• Rajani Katta MD

Why Prebiotics are So Important for Healthy Skin

Updated: Jun 6, 2019


We're hearing a lot about probiotics these days. Yogurt, kombucha, kefir: it seems as though probiotic foods are all the rage.


But what about PREBIOTICS?


You may not be hearing as much about prebiotics, but the evidence indicates that they may be even more important.


That's because prebiotic foods are critical for maintaining the health of our GI tract. And in dermatology, research has found a definite link between the health of our gut and the health of our skin.


This connection between the gut and the skin has been seen in conditions such as rosacea, eczema, psoriasis, and others.


Which brings up an important question: how do you keep your gut healthy? One of the most important ways is by making sure that the microbes that live in your gut are the "good" type.


The good microbes that live in our gut help us in many ways. These microbes help fight off harmful bacteria, help train our immune system, and help us digest our food. They've even been shown to calm down certain types of skin inflammation and strengthen our skin barrier.


That's why it's so important to feed them the right type of food. And that means prebiotic foods. Especially fruits and vegetables.



Prebiotic foods, such as fiber-rich fruits and vegetables, help encourage the growth of the "good" microbes in our gut


Good bacteria and bad bacteria: why some germs are our friends and protectors

Your body is covered in germs. Don't be alarmed: that's normal. In fact, it's a good thing.



Your skin, mouth, nose, and other body parts are covered in germs. But the part of your body that contains the most germs is actually inside of you: your gut (in medical terms, the gastrointestinal tract).

These germs, or microorganisms, have important roles to play in keeping us healthy. We now know that there actually trillions of these microbes on and inside your body. These microbes include bacteria, viruses, and other groups, and many of them act to help us.


This entire community of microbes is known as the microbiota. These microorganisms and the genes (genetic material) that they contain are called the microbiome.

You may have heard of the microbiome in medical news. That's because research has found that the microbiome has many roles to play in keeping us healthy. In a healthy gut, there may be some pathogens (harmful bacteria), but they're far outnumbered by the good guys: the good microbes.


These microbes act as teachers, as policemen, and as factory workers. That's because they've been shown to help train our immune system, fight off the harmful germs that sometimes find their way into our digestive system, and even actively help to break down and digest our food.


In fact, we need these helpful microbes to digest many of our foods. The human body alone doesn't produce all of the enzymes needed to digest all types of foods. Different microbes contain different enzymes. These enzymes are critical in the digestion of certain foods, such as fiber-rich vegetables. They help break down these fibers and extract the nutrients. They help in another way, also: by taking that fiber and producing helpful substances.



When your microbes are well fed, they really try to help you


When you feed your microbes fiber, they start digesting and fermenting that fiber. In the process, they produce some very helpful substances. These substances are called short chain fatty acids. There are different ones, including acetate, butyrate, and propionate. Resesarch has found that these short chain fatty acids (SCFAs) help fight inflammation and help protect the lining of our gut, which may help protect us from allergies and infections.



Good microbes are picky eaters, but they love fiber: Why a diet rich in fruits, vegetables, and whole grains is so good for the health of our gut When it comes to your health, it's always important to evaluate the research and then think about the actions that you can take. In this case, knowing that these good microbes are so important for our health, how can we make sure that they grow and flourish in our gut?


One major way is by feeding them the right kinds of foods. Research has shown that all of us have very distinct communities of microbes living on and inside of us. In other words, your germs are different than my germs. Studies have shown that this is due to many different factors. Genetics plays a role, as does your age and other medical conditions. The medications you take play a role as well. For example, we know that while taking broad-spectrum antibiotics (such as that Z-Pak for your sinus infection) can eradicate harmful, infection-causing bacteria, they can also kill off some of the good microbes.


But these aren't the only factors. A major factor is your diet.



Less foods that are processed and more foods that are naturally rich in fiber: why it's so important to fill up on whole foods

One of the most important ways that you can influence the health of your gut is through your diet. That's because the foods that you eat are the same foods that your gut microbes eat.


Your microbes eat what you eat.


And your gut microbes can be a picky lot. A diet high in added sugar and refined carbohydrates can cause some of your good microbes to die off. A diet rich in whole foods, on the other hand, helps them flourish.


Let's start with the research.


The foods that you eat are so important to the composition of your gut microbiome that you can see changes after just one day. In one study, researchers found that switching from a fiber-rich, plant-based diet to a more Westernized diet, high in sugar and high in fat, led to changes in the gut microbes after just ONE day. The changes go the other way, too. Researchers have found that if you start to eat more fiber, your gut starts to contain more of the good microbes.


Good microbes love to eat fiber. And they're really good at it too.


You actually need the help of bacteria to digest certain types of fiber. Without these bacteria living in our gut, we just can't digest certain fibers. That can result in pain, along with constipation and/or diarrhea. In fact, it's believed that some cases of irritable bowel syndrome (IBS) may be due to changes in the gut microbiome resulting in a loss of the "good bacteria."


The bottom line: To help grow more of good bacteria in your gut, you have to keep feeding them fiber.


Prebiotic foods: The importance of fruits, vegetables, and whole grains in growing more good gut microbes

Researchers have identified lots of different foods that can be considered prebiotics. The largest category is fiber-rich fruits, vegetables, and whole grains.


The list below is just a sampling. There are many, many other fruits, vegetables, and whole grains that contain prebiotic fibers. Some contain more, some contain less, but all are likely to be helpful.


Vegetables: Artichokes, asparagus, leafy greens, onions, jicama, soybeans, legumes

Fruits: Bananas, berries

Grains: Whole wheat, oats, barley

Nuts and Seeds: Almonds, walnuts, flaxseeds

Other: Garlic

The fiber found in certain fruits and vegetables, such as asparagus, helps encourage the growth of our good gut microbes



What other foods can help grow the good bacteria?


The major category of prebiotic foods are foods that are naturally rich in fiber. But research has found that other nutrients found in whole foods may also act as prebiotics.


For example, many fruits and vegetables contain polyphenols. These nutrients, such as the anthocyanins that are found in red grapes and red kidney beans, are powerful antioxidants. Research has found that they also encourage the growth of good gut microbes. Other nutrients may also act as prebiotics, such as certain fats.



The polyphenols found in foods such as red grapes act as antioxidants AND prebiotics



Processed foods labeled as "high fiber": why processed fiber may not be the same as the fiber consumed in vegetables


We've all heard of the benefits of fiber, of course. But that brings up an important question when you're actually in the supermarket staring at a shelf stuffed with "healthy" snack foods.


Is a "high fiber" granola bar good for you in the same way that a bowl of strawberries would be good for you?

They both contain fiber, but researchers have their suspicions about the fiber that's added to processed foods.


While some granola bars may be naturally rich in fiber (due to ingredients such as lightly processed dates and nuts), other granola bars need factories to make their fiber.


Some manufacturers start with fibers, such as chicory root fiber and inulin, and then pulverize those fibers to create fiber additives. These additives are then added back to the bars.


Here's the problem: we still don't know whether our gut microbes like these processed fiber additives as much as they like the fiber found in fruits and vegetables.


Until we know that for sure, I wouldn't recommend that you rely solely on "high-fiber" processed foods to feed your gut microbes. While it's possible that they may be helpful, you'll still need lots and lots of fruits, vegetables, and whole grains.



Bottom line: foods naturally rich in fiber are good. But how much fiber are we talking about?

The USDA recommends that women should consume 25 g of dietary fiber a day, and men should consume 38 g of dietary fiber a day.


Between fruits, vegetables, and whole grains, you can get there. But it's not an amount that's easy to achieve if you eat the typical American diet. You may have to make a concerted effort to slowly increase your fiber intake. These recipes that feature chickpeas, red kidney beans, black beans, and lentils are easy ways to start.



Foods that provide a strong dose of fiber, such as these red bean mushroom fritters, can help encourage the growth of good bacteria in our gut.



Dr. Rajani Katta is the author of Glow: The Dermatologist's Guide to a Whole Foods Younger Skin Diet. To receive future updates on preventive dermatology and the role of diet, sign up here.



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