Supplement Research Glossary

Plain-English definitions for the 99 study, dosing, pharmacology, and biology terms you'll see across SupStack.

Study Types

double-blind: A study design where neither the participants nor the researchers know who is receiving the treatment vs. placebo, reducing bias.Also known as: double blind, blinded
effect size: A measure of how large or meaningful an effect is, beyond just whether it exists. Larger effect sizes indicate more noticeable real-world benefits.
meta-analysis: A statistical analysis that combines results from multiple studies to draw stronger conclusions than any single study alone.Also known as: meta-analyses
placebo: An inactive treatment (like a sugar pill) given to control groups to compare against the real treatment.
RCT: Randomized Controlled Trial — the gold standard for testing if a treatment works. Participants are split randomly between the supplement and a placebo, so the only difference between groups is what they're taking.Also known as: randomized controlled trial, randomized trial
systematic review: A comprehensive summary of all available research on a specific topic, using rigorous methods to minimize bias.Also known as: systematic-review

Research Methods

acute: Short-term or immediate effects, typically from a single dose. Opposite of chronic (long-term).Also known as: acutely
chronic: Long-term effects from continued use over days, weeks, or months. Opposite of acute (immediate).Also known as: chronically
dose-dependent: Effects that increase or change based on the amount taken. Higher doses produce stronger effects (up to a point).
in vitro: Studies conducted in test tubes or petri dishes, outside a living organism. Useful for understanding mechanisms but doesn't prove effects in humans.
in vivo: Studies conducted in living organisms (animals or humans). More relevant to real-world effects than test tube studies.
preclinical: Research conducted before human trials, typically in animals or cell cultures. Promising preclinical results don't guarantee human benefits.
synergistic: When two substances work together to produce effects greater than either alone. The whole is greater than the sum of its parts.Also known as: synergy, synergies

Meta-Analysis & Statistics

95% CI: The 95% Confidence Interval — the range we're 95% confident contains the true effect. Narrow CI = precise estimate; wide CI = uncertain. A CI that crosses zero means the effect could plausibly be no different from placebo.Also known as: 95 CI, confidence interval, CI
Cohen's U3: A way to translate effect size into "how many users would notice an improvement". Specifically: the percentage of placebo participants whose outcome is worse than the average treated participant. Cohen's U3 of 69% means treatment helps roughly 2 in 3 users beyond placebo.Also known as: Cohen U3, U3
head-to-head comparison: A direct comparison between two supplements, computed here indirectly via the shared placebo arm: effect(A vs B) = effect(A vs placebo) − effect(B vs placebo). Lets us answer "is A better than B?" even when no trial directly compared them. Assumes placebo arms are roughly comparable across studies (transitivity); we flag pairs where they aren't.Also known as: head to head, indirect comparison, NMA
Hedges' g: A standardised effect size — pooled effect divided by the typical between-subject variability, so different studies (and even different outcomes) become comparable. Convention: 0.2 is a small effect, 0.5 moderate, 0.8 large. Hedges' g is the bias-corrected version of Cohen's d.Also known as: Hedges g, Hedges-g, standardized effect size, standardised effect size
Heterogeneity: How much the contributing studies disagree with each other beyond chance, measured as I² (0–100%). 0% = studies all point the same way; 25% low; 50% moderate; 75%+ high. High heterogeneity means the point estimate hides real disagreement — treat the range, not just the average, as the answer.Also known as: I², I-squared, I2, heterogeneity (I²)
Inconclusive: No usable quantitative evidence found in our index, or all extracted records contradict each other to the point where pooling produces no signal.
Moderate evidence: A few independent studies (≥3) agreeing reasonably well. Effect is real but the magnitude is less precise. Likely stable but not fully nailed down.
Pooled effect: The combined estimate from multiple studies, weighted so that bigger / more precise studies count more. A pooled effect is more reliable than any single study because random variation tends to cancel out across many trials.Also known as: pooled, pooled estimate
Prediction interval: The range a NEW study is most likely to find, accounting for both the imprecision in the pooled estimate and the genuine variation in true effects across studies. Wider than the 95% CI by definition. If the prediction interval crosses zero but the CI doesn't, future studies may still find no effect — the average is real but individual trials vary.Also known as: prediction-interval, 95% PI, PI
Preliminary: Single small study or very early evidence. Treat as a hypothesis to test, not a settled finding. Usually shouldn't change clinical decisions on its own.Also known as: preliminary evidence, Early evidence
Strong evidence: Multiple independent studies (≥5), large total sample, low between-study disagreement (I² < 50%), and tight confidence intervals. The effect is well-replicated and the size is precise.
Studies: How many separate studies contributed to this pooled estimate (k in the literature). More studies generally mean stronger evidence, but only if each study itself was well-designed.Also known as: k studies, study count
Tau squared: The estimated variance of the underlying true effects across studies (τ²). High τ² means studies aren't all measuring the same true effect — there's genuine variation, not just noise. Useful alongside I² because τ² is on the same units as the effect, making "how much do trials disagree" interpretable.Also known as: tau², τ², between-study variance
Total n: The total number of subjects across all contributing studies. Larger total n = more statistical power. Useful sanity check: 2,000 subjects in 4 RCTs is much stronger than 50 subjects in 4 small pilot trials.Also known as: total sample size, total participants
Weak evidence: Only one or two studies with limited sample size, OR multiple studies with high disagreement. The direction may be right but the magnitude is uncertain.Also known as: Limited evidence

Measurement

plasma: The liquid part of blood (before clotting). Similar to serum but contains clotting factors.Also known as: plasma levels
serum: The liquid part of blood after clotting. "Serum levels" refers to the concentration of a substance in the blood.Also known as: serum levels

Effect Types

anxiolytic: Having anti-anxiety effects. Reduces feelings of anxiety and promotes calm without necessarily causing sedation.
ergogenic: Performance-enhancing. Ergogenic aids are substances that improve exercise capacity, strength, or endurance.Also known as: ergogenic aid, ergogenic aids
neuroprotective: Protecting brain cells from damage, degeneration, or stress. Important for long-term cognitive health.Also known as: neuroprotection
sedative: Causing drowsiness or sleepiness. Sedatives slow down brain activity and are often used for sleep.
thermogenic: Increasing heat production in the body, which raises metabolism and energy expenditure. Often used for weight management.
vasodilation: Widening of blood vessels, which increases blood flow. Important for exercise performance and cardiovascular health.Also known as: vasodilator, vasodilating

Pharmacology

agonist: A substance that activates a receptor, mimicking the effect of the natural molecule. Opposite of antagonist.Also known as: agonists
antagonist: A substance that blocks a receptor, preventing its activation. Opposite of agonist.Also known as: antagonists
blood-brain barrier: A protective barrier that controls which substances can enter the brain from the bloodstream. Some supplements can cross it, others cannot.Also known as: BBB
inhibitor: A substance that slows down or blocks a specific enzyme or process. Example: MAO inhibitors affect mood-related enzymes.Also known as: inhibitors
receptor: A protein on cells that receives signals from molecules like neurotransmitters or hormones, triggering a cellular response.Also known as: receptors
reuptake: The process where neurotransmitters are reabsorbed back into nerve cells. Blocking reuptake increases neurotransmitter activity.

Delivery & Absorption

chelated: A mineral bound to an amino acid or organic compound, making it easier for the body to absorb. Common in high-quality mineral supplements.
enteric-coated: A coating that protects the supplement from stomach acid, allowing it to dissolve in the intestines instead. Reduces stomach irritation.Also known as: enteric coated
extended-release: A formulation designed to release the active ingredient slowly over time, providing longer-lasting effects and reducing the need for multiple doses.Also known as: sustained-release, time-release, slow-release
GI: Gastrointestinal - Relating to the stomach and intestines. "GI upset" means stomach discomfort, nausea, or digestive issues.Also known as: GI upset, GI discomfort, gastrointestinal
liposomal: Encapsulated in tiny fat bubbles (liposomes) that protect the nutrient and dramatically improve absorption into cells.
sublingual: Taken under the tongue, where it dissolves and absorbs directly into the bloodstream, bypassing the digestive system for faster effects.

Dosing

cycling: Taking scheduled breaks from a supplement to prevent tolerance, maintain effectiveness, or reduce side effects.
loading phase: An initial period of higher dosing to quickly build up levels in the body, followed by a lower maintenance dose.
maintenance dose: The ongoing daily dose taken after an initial loading phase to maintain optimal levels.
saturation: When body stores of a substance reach maximum levels. Further supplementation provides diminishing returns.
tolerance: Reduced response to a substance after repeated use, requiring higher doses for the same effect.

Mineral Forms

citrate: A mineral bound to citric acid. Well-absorbed and commonly used. May have mild laxative effects at high doses.
glycinate: A mineral bound to glycine (an amino acid). Highly absorbable and gentle on the stomach. Common for magnesium.
L-threonate: A form of magnesium that can cross the blood-brain barrier. Specifically researched for cognitive benefits.Also known as: threonate, magtein
malate: A mineral bound to malic acid. Well-absorbed and particularly good for energy production and muscle function.
oxide: A basic mineral form with poor absorption (often <10%). Inexpensive but not recommended for most supplements.

Biology & Physiology

acetylcholine: A neurotransmitter crucial for memory, learning, and muscle control. Decline is associated with cognitive aging.
antioxidant: A substance that protects cells from damage by neutralizing free radicals. Found in many supplements and foods.Also known as: antioxidants
ATP: Adenosine triphosphate - The primary energy currency of cells. All cellular processes require ATP for energy.
bioavailability: The percentage of a substance that enters your bloodstream and is available for your body to use. Higher bioavailability means better absorption.
circadian rhythm: Your body's internal 24-hour clock that regulates sleep-wake cycles, hormone release, and other processes.Also known as: circadian
cortisol: The primary stress hormone. Chronically elevated cortisol can impair sleep, mood, and immune function.
cytokine: Signaling proteins that regulate inflammation and immune responses. Some promote inflammation, others reduce it.Also known as: cytokines
dopamine: A neurotransmitter involved in motivation, reward, pleasure, and focus. Important for feeling motivated and satisfied.
GABA: Gamma-aminobutyric acid - The main calming neurotransmitter in the brain. It reduces neural activity and promotes relaxation.
half-life: The time it takes for half of a substance to be eliminated from your body. Longer half-life means longer-lasting effects.
inflammation: The body's immune response to injury or infection. Chronic inflammation is linked to many health conditions.Also known as: inflammatory, anti-inflammatory
melatonin: A hormone that regulates sleep-wake cycles. Naturally produced at night to signal sleepiness.
mitochondria: The "powerhouses" of cells that produce ATP (energy). More efficient mitochondria mean better energy production.Also known as: mitochondrial
neurotransmitter: Chemical messengers in the brain that transmit signals between nerve cells. Examples include serotonin, dopamine, and GABA.Also known as: neurotransmitters
oxidative stress: Cellular damage caused by free radicals (unstable molecules). Antioxidants help neutralize this damage.
serotonin: A neurotransmitter that regulates mood, sleep, and appetite. Often called the "feel-good" chemical.

Biological Processes

COX-2: Cyclooxygenase-2 - An enzyme that produces inflammatory compounds. COX-2 inhibitors (like curcumin) reduce inflammation.Also known as: COX-2 inhibitor
nitric oxide: A molecule that relaxes blood vessels and improves blood flow. Important for exercise performance and cardiovascular health.Also known as: NO
NMDA receptor: A brain receptor involved in learning, memory, and neural plasticity. Glycine and magnesium modulate NMDA receptor activity.Also known as: NMDA, NMDA receptors

Brain & Cognition

BDNF: Brain-Derived Neurotrophic Factor - A protein that supports brain cell growth, learning, and memory. Exercise and some supplements increase BDNF.Also known as: brain-derived neurotrophic factor
cognitive function: Mental processes including memory, attention, learning, problem-solving, and decision-making.Also known as: cognitive, cognition
neuroplasticity: The brain's ability to form new connections and reorganize itself. Important for learning, memory, and recovery from injury.Also known as: synaptic plasticity
NGF: Nerve Growth Factor - A protein that promotes the growth and survival of nerve cells. Important for brain health and nerve regeneration.Also known as: nerve growth factor

Sleep

REM sleep: Rapid Eye Movement sleep - The dream stage of sleep, important for memory consolidation and emotional processing.Also known as: REM
sleep architecture: The structure and pattern of sleep cycles throughout the night, including the balance of light, deep, and REM sleep.
sleep onset: The transition from wakefulness to sleep. "Sleep onset latency" is how long it takes to fall asleep.Also known as: sleep onset latency, onset latency
slow-wave sleep: Deep sleep (stages 3-4) when the body repairs tissues, builds muscle, and strengthens the immune system. Also called "deep sleep."Also known as: deep sleep, SWS

Safety

blood thinner: Medications that prevent blood clots (like warfarin or aspirin). Many supplements can enhance their effects.Also known as: blood thinners, anticoagulant, anticoagulants
contraindication: A condition or factor that makes a particular treatment inadvisable due to potential harm.Also known as: contraindications, contraindicated
drug interaction: When a supplement affects how a medication works, potentially increasing or decreasing its effects.Also known as: drug interactions, interactions

Supplement-Specific

adaptogen: A natural substance that helps the body adapt to stress and promotes balance. Examples include ashwagandha and rhodiola.Also known as: adaptogens, adaptogenic
amino acid: Building blocks of proteins. Some amino acids also function as neurotransmitters or their precursors.Also known as: amino acids
cofactor: A substance required for an enzyme to function properly. Many vitamins and minerals act as cofactors.Also known as: cofactors
methylation: A biochemical process essential for DNA repair, detoxification, and neurotransmitter production. Requires B vitamins as cofactors.
MTHFR: A gene that affects folate metabolism. Variants (present in 40-60% of people) may benefit from methylated B vitamins.
nootropic: A substance that enhances cognitive function, including memory, focus, or creativity. Also called "smart drugs" or cognitive enhancers.Also known as: nootropics
phospholipid: A type of fat that forms cell membranes. Important for brain health and cellular communication.Also known as: phospholipids
precursor: A substance that the body converts into another compound. For example, L-theanine is a precursor to GABA.Also known as: precursors

Supplement Terms

potentiate: To enhance or strengthen the effect of another substance. Example: Piperine potentiates curcumin absorption.Also known as: potentiates, potentiation
stack: A combination of supplements taken together for synergistic effects. Common in nootropics and fitness supplements.Also known as: stacks, stacking
titrate: Gradually adjusting the dose up or down to find the optimal amount. Starting low and increasing slowly.Also known as: titration