The simplest unsaturated aldehyde, created by the burning of glycerol in animal fat. Acrolein, a toxic, colorless liquid, is a strong irritant for the skin, eyes, and nasal passages of humans. It has a disagreeable, acrid smell, easily recognizable as the odor associated with burning fat.

An area of the brain located close to the hippocampus, in the frontal portion of the temporal lobe. The amygdala governs our responses to fear, arousal, and emotional stimulation. Poor sleep increases activity within the amygdala.

A naturally-occurring element found in soil, water, food, and air. Chronic arsenic exposure is associated with the development of several diseases, including cancer, cardiovascular disease, and diabetes. In utero and early childhood exposure to arsenic is associated with poor cognitive development and increased deaths in young adults.

A test used in laboratory medicine, pharmacology, environmental biology, and molecular biology to determine the content or quality of specific components.

The tendency for something to promote the formation of fatty deposits called plaques in the arteries.

The shrinking or wasting away of cells, organs, or tissues that may occur as part of a disease process, trauma, or aging.

A developmental disorder characterized by impaired social interaction, behavioral problems, and poor communication. Autism typically manifests in early childhood and is slightly more common among boys than girls. In clinical trials, sulforaphane, a compound derived from broccoli and broccoli sprouts, reduces the characteristic behaviors associated with autism.

An intracellular degradation system involved in the disassembly and recycling of unnecessary or dysfunctional cellular components. Autophagy participates in cell death, a process known as autophagic dell death. Prolonged fasting is a robust initiator of autophagy and may help protect against cancer and even aging by reducing the burden of abnormal cells.

The relationship between autophagy and cancer is complex, however. Autophagy may prevent the survival of pre-malignant cells, but can also be hijacked as a malignant adaptation by cancer, providing a useful means to scavenge resources needed for further growth.

A bidirectional cell signaling pathway that may regulate cell function, metabolism, or other aspects of physiology. Most signaling pathways are unidirectional. However, an axis may involve two or more signaling proteins and their secreting organs or cells in a type of feedback loop. For example, the growth hormone/IGF axis, also known as the Hypothalamic–pituitary–somatotropic axis, is a highly regulated pathway involving IGF-1 (produced by the liver), growth hormone (produced by the pituitary), and growth hormone-releasing hormone (produced by the hypothalamus).

"I expect to die at 110, shot by a jealous husband." - Thurgood Marshal

An aromatic hydrocarbon compound produced during the distillation and burning of fossil fuels, such as gasoline. It is also present in the smoke from forest fires, volcanoes, and cigarettes. Benzene is a carcinogen that targets the liver, kidney, lung, heart, and brain and can cause DNA strand breaks, chromosomal damage, and genetic instability.

A genus of bacteria known to inhabit the human gut. Bifidobacteria are anaerobic commensal bacteria. They are among the first bacteria to colonize the infant gut and may play critical roles in gut-mediated immune function.

The extent and rate at which drugs or other substances, such as plant-based dietary compounds, enter the body’s circulation. Bioavailability is influenced by a variety of factors, including dose, the presence of other foods or substances, and interindividual differences in metabolism due to gut absorptive surface and commensal microbial populations.

A measurable substance in an organism that is indicative of some phenomenon such as disease, infection, or environmental exposure.

A highly selective semi-permeable barrier in the brain made up of endothelial cells connected by tight junctions. The blood-brain barrier separates the circulating blood from the brain's extracellular fluid in the central nervous system. Whereas water, lipid-soluble molecules, and some gases can pass through the blood-brain barrier via passive diffusion, molecules such as glucose and amino acids that are crucial to neural function enter via selective transport. The barrier prevents the entry of lipophilic substances that may be neurotoxic via an active transport mechanism.

A wavelength of light emitted from natural and electronic sources. Blue light exposure is associated with improved attention span, reaction time, and mood. However, exposure to blue light outside the normal daytime hours may suppress melatonin secretion, impairing sleep patterns. In addition, blue light contributes to digital eye strain and may increase risk of developing macular degeneration.

A collective term for the various components of Cannabis sativa, also known as marijuana.

A person who is 100 or more years old.

A waxy lipid produced primarily in the liver and intestines. Cholesterol can be synthesized endogenously and is present in all the body's cells, where it participates in many physiological functions, including fat metabolism, hormone production, vitamin D synthesis, and cell membrane integrity. Dietary sources of cholesterol include egg yolks, meat, and cheese.

A steroid hormone that participates in the body’s stress response. Cortisol is a glucocorticoid hormone produced in humans by the adrenal gland. It is released in response to stress and low blood glucose. Chronic elevated cortisol is associated with accelerated aging. It may damage the hippocampus and impair hippocampus-dependent learning and memory in humans.

A broad category of small proteins (~5-20 kDa) that are important in cell signaling. Cytokines are short-lived proteins that are released by cells to regulate the function of other cells. Sources of cytokines include macrophages, B lymphocytes, mast cells, endothelial cells, fibroblasts, and various stromal cells. Types of cytokines include chemokines, interferons, interleukins, lymphokines, and tumor necrosis factor.

A mood disorder characterized by profound sadness, fatigue, altered sleep and appetite, as well as feelings of guilt or low self-worth. Depression is often accompanied by perturbations in metabolic, hormonal, and immune function. A critical element in the pathophysiology of depression is inflammation. As a result, elevated biomarkers of inflammation, including the proinflammatory cytokines interleukin-6 and tumor necrosis factor-alpha, are commonly observed in depressed people. Although selective serotonin reuptake inhibitors and cognitive behavioral therapy typically form the first line of treatment for people who have depression, several non-pharmacological adjunct therapies have demonstrated effectiveness in modulating depressive symptoms, including exercise, dietary modification (especially interventions that capitalize on circadian rhythms), meditation, sauna use, and light therapy, among others.

Animals characterized by higher activity during the day and sleeping more at night.

A major contributing factor to aging, cellular senescence, and the development of cancer. Byproducts of both mitochondrial energy production and immune activity are major sources of DNA damage. Additionally, environmental stressors can increase this base level of damage. DNA damage can be mitigated by cellular repair processes; however, the effectiveness of these processes may be influenced by the availability of dietary minerals, such as magnesium, and other dietary components, which are needed for proper function of repair enzymes.

A neurotransmitter best known for its role in motor, motivation, and pleasure control. Dopamine also functions as a paracrine (cell-to-cell) hormone in other parts of the body. It is derived from tyrosine and is the precursor to norepinephrine and epinephrine. Some evidence suggests that dopamine may also be involved in pain modulation.

The single layer of cells that lines the interior of the blood and lymphatic vessels. The endothelium participates in blood flow, platelet aggregation, and vascular tone. It also regulates inflammation, immune function, and angiogenesis. Endothelial dysfunction is a systemic pathological condition broadly defined as an imbalance between vasodilating and vasoconstricting substances produced by (or acting on) the endothelium. It is a robust predictor of heart attack and stroke risk.

A type of toxin released when bacteria die. Endotoxins can leak through the intestinal wall and pass directly into the bloodstream. The most common endotoxin is lipopolysaccharide (LPS), a major component of the cell membrane of gram-negative bacteria. If LPS leaks into the bloodstream, it can trigger an acute inflammatory reaction. LPS has been linked with a number of chronic diseases, including Alzheimer’s disease, inflammatory bowel disease (Crohn’s disease or ulcerative colitis), cardiovascular disease, diabetes, obesity, autoimmune disorders (celiac disease, multiple sclerosis, and type 1 diabetes), and psychiatric disorders (anxiety and depression).

Any of a group of complex proteins or conjugated proteins that are produced by living cells and act as catalyst in specific biochemical reactions.

A molecule composed of carboxylic acid with a long hydrocarbon chain that is either saturated or unsaturated. Fatty acids are important components of cell membranes and are key sources of fuel because they yield large quantities of ATP when metabolized. Most cells can use either glucose or fatty acids for this purpose.

Flavonoid are widely distributed in plants, fulfilling many functions. Flavonoids have been shown to have a wide range of biological and pharmacological activities in animal, human, and in-vitro studies. Examples include anti-allergic, anti-inflammatory, antioxidant, antimicrobial, anti-cancer, and anti-diarrheal activities.

A glucosinolate (see definition) found in certain cruciferous vegetables, including broccoli, Brussels sprouts, and mustard. Glucoraphanin is hydrolyzed by the enzyme myrosinase to produce sulforaphane, an isothiocyanate compound that has many beneficial health effects in humans.

An antioxidant compound produced by the body’s cells. Glutathione helps prevent damage from oxidative stress caused by the production of reactive oxygen species.

A naturally occurring substance capable of stimulating cellular growth, proliferation, healing, and differentiation. Growth factors typically act as signaling molecules between cells. Examples include cytokines and hormones that bind to specific receptors on the surface of their target cells.

A bidirectional signaling pathway between the gastrointestinal tract and the nervous system, often involving intestinal microbiota. Several studies have shown that the gut microbiota is involved in the regulation of anxiety, pain, cognition, and mood.

Naturally occurring metallic elements that adversely affect human health. Heavy metals enter the environment by natural means and through human activities. In very low concentrations, heavy metals maintain various biochemical and physiological functions, but at higher concentrations are often toxic. The most commonly found heavy metals in the environment include arsenic, cadmium, chromium, copper, lead, nickel, and zinc.

A small organ located within the brain's medial temporal lobe. The hippocampus is associated primarily with memory (in particular, the consolidation of short-term memories to long-term memories), learning, and spatial navigation. Amyloid-beta plaque accumulation, tau tangle formation, and subsequent atrophy in the hippocampus are early indicators of Alzheimer’s disease.

Biological responses to low-dose exposures to toxins or other stressors such as exercise, heat, cold, fasting, and xenohormetics. Hormetic responses are generally favorable and elicit a wide array of protective mechanisms. Examples of xenohormetic substances include plant polyphenols – molecules that plants produce in response to stress. Some evidence suggests plant polyphenols may have longevity-conferring effects when consumed in the diet.

A critical element of the body’s immune response. Inflammation occurs when the body is exposed to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective response that involves immune cells, cell-signaling proteins, and pro-inflammatory factors. Acute inflammation occurs after minor injuries or infections and is characterized by local redness, swelling, or fever. Chronic inflammation occurs on the cellular level in response to toxins or other stressors and is often “invisible.” It plays a key role in the development of many chronic diseases, including cancer, cardiovascular disease, and diabetes.

A peptide hormone secreted by the beta cells of the pancreatic islets cells. Insulin maintains normal blood glucose levels by facilitating the uptake of glucose into cells; regulating carbohydrate, lipid, and protein metabolism; and promoting cell division and growth. Insulin resistance, a characteristic of type 2 diabetes, is a condition in which normal insulin levels do not produce a biological response, which can lead to high blood glucose levels.

A group of signaling proteins made and released by host cells in response to the presence of several pathogens, such as viruses, bacteria, parasites, and tumor cells. Interferons are named for their ability to interfere with viral replication and are critical components of the body's innate immune response to viruses. SARS-CoV-2, the virus that causes COVID-19, impairs the body's interferon response.

A broad term that describes periods of voluntary abstention from food and (non-water) drinks, lasting several hours to days. Depending on the length of the fasting period and a variety of other factors, intermittent fasting may promote certain beneficial metabolic processes, such as the increased production of ketones due to the use of stored fat as an energy source. The phrase “intermittent fasting” may refer to any of the following:

• Time-restricted eating
• Alternate-day fasting
• Periodic fasting (multi-day)

A diet that causes the body to oxidize fat to produce ketones for energy. A ketogenic diet is low in carbohydrates and high in proteins and fats. For many years, the ketogenic diet has been used in the clinical setting to reduce seizures in children. It is currently being investigated for the treatment of traumatic brain injury, Alzheimer's disease, weight loss, and cancer.

A compound produced during the conversion of the amino acid tryptophan to the vitamin niacin (vitamin B3). Kynurenine is pivotal to the tryptophan metabolism pathway because it can change into the neuroprotective agent kynurenic acid or to the neurotoxic agent quinolinic acid, the latter of which has been implicated in many disorders such as stroke, epilepsy, and multiple sclerosis, and in neurodegenerative disorders such as Parkinson's disease, Huntington's, and Alzheimer's disease.

Lipid-protein complexes that allow fats to move through the watery environment inside and outside cells. Lipoproteins emulsify the lipid molecules.

A series of connective tissue membranes that surround the brain and spinal cord. The meninges are separated by cerebrospinal fluid, which acts as a cushion, supporting the brain and protecting it from damage that might be caused by movement or trauma.

The thousands of biochemical processes that run all of the various cellular processes that produce energy. Since energy generation is so fundamental to all other processes, in some cases the word metabolism may refer more broadly to the sum of all chemical reactions in the cell.

The collection of genomes of the microorganisms in a given niche. The human microbiome plays key roles in development, immunity, and nutrition. Microbiome dysfunction is associated with the pathology of several conditions, including obesity, depression, and autoimmune disorders such as type 1 diabetes, rheumatoid arthritis, muscular dystrophy, multiple sclerosis, and fibromyalgia.

Vitamins and minerals that are required by organisms throughout life in small quantities to orchestrate a range of physiological functions. The term micronutrients encompasses vitamins, minerals, essential amino acids, essential fatty acids.

The term "mindfulness" is derived from the Pali-term sati which is an essential element of Buddhist practice, including vipassana, satipatthana and anapanasati. It has been popularized in the West by Jon Kabat-zinn with his mindfulness-based stress reduction (MBSR) program. Large population-based research studies have indicated that the construct of mindfulness is strongly correlated with well-being and perceived health.

Tiny organelles inside cells that produce energy in the presence of oxygen. Mitochondria are referred to as the "powerhouses of the cell" because of their role in the production of ATP (adenosine triphosphate). Mitochondria are continuously undergoing a process of self-renewal known as mitophagy in order to repair damage that occurs during their energy-generating activities.

The process by which new mitochondria are made inside cells. Many factors can activate mitochondrial biogenesis including exercise, cold shock, heat shock, fasting, and ketones. Mitochondrial biogenesis is regulated by the transcription factor peroxisome proliferator-activated receptor gamma coactivator 1-alpha, or PGC-1α.

The selective degradation of mitochondria by autophagy. It often occurs in defective mitochondria following damage or stress. Mitophagy is key in keeping the cell healthy. It promotes turnover of mitochondria and prevents accumulation of dysfunctional mitochondria, which can lead to cellular degeneration.

A protein produced predominantly by skeletal muscle. Myostatin negatively regulates the growth and differentiation of muscle cells. Genetic variants in the gene for myostatin can cause muscle hypertrophy (excessive growth). Mice engineered to lack myostatin exhibit about a doubling of skeletal muscle mass throughout the body. Myostatin inhibitors block the action of myostatin and have been used therapeutically in muscle wasting diseases and also in the bodybuilding community.

A family of enzymes whose sole known substrates are glucosinolates. Myrosinase is located in specialized cells within the leaves, stems, and flowers of cruciferous plants. When the plant is damaged by insects or eaten by humans, the myrosinase is released and subsequently hydrolyzes nearby glucosinolate compounds to form isothiocyanates (see definition), which demonstrate many beneficial health effects in humans. Microbes in the human gut also produce myrosinase and can convert non-hydrolyzed glucosinolates to isothiocyanates.

The process of forming new neurons. Neurogenesis is essential during embryonic development, but also continues in certain brain regions throughout human lifespan.

A substance that is detrimental to the nervous system. Neurotoxins damage neurons, interrupting the transmission of signals. They can be found in the environment in both natural and man-made products. The body produces some substances that are neurotoxic. Examples of neurotoxins include lead, alcohol, tetrodotoxin (from pufferfish), and nitric oxide.

A highly toxic, addictive substance present in the tobacco plant. Nicotine is an alkaloid compound that stimulates the central nervous system by acting an agonist at the nicotinic cholinergic receptors in various regions of the brain. It promotes the release of several neurotransmitters, including acetylcholine, beta-endorphin, dopamine, norepinephrine, serotonin, and ACTH. Nicotine intake can cause peripheral vasoconstriction, tachycardia, and elevated blood pressure. Nicotine in breast milk can interfere with an infant's sleep patterns.

A substance produced in the brain. Norepinephrine acts as a hormone and neurotransmitter and is best known for its role in the body’s “fight or flight” response to stress. Its role as a neurotransmitter has been exploited as a molecular target for a class of drugs known as norepinephrine reuptake inhibitors, which were developed for the purpose of treating disorders ranging from ADHD to narcolepsy and depression. Norepinephrine also plays a role in converting white adipose tissue into brown adipose tissue via an uncoupling protein 1 (UCP-1) mediated mechanism.

A protein typically present in the cytoplasm of mammalian cells. Nrf2 can relocate to the nucleus where it regulates the expression of hundreds of antioxidant and stress response proteins that protect against oxidative damage triggered by injury and inflammation. One of the most well-known naturally-occurring inducers of Nrf2 is sulforaphane, a compound derived from cruciferous vegetables such as broccoli.

One of four nitrogen-containing molecules that comprise DNA. A nucleotide consists of one of four chemicals, called a “base,” plus one molecule of sugar and one molecule of phosphoric acid. Nucleotides are typically identified by the first letter of their base names: adenine (A), cytosine (C), guanine (G), and thymine (T). They form specific pairs (A with T, and G with C), and their bonds provide the helical structure of the DNA strand.

A type of polyunsaturated fat that is essential for human health. Omega-3 fatty acids influence cell membrane integrity and affect the function of membrane-bound cellular receptors. They participate in pathways involved in the biosynthesis of hormones that regulate blood clotting, contraction and relaxation of artery walls, and inflammation. They have been shown to help prevent heart disease and stroke, may help control lupus, eczema, and rheumatoid arthritis, and may play protective roles in cancer and other conditions. Omega-3 fatty acids include alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is found mainly in plant oils such as flaxseed, soybean, and canola oils. DHA and EPA are found in fish and other seafood. The human body can convert some ALA into EPA and then to DHA, but the efficiency of the process varies between individuals.

A result of oxidative metabolism, which causes damage to DNA, lipids, proteins, mitochondria, and the cell. Oxidative stress occurs through the process of oxidative phosphorylation (the generation of energy) in mitochondria. It can also result from the generation of hypochlorite during immune activation.

Capable of developing into any type of cell or tissue except those that form a placenta or embryo.

A class of chemical compounds produced in plants in response to stressors. Polyphenols contribute to the bitterness, astringency, color, flavor, and fragrance of many fruits and vegetables. They often serve as deterrents to insect or herbivore consumption. When consumed in the human diet, polyphenols exert many health benefits and may offer protection against development of cancers, cardiovascular diseases, diabetes, osteoporosis, and neurodegenerative diseases. Dietary sources of polyphenols include grapes, apples, pears, cherries, and berries, which provide as much as 200 to 300 mg polyphenols per 100 grams fresh weight.

Any enzyme that breaks down a protein into smaller subunits. Proteases can be found in Animalia, Plantae, Fungi, Bacteria, Archaea, or viruses.

A naturally occurring psychedelic compound produced by more than 200 species of mushrooms. As a prodrug, psilocybin is quickly converted by the body to psilocin, which has mind-altering effects including euphoria, visual and mental hallucinations, changes in perception, a distorted sense of time, and spiritual experiences, and can include possible adverse reactions such as nausea and panic attacks.

A compound produced during the metabolism of the amino acid, tryptophan. Quinolinic acid is a neurotoxin released by activated macrophages. It may play roles in inflammation and neurodegenerative disorders. Elevated quinolinic acid levels are correlated with the severity of neuropsychological deficits in people who have AIDS.

A polyphenolic compound produced in plants in response to injury or pathogenic attack from bacteria or fungi. Resveratrol exerts a diverse array of biological effects, including antitumor, antioxidant, antiviral, and hormonal activities. It activates sirtuin 1 (SIRT1), an enzyme that deacetylates proteins and contributes to cellular regulation (including autophagy). Dietary sources of resveratrol include grapes, blueberries, raspberries, and mulberries.

Resveratrol Autophagy ↑ Deacetylases (especially SIRT1) → ↓ Protein Acetylation → Autophagy

A mental disorder characterized by abnormal social behavior and failure to understand what is real. Common symptoms include false beliefs, unclear or confused thinking, hearing voices that others do not, reduced social engagement and emotional expression, and a lack of motivation. People with schizophrenia often have additional mental health problems such as anxiety disorders, major depressive illness, or substance use disorders.

A small molecule that functions as both a neurotransmitter and a hormone. Serotonin is produced in the brain and gut and facilitates the bidirectional communication between the two. It regulates many physiological functions, including sleep, appetite, mood, thermoregulation, and others. Many antidepressants are selective serotonin reuptake inhibitors (SSRIs), which work by preventing the reabsorption of serotonin, thereby increasing extracellular levels of the hormone.

A person who works on a schedule outside the traditional 9 AM – 5 PM day. Work can involve evening or night shifts, early morning shifts, and rotating shifts. Many industries rely heavily on shift work, and millions of people work in jobs that require shift schedules.

A class of drugs that lower blood cholesterol levels by blocking the production of an enzyme in the liver called hydroxy-methylglutaryl-coenzyme A reductase (HMG-CoA reductase). Taking statins may reduce the risk of cardiovascular disease in some people. Although statins are generally well tolerated, as many as 10 – 20 percent of people taking the drugs experience complications, including myopathy (muscle damage), liver damage, and cognitive problems, including issues with forgetfulness, memory loss, and confusion.

A cell that has the potential to develop into different types of cells in the body. Stem cells are undifferentiated, so they cannot do specific functions in the body. Instead, they have the potential to become specialized cells, such as muscle cells, blood cells, and brain cells. As such, they serve as a repair system for the body. Stem cells can divide and renew themselves over a long time. In 2006, scientists reverted somatic cells into stem cells by introducing Oct4, Sox2, Klf4, and cMyc (OSKM), known as Yamanaka factors.^[1]

An isothiocyanate compound derived from cruciferous vegetables such as broccoli, cauliflower, and mustard. Sulforaphane is produced when the plant is damaged when attacked by insects or eaten by humans. It activates cytoprotective mechanisms within cells in a hormetic-type response. Sulforaphane has demonstrated beneficial effects against several chronic health conditions, including autism, cancer, cardiovascular disease, diabetes, and others.

Distinctive structures comprised of short, repetitive sequences of DNA located on the ends of chromosomes. Telomeres form a protective “cap” – a sort of disposable buffer that gradually shortens with age – that prevents chromosomes from losing genes or sticking to other chromosomes during cell division. When the telomeres on a cell’s chromosomes get too short, the chromosome reaches a “critical length,” and the cell stops dividing (senescence) or dies (apoptosis). Telomeres are replenished by the enzyme telomerase, a reverse transcriptase.

A molecule composed of a glycerol molecule bound to three fatty acids. Triglycerides are the primary component of very-low-density lipoproteins (VLDL). They serve as a source of energy. Triglycerides are metabolized in the intestine, absorbed by intestinal cells, and combined with cholesterol and proteins to form chylomicrons, which are transported in lymph to the bloodstream.

An essential amino acid. Tryptophan plays key roles in the biosynthesis of proteins and is a precursor to several molecules with physiological significance, including melatonin, niacin, and the neurotransmitter serotonin. Inflammation causes tryptophan to be reallocated from serotonin synthesis to that of kynurenine, which then converts to the neurotoxin quinolinic acid, leading to depression. Dietary sources of tryptophan include most protein-based foods, such as meat, beans, or nuts.

A metabolic disorder characterized by high blood sugar and insulin resistance. Type 2 diabetes is a progressive condition and is typically associated with overweight and low physical activity. Common symptoms include increased thirst, frequent urination, unexplained weight loss, increased hunger, fatigue, and impaired healing. Long-term complications from poorly controlled type 2 diabetes include heart disease, stroke, diabetic retinopathy (and subsequent blindness), kidney failure, and diminished peripheral blood flow which may lead to amputations.

A fat-soluble vitamin stored in the liver and fatty tissues. Vitamin D plays key roles in several physiological processes, such as the regulation of blood pressure, calcium homeostasis, immune function, and the regulation of cell growth. In the skin, vitamin D decreases proliferation and enhances differentiation. Vitamin D synthesis begins when 7-dehydrocholesterol, which is found primarily in the skin’s epidermal layer, reacts to ultraviolet light and converts to vitamin D. Subsequent processes convert D to calcitriol, the active form of the vitamin. Vitamin D can be obtained from dietary sources, too, such as salmon, mushrooms, and many fortified foods.

A foreign substance that is introduced into the body from the environment and is subsequently metabolized. Xenobiotics can exert multiple effects (good or bad) on the body by disrupting or interacting with cellular communication pathways that regulate growth, development, and normal physiological function. They are subject to extensive biotransformation in the human body via Phase 1 and Phase 2 metabolism, with a goal toward elimination. Examples of xenobiotics include drugs, pollutants, and plant-based dietary compounds.