Adenosine Triphosphate

Adenosine triphosphate (ATP) is the “energy currency” of all living things. The body creates ATP through the breakdown of fats, carbohydrates, and proteins to supply the energy needed for muscle contraction, nerve conduction, and several other physiological processes.

ALT stands for “alanine aminotransferase,” a liver enzyme measured in the blood to estimate liver function.

Alternative Healthy Eating Index (AHEI)

The Alternative Healthy Eating Index (AHEI) was developed to expand on the Healthy Eating Index, which tracks how well Americans’ diets conform to the Dietary Guidelines for Americans. It takes into consideration the types of fat, forms of carbohydrates, and sources of protein.

Analgesic

An analgesic is something that acts to relieve pain.

Antiemetic

An antiemetic provides relief from nausea and vomiting, which are typically caused by motion sickness, pregnancy, stomach irritation, or side effects from certain drugs.

Area Under the Curve (AUC)

Area under the curve (AUC) represents the total quantity of the substance in the bloodstream over the duration of the measurement period. In nutrition research, AUC is commonly used to determine bioavailability and to measure a person’s glycemic response.

AST stands for “aspartate aminotransferase,” a liver enzyme measured in the blood to estimate liver function.

Beck Depression Inventory

The Beck Depression Inventory (BDI) is a self-reported questionnaire that can be used to screen for depression and assess depression severity. Clinicians may use the BDI, along with a person’s medical history, to make a diagnosis of depression.

Before-and-after study

A before-and-after study measures differences within a single group before and after an intervention. Unlike a randomized controlled trial, this type of study cannot provide definitive evidence that the intervention caused the differences seen in the study.

Bioavailability

Bioavailability refers to the amount of a substance that can be absorbed and utilized by the body. In the context of nutrition research, this term is generally interchangeable with “oral bioavailability”, which is the amount of a substance that is absorbed and utilized by the body when consumed orally.

Blood clotting

Blood clotting is a process that prevents excessive bleeding from an injury. When a blood vessel is injured, red blood cells, platelets, and clotting factors come together to help the blood to coagulate and stop flowing.

Cohort Study

In a cohort study, researchers follow a group of participants who share similar demographic, occupational, or lifestyle characteristics for a certain period of time to investigate the association between an exposure and a particular outcome of interest, for example, the link between smoking and lung cancer.

Colony-forming unit (CFU)

A colony-forming unit estimates the number of viable bacterial or fungal cells in a sample, defined as the number of cells that are alive and will divide to produce more cells by binary fission.

Confounder

A confounder is a factor — either observed or unobserved — which affects the relationship between two variables being studied. Not accounting for the potential effect of a confounder may lead to incorrect conclusions about the relationship between the variables.

Correlation

Correlation is a measure of the strength of the relationship between a pair of variables. It expresses the extent and direction to which two variables change together. Correlation does not imply causation.

Cross-Sectional Study

In a cross-sectional study, the outcome and exposure are measured at a single point in time in the population of interest. This type of observational study is valuable for determining the disease prevalence in a population or the association between exposures and outcomes, but it can’t determine causation or describe how an association changes over time.

Crossover Study

In a crossover study, the participants undergo each of a study’s treatment conditions (e.g., 4 weeks of taking a supplement and 4 weeks of taking a placebo) in random order, often with “washout” periods in between (during which they undergo no treatment). This study design allows for the participants to act as their own controls, eliminating the need for a designated control group.

Dietary acid load

A food’s acid load represents its content in acidifying and alkalizing nutrients. Whether a food’s acid load can affect our blood pH (or our health in general) is a topic of controversy.

Dietary Inflammatory Index

The Dietary Inflammatory Index (DII) is a model that attempts to predict the inflammatory potential of a diet based on its components.

DXA/DEXA

Dual energy X-ray absorptiometry (DXA, sometimes called DEXA) scans are a type of full-body X-ray scan used to determine bone mineral density and body composition.

Dysautonomia

Dysautonomia is characterized by over-activation or under-activation of automatic body functions run by the autonomic nervous system. The condition can present with symptoms related to involuntary functions like breathing and blood pressure.

Dysbiosis

Dysbiosis refers to an imbalance of microbial species in a microbial community. It occurs when the microbiome is disrupted in a way that shifts the type and/or ratio of microbial species, with unfavorable consequences for the host.

Effect Size

Effect size generally describes how large of an effect an intervention has, on average. It’s also used synonymously with “standardized mean difference”, which is an effect size that is independent of a particular measurement scale.

Ergogenic

An ergogenic is any training technique, mechanical device, nutritional ingredient, dietary practice, or supplement that improves physical performance or enhances training adaptations.

Etiology

Etiology is the cause of a disease state or condition.

Eucaloric Diet

A eucaloric diet is one in which a person's energy consumption matches their energy expenditure. Over time, a eucaloric diet is expected to produce no change in bodyweight.

Glycemic index

The glycemic index of a food is a measurement of the ability of the carbs in that food to raise blood glucose when eaten. The higher the number, the more the food raises blood glucose.

Heterogeneity

In a meta-analysis, heterogeneity generally describes the degree to which the included studies vary. This term’s often used synonymously with “between-study heterogeneity”, which refers to the variation in studies’ outcomes above and beyond sampling error. The most common way to quantify between-study heterogeneity is using I2, which ranges from 0% (no heterogeneity) to 100% (considerable heterogeneity).

HOMA-IR

The Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) is a measure of insulin resistance. A low HOMA-IR means that the body is sensitive to insulin and is able to manage blood sugar. A high HOMA-IR indicates that the body is resistant to insulin and may not be able to manage blood sugar levels effectively.

Hypercaloric Diet

A hypercaloric diet is one in which a person's energy consumption exceeds their energy expenditure. Over time, a hypercaloric diet is expected to produce an increase in bodyweight.

Hypocaloric Diet

A hypocaloric diet is one in which a person's energy consumption is less their energy expenditure. Over time, a hypocaloric diet is expected to produce a reduction in bodyweight.

In Vitro Study

In vitro (Latin for “within the glass”) refers to studies that are performed outside of a living organism. In scientific research, this often involves performing experiments on bacterial, animal, or human cells growing in lab culture dishes.

Macronutrients

Macronutrients are dietary elements that are required in large quantities to generate energy and build biological structures. In humans, macronutrients refer specifically to carbohydrates, proteins, and fats.

Mendelian Randomization

Mendelian randomization is a research technique that uses genetic data in an attempt to determine whether an exposure affects an outcome. This technique allows investigators to look for potentially causal relationships using observational data.

Meta-analysis

A meta-analysis is usually produced as part of a systematic review. It combines the numerical results from several studies into an average number. Studies that differ too much in design cannot be properly meta-analyzed.

Micronutrient

Micronutrients are dietary elements that are required in small amounts to support a wide variety of biological processes and functions. In humans, micronutrients generally refer to vitamins and dietary minerals such as vitamin D, folic acid, iron, or magnesium.

Multiple comparisons

The more outcomes a study measures, the greater the chance that at least one outcome will show a change, “proving” that the intervention had an effect. When a study doesn't adjust for multiple comparisons, its statistically significant results are less trustworthy.

Neonatal

Neonate is the medical term for a newborn child (birth to 1 month of age). Neonatal is a descriptor that refers to the newborn period.

Network meta-analysis

A network meta-analysis is a pooled analysis of effects from a network of studies designed to estimate comparative benefits of different interventions.

Observational study

An observational study is designed to find a relationship between natural exposures and outcomes. There are no intentional interventions by researchers in observational studies and a cause-and-effect relationship usually cannot be determined.

p-value

The p-value is a number between 0 and 1 that indicates how surprising a study's results would be if there was actually no effect, as long as the study and statistical analyses are well-designed.

Pathological

Something is pathological if it is changed by, caused by, or related to a disease. This term is related to the word “pathology”, which is the study of the cause and effects of disease.

Plasma

Plasma is the liquid portion of blood and is made up of water, nutrients, and protein. Over half of a person’s blood is composed of plasma.

Preregistration

Preregistration is the practice of depositing a detailed description of a study plan in a publicly accessible repository before collecting the study data. It is an important practice that promotes transparency, accountability, and research integrity.

Prophylactic

A prophylactic is something that is used to prevent a disease or condition.

Publication Bias

Publication bias refers to the tendency for studies reporting positive results to be more likely to be published than studies reporting negative results. This can give the false impression that an ineffective treatment, supplement, or protocol is effective, since some or all of the research showing it to be ineffective has not been published.

Randomized controlled trial

Randomized controlled trials (RCTs) are the gold standard for determining whether an intervention actually causes any effects. The use of randomization and control groups helps eliminate the effects of factors other than the treatment being studied.

Reactive Oxygen Species (ROS)

Reactive oxygen species are a group of molecules derived from molecular oxygen that are formed during the process of aerobic respiration. Although an overabundance of reactive oxygen species can be damaging to cells, these molecules also have a fundamental role in normal physiology as functional signaling molecules.

Serum

Serum is the clear, liquid component of blood. Serum can be obtained from blood once the blood has been coagulated, or thickened, by clotting.

Statistical significance

A p-value is statistically significant if it falls below a (somewhat arbitrary) threshold called a significance level, which is traditionally set at 0.05. Statistical significance suggests that the data aren’t explained well by the null hypothesis — the assumption that the intervention (or variable) being studied actually makes no difference to the outcome you’re studying. If the results are statistically significant, you can reject the null hypothesis and conclude that there actually is a difference.

Systematic review

A systematic review is a review and summary of the scientific evidence on a given topic. It uses a systematic approach so as to minimize bias and be reproducible by other researchers.

Transcription factor

A transcription factor is a protein that regulates specific genes by binding to DNA.

Zeitgeber

A zeitgeber refers to any external exposure that can regulate the circadian rhythm. As a result, zeitgebers can influence various biological processes, including the sleep/wake cycle. The most important zeitgeber is light exposure.

Glossary

Glossary