Microbiome Diet ~ 1. Dietary Fiber
What are the most important nutrients to support your gut microbiome? Which foods contain dietary fiber and which don't? Is it good for your health too?
This is part 1 of the articles on the Microbiome Diet. Read part 2: Microbiome Diet 2: Animal Foods .
What is dietary fiber and why is it so important?
You've probably heard of dietary fiber before. Or rather, foods that are said to be particularly rich in it.
There is no single exact definition of "dietary fiber," but it can be described as complex carbohydrates that our bodies cannot fully digest on their own. They pass through our intestines undigested until they reach the large intestine, where they are broken down by our gut microbiome.
In a process called fermentation, the good bacteria in our gut digest dietary fiber. Fiber is the bacteria’s favorite food. In this process, a lot of beneficial chemicals called short-chain fatty acids (SCFA) are produced. SCFA are essential for maintaining the functions of your gut and have anti-inflammatory effects.
Different types of fibers
"Dietary fiber" is not one single thing, but a term that describes a large and diverse group of coarse carbohydrates. This group can be divided into two subgroups: fibers that dissolve in water ( soluble dietary fiber) and fibers that do not ( insoluble dietary fiber) .
Soluble fiber is the preferred food for microbes in the colon and contributes greatly to the production of SCFA. Some soluble fiber forms a gel-like environment in the intestine, ensuring a more gradual absorption of sugar and cholesterol into our body. This directly contributes to reducing the risk of diseases such as diabetes.
Insoluble fiber softens your stool by attracting water to your intestines, helping to maintain good bowel habits.
Depending on your diet, your gut microbiome receives different types and amounts of fiber. Your fiber intake, in turn, affects the types of microbes that thrive in your gut, and thus the amount of beneficial SCFAs that are produced.
How do you ensure you get a sufficient and varied amount of fiber?
1. Vegetables
A diet rich in plant-based foods provides many different types of dietary fiber, thus supporting a diverse composition of bacteria in the gut microbiome.
We recommend eating at least three 100g portions of vegetables per day. Try to vary between coarse vegetables like cabbage and root vegetables; dark green vegetables like spinach, broccoli and kale; and colorful vegetables like carrots, tomatoes and red peppers. The more, the better!
2. Fruit
Fruit is another good source of fiber. Fruit also contains many polyphenols, which are not found in vegetables but are beneficial for your microbiome.
A daily intake of fruit of at least three portions of 100g per day is considered optimal. That is, one portion for each of the main meals. When possible, prioritize blue grapes, citrus fruits and berries such as blueberries, blackberries, strawberries, raspberries and blackcurrants.
3. Whole grains
There is evidence that consuming whole grains increases the number of bacteria, also called gut bacterial diversity, which is considered positive.
Eat at least two servings of whole grains daily, which is equivalent to about 75g per day. Always try to choose whole grain products when eating bread, pasta, rice, crispbread and breakfast cereals. This is also important to be aware of when buying sandwiches out or take-away.
4. Legumes
Legumes (beans, lentils, chickpeas, etc.) are a very important component of any diet. They are an excellent source of fiber and folate (vitamin B9), and are rich in protein and iron. In addition, they contain low amounts of fat and sodium, and are free of gluten and cholesterol. In addition, legumes have a low glycemic index, and therefore cause a low increase in blood sugar when consumed.
We recommend at least three to four servings per week. This equates to a serving of around 130g if you are vegetarian and around 50g if you are not.
5. Nuts and seeds
Like legumes, nuts and seeds have many benefits: they are rich in fiber, contain healthy fatty acids and protein. Walnuts in particular have been shown to have a positive effect on the gut microbiome. Tree nuts and peanuts also have this effect, but to a somewhat lesser extent.
We recommend three servings, approximately 30g or three tablespoons daily, to boost your gut microbiome. You will get the very best effect when eating nuts whole, where 30g of nuts can provide 1-3g of fiber.
Conclusion
Dietary fiber is key to a healthy microbiome. It is found in vegetables, fruits, whole grains, legumes, and nuts and seeds.
Consuming a variety of fibers from these food sources is strongly supportive of a diverse microbial community in the gut. This in turn is associated with a high level of health. Therefore, fiber-rich foods are an essential foundation for a “microbiome diet.”
Author: Cecilia Clausen (Clinical Dietitian)
