Harnessing the power of seaweed to improve gut health

• The bacterial ecosystem in the gut, the microbiome, underpins human health, and the right diet can increase the beneficial bacteria found there.
• Seaweed has unique prebiotic properties that promote the growth of these beneficial bacteria.
• Together with colleagues, Dr Emer Shannon, at the Irish Agriculture and Food Development Authority, is exploring the potential of seaweed for improving gut health.

The phrase ‘you are what you eat’ may not be strictly true, but researchers are only just realising the full impact of nutrition on our health. As our understanding has increased, we have begun to appreciate the role of the vast collection of bacteria, fungi, and viruses that live in our digestive system. This is the gut microbiome; a complex ecosystem that can influence more than just digestion, and which is often referred to as our second brain.

The full capabilities of the microbiome are still being explored, but research has shown it may influence metabolism, immune responses, and even mental health. For example, metabolic disorders, such as high blood pressure, type 2 diabetes, and obesity are associated with a disrupted balance of the gut microbiota. While it is not known whether this is cause or effect, or a combination of both, increasing the beneficial bacterial species in the microbiome may have significant health benefits, and offer an attractive treatment option to replace reliance on medications.

Given its importance for human health, how can a healthy gut microbiome be achieved?

Given its importance for human health, how can a healthy gut microbiome be achieved? One way is through prebiotics, compounds that fuel the growth and survival of the beneficial bacteria in the gut.

Feeding the gut microbiome

Dr Emer Shannon, at Teagasc, the Irish Agriculture and Food Development Authority, is exploring the prebiotic effect that seaweed may have on the gut microbiome. Shannon is working alongside Teagasc colleague Dr Maria Hayes, Dr Sarah Hotchkiss from CyberColloids, Ireland, and Dr Michael Conlon from the Commonwealth Scientific and Industrial Research Organisation, on a project called SeaHealth.

Shannon explains that whole seaweeds, as well as substances derived from seaweed, contain prebiotics such as polysaccharides (a type of carbohydrate) and polyphenols (which have antioxidant properties in addition to prebiotic activities). Prebiotics are sometimes classed as functional foods, foods which offer health benefits beyond their nutritional value. Among other investigations, SeaHealth will screen seaweed extracts for their impact on metabolic health, as well as their potential for prebiotic activity.

A secret superfood?

One part of the SeaHealth project focuses on the prebiotic properties of three types of seaweed, the Australian brown seaweeds Phyllospora comosa and Ecklonia radiata, and the green seaweed Ulva ohnoi. As well as looking at the whole seaweed, the team also extracted polysaccharides and polyphenols and carried out a variety of different analyses. Firstly, they subjected the samples to digestion with enzymes, as would normally occur in the human stomach and upper digestive tract. The researchers were also able to recreate a working human gut in the laboratory – which included human faecal matter – to simulate the way in which food products are fermented in the large intestine by our gut bacteria.

The team used a special kind of genetic sequencing, which can differentiate between each species of bacteria, to monitor the impact the seaweed and extracts were having on the bacteria in the model gut. This included looking at which populations of bacteria increased and decreased, as well as the overall diversity within the microbiome.

Several different groups of beneficial bacteria were increased after seaweed or its extracts had been applied.

Several different groups of beneficial bacteria were increased after seaweed or its extracts had been applied. These groups of bacteria are especially important because when they ferment and break down indigestible foods, such as prebiotics, they produce short chain fatty acids (SCFA). SCFA, especially butyrate, are well known for their role in improving gut health. One way they do this is by providing energy for the cells in the gut, but they also regulate the production of some immune cells and may even have positive impacts on behaviour and neurological health.

After 24 hours of fermentation, the levels of many beneficial bacteria including Actinobacteria, and lactic acid-producing probiotic Firmicutes, had increased when the gut was exposed to seaweed compared to a standard prebiotic control. This corresponded to an increase in SCFA production when compared to the control samples.

As well as an increase in good bacteria, Shannon and colleagues found that overall diversity within the microbiome increased. This is important because previous research has shown that more diversity means a more stable microbiome; if one type of bacteria should disappear there’s more chance another type of bacteria will be able to step in and carry out the same role.

Plant-based medicines

Seaweed represents a sustainable, often underused source of compounds with therapeutic properties, many of which are not found in terrestrial plants. The wider SeaHealth project aims to use seaweed to develop functional foods – foods that have enhanced nutritional profiles and health benefits while still looking, smelling, and tasting acceptable to consumers.

Shannon and colleagues have demonstrated that whole seaweeds and their extracts may be able to improve gut health, and even have knock-on benefits for other aspects such as immune function. Now that this has been tested in the lab, the next steps may involve testing the same ingredients in human participants.