It is also worth noting that the glycaemic index (GI) and load of 100%OJ are lower than that seen in a typical SSB with an equivalent sugar content. This may be due to the presence of pectin or a Data from food tables unless stated; b calculated from glycaemic index and portion sizes of 250 ml for 100%OJ and 330 ml for SSB. bioactive compounds. International GI tables state that 100% apple juice has a GI of 41, while 100%OJ has a GI of 50 – both categorised as ‘low’.
BEST TO DRINK FRUIT JUICE WITH MEALS?
A second new randomised crossover trial from Germany considered the most favourable time to drink 100%FJ from a metabolic perspective. 26 healthy adults were given a supply of 100%OJ to drink for 2 weeks, either between meals or with meals, i.e. 3 times a day. After this, there was a 1-week washout period before switching to the alternative condition. During the study, other citrus juices were not permitted.
Once again, the amount of 100%OJ consumed was equivalent to 20% of calculated daily energy requirement which was an average intake of 1.3 l per day, including 112 ±19 g per day of natural sugars. This is more than ten times higher than typical intakes in Europe.
The results revealed that drinking 100%OJ with a meal led to a small net decrease in average fat mass of -0.3 kg (p<0.05) while between meal consumption led to a modest net increase in average fat mass of 1.0 kg (p<0.05). Interestingly, the additional energy provided by the 100%OJ equated to 7700 kcal over 2 weeks which would have theoretically increased fat mass by 855 ±150 g. Clearly, in the case of ‘with meal’ consumption, this theoretical increase in fat mass did not materialise.
Insulin sensitivity, measured by HOMA-IR and Matsuda index, did not differ significantly after either intervention. Neither were differences seen in daylong glycaemia, insulin secretion, change in basal insulin sensitivity or triglyceride levels (all p>0.05). However, a liver function marker (gamma-glutamyl transferase) was significantly lower after the ‘with meal’ condition indicating a more favourable liver function.
This challenges the view that fructose in 100%FJ adversely affects liver function. The authors concluded that a conventional 3-meal structure served with 100%OJ had a more favourable impact on energy balance and fat mass than between-meal consumption. However, it should be noted that this study was short-term (2 weeks) and used excess intakes of 100%FJ. The results, therefore, need to be confirmed in studies using more typical intakes (150-250 ml).
100%FJ COMPARED WITH OTHER DRINKS
A small number of previous studies have compared 100%FJ with control beverages (typically sweetened) in terms of type 2 diabetes risk, bloof lipids or weight gain. A meta-analysis of 4 cohorts of adults found that consumption of fruit juices with added sugars was significantly associated with an increased risk of type 2 diabetes (RR=1.28) while consumption of 100%FJ was not associated (RR=1.03, p=0.62). For regulatory reasons, 100%FJ never contain added sugars. In a randomised, single-blinded, placebo-controlled clinical study, 36 overweight healthy participants received either 250 ml daily of 100%OJ or sweetened flavoured water for 12 weeks. Compared with the control, 100%FJ had no significant impact on fasting blood glucose and insulin sensitivity markers, suggesting that 100%FJ have a neutral effect overall on markers of glycaemic control. Nor did 100%FJ have any adverse effects on blood lipid profile.
Another study on blood lipids recruited adults with elevated or normal cholesterol levels to drink either 750 ml daily of 100%OJ from concentrate for 60 days versus a ‘no juice’ control. Low density lipoprotein cholesterol was significantly reduced by the end of the trial amongst those subjects with elevated cholesterol levels at baseline, whilst high density lipoprotein cholesterol was raised. These findings suggest that 100%OJ may facilitate free cholesterol transfer to high density lipoprotein cholesterol, which is a favourable effect in terms of normal heart health.
There is a belief that 100%FJ contribute to weight gain, despite a lack of support from high quality intervention studies. In a recent trial, 78 obese people were randomised to drink 500 ml daily of either 100%OJ or a control drink over 12 weeks as part of an energyreduced diet. Both groups lost similar amounts of weight, despite one group consuming high intakes of 100%OJ. In addition, vitamin C and folate intakes increased by 62% and 39% respectively in the 100%OJ group, but not in the control group. Daily energy intakes were unaffected by the drinks, suggesting energy compensation. Significant improvements in insulin and lipid profiles were seen in the 100%OJ group relative to the control.
These findings support other meta-analyses of randomised controlled trials, which have found a neutral impact of regular 100%FJ consumption on long-term glycaemic control, even at intakes of 400 ml daily.
EXPLAINING THE DIFFERENCES
As discussed, the nutritional composition of 100%FJ is markedly different to that of SSB. Whilst sugar and, thus, energy levels are similar, the micronutrient composition is far richer in 100%FJ. In the cases of potassium, vitamin C and folate, levels in 100%OJ are such that on-pack ‘source’ claims can be made.
100%OJ also contains bioactive flavanones such as hesperidin and narirutin, which have been associated with health effects. Polyphenol compounds in 100%FJ have been proposed to have an important role in glucose-insulin regulation by inhibiting glucose absorption, stimulating insulin secretion and glucose uptake by cells, and modulating cell signalling pathways as well as gene expression.
Bioactive constituents in 100%OJ have been linked with other health effects. For example, in an 8-week trial[x] volunteers drank 100% red OJ (high in lycopene) daily. Compared with the control group, 100%OJ intake led to statistically reduced blood pressure and insulin resistance