Potential contributions of the methodology to the variability of glycaemic index of foods

Table 1 Summary of glucose sources from 129 glycaemic index studies that used glucose as a reference standard

	Generic monohydrate	Generic anhydrous	Glucodin™	Glucolin™	Clintose®	Pre-mixed glucose drink	Does not specify
Source of glucose reference	10	17	10	23	1	11	57

Table 2 Summary of drink information reported across 155 glycaemic index papers

Not reported	Water	Tea/coffee allowed	No beverages allowed with meals	Non-caloric orange drink
63	77	13	1	1

Not reported: No mention of beverages consumed during testing; Water: Some mention of water being consumed during testing, but no other options; Tea/coffee allowed: If tea or coffee was an option for participants, even if water could also be selected; No beverages allowed with meals: Drinking anything was specifically mentioned as not permitted; Non-caloric orange drink: Non-caloric orange drink as an option instead of water during testing.

Table 3 Summary of glucose analysis methods from 155 papers glycaemic index studies using glucose as a reference standard

	Clinical chemistry analyser/plate reader				Glucometer (single reading or continuous)	Clinical enzymatic amperometric glucose detection	Not specified
Papers	121				24	2	8
Specific method	Glucose oxidase	Glucose hexokinase	Glucose dehydrogenase	Unknown
	66	19	3	33

Table 4 Amount of carbohydrates delivered in test and reference foods

50 g	25 g	Other amount	Doesn’t specify
126	33	2	2

Table 5 Reference standards used across the 155¹ glycaemic index papers

Bread	Glucose	Other
40	127	5

¹Because some papers compared mixed methods and compared reference standards combined total of table entries is > 155.

Table 6 Blood sampling across the 155¹ glycaemic index papers

Capillary	Venous	Intravenous catheter	Continuous glucose monitor	Not specified
123	24	7	1	7

¹Because some papers compared mixed methods and compared reference standards combined total of table entries is > 155.