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Prebiotics, Probiotics, Chicory, Kelp & Yeast in Pet Foods
Drs. Foster & Smith Veterinary Services Department
Katharine Hillestad, DVM
Daily Food Requirements
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Click here for a pdf version of this article. 

Several pet foods now on the market contain ingredients that may be unfamiliar to some consumers. These include chicory, prebiotic and probiotic supplements, kelp, algae, and yeast.

Chicory: A prebiotic

Chicory comes from the plant Cichorium intybus. Chicory root has been used in human food for years, as a coffee substitute. Now it is being used in pet food, where the claim is that it can help to improve health by promoting the growth of beneficial bacteria in the gastrointestinal system.

Chicory contains inulin, a form of dietary fiber, which although itself is indigestible, contains substances called oligosaccharides that are thought to promote the growth of beneficial intestinal bacteria. Proponents claim that high levels of 'friendly' intestinal bacteria can help to improve digestion, decrease disease, and strengthen the immune system. Supplements that contain substances (such as the inulin in chicory) thought to stimulate the growth and/or activity of beneficial intestinal microorganisms are called prebiotics.


There is another group of supplements called probiotics. These contain microorganisms that are thought to improve the microbial balance of the host's intestine. An example would be a supplement which contains cultures of microorganisms such as Lactobacillus acidophilus, and Lactobacillus casei, similar to the 'active cultures' found in some yogurts. Probiotics contain microorganisms, prebiotics do not. Both of these products are thought to stimulate the growth of helpful microorganisms in the large intestine.

Kelp and algae

Another pet food ingredient that may be new to some consumers is kelp. Seaweed, algae, and kelp can be good sources of minerals such as iron, iodine, potassium, and trace minerals. Sea vegetables have a high level of digestible protein. In addition:

  • Brown algae (kelp, fucus) is a good source of potassium.

  • Red algae (gigartina, nori, dulce, and Irish Moss) contains a high concentration of carrageenan, which gives it a gelatinous consistency. It maintains this form in the intestines and is thought to help absorb poisons and toxins, which will then be carried out of the body.

  • Green algae (sea lettuce) has a lower mineral content, but is a good source of iron. It also contains an element called 'cesium,' which is reported to bind with carcinogens and remove them from the digestive tract.

  • Blue-green algae is the earth's most concentrated source of chlorophyll. It contains vitamins (especially B12), minerals, and beta-carotene.


Brewer's yeast, nutritional yeast, or yeast culture may be on the ingredient list in some pet foods. These are not the same as the yeast used in home bread making, which is called active dry yeast and should not be eaten raw.

  • Brewer's yeast is a deactivated yeast that is a by-product of beer making and is rich in protein and B vitamins.

  • Nutritional yeast is made from the same strain of yeast (Saccharomyces cerevisiae) as brewer's yeast, but is grown on molasses and has a sweeter flavor.

  • Yeast culture may be an active or inactive supplement which contains B vitamins and enzymes. It is thought to encourage the growth of beneficial bacteria in the intestine.

Click here for a pdf version of this article.   
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