Can food really affect bacteria in my gut?

...as originally seen in The Observer

This is an excerpt from the article ‘Why is ketchup so delicious? Science answers the big food questions’ by Dr Ali Khavandi and Dara Mohammadi.

Can food really affect bacteria in my gut?

Friendly bacteria in our gut help digest our food and keep bad bacteria at bay. Scientists, though, are just beginning to understand how this legion of microbes, known as the gut microbiome, contributes to our health. They play a key role in how our immune system functions and thus might help to prevent chronic diseases including diabetes. They orchestrate how genes are turned on and off in many cells and even affect appetite, weight and mood.

“The type of food you eat has the single biggest impact on your gut microbial community,” says Suzanne Devkota, a gastroenterology and microbiomeresearcher at Cedars-Sinai Medical Center in Los Angeles. The evolutionary template for good health, she says, was set when humans were hunter-gatherers and ate plenty of fibre-rich, plant-based foods. Bacteria feed off the fibre in vegetables such as spinach or kale and in beans and pulses, helping them make important short-chain fatty acids. These fatty acids, in turn, are used as fuel by cells that line our gut to keep it functioning well. They also communicate with cells in other parts of your body including the brain and organs in your immune system. “It may not be a coincidence that our major reduction in fibre consumption has coincided with the rise in many modern diseases,” Devkota says.

Tim Spector, a professor of genetics at King’s College London, and author of The Diet Myth, says compounds called polyphenols in bright berries and nuts are another source of food for microbes. Being too prescriptive about what you feed your gut minions won’t help, though. “Diversity is key,” he says. “Eat as many different types of healthy foods as you can.”

From studies that look at the guts of healthy people versus unhealthy overweight people, we know that a healthy microbiome is a rich, diverse one. It makes sense, given bacteria have 100 times more digestive enzymes than we do, that the more different types you have the more nutrients you’ll be able to strip out of your food.

Given this, cheap meat pumped full of microbe-killing antibiotics, says Spector, is something you want to avoid. It might also make you think twice about taking a course of antibiotics you don’t really need. Likewise, some preservatives, additives and artificial sweeteners might cause havoc. In evolutionary terms, our gut bacteria have never seen these chemicals. As they don’t know how to digest such chemicals, they can cause metabolic disturbances.

It’s not just some modern food production but modern ideas about eating that cause some people harm. The diets that tell us to restrict what we eat to lose weight – rice crackers and cottage cheese, anyone? – aren’t good for a blossoming gut microbiome. Obese people, who often have a less diverse gut microbiome, can be fussy eaters who eat few vegetables. So restrictive diets that starve your gut microbiome could explain why some people yo-yo on and off diets for ever.

A good guiding principle if you want a healthy gut microbiome – and by extension a healthy you – is to remember that you’re eating for more than just one, so have a little bit of what everyone wants.

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