Written by Dr. Viv Rolfe
The gut is the centre of the body’s universe, (I say this because I’m a physiologist who has been fascinated by it for thirty years). But people’s recognition of the importance of a healthy gut is not new and Ayurveda places emphasis on our agni or “digestive fire” which is responsible for strength and the healthy state of the body. Ayurveda states we need to provide it with the right nourishment to keep it balanced and regular (1).
So how do our digestive fire’s fair today? With the advent of ultra-processed foods and the over-use of pharmaceuticals, what do we know about the impact this is having? The ‘omics’ revolution of recent decades has shed incredible light on our body’s molecules and the intricate relationship between our own cells and the trillions of microbes – fungi, bacteria, viruses – that are harboured within us, including within the gut. These biological sciences include genomics, transcriptomics, proteomics, or metabolomics. They have shown us the importance of the symbiotic relationship between our bodies and our bugs, and the damaging effects that our habits and lifestyles can have. In Ayurvedic terms, the outlook for agni looks rather irregular and possibly even bleak.
The onslaught of modern living
On a daily basis, we are eating more than we did fifty years ago, with calories in the US and Western Europe topping 3,500 kcal per day (2). One underlying factor is greater consumption of high calorie ultra-processed foods. In the UK these are estimated to account for 57% of our total energy intake and provide two thirds of the total free sugars in our diets (3). These foods are processed and can be characteristically sugary or salty to make them more palatable. We all enjoy tucking into burgers or chocolate, and population-based studies have found that consumption of ultra-processed food is associated with almost every chronic disease (4).
The ‘omic’ studies are showing us that these foods alter the balance of our gut microbiota from helpful Bacteroides species that metabolise non-digestible polysaccharides, leading to a loss of healthy bi-products like butyrate. By unbalancing the system this allows less helpful bacteria to occupy niches in the intestine (5). In almost every other instance of our modern lifestyles, we see a similar pattern of dysregulation of our microbiota. Exposing it to environmental pollutants initiates a protective response by the gut that releases inflammatory compounds that damages the gut wall – the delicate single layer of epithelial cells on the inner most surface (6). A commonly used insecticide diazinon disrupted the microbiome in animals for up to 13 weeks following a single dose (7). Multiply that up by the thousands of pesticides used globally (8), even if our agricultural and food systems can adhere to safe levels, the impact on our planetary microbiota – be it the bugs within our soils or our life-giving human and animal microbiomes – is not fully known.
Another area of our modern living that may have a detrimental impact on our microbiomes is our choice of healthcare. In one study, a quarter of commonly used pharmaceuticals were found to prevent the growth of our microbes, potentially adversely affecting our health and also contributing to the risk of antibiotic resistance (9). Antibiotics are known to create competition within microbial communities and upset the balance of mutually beneficial co-habitation (10). Whilst it might be the case that in adults they can recover from a course of antibiotic treatment, in infants there may be lasting changes along with the risk of building the pool of antibiotic-resistance genes in our residing communities (11).
At this half-way point, there is a picture emerging from the research that how we treat our gut through our foods and medicines causes disturbances that can have lasting ill-effects. However, I believe the gut is not called the “little brain” for nothing (from Michael Gershon MD) and it is well poised to offer us help using herbs and spices.
Our gut to the rescue
What we do know is that positive lifestyle changes such as eating more nutritiously can improve health at any stage of life (12). Research is putting the benefits of herbs and spices into the spotlight, with Turmeric increasing beneficial butyrate-producing gut bacteria and other herbs also modifying our microbiota (13). The wide-ranging effects of herbs and spices may reflect the array of polyphenols and plant compounds that we ingest and are consequently metabolised by our bugs.
There is also much more intrigue beyond the gut microbiota. Why is it that our gut walls contain a myriad of receptors for plant-based compounds? I can’t help but think why are they there, and what is their importance? We evolved to eat a diverse plant species that were seasonally available, and this has dwindled in our modern diets. So, can we use herbs and spices to kick-start our physiology again?
Firstly, it is recognised that bitter receptors are located throughout the mouth, throat and gastrointestinal system and enhance digestive processes (increasing secretions and supporting the cardiovascular system in diverting blood flow to the gut). Bitter herbs – ‘bitters’ – like gentian and wormwood have longstanding use as aperitifs as digestive aids (14). Within the gut are also an abundance of cannabinoid receptors which regulate gut function and barrier integrity, located throughout the epithelial cell lining and extensive enteric nervous system (15). Capsaicin which is a plant compound from chilli peppers binds to vanilloid receptors and also stimulates gut function (16). It is suggested that our body’s processes are now at odds with our unhealthy lifestyles. Just as we need vitamins and minerals in our diets, the presence of these receptors suggests that consumption of herbs, spices and green leafy vegetables, might be just as essential to reset our systems.
Is diversity the secret to life?
The notion of diversity increasingly seems to hold the key to the future, whether we are talking about diversity in our diets, diversity of gut microorganisms, or the diversity of receptors in our gut.
Concepts like the dietary phytochemical index may help us understand the importance of diverse plant compounds like polyphenols and phytoestrogens in our foods and how these relate to our gut processes and body’s health (17). The latest research is helping us understand the significance of our bug’s bugs – the viruses known as bacteriophages that interact with our bacteria. In this intriguing area of science, the phages become more diverse shortly after birth, and they manipulate our gut bacteria to have both good and bad effects on our health (18).
We know that our modern lifestyles do not allow the orchestral capabilities of our microbiomes or gut receptors to be fully played. The science points towards plant compounds within our herbs and spices as being important elements within these systems. More research is needed to see how we can encourage lifestyle changes to off-set some of our poor habits, and how we can spice up our lives so that our digestive systems can flourish and bring our bodies into better health.
- Agrawal A, Yadav C, Meena M. Physiological aspects of Agni. AYU (An International Quarterly Journal of Research in Ayurveda). 2010;31(3):395. doi:10.4103/0974-8520.77159
- Daily supply of calories. Our World in Data. https://ourworldindata.org/grapher/food-supply-kcal?tab=chart&time=1961..2013&country=OWID_WRL~Europe%2C+Western~Eastern+Europe~Africa~Asia~South+America~Northern+America. Published 2021. Accessed October 29, 2021.
- Rauber F, Louzada M, Martinez Steele E et al. Ultra-processed foods and excessive free sugar intake in the UK: a nationally representative cross-sectional study. BMJ Open. 2019;9(10):e027546. doi:10.1136/bmjopen-2018-027546
- Consumption of ultra-processed foods and health outcomes: a systematic review of epidemiological studies – Nutrition Journal. Nutrition Journal. https://nutritionj.biomedcentral.com/articles/10.1186/s12937-020-00604-1). Published 2020. Accessed October 29, 2021.
- Martínez Leo E, Segura Campos M. Effect of ultra-processed diet on gut microbiota and thus its role in neurodegenerative diseases. Nutrition. 2020;71:110609. doi:10.1016/j.nut.2019.110609
- Defois C, Ratel J, Garrait G et al. Food Chemicals Disrupt Human Gut Microbiota Activity And Impact Intestinal Homeostasis As Revealed By In Vitro Systems. Sci Rep. 2018;8(1). doi:10.1038/s41598-018-29376-9
- Gao B, Bian X, Mahbub R, Lu K. Sex-Specific Effects of Organophosphate Diazinon on the Gut Microbiome and Its Metabolic Functions. Environ Health Perspect. 2017;125(2):198-206. doi:10.1289/ehp202
- Pesticide Residues in Food. Report of the 1974 Joint Meeting of the FAO Working Party of Experts on Pesticide Residues and the WHO Expert Committee on Pesticide Residues. Food Cosmet Toxicol. 1976;14(5):491. doi:10.1016/s0015-6264(76)80206-4
- Maier L, Pruteanu M, Kuhn M et al. Extensive impact of non-antibiotic drugs on human gut bacteria. Nature. 2018;555(7698):623-628. doi:10.1038/nature25979
- Seelbinder B, Chen J, Brunke S et al. Antibiotics create a shift from mutualism to competition in human gut communities with a longer-lasting impact on fungi than bacteria. Microbiome. 2020;8(1). doi:10.1186/s40168-020-00899-6
- Gibson M, Crofts T, Dantas G. Antibiotics and the developing infant gut microbiota and resistome. Curr Opin Microbiol. 2015;27:51-56. doi:10.1016/j.mib.2015.07.007
- Calder P, Carding S, Christopher G, Kuh D, Langley-Evans S, McNulty H. A holistic approach to healthy ageing: how can people live longer, healthier lives?. Journal of Human Nutrition and Dietetics. 2018;31(4):439-450. doi:10.1111/jhn.12566
- Peterson C, Rodionov D, Iablokov S et al. Prebiotic Potential of Culinary Spices Used to Support Digestion and Bioabsorption. Evidence-Based Complementary and Alternative Medicine. 2019;2019:1-11. doi:10.1155/2019/8973704
- McMullen M, Whitehouse J, Towell A. Bitters: Time for a New Paradigm. Evidence-Based Complementary and Alternative Medicine. 2015;2015:1-8. doi:10.1155/2015/670504
- Hasenoehrl C, Taschler U, Storr M, Schicho R. The gastrointestinal tract – a central organ of cannabinoid signaling in health and disease. Neurogastroenterology & Motility. 2016;28(12):1765-1780. doi:10.1111/nmo.12931
- Du Q, Liao Q, Chen C, Yang X, Xie R, Xu J. The Role of Transient Receptor Potential Vanilloid 1 in Common Diseases of the Digestive Tract and the Cardiovascular and Respiratory System. Front Physiol. 2019;10. doi:10.3389/fphys.2019.01064
- Sotoudeh G, Abshirini M, Mahaki B, Bagheri F, Siassi F, Koohdani F. Higher intake of phytochemical-rich foods is inversely related to prediabetes: A case-control study. Int J Prev Med. 2018;9(1):64. doi:10.4103/ijpvm.ijpvm_145_18
- Townsend E, Kelly L, Muscatt G et al. The Human Gut Phageome: Origins and Roles in the Human Gut Microbiome. Front Cell Infect Microbiol. 2021;11. doi:10.3389/fcimb.2021.643214