MACS: A New Buzzword You Need to Know

by Ashleigh Feltham,  Accredited Practising Dietitian and Accredited Nutritionist

Gut health is essential for your overall health and evidence on the importance of gut health continues to grow. A new buzzword you need to know is MACS or microbiota accessible carbohydrates.

You may know about prebiotics or the food which feed specific types of good bacteria in your gut. MACS are carbohydrates food that feeds your gut but is the fuel for a broad type of gut microbes.

They are more like food that everyone loves and a staple on the menu. You can find MACS in whole grains, legumes, nuts, seeds, fruits, and vegetables.


MACS are important because they feed the majority of the microbes in your gut. This ensures that you maintain the health of your gut including a good diversity and number of good bacteria. Most western diets lack MACS, and this has been proposed as the main contributor of poor gut health with less healthy microbes.

When there are lower amounts of MACS in your diet there is less production of signals produced by your gut microbes called short-chain fatty acids. These short-chain fatty acids send signals all throughout your body and are a major contributor to optimal health and function in your body. Without these healthy signals and a lower amount and diversity of good microbes, this increases the inflammatory state of your body. As a result, this can lead to many ill-health consequences like chronic and immune diseases.

So, all prebiotics are MACS but not all MACS are prebiotics. Inulin is an example of a prebiotic and MAC found in foods like:

Take home message:

By including a diverse range of different plant foods you can make sure that you set your body up for the best health possible. Aim to include 30 different plant foods each week for optimal exposure of both MACS and prebiotics to feed the good bacteria in your gut.


Sonnenburg ED, Sonnenburg JL. Starving our microbial self: the deleterious consequences of a diet deficient in microbiota-accessible carbohydrates. Cell Metab. 2014 Nov 4;20(5):779-786. doi: 10.1016/j.cmet.2014.07.003. Epub 2014 Aug 21. PMID: 25156449; PMCID: PMC4896489.