Background: New Zealand blackcurrant extract has been shown to enhance exercise-induced fat oxidation during walking and cycling. We examined the effects of 14-day intake of New Zealand blackcurrant extract on the metabolic and physiological responses during supine rest in males.

Methods: Healthy physically active males (n=16, age: 24±6 yr, body mass: 78±16 kg, height 178±6 cm, BMI: 24.7±4.1 kg·m-2 (8 normal weight, 7 overweight, 1 obese), body fat: 15±6%) volunteered. Participants were tested at baseline (no supplementation) and after 14-days intake of New Zealand blackcurrant extract in a randomized, crossover design. Two capsules of New Zealand blackcurrant extract (600 mg containing 210 mg of anthocyanins) were consumed every morning with breakfast. The last 2 capsules were taken two hours before the visit with one slice of bread and water 3 hours before the visits. There were no differences for carbohydrate, fat, and protein intake between the visits. Resting expired air was collected for two times for 10 min with Douglas bags and recording of heart rate. Rates of whole-body resting fat and carbohydrate oxidation were calculated. Responses for the 10 min with the lowest minute ventilation were analysed.

Results: During supine rest, there was no effect on heart rate (baseline: 61±10, 14-day: 61±10 beats·min-1, P=0.96), minute ventilation (baseline: 8.10±1.43, 14-day: 7.82±0.98 L·min-1, (P=0.38), oxygen uptake (baseline: 0.293±0.060, 14-day: 0.285±0.057 L·min-1, P=0.43), carbon dioxide production (baseline: 0.245±0.051, 14-day: 0.233±0.041 L·min-1, P=0.24) and energy expenditure (baseline: 1.49±0.30, 14-day: 1.44±0.27 kcal·min-1, P=0.33). Lower respiratory exchange ratio (baseline: 0.840±0.045, 14-day: 0.820±0.058, P=0.03), higher fat oxidation (baseline: 0.078±0.031, 14-day: 0.088±0.043 g·min-1, P=0.05), and lower carbohydrate oxidation (baseline: 0.168±0.062, 14-day: 0.134±0.066 g·min-1, P=0.03) were observed with 14-day intake of New Zealand blackcurrant extract during supine rest. Twelve participants (75%) had higher fat oxidation during supine rest with for those an increase of 21±17%.

Conclusions: Whole-body fat oxidation during supine rest was enhanced by 14-day intake of New Zealand blackcurrant extract in males. Enhanced whole-body resting fat oxidation may be due to combined effects of an increase in lipolysis, an increase in blood flow, and increased metabolic handling of fatty acids in the muscle. Our observations on resting substrate oxidation in the present study may indicate that New Zealand blackcurrant extract has application for weight management. However, the dosing strategy to maximize whole-body resting fat oxidation with intake of New Zealand blackcurrant extract is not known.

Acknowledgements: Supplementation was provided by Health Currancy Ltd (United Kingdom) and CurraNZ Ltd (New Zealand). Financial support for conference attendance was obtained from Blackcurrant New Zealand Inc (New Zealand).