The first benefit everyone notices from trying herbal bitters is improved digestion. You feel it right away– the tongue awakens, your brow furrows, and in a few minutes a familiar rumble begins in the belly. Bitters make themselves known. But as we keep finding, the injection of digestive prowess that follows a bitter taste stimulus is just the tip of the iceberg.
Bitter taste receptors (part of a group of cell-surface receptors known as G-protein- coupled receptors, specifically of the T2R subfamily) are found almost everywhere in the body, and we are developing a new understanding about their importance in a range of functions: digestion and liver function, to be sure, but also immunity, blood sugar balance, mood, and most recently, cardiovascular function.
Taken as a whole, the effects that come from stimulating bitter T2R receptors conspire to moderate and balance many physiologic processes, generally improving their efficiency and making us more resilient in the face of challenge. While we used to think this just meant challenging foods – like poisons, for example – we are now finding that T2R receptors are able to help us weather a range of other challenges, too. First and foremost is immunity1: in the airways and sinus passages, T2R receptor stimulation initiates a strong and effective immune response2, helping to guard against bacterial (and even viral) incursion. This is because many of the substances bacteria use to communicate taste quite bitter, and in response, we secrete a range of immune-active compounds (from nitric oxide to immunoglobulins) to neutralize the potential invaders. This happens even before the microbes enter our system: we are literally “tasting” them, albeit subconsciously, and getting a jump start on dispatching them. This mirrors the “jump start” bitters give to digestion and detoxification, helping to neutralize poisons (and potentially antigenic proteins and irritating carbohydrates) before they reach more delicate parts of our physiology.
But it seems that T2R receptors are involved in another crucial physiologic system, one that is particularly vulnerable in our modern Western culture. It seems the heart and blood vessels also are studded with T2Rs, and exposing these receptors to bitter stimuli has consistent, reproducible effects. We first started seeing evidence of this fact when herbalist Julie Whitehouse and others reported that the strong digestive bitters like gentian (Gentiana lutea) and wormwood (Artemisia absinthium) supported the shift in blood flow to digestive organs that occurs after a meal3, helping the heart shunt blood to where it’s most needed without the rise in blood pressure4 that accompanies a meal without bitters.
Based on new evidence, it seems clear that bitters are more generally cardio-protective, regulating the strength and intensity of the heartbeat and helping to strengthen a failing heart. This is of course something most good herbalists already understand, since it is a well-known tenet of traditional Chinese medicine: the bitter flavor is considered an important part of regulating and strengthening the heart, or fire, phase. But it is always interesting to note when modern research uncovers some of the mechanisms behind this age-old wisdom.
Simon Foster, who works at the University of Queensland in Brisbane, Australia, has spent the last few years teasing out the roles T2R play in cardiovascular health5. First off, it is noteworthy just to realize that there are many T2Rs on the heart muscle and on the great vessels leading out of the heart, like the aorta and pulmonary vein. In fact, Foster has found at least 15 of the 25 types of human T2R receptors on the heart, and they are as abundant as receptors for angiotensin (a hormone that increases blood pressure) and beta-adrenergic receptors (sensitive to adrenaline, another hormone that increases blood pressure)6. Think about this: we spend huge amounts of time and money blocking angiotensin and beta-adrenergic receptors on the hearts of patients with high blood pressure (over $20 billion a year in the United States as of 20107, but almost completely ignore another receptor that is equally as abundant.
So perhaps we should focus a whole lot more on cardiac T2Rs: Foster found that, when stimulated, they reliably and consistently reduce the force of the heart’s contractions, helping to control elevated blood pressure8. This dovetails well with Whitehouse’s work. The reasons why are still speculative: it seems that the heart increases the amount of T2Rs when animals experience starvation, so perhaps it is a protective response to inadequate nutrition (since bitters were so often present during meals). But the heart also bumps up T2R production when it is failing9, and this seems to help slow the rate of cardiovascular decline. So although the reasons why are still unclear, it seems that bitter taste receptors protect the heart from strain and stress as much as they protect our airways from pathogens and our guts from undigested foods, bacteria, and poisons.
This is fascinating stuff in and of itself, and makes us think about plants like motherwort, traditionally used for cardiovascular support. Why, for example, do herbalists choose this particular Lamiacea for heart health, and not peppermint or sage? Part of the answer may lie in its strongly bitter flavor which, coupled with the vasorelaxant effects of its volatile oils, makes a perfect combination for blood pressure and heart muscle longevity and elasticity. But there is one more interesting piece to the powers of bitters in heart health: since bitter taste receptors rely on the G-protein secondary messenger system, they tend to lead to a temporary increase in other secondary messengers like IP3 to accomplish their action. This increase is also connected to an increased production of immunoglobulins like IgG and IgM in immune cells – which circles back to the immunological response. So bitters may also help increase circulating levels of IgG and IgM. And in a fascinating piece of research from the spring of 2016, researchers at Imperial College, London found that cardiac patients with higher levels of circulating immunoglobulins had a much lower risk of coronary heart disease over a 5-year follow-up period (33% less, in fact)10.
Take heart. Try bitters.
References:
1. https://www.urbanmoonshine.com/blog/bitters-a- taste-for- immunity/
2. Lee, Robert J., and Noam A. Cohen. “Taste receptors in innate immunity.” Cellular and Molecular Life Sciences 72.2 (2015): 217-236.
3. McMullen, Michael K., Julie M. Whitehouse, and Anthony Towell. ” Bitters: time for a new paradigm.” Evidence-Based Complementary and Alternative Medicine 2015 (2015).
4. Sidery, M. B., et al. “Cardiovascular responses to high-fat and high-carbohydrate meals in young subjects.” American Journal of Physiology-Heart and Circulatory Physiology 261.5 (1991): H1430-H1436.
5. http://espace.library.uq.edu.au/uqsfost1
6. Foster, Simon R. “Odorant and taste receptor systems in the heart: investigation of novel cardiac biology.” (2013).
Davis, Karen E. “STATISTICAL BRIEF# 404: Expenditures for Hypertension among Adults Age 18 and Older, 2010: Estimates for the US Civilian Noninstitutionalized Population.” Retrieved April 12 (2013): 2014.
7. Roura, Eugeni, et al. “Taste and hypertension in humans: targeting cardiovascular disease.” Current pharmaceutical design 22.15 (2016): 2290-2305.
8. Foster, Simon R., et al. “Bitter taste receptor agonists elicit G-protein- dependent negative inotropy in the murine heart.”The FASEB Journal 28.10 (2014): 4497-4508.
9. Khamis, Ramzi Yousef, et al. “HIGH SERUM IMMUNOGLOBULIN G AND M LEVELS IMPROVE CARDIOVASCULAR RISK DISCRIMINATION IN HYPERTENSION: A NESTED CASE-CONTROL SUBSTUDY OF THE ANGLO-SCANDINAVIAN CARDIAC OUTCOMES TRIAL.” Journal of the American College of Cardiology 67.13_S (2016): 1912-1912.
