It started innocently enough. Friday night is pizza night at our house, and my kids wanted pepperoni instead of plain cheese.

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But something changed, and it wasn’t good. The boys were irritable and bickering and so were their parents. What previously had been a happy end of the week tradition had taken a turn. I wracked my brain to figure out the sudden mood shift.

After a few Friday meltdowns, I decided it had to be the pizza. The only change to our routine was adding pepperoni to the pie from the local pizza joint. So, I left it off. Peace reigned and pepperoni was dropped from the rotation. At least in our house, food and mood were definitely linked.

Does food really impact your mood?

Many researchers — from the National Institutes of Health to the crowdsourced American Gut Project — are now trying to unlock the mysteries of our digestive tracts and how they impact our moods and overall health.

For instance, in a 2012 study, Penn State University researcher Helen Hendy found that the combination of calories, fat, and sodium caused lousy moods in her subjects two days later. And what is a pepperoni pizza, if not a combination of calories, saturated fat, and sodium?

What does your gut have to do with it?

But it’s not necessarily that easy to draw the connection.

“Mood and food have a complex relationship to each other,” says Caroline Passerrello, Pittsburgh-based spokesperson for the Academy of Nutrition and Dietetics.

She says there’s more research than ever being done in this field on good and bad bacteria in the digestive tract, genetics, and how digestion can vary person to person — even in families.

What makes one person’s mood turn sour after eating a meal may not impact an entire population because of variations in bacteria in our digestive systems, she says. Even factors like the smog in the air when our mothers were pregnant can impact the bacteria in our digestive tracts, she adds.

Food can take up to two days to fully digest, so it can impact how you’re feeling physically and emotionally for days, Passerrello says.

“Keeping a mood and food log and reviewing it with a registered dietitian or nutritionist is especially useful to help identify potential problematic foods for the individual,” she says.

Of course, food can make you feel great, too. I, for one, feel like Wonder Woman after eating a kale salad. Passerrello explains that part of this “high” can also be psychological. Eating something perceived as healthy can be a mood booster in itself, just like eating a bag of cookies can do the opposite.

A 2013 study published in the Journal of Health Psychology concluded that healthy young adults were in better moods on days that they consumed fruit and vegetables. The study, of 281 young men and women over 21 days, found that eating about seven or eight servings of fruits and vegetables correlated with better moods.

The American Gut project crowdsources samples from willing participants. Their research shows alcohol affects a person’s microbiome, which are the collection of organisms that make up the human body. Those that had at least one drink per week had more diverse microbiome than those who didn’t drink.

The wider variety of plants a person eats, the higher their gut microbiome diversity is, according to The American Gut. This constantly changing collection of organisms is to your benefit.

Your ever-changing body

But what bothers you one day may not bother you the next. Your gut isn’t static, according to Passerrello. Thinking about what you were feeling before you ate, when you ate, and after you ate, are questions to ask yourself to identify your own food-mood link.

Had I done so, I would’ve figured out the pepperoni blues in my house much quicker. A few years earlier, I had a similar episode with coffee. As suggested by my doctor, I stopped drinking caffeine when I was pregnant the first time. After my son was born, I was psyched to get back to my caffeinated ritual of one to two cups of regular coffee a day.

But my husband noticed coffee didn’t bring out my best side and suggested I switch to decaf. He was right: I felt like a Wicked Witch after a cup in the morning. I kept the ritual of coffee with a splash of milk but switched to decaf.

My husband has his own issues. Too much salt in processed foods makes him grumpy. He knows it. My sons and I know it, too. We limit processed and restaurant food (except for cheese pizza on Friday nights).

It seems so obvious in hindsight. But hopefully we’ll continue to learn more about the dynamic link between our moods and the food we eat. In the meantime, consume with caution.

Ellen Rooney Martin is an award-winning journalist who has contributed stories to numerous print, online, and Fortune 500 Companies covering everything from parenting to data analytics. Her work has appeared in the American Bar Association Journal, Parenting,,, and others.