If your Grandma ever told you to eat all your Brussel’s sprouts, she wasn’t wrong. But now science is telling us more about why vegetables like Brussel’s sprouts are good for us. Vegetables (as well as fruits and whole grains) are chock full of non-digestible carbohydrates called fiber. Not only is fiber good for the human body, it turns out that it also benefits the bacteria that live in your gut, which fight off bad bacteria and support healthy intestines. Fibers that feed these beneficial bacteria are called prebiotics, and leading healthcare providers like Harvard Medical School and the Mayo Clinic recommend that Americans increase their consumption of them, significantly, to get healthier. But what are prebiotic foods?

What are prebiotics?

All prebiotics are fiber, but not all fibers are prebiotics (you can learn more about the benefits of fiber here). To be a prebiotic, a fiber must fulfill the following criteria:

• Not digestible by mammals.
• Be fermented (i.e., digested) by microbes.
• Be able to improve activity and viability of beneficial microbes.

Different microbes digest different prebiotics, which is one reason why prebiotics are associated with distinct beneficial effects. 

What are the health benefits of prebiotics?

Fibers that are prebiotics deliver a one-two punch of health benefits. They indirectly support human health by promoting the growth and activity of beneficial microbes in your gut, and they also directly impact human physiology. 

Many of the microbes that digest prebiotics produce molecules called short chain fatty acids (SCFAs), which help maintain a strong intestinal barrier, induce the production of protective mucus, reduce inflammation, and help prevent illness brought on by bad bacteria. Additionally, prebiotics have been associated with a reduced risk of colorectal cancer. 

Prebiotics can also help your body absorb nutrients (such as calcium), improve lipid metabolism, and regulate the function of liver enzymes that promote SCFA production by gut microbes. Additionally, prebiotics can aid in regulating your blood sugar and your weight, important for reducing the risk of diabetes.

Best prebiotic foods list

Ensuring you eat a diet full of a variety of prebiotic foods can help you keep your gut—and body—healthy and happy. You can boost your consumption of prebiotic fibers by concentrating on this probiotic foods list:

• Grains: barley, wheat, oats, bran
• Vegetables: artichoke, asparagus, garlic, leeks, blue agave plant, onions, chicory root
• Fruits: bananas, berries, apples, citrus 
• Legumes: soybeans
• Dairy foods (for their ability to promote probiotic microbes such as Bifidobacterium and Lactobacillus)

The prebiotics superfoods

There are also several additional natural prebiotics that can be obtained from a handful of specific foods. Similar to synthetic prebiotics, these prebiotic foods promote the growth and activity of beneficial microbes, aid in nutrient absorption, and support a healthy immune system:

Promote growth of beneficial microbes:

• Chia seeds
• Almonds
• Onion

Enhance the production of beneficial metabolites:

• Chicory root
• Dandelion greens
• Garlic

Improve calcium absorption:

• Garlic 
• Oats
• Barley

Improve immunity/decreased risk of allergy:

• Flaxseed
• Artichoke
• Chia seeds

A word of caution: Because some of these foods (for example, onions and garlic) can actually make irritable bowel syndrome (IBS) symptoms worse in some patients, these foods may be better avoided by those individuals.

The benefits of synthetic prebiotics

While all prebiotics are originally found in foods, most prebiotics consumed by humans today have been extracted from their foods of origin and either consumed as a supplement or as an additive in other foods. These are called synthetic prebiotics. While inulin, galactooligosaccharides (GOS) and fructooligosaccharides (FOS) have been considered the chief synthetic prebiotics, they are only three of many. 

If you don’t think you can consume enough natural food-sourced prebiotics, you may want to consider these prebiotics from supplements or fortified foods:

• GOS: promote growth and metabolic activity of Bifidobacterium. 
• FOS: promote the growth of beneficial bacteria while inhibiting the growth of bad bacteria, improve immunity, aid in mineral absorption, decrease cholesterol, promote vitamin B synthesis, regulate obesity and diabetes, and prevent progression of colon cancer.
• Xylooligosaccharides (XOS): promote growth and metabolic activity of Bifidobacterium and Lactobacillus and inhibit the growth of bad bacteria.
• Fructans: promote growth and metabolic activity of Bifidobacterium and Lactobacillus and inhibit the growth of bad bacteria, regulates blood glucose and lipid metabolism, decrease lipopolysaccharides (LPS) and diacylglycerol (DAG) in cell membranes.
• Isomaltooligosaccharides (IMO): in combination with green tea extract, promotes growth and metabolic activity of Akkermansia muciniphila, Bifidobacterium, Lactobacillus, and Roseburia, improves glucagon, insulin, and leptin levels.
• Soybean oligosaccharides (SOS): promote growth and metabolic activity of Bifidobacterium and Lactobacillus and inhibit the growth of bad bacteria; longer digestion of SOS leads to a prolonged effect compared to other prebiotics.
• Guar gum: promotes growth of Bacteroides, Faecalibacterium, and Ruminococcus.
• Pectin Oligosaccharides: promote growth of Bacteroidetes and Firmicutes and promote anti-inflammatory effects of microbes.
• Resistant starches: Promote growth of Akkermansia muciniphila, Bifidobacterium, Lactobacillus, and other beneficial microbes and inhibit the growth of bad bacteria.

Key takeaways

Prebiotics — the type of fiber found in vegetables, fruits and whole grains — can elevate your health status in the many important respects detailed in this report. The types and sources of prebiotics are as diverse as the bacteria that break them down, and each prebiotic has its own unique combination of benefits for humans. The best way to support general health and well-being with prebiotics is to maximize their range of effects by consuming the wide variety of prebiotic-rich foods we list. And if you have specific health conditions that you’d like to address with prebiotics, you can work with your doctor to find the right combination of foods and/or supplements. 

Check out our article on prebiotics vs probiotics for more information.