Table 8.
Effects of hazelnut consumption on glycaemic outcomes (n = 9).
| Author, Year | Study Design | Participant Characteristics | Duration | Treatment | Outcome Measurements: Results |
|---|---|---|---|---|---|
| Acute study | |||||
| Devi et al., 2016 [40] | Randomised crossover 4 treatments |
32 (11 M 21 F) healthy | Acute 2 h | (i) Bread containing 30 g finely sliced hazelnuts per 120 g | 2 h iAUC for blood glucose (i) 152 mmol/L·min |
| (ii) Bread containing 30 g defatted hazelnut flour per 120 g | (ii) 137 mmol/L·min | ||||
| (iii) Bread containing 15 g finely sliced hazelnuts and 15 g defatted hazelnut flour per 120 g | (iii) 154 mmol/L·min | ||||
| (iv) Control white bread with no nuts | (iv) 179 mmol/L·min All hazelnut breads had a lower iAUC compared to the control bread (all p < 0.001). There were no significant differences between breads. |
||||
| Chronic studies | |||||
| Adamo et al., 2017 [36] | Randomised parallel 6 treatments |
61 (31 M, 30 F) Healthy BMI |
2 weeks | Breakfasts including: (i) 30 g peeled hazelnut paste |
Insulin and HOMA-IR Insulin and HOMA-IR remained stable in those consuming the hazelnut-only enriched breakfasts. Actual data was not presented. |
| (ii) 30 g unpeeled hazelnut paste | |||||
| (iii) snack with 30 g peeled hazelnut paste | |||||
| (iv) snack with 2.5 g cocoa powder | |||||
| (v) Snack with 30 g/d peeled hazelnut paste and 2.5 g cocoa powder | |||||
| (vi) no snack control group N.B. Data was only presented for treatments vs. control i.e., no other between-group comparisons were reported | |||||
| Alphan et al., 1997 [51] | Sequential intervention periods 2 treatments |
19 (5 M, 14 F) Type 2 diabetics |
30 days | (i) High CHO diet (60% CHO, 25% fat): HbA1c Baseline: 8.1% End: 7.8% Change: −0.3% FBG Baseline6.92 mmol/L End: 6.94 mmol/L Change: +0.02 mmol/L PPBG Baseline9.16 mmol/L End: 8.49 mmol/L Change: −0.67 mmol/L Fasting insulin Baseline: 86.4 pmol/L End: 72.6 pmol/L Change: −13.4 pmol/L PP insulin Baseline 249.0 pmol/L End: 196.8 pmol/L Change: −52.2 pmol/L |
Between-group analysis NR. |
| (ii) Hazelnut diet (40% CHO, 45% fat, amount of hazelnuts NR): HbA1c Baseline: 8.3% End: 7.2% Change: −1.1% a FBG: Baseline: 7.28 mmol/L End: 7.28 mmol/L Change: 0.00 mmol/L PPBG Baseline: 8.37 mmol/L End:8.28 mmol/L Change: −0.09 mmol/L Fasting insulin Baseline: 78.0 pmol/L End:97.2 pmol/L Change: +19.2 pmol/L PP insulin Baseline: 223.2 pmol/L End: 225.0 pmol/L Change: +1.8 pmol/L | |||||
| Damavandi et al., 2012 [37] | Randomised parallel 2 treatments |
50 (16 M, 34 F) participants with type 2 diabetes | 8 weeks | (i) Control: No hazelnuts FBG Baseline: 8.69 mmol/L End: 8.97 mmol/L Change: +0.28 mmol/L |
Fasting blood glucose There were no significant differences in fasting blood glucose concentrations |
| (ii) 10% of total energy hazelnuts FBG Baseline: 8.10 mmol/L End: 8.04 mmol/L Change: −0.06 mmol/L | |||||
| Michels et al., 2018 [56] | Single intervention | 32 (10 M, 22F F) healthy, non-frequent nut consumers, Vit E intake <10 mg a-tocopherol/d, no Vit E supplements in previous 12 months | 16 weeks | (i) Baseline FBG: 5.67 mmol/L Fasting insulin: 48.6 pmol/L |
Significant reduction in plasma FBG (−3.4%, p = 0.03) after 16 weeks consuming 57 g/day hazelnuts. There was no significant change in fasting insulin. |
| (ii) Hazelnuts, dry roasted (~57 g/day) FBG: 5.5 mmol/L Fasting insulin: 49.8 pmol/L | |||||
| Orem et al., 2013 [57] | Double control sandwich model intervention | 21 (18 M, 3 F) Hyper-cholesterolaemic | 4 weeks | (i) 4 week no-nut (Control I) diet FBG: 5.22 mmol/L Fasting insulin: 42.6 pmol/L HOMA-IR: 1.69 |
There was no significant difference in FBG, fasting insulin, or HOMA-IR between treatments. |
| (ii) 4-week hazelnut-enriched diet (49–86 g/d (18–20% TER)) FBG: 5.11 mmol/L, Δ: −1.52% Fasting insulin: 45.6 pmol/L, Δ: +14.7% HOMA-IR: 1.78, Δ: +13.1% | |||||
| (iii) 4-week no-nut (Control II) diet FBG: 4.89 mmol/L, Δ: −3.51% Fasting insulin: 37.8 pmol/L, Δ: −11.9% HOMA-IR: 1.39, Δ: −12.7% | |||||
| Santi et al., 2017 [58] | Double control sandwich model intervention | 24 (14 M, 10 F) Healthy BMI > 19 kg/m2, <30 kg/m2 |
6 weeks | (i) 2-week ‘standard’ diet FBG: 4.79 mmol/L |
There was no significant difference in FBG between treatments. |
| (ii) 6-week 40 g raw hazelnut FBG: 4.76 mmol/L | |||||
| (iii) 6-week ‘standard’ diet ‘washout’ FBG: 4.77 mmol/L | |||||
| Tey et al., 2017 [49] | Randomised Crossover 2 treatments |
72 (24 M, 48 F) Aged 18 years and above |
4 weeks | Fasting blood glucose Baseline: 4.82 mmol/L (i) Raw hazelnuts (30 g/d): 4.80 mmol/L Change: −0.02 mmol/L |
There was no significant difference in fasting blood glucose between the treatments. |
| Baseline: 4.82 mmol/L (ii) Dry roasted, lightly salted hazelnuts (30 g/d): 4.81 mmol/L Change: −0.01 mmol/L | |||||
| Yilmaz et al., 2019 [50] |
Randomised Parallel 4 treatments |
37 (0 M, 37 F) Hyperlipidaemia, Obese |
6 weeks | Fasting blood glucose Baseline: 5.23 mmol/L (i) Hazelnuts (50 g/d): 5.18 mmol/L Change: −0.05 mmol/L |
There was no significant difference in fasting blood glucose between the treatments. |
| Baseline: 5.16 mmol/L (ii) Raisins (50 g/d): 5.64 mmol/L Change: +0.48 mmol/L | |||||
| Baseline: 5.33 mmol/L (iii) Hazelnuts (50 g/d) and Raisins (50 g/d): 5.17 mmol/L Change: −0.16 mmol/L | |||||
| Baseline: 5.26 mmol/L (iv) Control (Cardioprotective diet): 5.47 mmol/L Change: +0.21 mmol/L | |||||
To convert mmol/L blood glucose to mg/dL, multiply mmol/L by 18. Abbreviations used: F, female; FBG, fasting blood glucose; HbA1c, glycated haemoglobin; HOMA-IR, homeostasis model-insulin resistance; iAUC, incremental area under the curve; M, male; NR, not reported; PP, postprandial; PPBG, postprandial blood glucose; TER, total energy requirement. All values are arithmetic means unless otherwise stated. a p < 0.05 only for those which reported within-group change.