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How seaweed could support your microbiome and metabolic health

Dr. Adele Costabile, PhD


Rachel Lett, RNutr


Short Read

  • Our microbiome is made of trillions of bacteria that continuously adapts with diet, lifestyle and environment.
  • The microbiome plays an integral role in hormone regulation, energy homeostasis, metabolism and immunity.
  • Poor gut health can lead to metabolic syndrome (MetS), which is a constellation of conditions like high blood pressure, obesity, insulin resistance, abnormal blood lipids, cardiovascular disease and diabetes.
  • Bioactive compounds from seaweed could have the potential to support gut health and improve biomarkers for MetS.

What is the microbiome

We are home to trillions of bacteria that reside on and in our bodies. Incredibly our precise bacterial mix is unique - like fingerprints, no two people have exactly the same combination of bacteria.

The intricate universe of gut bacteria — collectively known as the microbiome —  is continuously adapting with our diet, lifestyle and environment. As we are discovering through recent research, the microbial diversity and richness vary along the longitudinal compartments largely referring to the small intestines and the large intestines where differences in nutrient availabilities, chemical environments and physiological functions influence the formation of distinct microbiome niches[1-3].

Differences in microbial biogeography also exist along the transverse compartments (i.e. from the lumen to the mucosa), as evidenced by the presence of these niches. However, inconsistencies in mucosa-associated species are found between studies largely due to the differences in sampling sites indicating that there could also be spatial variation within the mucosa community.

These differences serve as reminders that while faecal samples, due to their accessibility, have been the primary sample type for studying the colonic microbiota, care should be taken when using them to infer functional significance of the entire colonic community.

Why is the microbiome so important

The intestinal lumen is the primary habitat for the gut bacteria since there is a constant stream of nutrients passing through. Beneath the lumen lies the mucosa compartment where they are separated by a layer of mucus whose thickness increases from approximately 20 μm in the small intestine to 830 μm in the colon.

The primary purpose of the mucus layer is to protect the epithelium from direct contact with the harsh chemicals and bacteria in the lumen and thus the significantly thicker mucus layer in the colon reflects its dense bacterial load. Mucus is a gel-like structure made of mucin that is excreted from the goblet cells, which then expands extracellularly into a mesh network.

Microbial metabolites are the chemical signals used by the microbiota to establish communication with the host and exert their regulatory effects. The most prominent microbial activity in the colon is the anaerobic fermentation of dietary fibre which produces short chain fatty acids (SCFAs i.e acetate, butyrate and propionate) along with gases such as hydrogen, methane and carbon dioxide. Microbial cross-feeding can result in the production of SCFAs via different intermediate metabolites such as lactate and succinate. In addition to their localised effect on the gut epithelium, SCFA can exert system wide effects modulating processes such as satiety and energy homeostasis, which has been implicated in the development of insulin resistance and obesity.

So, the gut microbiome is integral to human health as they extend the metabolic functionality of the host and participate in immune development and regulation. Moreover, the diversity, composition density of the microbiome not only influences our response to different foods, but also impacts our disease risk.

How the gut microbiome affects health

Studies have shown that significant change to the microbiome due to prolonged stress, medications and diet plays a role in developing metabolic syndrome (MetS). [3-8]. It is estimated that MetS affects 1 in 3 older adults (>50 years)  in the UK, and the numbers are climbing.

It is a constellation of risk factors comprising abdominal obesity, increased blood pressure (BP), increased fasting plasma glucose (FPG), increased triglycerides (TG), and decreased high density lipoprotein cholesterol (HDL-C) that lead to an increased risk of developing cardiovascular diseases (CVDs), type 2 diabetes mellitus (T2DM) and all cause mortality. Treating MetS is of crucial importance in preventing progression to type 2 diabetes and in reducing mortality and morbidity from type 2 diabetes and CVDs.

In recent years, marine organisms, especially seaweeds, have been highlighted as potential natural sources of bioactive compounds and useful metabolites, with many biological and physiological activities to be used in functional foods or in human nutraceuticals for the management of MetS comorbidities.

How we can improve our gut microbiome through seaweed

Among the three groups of seaweeds, brown seaweeds are known to contain more bioactive components than either red or green seaweeds that could help for the control of metabolic syndrome risk factors.

The most abundant polysaccharides in brown seaweeds are laminarin, fucoidan and alginates.

Laminarins have been reported to exert bioactive properties in the gastrointestinal tract and are recognized as a regulator of intestinal metabolism through its impacts on mucus structure, intestinal pH and short chain fatty acids production. Furthermore, laminarins provide protection against infection caused by bacterial pathogens and protection against severe irradiation, boosts the immune system by increasing the B cells and helper T cells and can also act on typical mechanisms involved in MetS, since they lower the systolic blood pressure, cholesterol absorption in the gut and consequently the levels of cholesterol and total lipid both in serum and liver.

Fucoidans have been reported to reduce hyperglycaemia via the inhibition of α-amylase and α-glucosidase, consequently decreasing intestinal absorption of glucose and enhancing the insulin-mediated glucose uptake due to the ability of fucoidans to modulate relevant pharmacological targets including glucose transporter GL UT-4 and AMP-activated protein kinase (AMPK).

Alginates have been shown to inhibit the digestive enzymes pancreatic lipase and pepsin and diminish the intestinal absorption of triacylglycerols, cholesterol and glucose. It has been also shown that, as with other dietary fibres, the consumption of alginates could delay gastric emptying, increase digestive fluid viscosity and reduce calorie intake through enhanced satiety.

Curious to find out more?

Our first pilot study demonstrated significant reductions in plasma glucose, total cholesterol,

LDL cholesterol and increase in HDL cholesterol levels. Along with that, significant reductions were observed in body weight, body fat percentage, fat mass and waist and hip circumferences during the study period of 2 weeks. Thus, we sought to determine the long terms benefits of brown seaweed extracts on gut health, immunity and metabolic disorders.

If this sounds interesting and you have a BMI between 20-35 kg/m2 and aged between 18 to 65 years, please get in touch with us. You will be required to consume either the brown seaweed extract, berberine or a placebo capsule three times a day, 30 minutes prior to having a meal, during the treatment period of 4 weeks followed by a 4-week washout period where no products will be consumed.

N.B. All products in this study are safe to human consumption and do not pose any risk to study participants. All information collected will be strictly keep confidential and you will get reimbursed for your time at the completion of the study.

For more information, get in touch with Adele Costabile at

Written by Adele Costabile

Associate Professor (Reader) in Nutrition at Roehampton University. With over 14 years working in gut microbiology, she is an expert in gut health. Her recent work has been focusing on the gut microbiota as a therapeutic target for nutritional interventions.

Curious about the science behind all this?

Donaldson GP et al. Nat Rev Microbiol. 14(1), (2016).

Pereira FC, Berry D. Environ Microbiol. 19(4):1366–1378 (2017).

Hillman ET, et al. Microbes Environ, 32(4):300–313 (2017).

D’Aversa F, et al. Internal and emergency medicine 8(1):11-15 (2013).

Festi D, et al. 20(43):16079 (2014).

Dabke K, et al. J Clin Invest 129(10):4050-4057 (2019).

Mazidi M, Kengne AP. Clinical Nutrition. 38(4):1672-1677 (2019).

Wang P, et al.Chin Med J, 133(7):808 (2020).

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