Research Glossary

Key terms and definitions to help you understand supplement research and evidence.

Research Methodology Statistical Terms Evidence Terms Supplement Terms

Research Methodology

Terms describing how scientific studies are designed and conducted.

RCT (Randomized Controlled Trial)

The gold standard for clinical research. Participants are randomly assigned to either the treatment group or control group. Randomization helps eliminate bias and ensures any differences in outcomes are due to the treatment being studied rather than other factors.

Meta-analysis

A statistical method that combines results from multiple independent studies to provide a more precise estimate of an effect. Meta-analyses increase statistical power and can detect effects that individual studies might miss.

Systematic Review

A comprehensive review that identifies, evaluates, and synthesizes all relevant studies on a specific question. Unlike narrative reviews, systematic reviews follow a rigorous, predefined methodology to minimize bias.

Double-blind Study

A study design where neither the participants nor the researchers know who is receiving the treatment versus the placebo. This prevents both groups' expectations from influencing the results.

Placebo-controlled

A study design where the control group receives an inactive substance (placebo) that looks identical to the treatment. This helps determine whether observed effects are due to the treatment itself or psychological factors.

Cohort Study

An observational study that follows a group of people over time to see how certain factors affect health outcomes. Unlike RCTs, researchers observe but don't intervene, making them useful when randomization isn't ethical or practical.

Case Study

An in-depth examination of a single individual or small group. While case studies can generate hypotheses, they cannot establish causation and are considered weak evidence compared to controlled trials.

Statistical Terms

Terms used to describe and interpret research results.

Effect Size

A measure of the magnitude of a treatment effect, independent of sample size. Common measures include Cohen's d and relative risk. Effect size helps determine whether a statistically significant result is also practically meaningful.

Statistical Significance

The likelihood that observed results are not due to random chance. Typically, a result is considered statistically significant if the p-value is less than 0.05 (5% probability the result occurred by chance).

Confidence Interval (CI)

A range of values that likely contains the true population effect. A 95% CI means if the study were repeated 100 times, 95 of those intervals would contain the true effect. Narrower intervals indicate more precise estimates.

P-value

The probability of obtaining results at least as extreme as observed, assuming there is no real effect. A p-value of 0.01 means there's a 1% chance of seeing these results if the supplement had no effect.

Sample Size

The number of participants in a study. Larger sample sizes generally provide more reliable results and greater statistical power to detect true effects.

Evidence Terms

Terms describing the strength and nature of research evidence.

Grade A (Strong Evidence)

Multiple high-quality studies (RCTs, meta-analyses) with consistent results. This represents the highest level of confidence in the findings.View Grade A evidence →

Grade B (Moderate Evidence)

Good supporting evidence from quality studies, but more research is needed to confirm effects. Results are promising but not yet conclusive.

Grade C (Limited Evidence)

Limited number of studies or studies with methodological limitations. Evidence suggests potential but is not definitive.

Grade D (Very Limited Evidence)

Preliminary research only, which may include animal studies, in-vitro studies, or very small human trials. Cannot draw reliable conclusions from this level of evidence.

Effect Magnitude

Describes the size of observed effects: Large (substantial, clinically meaningful), Moderate (notable, may be meaningful), or Small (statistically significant but modest).

Effect Direction

Indicates whether a supplement increases or decreases a measured outcome. Whether increase or decrease is beneficial depends on the specific outcome being measured.

Supplement Terms

Terms specific to dietary supplements and their use.

Bioavailability

The proportion of a supplement that enters circulation and is available for use by the body. Factors affecting bioavailability include the supplement form, timing of intake, and interactions with food or other substances.

Standardized Extract

An herbal preparation processed to contain a consistent, specified amount of one or more active compounds. Standardization helps ensure consistent dosing across different batches and brands.

Active Compound

The specific molecule(s) in a supplement responsible for its biological effects. Some supplements contain multiple active compounds that may work synergistically.

Mechanism of Action

The specific biochemical process by which a supplement produces its effects in the body. Understanding mechanisms helps explain how supplements work and predict potential interactions.

Contraindication

A condition or factor that makes a particular supplement inadvisable or potentially harmful. Common contraindications include pregnancy, certain medical conditions, or use of specific medications.

Drug Interaction

When a supplement affects how a medication works, or vice versa. Interactions can increase or decrease the effectiveness of either substance or cause adverse effects.

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