What the science says

For 779 substances we searched PubMed for meta-analyses, systematic reviews and randomized controlled trials in humans. The grade shows how deep the research base is; each substance page shows what the reviews actually concluded.

AStrong research base426

3+ meta-analyses or systematic reviews and 10+ randomized controlled trials in humans.

BModerate research base195

At least one meta-analysis, or 5+ randomized controlled trials.

CLimited research68

1–4 randomized controlled trials, no meta-analysis yet.

DNo human trials found90

No randomized controlled trials in humans found on PubMed.

Users ahead of science

Popular and well-rated by users, but little clinical research so far.

Science ahead of users

Heavily studied, but users report modest results.

Most-studied substances

Substance	Grade	Meta-analyses	RCTs	User score
CalciumSupplement	A	3,919	10,361	27
Vitamin DSupplement	A	3,251	4,560	52
ProbioticsSupplement	A	2,293	2,235	45
TyrosineSupplement	A	2,190	1,766	31
AspirinMedication	A	2,128	5,064	26
FiberSupplement	A	1,399	3,260	44
MetforminMedication	A	1,367	3,450	25
Omega-3Supplement	A	1,341	3,093	51
NicotineSubstance	A	1,323	3,241	46
CannabisSubstance	A	1,197	1,041	36
PotassiumSupplement	A	1,135	4,061	40
Vitamin KSupplement	A	1,080	714	31
GLP-1Medication	A	1,037	1,604	26
ProgesteroneMedication	A	1,020	2,324	34
GlutathioneSupplement	A	967	1,685	48
Folic AcidSupplement	A	911	1,495	22
KetamineMedication	A	854	1,957	36
IodineSupplement	A	853	1,619	28
Hyaluronic AcidSupplement	A	816	1,179	31
CreatineSupplement	A	763	2,794	56
FolateSupplement	A	744	1,173	48
Vitamin CSupplement	A	738	2,072	47
MelatoninSupplement	A	688	1,128	47
CaffeineSubstance	A	680	2,072	52
Vitamin ESupplement	A	680	1,761	24
Vitamin BSupplement	A	638	541	21
MarijuanaSubstance	A	615	629	23
OxytocinPeptide	A	611	1,989	23
ArginineSupplement	A	585	1,869	37
LithiumSupplement	A	581	979	25
CopperSupplement	A	569	792	29
EPASupplement	A	559	1,301	42
TurmericSupplement	A	538	553	38
CurcuminSupplement	A	538	553	32
FluoxetineMedication	A	534	1,257	28
Vitamin aSupplement	A	533	1,109	23
GabapentinMedication	A	532	672	31
PrebioticsSupplement	A	526	415	23
IbuprofenMedication	A	511	1,743	35
MsmSupplement	A	506	423	41
CocaineSubstance	A	500	1,402	19
RapamycinMedication	A	497	1,245	18
Growth HormoneMedication	A	468	2,548	27
SemaglutideMedication	A	421	307	65
BupropionMedication	A	411	617	38
GlycineSupplement	A	392	620	55
NACSupplement	A	387	767	51
PregabalinMedication	A	387	599	21
MethylphenidateMedication	A	383	1,123	32
Vitamin B12Supplement	A	376	572	49
DHASupplement	A	365	1,607	36
GlutamineSupplement	A	361	787	35
LamotrigineMedication	A	343	320	19
HcgMedication	A	324	972	29
SertralineMedication	A	318	906	24
NaltrexoneMedication	A	317	926	27
VenlafaxineMedication	A	314	562	22
ClonidineMedication	A	311	1,394	19
CBDSupplement	A	286	344	55
ResveratrolSupplement	A	282	263	38
CholineSupplement	A	280	460	45
TryptophanSupplement	A	274	818	50
P21Peptide	A	271	51	25
CarnitineSupplement	A	269	636	22
PropranololMedication	A	268	1,961	49
AmphetamineMedication	A	258	521	34
THCSubstance	A	249	488	25
B ComplexSupplement	A	246	106	51
Human Growth HormoneMedication	A	246	451	31
IronSupplement	A	243	693	54
Vitamin B ComplexSupplement	A	237	64	31
MemantineMedication	A	236	311	46
SildenafilMedication	A	233	699	26
MethamphetamineSubstance	A	226	421	12
ZincSupplement	A	220	555	43
EscitalopramMedication	A	219	659	29
GinsengSupplement	A	215	243	49
DHEASupplement	A	215	637	37
TirzepatideMedication	A	214	132	70
InositolSupplement	A	209	248	60
Ginkgo BilobaSupplement	A	207	284	50
GinkgoSupplement	A	207	284	29
DmtSubstance	A	207	121	27
QuercetinSupplement	A	207	232	26
PsilocybinSubstance	A	189	138	44
GingerSupplement	A	184	255	33
LysineSupplement	A	180	469	18
COQ10Supplement	A	176	405	40
MirtazapineMedication	A	174	262	30
L-CarnitineSupplement	A	170	466	32
BaclofenMedication	A	168	214	34
LevothyroxineMedication	A	166	296	31
PhenylalanineSupplement	A	158	648	22
ModafinilMedication	A	155	297	46
Vitamin B6Supplement	A	152	261	29
AtomoxetineMedication	A	152	268	15
PsychedelicsSubstance	A	149	104	26
LycopeneSupplement	A	147	301	11
NiacinamideSupplement	A	144	72	19
GarlicSupplement	A	142	194	35
AmphetaminesSubstance	A	139	67	42
RetinolSupplement	A	138	893	37
Methylene BlueSubstance	A	131	382	31
LavenderSupplement	A	129	272	21
LSDSubstance	A	122	202	54
GalantamineSupplement	A	122	148	42
AstragalusSupplement	A	122	83	18
TadalafilMedication	A	120	347	62
NicotinamideSupplement	A	120	239	19
PiracetamSupplement	A	119	117	51
ColostrumSupplement	A	118	206	22
GelatinSupplement	A	116	552	35
ThiamineSupplement	A	116	155	29
NiacinSupplement	A	114	379	47
FinasterideMedication	A	113	332	49
Omega-3 Fatty AcidsSupplement	A	113	1,153	34
TaurineSupplement	A	112	227	51
DimSupplement	A	111	297	26
BerberineSupplement	A	109	110	50
NAD+Supplement	A	109	168	45
B VitaminsSupplement	A	107	248	35
GlucosamineSupplement	A	107	209	25
L-ArginineSupplement	A	106	765	45
TrazodoneMedication	A	105	165	55
SeleniumSupplement	A	105	209	28
Myo-InositolSupplement	A	102	143	31
ClonazepamMedication	A	101	133	34
LuteinSupplement	A	101	331	29
Alpha Lipoic AcidSupplement	A	100	243	43
ALASupplement	A	100	243	15
MDMASubstance	A	99	165	23
Whey ProteinSupplement	A	97	691	37
TRTMedication	A	96	195	47
Beta-AlanineSupplement	A	95	134	46
PeaSupplement	A	90	262	22
Potassium ChlorideSupplement	A	90	226	15
MinoxidilMedication	A	89	186	51
SaffronSupplement	A	88	119	57
MagnesiumSupplement	A	82	210	54
CabergolineMedication	A	81	96	19
EphedrineSubstance	A	80	614	56
TretinoinMedication	A	76	265	44
TestosteroneMedication	A	75	125	45
CinnamonSupplement	A	75	95	21
BeetrootSupplement	A	74	360	29
Testosterone Replacement TherapyMedication	A	72	106	61
BuspironeMedication	A	68	240	22
Nigella SativaSupplement	A	67	86	28
MultivitaminsSupplement	A	67	203	11
CacaoSupplement	A	66	24	21
BCAASupplement	A	65	287	26
Black TeaSubstance	A	64	126	43
SelegilineMedication	A	64	153	43
ChamomileSupplement	A	59	93	40
Panax GinsengSupplement	A	59	91	40
Nicotine PatchSubstance	A	58	490	43
DutasterideMedication	A	54	190	22
GuanfacineMedication	A	53	116	57
WeedSubstance	A	53	20	25
SpirulinaSupplement	A	52	83	30
CitrullineSupplement	A	51	258	51
UridineSupplement	A	50	75	34
Psyllium HuskSupplement	A	49	145	77
AshwagandhaSupplement	A	48	59	50
DextroamphetamineMedication	A	48	119	21
Vitamin B1Supplement	A	47	84	38
L-DopaSupplement	A	47	286	19
Acetyl-L-CarnitineSupplement	A	46	86	34
ALCARSupplement	A	46	86	33
Methylated B VitaminsSupplement	B	46	0	26
EgcgSupplement	A	45	149	27
PhosphatidylcholineSupplement	A	45	248	11
KavaSupplement	A	41	37	43
CarnosineSupplement	A	41	125	11
BcaasSupplement	A	40	108	15
AstaxanthinSupplement	A	39	84	49
CiticolineSupplement	A	39	106	48
Nicotine GumSubstance	A	39	267	34
BoronSupplement	A	38	39	31
Activated CharcoalSupplement	A	37	183	18
Vitamin K2Supplement	A	36	99	41
ApigeninSupplement	A	36	11	32
BoswelliaSupplement	A	35	78	29
ArmodafinilMedication	A	34	44	41
HydroxyzineMedication	A	34	166	25
BromelainSupplement	A	34	53	21
Nicotine PatchesSubstance	A	33	236	35
FenugreekSupplement	A	33	45	32
Green Tea ExtractSupplement	A	32	144	42
Nicotinic AcidSupplement	A	32	143	28
N-Acetyl Cysteine (nac)Supplement	A	31	84	31
GhbSubstance	A	31	110	28
MolybdenumSupplement	A	31	36	18
CerebrolysinPeptide	A	30	60	52
ValerianSupplement	A	30	59	50
BiotinSupplement	A	30	77	26
MT2Peptide	A	29	32	37
Grape Seed ExtractSupplement	A	29	60	31
BlueberriesSupplement	A	29	61	30
PalmitoylethanolamideSupplement	A	28	69	25

Counts come from PubMed searches on the substance name in titles and abstracts; trial counts are limited to human studies. A grade reflects how much research exists, not whether the results were positive. Method details