It Takes Guts to Be in the Holiday Spirit

By William B. Miller, Jr., M. D.

Have you ever been chided for not being in the holiday spirit? Who wouldn't be in a sour mood when dealing with all of the stress that comes with this time of year? From choosing the perfect gift for relatives and trying to perfect the perfect pie to traveling, decorating, hosting... it can be excruciating. So, it has always been our natural assumption that feeling low around the holidays is a reaction to these obvious negatives. However, recent research has revealed some surprises. It might be that you just don't have the guts to take the holidays.
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In the last few years, evidence has accumulated that microbes are a crucial hidden modulator of our personalities, moods and tastes. In fact, our relationship to the microbial realm is extraordinarily deep and intimate. Our assumption has always been that we are singular beings. It seems so obviously true. We can look in any mirror and see our own reflection. Except, even if disturbing to confront, this is mostly an illusion.

Nature sees us quite differently. Its interactions with us are according to our microscopic cellular selves. Therefore, a more accurate understanding of our human selves is as a vast collection of complex inter-related cellular collaborations. Even more surprisingly, those cellular networks are comprised by both our own innate cells and a highly influential microbial constituency that assists in governing our metabolism, moods and choices.
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Recent research has revealed that our gut bacteria can significantly affect our food choices and resulting moods. The focal point of this interaction is now believed to be through connections between an important nerve, the vagus nerve, and the 100 million nerve cells that are part of our digestive tract and its trillions of companion microbes. Through these connections, microbial signals pass from our gut to the base of our brain. This is the way that our personal microbes have the capacity to manipulate our behavior and mood.

Their metabolism alters the signals that get sent to the vagus nerve and are further transmitted to our brain. These interactions can change our taste receptors and then, even our most basic choices. Through these pathways, some of the released microbial metabolites are perceived as chemical rewards. These can improve our mood.

Others can make us feel unwell. For example, in an experiment with mice, certain strains of bacteria increase anxious behavior. In a human trial, drinking a probiotic containing Lactobacillus casei, a significant gut microbe, improved mood assessment for some participants.

Contemporary research is uncovering many such previously unsuspected physiological pathways between the crucial microbial life within us or on us and our own cells. Previously, it was believed that we merely co-exist with this additional life. Our newer understanding is that these microbes are essential for our wellbeing. And this new science, now termed the science of the 'hologenome', is revealing a number of surprises:

1. The number of these participating microbial cells outnumber our own native cells by a factor of 10 to 1. There are over 100 trillion of them in you and on you.

2. The amount of genetic material in those cells outnumbers our 'own' genetic material by more than 100 to 1. At least 10,000 species of microbes are part of you.

3. Our intestines have more nervous tissue than our spinal cords, which is one reason that our gut can modulate brain activity.

4. Foods we eat can alter these microbial communities, which can affect complex human behaviors such as anxiety, learning, memory, satiety, appetite and social interactions. Preliminary research is indicating that the regular consumption of probiotics, like some yogurts, may have beneficial effects on brain function by affecting our emotions, sensation, and thinking.

5. Our microbial partners have a crucial impact our immune systems and neurological functions. New therapies for neurological disorders are being evaluated including microbial treatments for multiple sclerosis and autism.

6. Our crucial metabolic functions such as energy expenditure, fat metabolism and inflammatory responses are heavily dependent on our microbial inhabitants. Obesity, diabetes, arthritis, autoimmune disorders and even depression may one day be treated by adding specific microbes to our diets or by microbial transplants.

All of this new information represents exciting new avenues for research, unbiased evaluation and testing. Right now though, there is a practical opportunity that might influence your holiday choices. Gauge your reaction to the influx of highly caloric foods that characterize the holiday season. It may not suit your system and your mood may suffer. You can experiment with foods and try to carefully assess how they influence your own unique body rhythms and demands. Try some probiotics and see if they affect your sense of wellbeing or lead to a lower level of anxiety.

Most significantly, the message of the hologenome is plain. You make human choices, but your inescapable microbial fraction also responds. Modern science understands this crucial partnership that has previously remained hidden throughout human history. Our better health is centered within that nuanced understanding.

Dr. Bill Miller has been a physician in academic and private practice for over 30 years. He is the author of "The Microcosm Within: Evolution and Extinction in the Hologenome." He currently serves as a scientific advisor to OmniBiome Therapeutics, a pioneering company in discovering and developing solutions to problems in human fertility and health through management of the human microbiome.