Recently, I came across a rather strange story. It was about a person who ate three regular meals every day, yet was diagnosed with gallstones during a hospital checkup. People around them were puzzled, wondering how someone with such a regular eating schedule could develop gallstones. After several rounds of in-depth questioning, the doctor finally found the reason.
It turned out that this person often watched “mukbang” (eating broadcasts) on an empty stomach. That’s right—watching people eat. The brain, stimulated by the sight, was tricked into thinking the person was eating, and it signaled the body to release bile. But with an empty stomach, this released bile could turn into stones.
So, how does this make you feel? Do you think it’s something that could end up on the “myth-busting” list by the end of the month? If you asked an AI about the other effects of watching eating broadcasts on an empty stomach, it would tell you that it might trigger the brain to stimulate stomach acid production. Without food to digest, excessive stomach acid can cause discomfort and, over time, may lead to gastritis or even stomach ulcers.
However, it’s important to emphasize two things. First, the causes of gallstones are complex, and there isn’t a simple cause-and-effect relationship with diet. Second, regarding this story, this is merely a possible explanation, not a definitive conclusion. One thing we do know for sure is that there is indeed a connection between the brain and the digestive system. Today, let’s dive deeper into this topic.
The impact of emotions on the microbiome is bidirectional: intervening in the microbiome can influence biological signals, and influencing biological signals can, in turn, affect the microbiome. For example, when a person feels anxious, stressed, or under pressure, the body produces more cortisol and adrenaline, which impact E. coli bacteria, leading them to release bacterial toxins.
In simple terms, negative emotions can increase harmful bacteria in the body. To stay healthy, try to keep a positive mindset.
But, that said, how does the brain communicate with the gut, which is physically quite distant? Actually, there are three main bidirectional communication pathways between the brain and the digestive system.
The first pathway is the endocrine system. There are numerous endocrine cells in the animal gut, which release biological signals into the bloodstream, enabling them to reach the brain and influence our mood. Conversely, biological signals generated by the brain can circulate in the bloodstream, impacting gut microbiota. These signals have significant effects on the gut, increasing the count of certain microbes by over 1,000 times.
The second pathway of communication between the brain and the digestive system is the vagus nerve. The vagus nerve, the longest and most widely distributed cranial nerve, connects the brain at its upper end and spreads throughout the chest and abdominal cavities. In fact, your abdominal cavity is an extension of the brain. Some of the bidirectional effects between the brain and the digestive system are mediated through the vagus nerve. Interestingly, more information travels from the gut to the brain than from the brain to the gut.
The third pathway is the lymphatic system, which was only discovered more recently. The lymphatic system, part of the immune system, helps guard against invading bacteria. Previously, it was thought that there were no foreign bacteria in the brain, so no lymphatic vessels would exist there. However, in 2015, scientists confirmed that there are indeed hidden lymphatic vessels in the brain.
If someone has intestinal disease, their risk of depression is higher than average. This is because the lymphatic system transmits inflammatory signals from the gut to the brain. It’s crucial to note that out of these three pathways, only the lymphatic system can convey inflammation signals from the gut to the brain.
So, what we’ve discussed is how the brain and digestive system affect each other. In summary, diet impacts gut microbiota, and gut microbiota, in turn, interacts with the brain.
In other words, diet is very important.
So, what should you eat to best support brain health?
First, eat in moderation and avoid overeating.
I recently read a study on “Dingxiangyuan” shared by a team from Beijing Friendship Hospital, affiliated with Capital Medical University, published in Health Data Science. Traditionally, we thought that body fat and brain health were positively correlated, but this study shows the opposite: a bigger belly means a smaller brain.
In this study, a large belly represents a high BMI. The data came from a sample of 1,074 adults in Kailuan, Hebei, China, collected from 2006 to 2022.
Two key findings were highlighted. First, for adults under 45, those with a cumulative BMI over 26.2 had 17.9 ml less brain tissue from 2006 to 2022.
Here, cumulative BMI refers to a person’s accumulated BMI over a period, meaning they were consistently overweight. The study mentions “brain parenchyma,” which is essentially what we commonly refer to as the brain, encompassing gray and white matter. Losing 17.9 ml of brain parenchyma is equivalent to 12 years of brain aging.
Second, for adults over 60, a high BMI also negatively impacts the brain. For this group, a cumulative BMI over 26.2 results in 6 ml more brain white matter lesions than average.
In short, for both younger adults under 45 and older adults over 60, a consistently high BMI is detrimental to brain health.
So, under the premise of moderate eating, what foods benefit the brain?
Recently, I came across a book called This is Your Brain on Food by Uma Naidoo. She’s an interesting figure—a psychiatrist, nutrition expert, and chef with excellent cooking skills.
Given the complexity of brain research and the challenges of sample statistics, Uma’s recommendations come with certain limitations. Still, they provide valuable insights.
First, be optimistic and eat less sugar. You might find this odd, as sugar often brings a sense of pleasure—hence why sugary sodas are sometimes called “happy drinks.” Short-term, sugar can indeed boost happiness, but in the long run, excessive sugar may decrease optimism. In other words, consuming too much sugar over time can cause a downward emotional trend.
This is mainly due to a substance in the body called serotonin, which promotes feelings of optimism. For example, if you’re lost in a forest—a potentially dangerous situation—serotonin helps lower pessimism, making you feel as if everything will be okay.
Typically, men have twice as much serotonin as women, which is why men often appear more carefree. For example, if they take a wrong turn while driving, they may feel unbothered, while women might feel more anxious. This difference might be an evolutionary trait since men needed to be optimistic while hunting or taking risks, while women, who had to nurture children, had to be more cautious.
Serotonin has a helper called testosterone, which enhances its effects. However, sugar is an enemy of testosterone, suppressing its production. The more sugar you consume, the lower your testosterone level may be.
In other words, sugar inhibits testosterone, which, in turn, dampens serotonin levels, reducing optimism. So, if you want to maintain optimism, don’t consume too much sugar, especially if you’re a woman.
Second, what foods can protect memory? Uma provides a list.
For instance, soybeans. Certain components in soybeans, like isoflavones and phosphatidylserine, can improve memory and cognitive function.
Another example is coffee. A 21-year study showed that middle-aged individuals who drank coffee had a lower risk of Alzheimer’s later in life. Those who drank three to five cups of coffee daily had the lowest risk of dementia. Although not all coffee components are beneficial, Uma still suggests that moderate coffee consumption has more pros than cons.
Researcher Martha Clare Morris, who focuses on diet and health, developed a brain-healthy diet that highlights ten types of brain-beneficial foods, including leafy greens, other vegetables (like peppers, carrots, and broccoli), nuts, and others…
