In this article:

  1. Why are processed foods bad for you?
  2. How do processed foods affect gut health?
  3. Things that harm the microbiome
  4. The bottom line

Your gut microbiome is home to trillions of bacteria, fungi, and other microorganisms, both advantageous and detrimental.

When you maintain the right balance of good and bad bacteria in your gut, you set yourself up for improved digestion, reduced inflammation, decreased stress, better sleep, improved moods, and even increased focus.

A healthy balance of gut microbes may also boost your metabolism, reduce cravings, and help you lose weight. In short, your gut is linked to virtually every other part of your body, so it’s a good idea to take care of it!

Why are processed foods bad for you?

Eating the right foods supports a healthy, balanced gut microbiome — which, as you can gather from the benefits listed above, is critical to your overall health and well-being.

Ultra-processed foods like packaged breads and pastries, frozen pizzas and chicken nuggets, sugar-sweetened sodas, and potato chips contain substances made in laboratories (such as food colorings), ingredients extracted from food (sugar and starch), and/or compounds added from food constituents (hydrogenated oils).

These kinds of processed foods are designed to be addictively tasty and cost-effective, which is why they are so prevalent in supermarkets, convenience stores, restaurants, and vending machines. It’s also why they’re so hard to put down once you pick them up and have a taste.

How do processed foods affect gut health?

As good as those foods may taste, a poor diet loaded with refined sugars, trans fats, artificial flavorings, and other harmful ingredients, causes shifts in your microbiome that are detrimental to your microbial balance.

Processed foods break down into compounds that the bad guys in your gut love to gobble, and if you feed them too much, they’ll grow to outnumber the good guys and reduce the species diversity in your gut — a clear marker of an unhealthy gut.

Your microbiome changes in response to what you feed it. If you feed it fiber-rich and fermented foods full of probiotics, your microbiome will respond with thriving colonies of beneficial bacteria. If you feed it fast food, packaged snacks, and frozen meals laden with harmful ingredients, your microbiome will respond with an overgrowth of unfriendly microbes.

On top of that, many food additives are known irritants of the digestive system that cause inflammation in the intestines and decrease nutrient absorption, among other things (not exactly conducive to establishing a healthy gut).

Things that harm the microbiome

When you feed yourself, you also feed the trillions of microorganisms in your belly.

Here are a few common processed foods to stay away from:


Refined white sugar is generally thought of as the evil of all foods, but sugar in any form has the potential to impact your gut health. High-sugar diets are shown to wreak havoc on digestion, body weight and metabolic disease risk.

Fried foods

Fried foods, especially the deep-fried variety, are of concern because frying oil undergoes a series of chemical changes when it is continuously exposed to high heat. Deep-fried oil consumption is associated with unfavorable changes in the microbiome.

Artificial sweeteners

You may reach for zero-calorie or low-calorie sweeteners in place of sugar when your sweet tooth kicks in. While sugar alternatives may be good for weight loss, research increasingly exposes negative effects in the gut caused by artificial sweeteners. These effects include changes to the gut microbial composition, increased glucose intolerance and higher rates of metabolic disease.

Packaged snacks

Your favorite chips, pretzels, or granola may be to blame for gas, bloating, and other gut-related symptoms. Packaged snacks with long shelf lives are often brimming with additives like colorings, artificial flavors, and hydrogenated fats that are harmful to gut health.

Deli meats

We won’t argue that lunch meat is a hearty source of protein, but it pales in comparison to other meat options. Deli meats often contain antibiotics and hormones that can disrupt your microbiome’s delicate balance.

The bottom line

If you eat nutritionally imbalanced foods, your gut will become imbalanced and you’ll feel unbalanced, too.

Don’t stress, though: moderation is key!

You don’t need to completely avoid all of the foods on this list indefinitely. Just take small steps to reduce your consumption of them, while at the same time taking steps to increase your intake of fiber-rich and probiotic-friendly foods.

Editor’s note: This post has been updated for relevancy. Its first publish date was July 28, 2019.


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