We know that microbiome diversity is linked to human health and we know that while several factors influence our microbiota, what we eat seems to be one of the key influencers. So what should we eat to promote healthy gut microbiota diversity? Our gut bugs eat what we eat. Specifically, they eat “Microbiota- accessible carbohydrates” or MACs, a term coined by Erica and Justin Sonnenburg, a husband and wife duo who lead a team of microbiota researchers at Stanford University. MACs are carbohydrates we can’t easily digest ourselves but that our gut bugs can ferment or metabolise into beneficial compounds such as short-chain fatty acids. Essentially, MACs are the components within dietary fibre on which gut microbes feed. So eating more MACS can provide more nourishment to the microbiota, help gut microbes thrive, and improve the diversity of this community. The most common source of MACs is fibre – both soluble and insoluble – which includes fruits, vegetables, starchy plants, unrefined whole grains, nuts, seeds, legumes, and other foods that are poorly absorbed by us, but can be utilised by our gut bugs as a food source.
 
Unfortunately you can’t read a food label or ingredient list to get an idea of the MACs contained in different foods. But it is clear that when we’re eating a typical Western diet high in bad fat and simple carbohydrates, many of us are not getting enough dietary fibre. The average American consumes a measly 16 grams of dietary fibre per day. This falls far short of the 25-38 grams recommended by the FDA, and is even farther still from the 100-150 grams of fibre consumed by modern day hunter-gatherers such as the Hadza of Tanzania. In practice, a “Big MAC diet” means that each meal should include a healthy portion of plant foods so that you are consuming at least 29-38 grams of dietary fibre per day. For example, the Sonnenburgs recommend that your day could start with a bowl of steel cut oatmeal topped with berries, then a leafy green salad sprinkled with nuts and seeds for lunch, and finally a dinner comprised of a veggie-filled Mediterranean bean soup. This type of diet ensures that our microbes have plenty to eat so they can maintain a robust and thriving community within your gut. Although research on the gut microbiome is still in its early days, I think you’d be hard-pressed to find a doctor who would argue that eating more fresh fruit, vegetables, whole grains, nuts, seeds, and legumes is fundamentally unhealthy.

Our good friend Katrina Lau Hammond has put together a delicious collection of recipes designed to nourish your microbiome.

You can download the cookbook for free here.

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