5 Foods That Are Making Your Brain Fog Worse

Mark Hyman (0:00)

Why do some foods leave you mentally exhausted? What can you do about it? Well, if your brain feels like it's running in slow motion, you can't focus, you lose your train of thought, you walk in a room and forget while you're there, you struggle to find the right words, you might be thinking you're just getting older. Well, you're probably not. Well, you are getting older, that's probably not the reason. One of the biggest myths about brain fog is that it's a normal part of aging. It is not. In functional medicine, we don't think of brain fog as a diagnosis. We think of it as a symptom, a warning light on your body's dashboard, telling you something deeper needs attention. And one of the biggest drivers may surprise you. It isn't your brain, it's your gut. I know how frightening brain fog can be because I have experienced it myself. After suffering mercury poisoning, I developed severe brain fog. I felt like I was trying to think through wet cement. My memory wasn't sharp, I couldn't concentrate. I mean, even simple tasks suddenly really felt difficult. That experience completely changed the way I think about brain health, because I learned this. Your brain doesn't function in isolation. It's constantly communicating when you're cut, with your immune system, with your metabolism, and even the trillions of bacteria living inside your digestive tract. Today, I'm going to show you the five foods I most commonly see contributing to brain fog in susceptible people, and why they affect your gut, and how that disruption can ripple all the way to your brain.

And most importantly, what you can do to start thinking more clearly again. Because brain fog isn't something you simply have to live with. It's often your body is asking you to look a little deeper. Brain fog isn't a disease, it's a symptom. Just like a cough or a fever. You can have dozens of causes. Poor sleep, stress, dehydration, nutrient deficiencies, hormonal changes, environmental toxins, blood sugar swings, even certain medication.

Today, we're focusing on one piece of that puzzle, one of the biggest and one of the most overlooked, the gut. Now, at first, that might sound strange, but what does your digestive system have to do with your ability to think clearly? Well, the answer is almost everything. Your gut and your brain are in constant communication. Now, scientists often refer to this as the gut-brain axis. Think of it like a two-way highway. Your brain is constantly sending messages to your gut, and your gut is constantly sending messages back to your brain. One of the main communication pathways is remarkable nerve called the vagus nerve. It's the longest cranial nerve in your body, running from your brain stem all the way down to your digestive tract. It's constantly carrying information in both directions. In fact, much of the traffic travels from your gut to your brain, not the other way around, which means what's happening in your gut has enormous influence on how your brain feels and functions.

Then there are trillions of bacteria living inside your digestive tract, what we call the gut microbiome. These microbes aren't just helping you digest food. They're producing vitamins, they're training your immune system, they're helping regulate inflammation, even producing or influencing many of the chemical messengers your brain relies on. For example, about 90% of your body's serotonin is produced in the gut. Now, serotonin made in the gut doesn't simply travel into the brain because of the blood-brain barrier, but it still plays an important role in the gut itself. It communicates with the nervous system in ways that can influence mood, digestion, and your overall health. Your gut microbiome also helps produce compounds called short-chain fatty acids. These help nourish the cells lining your colon. They help reduce inflammation. They support the integrity of your gut lining. They may even influence brain function through immune and nervous system signaling. In other words, a healthy gut creates an environment that supports a healthier brain. But when the gut becomes unhealthy, which is a lot of the time, the opposite can happen. One problem we often see in functional medicine is something called intestinal permeability increase or leaky gut. Your intestinal lining is designed to act like a highly selective filter. It lets nutrients pass through into your bloodstream, while keeping bacteria, toxins, and partially digested food where they belong.

But when that barrier becomes damaged, some of the substances can slip through and only would. Your immune system recognizes them as foreign, and then it mounts an inflammatory response. And that inflammation doesn't stay confined to your gut. It can affect your entire body, including your brain. When inflammation reaches the brain, people experience it as mental fatigue or trouble concentrating or poor memory or what we commonly call brain fog.