A CHANGING WORLD
In the United States, over 80,000 chemicals are currently registered for use, with around 2,000 novel varieties introduced each year (1). These chemicals are most commonly added to foods, cosmetics or body care products, prescription drugs, cleaning products, and landscaping or agricultural products. The CDC’s Fourth Report on Human Exposure to Environmental Chemicals, updated in January 2017, provide data for detection of 308 chemicals in human bodily fluids (blood, serum, urine) (2). Due to legislation, logistical time constraints, and marketing momentum, the EPA has difficulty reviewing all of the chemicals prior to their public release and many chemicals will enter the market without safety testing (3). The long-term health risks associated with exposure are still under investigation and much is left unknown.
In the face of this data, consumers have voiced concern. Perhaps not surprisingly, we've seen a rising commercial popularity of “detox” diets, supplements, and fad “cleanses” on the market. While we may have good reason to be concerned over the potential environmental and health impact of increasing chemical encounters, no convincing evidence exists to warrant use of most detox or cleansing programs. In fact, the U.S. Food and Drug Administration (FDA) and Federal Trade Commission have taken action against several companies selling detox/cleansing products after it was reported that they contained illegal and potentially harmful ingredients and/or were marketed using false claims that they could treat serious diseases (4).
Without question, it is important for us to minimize environmental exposure to certain highly questionable chemicals, such as BPA (5). However, it will also be important to avoid fad "detox" products and recall that our body possesses its own innate robust detoxification system.
In Part I of this 3-part series, we will explore how the body's innate detoxification system works and what we can do to optimize it without falling prey to pseudo-scientific detoxification product marketing scams that may make us feel worse or drain our wallets without offering adequate support for overall health.
In Part II and III, we will build on the information in Part I; advancing our knowledge of detoxification processes, especially in the liver. We will develop a deeper understanding of how specific drugs and foods/nutrients affect liver biotransformation pathways. I will also offer some practical medical nutrition therapy advice for how to support your body’s innate detoxification processes.
THE BODY'S DETOXIFICATION SYSTEM
If our bodies are working well, we are perpetually generating waste products, ridding ourselves of unwanted pathogens, and processing the foreign compounds found in air, food, water, cosmetics, cleaning products, and other household or industrial xenobiotics. Detoxification, or biotransformation, is the process by which the body transforms various metabolic waste products and foreign chemical substances/xenobiotics into compounds that can be easily excreted without harm. Our body is also constantly identifying microbial pathogens and targeting them for removal. Many systems participate in these diverse processes of detoxification, including the skin, respiratory system, kidneys, gastrointestinal tract, immune system, and liver. Let’s take a look at the key detoxification features of each of these below.
The Skin
The skin is the body’s largest organ and its primary function is to act as a barrier against unwanted environmental contaminants such as pathogenic microbes. Though the skin behaves as a barrier, lead and other toxic elements, especially those lipophilic in nature, may be absorbed via the skin. Heavy metals such as arsenic, cadmium, mercury, and lead have also been found to be excreted in small amounts in sweat (6). However, the majority of toxic metals in the body will be excreted through urine or feces as opposed to sweat (6). Sweating itself is very important for thermoregulation.
The Respiratory System
The respiratory system not only traps and expels fine particles inhaled from the environment, but also controls the amount of carbon dioxide exhaled as a means of regulating the acid-base balance of the body. In order to survive, human life requires a tightly controlled acid-base balance in the serum, with a pH of about 7.4. This tight regulation is necessary for normal cellular activity. Changes in acidity can impair the function of enzymes. Together with the kidneys, the lungs are the primary player in regulating this acid-base balance. They do this through retaining or excreting the gas, carbon dioxide, in the process of breathing.
The Kidneys
The kidneys are hard at work filtering about 50 gallons of blood each day. Though the kidneys participate in a wide variety of non-detoxification related functions – including releasing hormones that regulate blood pressure – their role in detoxification is substantial. The kidneys help to remove drugs and other metabolic waste products from the body in urine. Along with the lungs, they help to regulate the acid-base balance of the body. The kidney’s main response to an increased acid load is to increase acid excretion in the form of hydrogen ion buffers, such as organic acids and ammonium, while reabsorbing bicarbonate.
Gastrointestinal Tract
The GI tract plays a powerful and multifaceted role in detoxification. The GI tract is considered a lymphoid organ and the immune tissue it contains is called the gut-associated lymphoid tissue (GALT). This means that the GI tract plays a role in immune-modulation and is itself a component of the immune system. The mucosal barrier lining the GI tract houses the lymphoid follicles, known as Peyer’s Patches. This mucosal barrier is also home to a variety of microbes which influence immune function, waste product metabolism including drug metabolism, and a variety of other incredibly important processes still under investigation (7, 8).
The GI tract is also responsible for mobilizing metabolic waste from bile (arising from liver metabolism) and facilitating fecal transit. Additionally, the GI mucosa houses cytochrome P450 enzymes, which have special detoxification properties and which we will be talking more about in sections, Part II and III (9, 10) .
The Immune System
Components of the immune system can be found throughout the body and include a wide variety of specialized cells and molecules working together to identify foreign substances and facilitate their efficient elimination from the body. It is in charge of differentiating foreign substances such as microbial pathogens, unwanted compounds, and even cancerous cells from healthy cells in the body. While a comprehensive discussion of this highly complex system is beyond the scope of this piece, it is important to recognize that without the immune system performing at its best, overall detoxification will be impaired. Many things contribute to the function of the immune system, and nutritional status is highly influential (11).
The Liver
Last, but certainly not least, we have the body’s metabolic hub of biotransformation – the liver. The role of the liver in the processes of detoxification is so essential, that both Part II and III will focus primarily on this magnificent organ!
The liver filters blood coming from the digestive tract, gall bladder, pancreas, and spleen via the hepatic portal vein. It stores a host of nutrients, participates in protein synthesis, hormone production, glycogen storage, and breakdown of red blood cells. It concentrates toxic substances and metabolic waste products for detoxification/biotransformation and ultimate removal. The liver also makes bile, which is involved in cholesterol metabolism and needed for the digestion of fat and fat-soluble vitamins. Bile will also be an avenue for mobilization of the liver's metabolic waste products. As you can see, the liver stays very busy.
Understanding how the liver’s biotransformation pathways operate is imperative for understanding the importance of nutrition in supporting overall detoxification function of the body. It is necessary for appreciating the unique power of properly-applied medical nutrition therapy in addressing the role of environmental burden (including prescription drug use) in our modern lives.
For further discussion, proceed to Part II.
(1) US Department of Health and Human Services, National Toxicology Program website https://ntp.niehs.nih.gov/about/index.html. Updated Sept 11, 2017. Accessed October 10, 2017
(2) CDC Fourth National Report on Human Exposure to Environmental Chemicals website www.cdc.gov/exposurereport/pdf/FourthReport_UpdatedTables_Volume1_Jan2017.pdf. Updated January 2017. Accessed October 10, 2017
(3) Test Guidelines for Pesticides and Toxic Substances. United States Environmental Protection Agency, website www.epa.gov/test-guidelines-pesticides-and-toxic-substances. Updated June 23, 2017. Accessed October 10, 2017
(4) US Food and Drug Administration, website www.fda.gov/drugs/resourcesforyou/consumers. Updated October 6, 2017. Accessed October 10, 2017
(5) National Biomonitoring Program, Bisphenol A. website www.cdc.gov/biomonitoring/bisphenola_factsheet.html. Updated December 23, 2016. Accessed October 10, 2017
(6) Sears ME, Kerr KJ. Arsenic, Cadmium, Lead, and Mercury in Sweat: A Systematic Review. J Environ Public Health. 2012; 2012: 184745
(7) Geuking MB, Köller Y, Rupp S. The interplay between the gut microbiota and the immune system. Gut Microbes. 2014 May-Jun;5(3):411-8
(8) Flint HJ, Scott KP, Louis P. The role of the gut microbiota in nutrition and health. Nat Rev Gastroenterol Hepatol. 2012 Sep 4;9(10):577-89
(9) McKinnon RA, McManus ME. Localization of cytochromes P450 in human tissues: Implications for chemical toxicity. Pathology. 1996; 28:148-155
(10) McKinnon RA, Burgess WM, Hall PM. Characterization of Cyp3A gene subfamily expression in human gastrointestinal tissues. Gut. 1995; 36:259-267
(11) Pae M, Meydani SM, Wu D. The Role of Nutrition in Enhancing Immunity in Aging. Aging Dis. 2012 Feb; 3(1): 91–129
About the Author
Heather Davis, MS, RDN, LDN, holds a master's degree in nutrition science and is accredited by the Academy of Nutrition and Dietetics as a registered dietitian nutritionist (RDN). She works as a clinical dietitian, educator, and medical writer specializing in neuroendocrine nutrition and advanced chronic disease medical nutrition therapy