweeteners in use by food manufacturers today. Other lesser-known compounds are erythritol, lactitol, maltitol, sorbitol, and xylitol. These sugar replacements are increasingly common in foods that purport to be “healthy” by helping you cut down on calories. Several studies have demonstrated that artificial sweeteners can be toxic to the brain, altering brain concentrations of mood-regulating neurotransmitters. People who consumed more fried foods were also more likely to develop depression in their lifetime. I’m betting a few hours after the last time you indulged in a fried-food feast you felt bad—like you had too much and overdid it. While we usually think these bad feelings are simply due to the guilt of overeating, they might be feeding into more serious feelings of depression over time. Fried foods are likely such mood killers because they’re usually fried in unhealthy fats. In recent years, the conversation around fat in the diet has changed from all fats being unhealthy to a clearer distinction between “bad fats” (for instance, margarine, shortening, and hydrogenated oils) known to cause cardiovascular disease and other woes, and “good fats” (for instance, avocados, almonds, and olive oil) that can help prevent disease and benefit well-being. MUFAS (monounsaturated fats) should make up the majority of the fats in your diet. In addition to olive oil, MUFAs are found in nuts (almonds, walnuts) and nut butters (almond and cashew butter) as well as avocados. Nitrates may be connected with depression and are used as a preservative and to enhance color in deli slices and cured meats like bacon, salami, and sausage. One type of fat, Omega-3s, are important for normal body metabolism—they are a vital part of cell membranes and provide the starting point for making the hormones that regulate blood clotting, contraction and relaxation of artery walls, and inflammation. We cannot produce Omega-3s on our own, we must get our omega-3s from our diet. This is why we call them essential fats. The three main omega-3 fatty acids are alpha-linolenic acid, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). All three are important to the body, performing a number of tasks, especially in cell membranes. EPA and DHA are the two omega-3s that play the most critical role in mood disorders, so it’s particularly important to ensure that you get enough of them. Omega-3s promote brain health by lowering inflammatory markers and protecting neurons from excessive inflammation. The key is to maintain a healthy balance between omega-3s and omega-6s, which are found in different foods. In a typical Western diet, omega-6s are quite common, while omega-3s are much rarer, leading to an omega-6 to omega-3 ratio of somewhere around 15 to 1. The ideal ratio is more like 4 to 1.27. That means most Americans need to cut down on omega-6s while eating more omega-3s. This means that eating foods high in omega-6s like full-fat cheese, high-fat cuts of red meat, corn oil, and palm oil may increase your chances of depression. On the contrary, eating foods high in omega-3s like fatty fish, walnuts, vegetable oils, and dark, leafy vegetables may protect you against depression. Many vitamins play key roles in preventing and easing depression. The most important are folate (B9) and B12. Their functions in the body are inextricably linked: a deficiency in vitamin B12 results in a folate deficiency, which can ultimately contribute to a loss of brain cells, chiefly those located in the hippocampus. Termed “hippocampal atrophy,” this loss of brain cells is associated with depression. The hippocampus is a critical brain structure that plays an important role in learning and memory, so depressed patients may lose their ability to learn new ways to cope with their stress. Optimized to prevent or treat depression, enjoy ample amounts of legumes, citrus fruits, bananas, avocados, leafy green and cruciferous vegetables, asparagus, nuts and seeds, and fish and shellfish. Vitamin A is also important in helping curb depression. The amount of vitamin A you would have to consume to suffer the ill effects of too much vitamin A are far beyond what you will eat in a healthy, varied diet, so feel free to eat vitamin A–rich foods such as sweet potatoes, carrots, spinach, and blackeyed peas. Vitamin C is important for proper brain functioning, as it’s responsible for the regulation of neurotransmitter synthesis. Get your vitamin C from citrus fruits, cantaloupe, strawberries, and cruciferous vegetables including broccoli, cauliflower, and Brussels sprouts. In the brain, iron helps make up the covering that protects neurons and helps control the synthesis of chemicals and chemical pathways involved in mood. Good food sources of iron include shellfish, lean red meats and organ meats (in moderation), legumes, pumpkin seeds, broccoli, and dark chocolate (though any sweet should be eaten in moderation). Several case studies, in which patients were treated with 125–300 mg of magnesium, have demonstrated rapid recovery from major depression, often in less than a week. How can you get enough magnesium in your diet? Eat more avocados, nuts and seeds, legumes, whole grains, and some omega-3-rich fish (such as salmon and mackerel). Most evidence strongly supports a positive association between zinc deficiency and the risk of depression, with zinc supplements reducing depressive symptoms. Zinc probably helps because it reduces brain inflammation. Zinc can be found in seafood (especially cooked oysters), lean beef, and poultry, with lower amounts found in beans, nuts, and whole grains. Saffron: While its precise mechanism of action is not known, in animals saffron increases levels of the good-mood neurotransmitters glutamate and dopamine. Turmeric: curcumin was significantly more effective than placebo in reducing depressive symptoms. How is it capable of such profound effects? Simply put, it adjusts brain chemistry and protects brain cells against toxic damage that leads to depression. Oregano is likely to help protect brain tissue. While the Mediterranean diet wasn’t formulated expressly with mental health in mind, it incorporates all the depression-busting foods just mentioned, and in healthy ratios to help you achieve the nutrient balance needed for optimal brain functioning and mood regulation. And, of course, it’s healthy for your body in many other ways. Some daily foods in the original Mediterranean diet should include: 3–9 servings of vegetables, –2 servings of fruit, 1–13 servings of cereals (bread and other grains, preferably whole grains), and up to 8 servings of olive oil per day. Now, diet is associated with restriction, while, truly, this dietary approach is all about the delicious foods you can add to your life to enhance your meals and feel better in the process. Here are the recommended servings for a Mediterranean lifestyle: Whole grains: 5–8 per day, Vegetables: 6 per day, Fruit: 3 per day, Legumes: 3–4 per week, Low-fat and unsweetened dairy foods: 2–3 per day, Raw and unsalted nuts: 1 per day, Fish: at least 2 per week, Lean red meats: 3–4 per week, Chicken: 2–3 per week, Eggs: up to 6 per week, Olive oil: 3 tablespoons per day, “Extras” foods: Wine (red preferred): up to 2 glasses per day, with meals, No more than 3 per week: sweets, refined cereals, fried food, fast food, processed meats, and sugary drinks.
DEPRESSION CHEAT SHEET The Mediterranean eating pattern is a great guideline to give you a complete diet that will fight depression and keep your brain healthy. Foods to Embrace: Probiotics: Yogurt with active cultures, tempeh, miso, natto, sauerkraut, kefir, kimchi, kombucha, buttermilk, and certain cheeses. Prebiotics: Beans, oats, bananas, berries, garlic, onions, dandelion greens, asparagus, Jerusalem artichokes, and leeks. LowGI carbohydrates: Brown rice, quinoa, steel-cut oatmeal, and chia seeds. Medium-GI foods, in moderation: Honey, orange juice, and whole-grain bread. Healthy fats: Monounsaturated fats like olive oil, nuts, nut butters, and avocados. Omega-3 fatty acids: Fish, especially fatty fish like salmon, mackerel, tuna, herring, and sardines. Vitamins B9, B12, B1, B6, A, and C. Minerals and micronutrients: Iron, magnesium, potassium, zinc, and selenium. Spices: Saffron and turmeric. Herbs: Oregano, lavender, passionflower, and chamomile. Foods to Avoid: Sugar: Baked goods, candy, soda, or anything sweetened with sugar or high-fructose corn syrup. High-GI carbs: White bread, white rice, potatoes, pasta, and anything else made from refined flour. Artificial sweeteners: Aspartame is particularly harmful, but also saccharin, sucralose, and stevia in moderation and with caution. Fried foods: French fries, fried chicken, fried seafood, or anything else deep-fried in oil. Bad fats: Trans fats such as margarine, shortening, and hydrogenated oils are to be avoided totally; omega-6 fats such as vegetable, corn, sunflower, and safflower oil should only be consumed in moderation. Nitrates: An additive used in bacon, salami, sausage, and other cured meats.
Next week we will dive into Anxiety and PTSD.
