Table 3.
Findings from published reports on the effects of free or added sugar consumption on cognition in healthy subjects.
| Author and Year | Design | Timeframe/ Follow-Up |
Subjects | Tasks/Measures | Intervention/ Independent Variable |
Significant Findings |
|---|---|---|---|---|---|---|
| Human studies | ||||||
| Adan & Serra-Grabulosa, 2010 [179]. | RCT | 0–30 min (unclear) | Fasted adults, aged 18–25y; n = 72; glucose group, n = 18. | RAVLT Purdue-Pegboard JoLO WCST CalCAP Digit Span of WAIS VAS |
75 g glucose | ↑ Perdue pegboard assembly ↑ Reaction time -No effect of glucose on learning or memory |
| Azari, 1991 [191]. | Double-blind, Repeated measures trial. |
30 min | Aged 19–25; n = 18. Fasted with standardized breakfast. |
Word list recall and recognition | 30 g or 100 g glucose | -No effect of glucose |
| Benton & Owens, 1993 [202]. | RCT | 15 min | Young adults, mean age 21y; n = 153 | Word list recall Spatial memory test Wechsler story Blood glucose |
50 g glucose | -No effect of glucose solution |
| Brandt, 2015 [177]. | Double-blind, placebo-controlled trial. (Glucose compared to aspartame) |
15 min | Fasted young adults; mean age 19.47y; n = 41; BMI = 18.5 to 30 kg/m2 | Word recall task (recognition, recollection or familiarity). | 25 g glucose | ↓ Familiarity |
| Chong et al., 2019 [8]. | Cross-sectional survey | NA | Adults aged ≥ 60 years | FFQ (total sugars, free sugars, fructose, glucose, sucrose, maltose, lactose) MMSE |
↑ Total and free sugar intake. | ↓ MMSE score |
| Flint & Turek, 2003 [203]. | Randomised placebo-controlled trial. (Comparison groups: 10, 100, and 500 mg/kg, or 50 g glucose or saccharin placebo) |
2 min | Fasted adults aged 18–50 (n = 67) | TOVA program | 100 mg/kg glucose | ↓ Attention (impaired impulsivity and disinhibition) |
| Gagnon et al., 2010 [178]. | Double-blinded, placebo-controlled trial. (Glucose compared to saccharin) |
15 min | Fasting older adults (aged 60 years and over; n = 44) | STROOP Trail making tests A and B Computerised dual task |
50 g glucose | ↑ Switching ↑ Inhibition ↑ Trail Making Test A, but not B. ↑ Attention |
| Gui et al., 2021 [44]. | Cross-sectional survey | NA | Children; mean age 8.6 years; n = 6387 | FFQ (SSB) | ↑ SSB consumption | ↓ Executive functions ↑ Risk of executive dysfunction |
| Hope et al., 2013 [176]. | Double-blind placebo-controlled experimental trial. | Immediate | Adults; mean age 25.1y; n = 12. Tested after consumption of standardised breakfast. |
Erikson Flanker Task | 25 g glucose | ↓ Sensorimotor processing speed |
| Kennedy & Scholey, 2000 [180]. | Randomised crossover design. (Glucose compared to saccharin) |
20 min | Fasted young adults; aged 19–30; n = 20 | Serial threes Serial sevens |
25 g glucose solution | ↑ Performance on Serial Sevens |
| Macpherson et al., 2015 [181]. | Repeated measures RCT. (Glucose compared to saccharin) |
5–30 min (unclear) | Fasting young adults; mean age 20.6y; n = 24; Fasting older adults; mean age 72.5y; n = 24 | Memory task Tracking task |
25 g glucose solution | Older adults: ↑ Recognition memory ↑ Tracking precision Younger adults: No effects |
| Martin & Benton, 1999 [194]. | RCT. 4 block design: glucose vs placebo; fasted vs breakfast (mean 1049 ± 767 kJ; 42.6 ± 30.3 g carbohydrate). |
20 min | Female adults; mean age 22.6y; n = 80 | Brown–Petersen task | 50 g glucose (fasted condition) | ↑ Recall |
| 50 g glucose (breakfast condition) | -No effect of glucose | |||||
| Miao et al., 2021 [28]. | Prospective cohort study (FHS). | 19y (mean) | Adults; n = 1384 | FFQ (SSB) Clinical surveillance |
↑ SSB | ↑ Dementia ↑ AD |
| Munoz-Garcia et al., 2020 [45]. | Prospective cohort study | 6y | University graduates; aged over 55y; n = 1069 | FFQ (SSB) STICS-m |
↑ SSB | ↓ Cognition |
| Owen et al., 2010 [182]. | Between-participant, double-blind, placebo-controlled design. |
15 min | Fasted young adults; aged 18–30; n = 90 | Word presentation Immediate word recall Face presentation Implicit memory task Delayed word recall Delayed word recognition Face recognition |
25 g glucose | ↓ Word recognition (increased errors) |
| 60 g glucose | ↑ Immediate free recall ↑ Word recognition ↑ Implicit memory |
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| Scholey et al., 2009 [183]. | RCT. (Glucose compared to saccharin) |
20 min | Fasted young adults (mean age 21.6 years; n = 120 | Word recognition Tracking task |
25 g glucose solution | ↑ tracking performance -No effect on memory |
| Stollery & Christian, 2016 [175]. | Experimental. glucose or saccharin (no sugar). |
10 min | Fasting adults; n = 31 | Object location binding task | 30 g glucose | ↑ Object location binding memory ↑ Location memory |
| Sunram-Lea et al., 2011. | Double-blind, placebo-controlled, balanced, crossover trial. (Glucose compared to saccharin) |
15 min | Fasted young adults; n = 30 | Immediate word recall Serial threes Serial sevens Corsi block-tapping task Delayed word recall Delayed word recognition |
15 g, 25 g, 50 g, or 60 g glucose solution | U-shaped dose-response. -Spatial WM, immediate recall, delayed recall, and recognition memory were all improved at 25 g only. |
| Ye et al., 2011 [46]. | Cross-sectional survey. | NA | Aged 45–75y; n = 1500 | FFQ (Sucrose, glucose, fructose, galactose, lactose, maltose, fruit juice, or sugar-sweetened solid foods). MMSE Word list learning Digit span Clock drawing Figure copying STROOP Verbal fluency tests |
↑ Total sugars/added sugars/sucrose/glucose/fructose | ↓ MMSE -No effect of increased natural fructose, galactose, lactose, maltose, fruit juice, or sugar-sweetened solid foods. |
| Zhang et al., 2022 [47]. | Cross-sectional survey | NA | Aged 13–18y; n = 1427 | FFQ (SSB) Questionnaire |
↑ SSB | ↓ Inhibition ↓ WM ↓ Cognitive flexibility |
| Animal studies | ||||||
| Beecher et al., 2021 [10]. | Longitudinal experimental study. (Sucrose compared to water) |
12 weeks | Adolescent mice; n = 46 | Elevated-plus-maze Novelty suppressed feeding Marble burying Open field test Forced swimming test NOR MWM Pathology tests |
25% sucrose solution | ↓ Episodic and spatial memory ↓ Overall density of dentate gyrus proliferating cells ↑ Locomotor activity |
| Fierros-Campuzano et al., 2022 [48]. | Longitudinal experimental study. (Fructose compared to water) |
12 weeks | Adolescent male Wistar rats; aged 5–6 weeks; n = 60 | Barnes Maze Pathology tests |
10% fructose solution | ↓ Spatial memory ↓ Neurogenesis in hippocampus ↑ Inflammatory markers in PFC ↑ GFAP expression in hippocampus and PFC |
| Hamelin et al., 2022 [49]. | Longitudinal experimental study. (Sucrose compared to water or artificial sweetener) |
6 weeks | Adult male mice; n = 297 | Mouse gambling task Pathology tests |
1% sucrose solution (25% daily sugar intake). | ↓ DA and DA turnover in PFC ↓ Decision-making ↓ c-Fos expression in prelimbic cortex, nucleus accumbens, and striatum. ↑ Activity in BLA |
| Hsu et al., 2015 [50]. | Longitudinal experimental study. (Sucrose or fructose compared to water) |
30 days | Adolescent (n = 38) and adult (n = 38) male Sprague Dawley rats. | Barnes maze test Y-maze |
SSB (11% sucrose) | Adolescents: ↓ Spatial learning Adults: -No effect observed |
| HFCS (11%) | Adolescents: ↓ spatial learning and memory retention ↑ Hippocampal inflammatory markers Adults: -No effect observed |
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| Kageyama et al., 2022 [60]. | Longitudinal experimental study. | 40 days | Postnatal, adolescent, and adult Sprague Dawley rats (n = 7–8 per group). | Pathology results | 20% HFCS | ↓ BDNF expression in childhood and adolescence -No effect in adult rats |
| Lee et al., 2021 [51]. | Longitudinal experimental study. (Comparison of high sucrose to high-fat and control diets) |
21 days | Older Sprague Dawley rats; 15 months old; n = 36; high sucrose group, n = 17 | T-maze | Sucrose as 70% of carbohydrate kcal | ↓ Cognitive learning |
| Lemos et al., 2016 [52]. | Longitudinal experimental study. | 9 weeks | Male Wistar rats; 12 weeks old; n = 6–8 rats per group. | Open field test Object displacement NOR Forced Swimming test Western Blot |
35% sucrose | ↓ Memory performance ↑ Inhibitory Adenosine A1 receptor in hippocampus |
| Messier et al., 2007 [204]. | Repeated measures RCT. (Comparison of high-fructose diet to high-fat and control diets) |
3 months | 7-week-old C57BL/6 mice; n = 38; fructose group n = 8 | Operant bar pressing task | 15% fructose | ↑ Learning (on 2 of 5 testing days) |
| Miles et al., 2021 [205]. | Longitudinal experimental study. | 14 days | Adult male Wistar rats; 8 weeks old; n = 16 | Location Discrimination task Pairwise Discrimination acquisition and reversal learning Processing speed |
10% sucrose (approx. 70 mL per day) | -No effect of sucrose |
| Noble et al., 2019 [53]. | Longitudinal experimental study. | 30 days (Postnatal day 26 to 56) | Juvenile, male Sprague Dawley rats (n = 24). | Zero Maze Novel object in context task |
11% w/v HFCS | ↓ later-life hippocampal-dependent episodic contextual memory -No impact on glucose tolerance, weight, anxiety |
| Reichelt et aal., 2022 [57]. | Longitudinal experimental study. | 28 days | male albino Sprague Dawley rats; 4 weeks old; n = 32 | Object-in-place task Locomotor behaviour Biconditional discrimination Immunohistochemistry |
200 mL 10% sucrose, 2 h per day. | ↓ Context-appropriate responses ↓ Hippocampal PV+ cells |
| Ross et al., 2009 [206]. | Longitudinal experimental study. | 18 weeks | Male Sprague Dawley rats; n = 29. | Spatial Water Maze | 60% fructose | ↓ Retention performance -No impact on acquisitional performance |
| Sanguesa et al., 2018 [61]. | Longitudinal experimental study. (Comparison of fructose, glucose, water) |
28 weeks | Female, adult, Sprague Dawley rats; n = 36; control, n = 12; Fructose, n = 12; glucose, n = 12 |
NOR MWM Immunohistochemistry |
10% w/v fructose | ↓ NOR ↓ BDNF ↓ IRS-2 protein expression ↓ Akt phosphorylation |
| Wong et al., 2017 [54]. | Longitudinal experimental study. | 24 days | Adolescent and young adult Sprague Dawley rats; n = 48 | Object and place recognition memory Delay-discounting task Progressive ratio T-maze forced alternation. |
10% sucrose solution, 2 h per day. | ↓ Spatial memory |
| Wu et al., 2015 [55]. | Longitudinal experimental study. | 8 months | Male Sprague Dawley rats; 8 weeks old; n = 19 | MWM | 10% fructose solution | ↓ Spatial learning and memory |
| Xu & Reichelt, 2018 [56]. | Longitudinal experimental study. | 28 days | Male Sprague Dawley rats; 3 weeks old; n = 36 | Open field test NPR NOR Immunohistochemistry |
10% sucrose, 2 h per day | ↓ NPR ↓ NOR ↓ Hippocampal PV+ cells |
Abbreviations: RCT, randomised control trial; mins, minutes; y, years; RAVLT, Rey Auditory Verbal Learning Memory Test; JoLO, Benton Judgement of Line Orientation Test; WCST, Wisconsin Card Sorting Test; CalCAP,, California Computerized Assessment Package; WAIS, Wechsler Adult Intelligence Scale; VAS, Visual Analogue Scale; ↑ increased/increasing; ↓ decreased/decreasing; MMSE, the Mini Mental State Examination; TOVA, Test Of Variables of Attention program; SSB, sugar-sweetened beverage; FHS, Framingham Heart Study; STICS-m, Spanish version of the modified Telephone Interview of Cognitive Status; WM, working memory; NOR, novel object recognition; MWM, Morris Water Maze; PFC, prefrontal cortex; GFAP, Glial fibrillary acidic protein; DA, dopamine; BLA, basolateral amygdala; HFCS, high-fructose corn syrup; AD, Alzheimer’s disease; BDNF, brain-derived neurotrophic factor.