Spices sets a healthy gut by modulating the resident bacteria

For centuries spices are being used to flavour our food. Being tiny culinary ingredients, do they really possess any nutritional or health benefits other than satisfying our taste buds, is a question being raised by many for centuries. However, during the past several decades, scientists are attempting to find an answer to this million dollar question and this view is beginning to change. As a result, there is an increasing body of evidence suggesting the benefits of spices from a health perspective. But what is needed is to expose and explain by scientific means how these health benefits operate in the human body. In a recent publication in Scientific Reports, scientists of the National University of Singapore have proved that serving even a single meal containing mixed spices can modify the gut microbiome within a day or two.

Spices and dietary polyphenols

Earlier research focused on the diverse phytochemicals present in spices. Among the phytochemicals, the polyphenols predominate in spices. In fact, spices are the richest source of polyphenols. Polyphenols are a large family of structurally diverse compounds but the predominant class/group of polyphenols in spices are the phenolic acids and flavonoids. They confer several biological properties like anti-oxidant, anti-inflammatory and antimicrobial properties. Studies have shown that around 90% polyphenols pass from the stomach, through the small intestine and into the large intestine undigested. There is a growing amount of literature on the positive role of polyphenols and polyphenol rich foods on gut health. But how they interact with gut was unclear till recently. Several recent studies indicate that the polyphenols act in combination and there is a synergy in their bioactivity which is difficult to prove in a laboratory.

Microbiome, the second genome

The microbes that live in and on our bodies are collectively called the microbiome. Technological advances in genome sequencing have helped to understand the diversity of the microbial flora.  The gastro intestinal (GI) tract contains the bulk of microbiota associated with the human body and has been one of its most thoroughly examined ecosystems. Studies suggest that more than 5,000 bacterial taxa may reside in the gut. Among the various regions of GI tract, the human large intestine harbours the highest accumulation of microorganisms (up to 1012 bacteria per gram of colonic content) in the environment that has been reported to date. However, the composition of this bacterial assemblage is influenced by multiple and diverse factors, such as age, origin, environment, dietary habits (including probiotics) and the application of antibiotics. Because of this, each individual has his or her own unique profile of microbial species which is closely linked to the health, wealth and even mood of the host. On the other hand, the majority (98% of all species) belong to only four bacterial phyla: Firmicutes (64%), Bacteroidetes (23%), Proteobacteria (8%) and Actinobacteria (3%), whereas there is tremendous species diversity. Firmicutes and Bacteroidetes dominate in the large intestine, while in the jejunum Proteobacteria are more abundant than Bacteroidetes. For many years, the function of the large intestine was perceived to be limited to the reabsorption of water and salt and the removal of unused food debris. Nobody bothered about the diverse  microbiota present there. Currently, it is known that it has an important, possibly crucial, role in the metabolism of chemical compounds found in foods. Scientific evidences are pouring in underlining the significant role of gut microbiota in obesity, diabetes, and many other metabolic diseases. Recent studies suggest that specific members of the gut microbiota play a functional role in inflammatory bowel disease (including Crohn’s disease), colorectal cancers, obesity and allergies.

The gut microbiome is a dynamic and complex community of bacteria that is dependent on extrinsic and intrinsic factors. Among these dietary patterns can directly affect gut microflora composition. Over the course of evolution, the human beings have developed tools indispensable for the utilisation of sugars, lipids and proteins that we intake. In spite of this, many of these compounds enter further segments of the GI tract undigested. Bacteria use these compounds as a source of energy and nutrients via their own enzymes, some of which cannot be produced by human tissues. This biotransformation processes by the intestinal bacteria detoxify such undigested compounds which is quite different from what is done by the liver. The bacterial metabolism occurring under anaerobic conditions is quite different from the hepatic metabolism and result in non-polar low molecular weight products.

Spices modulate gut microbiota

Spices rich in polyphenols are expected to interact and modulate the gut microbiome. A pilot study published in 2019 from United States has proved for the first time that a mixture of spices at culinary doses affects the composition of gut microbiota. A daily intake of 5 g of mixed spices for two weeks in healthy subjects resulted in shifts in Firmicutes and Bacteroidetes abundance, two prominent bacterial phyla among gut microbiota. Subsequently, the study from Singapore has clearly showed that a single intake of curry containing mixed spices could increase the beneficial Bifidobacterium and suppress the pathogen Bacteroides within a 24–48 hour timeframe. There are even reports indicating modulation of gut microbiota by herbs to inhibit gut-derived cardio-vascular disease risk factors. All these studies are undertaken in White/Caucasian participants and not in traditional spice consuming communities.

Conclusion

So many factors influence your gut health but your diet is key to your gut health. While the above initial reports sounds promising, more studies are needed to better understand the impact of spices on our gut microbes. However, the leads obtained clearly suggest us to include lots of variety in our diet so as to look after our gut microbes. In short, when you’re adding spices to your food, it more likely to be increasing the beneficial bacteria in your intestines!  

Additional Reading

• Khine WWT et al. 2021. A single serving of mixed spices alters gut microflora composition: a dose–response randomised trial. Scientific Reports 11: 11264. https://doi.org/10.1038/s41598-021-90453-7

• Lu Q-Y et al. 2019. Mixed spices at culinary doses have prebiotic effects in healthy adults: A pilot study. Nutrients 11(6): 1425. https://doi.org/10.3390/nu11061425

• Petersen K et al. 2021. Herbs and spices modulate gut microbiota composition: A randomized, crossover, controlled-feeding study. Current Developments in Nutrition 5 (Suppl.): 360. https://doi.org/10.1093/cdn/nzab037_070

[Published in Spice India August 2022]