Fructose metabolism in humans – what isotopic tracer studies tell us

Nutrition & Metabolism

Table 2 Conversion from Fructose to Glucose, Tracer Studies in Adults ⁽¹⁾

Subjects	Exercise	Hours	Fru dosages	Tracer	Blood glu (mmol/L)	Fru to glu conversion	Reference
9 M	No	6	3x0.3 g/kg bw	¹³C-fru^(L1)	5.94%⁽²⁾	37.4%
9 F	No	6	3x0.3 g/kg bw	¹³C-fru	4.87%⁽²⁾	28.9%	[70]
4 M + 4 F	No	3	3x0.3 g/kg bw	¹³C-fru^(L3)	5.2	36.4%⁽³⁾
7 obese F	No	3	3x0.3 g/kg bw	¹³C-fru	5.3	29.5%⁽³⁾
8 type-2 (4 M)	No	3	3x0.3 g/kg bw	¹³C-fru	7.7	30.2%⁽³⁾	[52]
3 M + 3 F	No	6	0.5 g/kg bw	¹³C-fru^(L2)	4.56	54.0%
	No	6	1.0 g/kg bw	¹³C-fru	4.66	50.7%	[49]
3 M + 3 F	No	0-3	3 mg/kg/min⁴	¹³C-fru^(L1)	NA	28.0%⁽⁴⁾
	No	4-6	6 mg/kg/min⁴	¹³C-fru	NA	22.0%⁽⁴⁾	[71]
7 M	Yes	2	96 g fru + 144 g glu	¹³C-fru^(L1)	6.2	29%⁽⁵⁾	[51]
6 M	Yes	3	6x25 g	¹³C-fru^(L2)	NA	55-60%⁽⁶⁾	[50]

For superscript numbers: (1), except Jandrain’s study[50], the subjects in the other studies were under glucose infusion; Hours = study monitoring hours, fru = fructose, glu = glucose; bw = body weight; M = male, F = female; type-2 = type-2 diabetes; NA = not available. (2), increases from baseline. (3), data were calculated based on reported parameters. (4), fructose administrated by infusion. (5), under steady state of carbohydrate flux. (6), percent of circulating glucose in the 2^nd half of study hours. In the column of “Tracer”, superscripted L1 = labeled uniformly, L2 = naturally enriched, and L3 = labeled at position 1.

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