Gut health debunked: 9 best and worst foods for digestion, according to an expert

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Contact a qualified medical professional before engaging in any physical activity, or making any changes to your diet, medication or lifestyle.

We've all heard the phrase "you are what you eat." But as it turns out, the food you consume can dramatically impact the bacteria in your gut — also known as the microbiome — which can disrupt your overall health.

According to the Canadian Digestive Health Foundation (CDHF), more than 20 million Canadians suffer from digestive disorders every year, such as Irritable Bowel Syndrome, bloating, diarrhea, Crohn's disease, lactose intolerance and gastroparesis.

The good news? It's never too late to incorporate gut-healthy habits. Having a healthy gut can help keep chronic diseases like cancer and diabetes at bay, and according to gastroenterologist and gut health expert Dr. Will Bulsiewicz, optimizing your gut microbes can also slow ageing, reverse conditions such as Parkinson's and Alzheimer's, and reduce general inflammation.

With Bulsiewicz's help, we've rounded up a list of 9 best and worst foods for gut health.

Best foods for gut health

1. Fermented foods

Fermenting is a method of preserving foods using yeast and bacteria, which promotes the development of live cultures. Fermented foods — such as yogurt and kefir — contain probiotics, or living microbes that are beneficial to human health by balancing gut bacteria and promoting immunity.

"If you choose the plant-based options like tempeh, sauerkraut, pickles and kimchi then you'll also get prebiotics, meaning food that empowers your gut microbes. No wonder research from Stanford University recently found that adding fermented food to your diet improves gut health and reduces inflammation," says Bulsiewicz.

2. Sprouts

We aren't talking about your average backyard weeds! According to Bulsiewicz, sprouts, such as alfalfa, broccoli and onion, "are a nutritional gift from nature. When a seed or legume sprouts to life, it increases its fiber, protein, minerals and vitamins in just a few quick days."

The higher amounts of insoluble fibre in sprouts helps to ease digestion and reduce the likelihood of constipation.

Click here to learn how to grow your own sprouts from home.

3. Legumes and whole grains

Legumes, such as beans, peas and lentils, as well as whole grains including oats, barley, brown rice and quinoa, are digestive powerhouses due to their probiotic nature and high fibre content.

"They're similar in that they both contain fibre, resistant starches and polyphenols. These are the three main prebiotics, or foods for the gut microbiome, and it's special to get access to all three in one source," explains Bulsiewicz. "These foods have also been tied to enhanced longevity."

4. Greens

There's a reason your mother told you to eat your greens. Whether it's collards, kale, spinach, arugula or chard, some of the world's most healthiest leaves contain sugars that grow healthy gut bacteria.

"What ties all the different kinds of greens together is that they are the most nutrient dense foods on the planet, meaning that calorie for calorie their nutritional content is unmatched," says Bulsiewicz. "They also contain fibre for digestion."

Are you tired of the same old kale salads? Take notes from TikTok chefs, who are transforming kale into "surprisingly delicious" creations.

Worst foods for gut health

1. Sugars

The average Canadian is crushing an astounding 138 pounds of sugar per year, and that's only where the problems start.

According to Bulsiewicz, "added sugar has zero fibre but also drives up inflammatory bacteria."

Reducing or eliminating sugar also stabilizes levels of the cortisol hormone, which positively impacts sleep. So when you cut back on your late night Jolly Ranchers, not only are you promoting digestion and gut health, but you're contributing to a better night's rest!

Not sure how to satisfy your dessert craving while also keeping added sugars at bay? Check out these 9 low-sugar recipes that don't skimp on taste.

2. Refined carbohydrates

Refined carbohydrates, such as white bread, pastries and white pasta, are stripped of nutritional value and don't contain fibre or probiotics that improve digestion and regulate the microbiome. The empty calories also lead to rapid spikes in blood sugar and insulin levels, putting you at greater risk for heart disease and diabetes.

"White flour might as well be sugar," adds Bulsiewicz. "They're really not any different in the sense that your body treats them the same way."

3. Ultraprocessed foods

Processed foods, including canola oil, sausage, cheese slices, microwavable meals and certain crackers "are designed to sit on the shelf for years without changing thanks to the preservatives and other additives designed to prevent mold or microbes from taking hold," according to Bulsiewicz. "So then what happens when those same preservatives and additives come into contact with our gut microbiota? Nothing good."

These foods irritate the intestines and promote inflammation which can lead to asthma, cancer and even depression.

Still not convinced? Learn the seven dangerous ingredients hiding in your favourite processed foods.

4. Saturated fat

"Most commonly in animal foods but also found in coconut and palm oil, saturated fat has been shown to cause injury to the gut microbiome and drive up the presence of inflammatory microbes," explains Bulsiewicz.

We hate to break it to you, but although foods such as butter, fatty meats, lard and cheese are ultra-tasty, they may be contributing to digestive upset and general malaise.

"Saturated fat also slows digestion which makes you feel super sluggish," adds Bulsiewicz.

5. Alcohol

While cocktails with friends or a relaxing glass of wine might help you unwind after a long day, they also wreak havoc on your digestion.

"Consumed in moderation is not the same as drinking to the point of having a hangover, but the point is that alcohol is designed to kill bacteria so when it is consumed to excess you are causing injury to your gut microbes," says Bulsiewicz.

Thinking about taking a break from alcohol? Read our guide on what it means to be sober-curious.

Let us know what you think by commenting below and tweeting @YahooStyleCA! Follow us on Twitter and Instagram and sign up for our newsletter.