A Randomized Study of the Effects of Additional Fruit and Nuts Consumption on Hepatic Fat Content, Cardiovascular Risk Factors and Basal Metabolic Rate

Abstract

Background: Fruit has since long been advocated as a healthy source of many nutrients, however, the high content of sugars in fruit might be a concern.

Objectives: To study effects of an increased fruit intake compared with similar amount of extra calories from nuts in humans.

Methods: Thirty healthy non-obese participants were randomized to either supplement the diet with fruits or nuts, each at +7 kcal/kg bodyweight/day for two months. Major endpoints were change of hepatic fat content (HFC, by magnetic resonance imaging, MRI), basal metabolic rate (BMR, with indirect calorimetry) and cardiovascular risk markers.

Results: Weight gain was numerically similar in both groups although only statistically significant in the group randomized to nuts (fruit: from 22.15 ± 1.61 kg/m(2) to 22.30 ± 1.7 kg/m(2), p = 0.24 nuts: from 22.54 ± 2.26 kg/m(2) to 22.73 ± 2.28 kg/m(2), p = 0.045). On the other hand BMR increased in the nut group only (p = 0.028). Only the nut group reported a net increase of calories (from 2519 ± 721 kcal/day to 2763 ± 595 kcal/day, p = 0.035) according to 3-day food registrations. Despite an almost three-fold reported increased fructose-intake in the fruit group (from 9.1 ± 6.0 gram/day to 25.6 ± 9.6 gram/day, p<0.0001, nuts: from 12.4 ± 5.7 gram/day to 6.5 ± 5.3 gram/day, p = 0.007) there was no change of HFC. The numerical increase in fasting insulin was statistically significant only in the fruit group (from 7.73±3.1 mIE/L to 8.81±2.9 mIE/L, p = 0.018, nuts: from 7.29±2.9 mIE/L to 8.62±3.0 mIE/L, p = 0.14). Levels of vitamin C increased in both groups while α-tocopherol/cholesterol-ratio increased only in the fruit group.

Conclusions: Although BMR increased in the nut-group only this was not linked with differences in weight gain between groups which potentially could be explained by the lack of reported net caloric increase in the fruit group. In healthy non-obese individuals an increased fruit intake seems safe from cardiovascular risk perspective, including measurement of HFC by MRI.

Trial registration: ClinicalTrials.gov NCT02227511.

Fig 1. Flow chart of the study.

Fig 2. Individual changes of basal metabolic rate in the groups randomized to consume extra fruit or extra nuts.

The basal metabolic rate measured by indirect calorimetry increased in the nut group only (fruit group: from 1787 ± 278 kcal/24h to 1845 ± 240 kcal/24h, p = 0.26, nut group: from 1931 ± 221 kcal/24h to 2031 ± 294 kcal/24h, p = 0.028).