Glossary of Scientific Terms


Adenosine triphosphate

/uh·deh·nuh·seen try·fos·fayt/

A complex molecule, also known as ATP, that creates energy in your cells. The food you consume goes through three phases to become ATP — glycolysis, the Krebs Cycle, and the electron transport chain — and all require NAD+.


/ˌbæk təˈrɔɪ diz/

A genus of anaerobic bacteria making up the majority of the mammalian microbiota that play a fundamental role in processing complex molecules. While Bacteroides is considered a “beneficial” strain, the majority presence of Bacteroides in the gut later in life may indicate that a host’s microbiome is not as diverse as it could be.

Biological age

/ˌbɑɪ·əˈlɑdʒ·ɪ·kəl/ /eɪdʒ/

Everyone ages at a different rate. Scientists estimate that genetics account for only 25% of this variation, with lifestyle and environmental factors providing the greater influence. Unlike chronological age, which tells you the number of years you’ve been alive, biological age measures the age your body is expected to perform or function, providing insights into your overall health. Furthermore, biological age is calculated based on your epigenetics—chemical modifications attached to your DNA that determine how your genes are expressed—which are dynamic and modifiable. By monitoring your biological age over time, you can determine how diet and other lifestyle changes impact your rate of aging. 

Cellular metabolism

/ˈselyələr məˈtabəˌlizəm/

Cellular metabolism encompasses the many enzymatic and chemical reactions in cells that provide the blueprint to sustain life. These include steps in making the building blocks for nucleic acids, proteins, and lipids, as well as steps in degrading complex molecules in food to provide energy to cells.

Cellular senescence

/ˈselyələr səˈnesəns/

Senescent cells accumulate across many organs and tissues with aging, but also in younger people at sites of chronic conditions. These senescent cells rarely, if ever, divide, but are active: they resist dying. Some produce a range of factors that damage cells, interfere with progenitor function, and spread senescence to previously normal cells. Senescent cells are normally removed by the immune system, but above a threshold burden, they can resist immune clearance and spread faster than the immune system can keep up.



Short for “clustered regularly interspaced short palindromic repeats,” CRISPR are stretches of DNA that, combined with Cas proteins (hence, CRISPR-Cas9) act as a bacterial immune system by tracking down and cutting out DNA of invaders. Scientists have adapted CRISPR to edit the genome.



An enzyme that removes an acetyl group from proteins (e.g. sirtuins), changing the chemical structure of the protein and affecting a wide range of activities, from gene expression to metabolism and aging.



Every cell in the body has essentially the same genetic sequence (the combination of A, C, G, and T nucleotides that make up a strand of DNA). On top of that sequence, there is also a biochemical program (you can think of it as your cell’s operating system) that dictates how the genome is used in each cell—this is epigenetics. It decides which proteins the cell makes, how quickly it divides, whether it can transform into a different cell type (as in the case of stem cells), etc. Epigenetics is also what enables two cells with the exact same DNA to have vastly different phenotypes—what makes a neuron a neuron and a white blood cell a white blood cell.

Epigenetic alteration

/ˌepəjəˈnedik ˌôltəˈrāSHən/

A change in the chemical structure of DNA that does not change the DNA coding sequence. As cells are exposed to environmental factors, they are subject to different types of epigenetic alterations: changes in DNA methylation patterns, histone modifications, and chromatin remodeling. These changes, which impact gene expression, accumulate over time and have been correlated with aging. Because DNA methylation patterns change reliably with age-related comorbidities along with lifestyle and environmental factors, epigenetic clocks like Index can be used to predict biological age.



The complete set of genetic instructions in an organism.

Gray matter

The parts of the brain and spinal cord that consist primarily of neuronal cell bodies. The gray matter includes regions of the brain involved in muscle control, memory, speech, decision-making, and other sensory perceptions. It gets its name from its grayish color.

Gut microbiome

/gút ˌmīkrōˈbīōm/

The complex, dynamic population of microorganisms that help maintain immune and metabolic homeostasis.



There’s roughly six feet of DNA packed into each human cell. How does it all fit? It’s wrapped around proteins called histones. Think of histones as spools and the DNA as thread. In addition to helping package the DNA, histones also regulate access to DNA as genes are turned on and off.



An amino acid that circulates in the blood. Normal levels of homocysteine have been associated with good B-vitamin status, while high levels of homocysteine have been associated with a variety of health problems.

Hot flash

A sudden feeling of feverish heat in the upper body. Hot flashes are one of the symptoms of menopause and on average, persist for more than seven years. Hot flashes can cause flushing, increased heart rate, heavy sweating, cold shivering, and long-term sleep disruptions. Symptoms may be mild or so intense as to disrupt daily activities. Most hot flashes last from 30 seconds to 10 minutes and can occur several times per hour or week.



A neuropeptide produced by a subset of neurons in the hypothalamus that promotes the awake state.



A substance that produces an immune response. Immunogens can be fragments of DNA or RNA (that encode for parts of the pathogen), proteins, or even whole pathogens (either dead or weakened).



Inflammaging’ refers to the infiltration of immune cells and/or increases in factors that can cause pain, swelling, stiffness, warmth, and swelling in different tissues, such as in the skin, around joints, in muscles, and fat, in the eyes, or in internal organs that can occur with aging. Inflammaging can also occur in the tissues of younger people who have a number of different chronic conditions linked to fundamental aging processes.



Leptin is a hormone released from fat cells in adipose tissues. Leptin sends signals to the hypothalamus in the brain and helps the body regulate fat storage.



A hormone secreted by the posterior lobe of the pituitary gland at the base of the brain, released when people touch and bond socially.



In molecules, “phenol” refers to a certain chemical structure, and “poly” means to have more than one of the structures. Polyphenols are a family of beneficial molecules found in plants, where one of their main jobs is to fight off pathogens. When eaten by humans, polyphenols may serve as powerful antioxidants. Examples include pterostilbene, resveratrol, curcumin, quercetin, and anthocyanins.

Polyunsaturated fat

/pälēən•ˈsaCHə•rādəd/ /fat/

Polyunsaturated fat is a type of dietary fat found in olive oil, nuts, avocado, and fish. What makes it “polyunsaturated” is the chemical structure: In its fatty acid chain, two or more of the carbon atoms have double bonds rather than being fully “saturated” — or connected to — hydrogen atoms.



A precursor, in human biology, is an inactive substance converted to an active one (a coenzyme, hormone, or antioxidant). For example, when you take your vitamin A supplement, you’re actually consuming beta carotene—your body knows exactly what to do next, and turns that into the vitamin that helps you protect your eyes. The efficiency of this process depends on many things, including the bioavailability of the precursor.



A process that not only delays aging but reverses it, leading to a younger cell, tissue, or body.

Salvage pathway

The route for precursors nicotinamide riboside, or NR, and nicotinamide, or Nam, which each become NAD+ by following different steps. Nam gets to NAD+ through three steps while NR gets to NAD+ in just two.



Senolytics are used to target and help clear away senescent cells—ones that lose their functional abilities but linger in the system. These cells are sometimes referred to as “zombie cells,” and they can trigger inflammation and obstruct a body’s immune response. Senolytics induce apoptosis—a natural process of cell death—so that the cells can be eliminated by the body.

T cell

Born from blood stem cells, T cells coordinate multiple aspects of adaptive immunity. In infancy and early childhood, naive T cells play a critical role in developing immunity to common antigens and pathogens. In adulthood when fewer novel antigens are encountered, T cells play a role in maintaining immune homeostasis. In later stages of life, T cell function declines along with a corresponding increase in susceptibility to infection, cancer, and autoimmunity.



A repetitive sequence of DNA found on the ends of chromosomes. Telomeres protect the chromosomes from becoming frayed or sticking to each other (like the plastic tips on shoelaces), preventing our genetic data from becoming destroyed. As cells divide, these protective sequences get shorter and shorter, until they become too short for the cell to continue replicating. Telomere attrition is one of the hallmarks of aging.



Derived from the Greek word thermos (or “heat”), thermogenesis is any metabolic process that generates heat. In mammals, thermogenesis is commonly used to describe the heat-producing process involved in defending core body temperature or burning excess calories (diet-induced thermogenesis). Brown adipose tissue (brown fat) is a significant source of thermogenesis and, when activated, increases energy expenditure. NAD+ metabolism is essential to this process and boosting NAD+ levels with precursors like NMN can help activate brown fat thermogenesis.



Vitamins are organic compounds required by the body for biological functions, but which aren’t created in sufficient quantities endogenously. The families of vitamins are A, B1, B2, B3, B5, B6, B7, B9, B12, C, D, E, and K.

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