Table 1.

Summary of the antidiabetic effects of T3 from human studies.

T3 Isoform	Treatment Condition and Population	Main Outcomes	References
Dietary intake of T3	The risk of diabetes and dietary intake of T3 was investigated via The Finnish Mobile Health Examination survey (cohort study) on 4504 healthy subjects	Only β-T3 was significantly associated with lower risk of T2DM	[68]
	The risk of diabetes and dietary intake of T3 was investigated via ATBC cohort study on 25,505 healthy subjects	None of the T3 isoforms was associated with lower risk of diabetes after multivariate adjustment	[69]
T3 (unknown T3 composition)	Oral mixed T3 (400 mg/day) capsules were supplied to 229 diabetic patients with diabetic peripheral neuropathy syndromes (VENUS study)	400 mg/day is considered as safe to human Improved glycemic control Failed to reduce diabetic neuropathic symptoms	[71]
Palmvitee (16% T3)	Palmvitee (1800 mg) or refined palm oil capsules were provided to 32 T2DM patients for 60 days, followed by 60 days washout period and then crossed over the supplementation for another 60 days	T3-containing Palmvitee supplement reduced lipid peroxidation but not improving patients’ lipid profile and HbA1c level	[72]
TRF (14.6% α-T3, 2.2% β-T3, 38.8% γ-T3, and 2.4% unidentified T3)	TRF treatment (6 mg/kg bw/day) was supplied to 19 T2DM patients for 60 days (RCT study)	Improved several lipid profile parameters but had no effect on the glycemic status and blood pressure	[73]
TRF (24.5% α-T3, 3.5% β-T3, 35.4% γ-T3, 12.7% δ-T3, and 23.9% α-tocopherol)	552 mg/day of TRF capsules was supplied to 86 T2DM patients with impaired vascular function for 8 weeks (RCT study)	Increased plasma T3 isoforms levels upon supplementation. No effect on inflammation, lipid profiles, glucose metabolism, vascular function, systolic, and diastolic pressure	[74]
T3 mixture (13.2% α-T3, 16.6% γ-T3, 8.6% others T3, and 16% α-tocopherol)	200 mg/day of T3 mixture was supplied to 44 T2DM patients for 8 weeks (RCT study)	Reduced microalbuminuria and hsCRP level Had no effect on serum NO level and renal function	[80]
	200 mg/day of T3 mixture was supplied to 45 T2DM patients for 8 weeks (RCT study)	Reduced fasting blood glucose level Increased total antioxidant capacity and suppressed lipid peroxidation	[70]

Abbreviations: ATBC = Alpha-Tocopherol, Beta-Carotene Cancer Prevention study, HbA1c = glycated hemoglobin A1, NO = nitric oxide, RCT = randomized controlled trial, T2DM = Type 2 diabetes mellitus, T3 = tocotrienol, TRF = tocotrienol-rich fraction, VENUS = The Vitamin E in Neuroprotection Study.