Eat your fruits and vegetables. We have all heard this saying before, and fruit consumption has long been advocated as a nutrient source full of vitamins, fiber, and antioxidants. One the other hand, there are health circles that caution against consuming excessive fruit because of its high sugar content, especially fructose. Similarly, nuts are regarded as an excellent source of “healthy” fats, minerals, and fiber among some, and a harmful brew of anti-nutrients and “bad” fats (referring exclusively to linoleic acid) by others.
The question remains, what actually happens when healthy individuals drastically increase their consumption of either. We can argue back and forth about the hypothetical outcomes all we want and never make progress, which is why Agebratt et al recruited 30 university students to supplement their diets with 7 kcal per kg of bodyweight of fruit or nuts every day for 2 months. Blood samples, nutritional intake, activity levels, metabolic rate, body composition, and liver fat were assessed before and after the intervention to finally put an end to the bickering.
Consuming an extra 7 kcal/kg bodyweight of fruits and nuts is no small feat. For a person weighing 165 lbs (75 kg), this would correspond to eating about 2 lbs (1 kg) of apples and 3 ounces of almonds daily. Importantly, no particular instructions were given for what food to eat during the intervention, although the fruit and nuts were recommended to be consumed between the regular meals and the fruit had to be fresh and not processed.
Accordingly, there was some diversity in the food choices. The most commonly eaten fruits were bananas (38.7%), apples (19.4%) citrus fruits (14.8%), pears (8.2%), melons (3.9%), grapes (3.2%), and mangos (3.0%), and the most commonly eaten nuts were cashews (47.4%), peanuts (14.1%), walnuts (8.1%), almonds (8.0%), pistachios (7.8%), hazelnuts (5.8%), and Brazil nuts (3.5%).
Acknowledging the limitations of weighted 3-day food logs, it does appear that eating extra fruit was more difficult than eating extra nuts. This is because reported caloric intake from nuts increased to a significantly greater extent (+538 kcal/day) than caloric intake from fruit (+423 kcal/day). Additionally, incorporating more fruit into the diet led to greater dietary compensation for the added calories, as total daily caloric intake remained unchanged in the fruit group despite the increase in fruit calories, whereas it increased significantly in the nut group by about 10%. As for the demon-spawn fructose, it increased 3-fold in the fruit group and halved in the nut group.
Eat more, gain more
Whereas the dietary data may be prone to human error (memory or otherwise), the scale doesn’t lie. Both groups showed a similar amount of weight gain, amounting to about 1.5 lbs. Interestingly, this was despite the fruit group showing a trend for reduction in energy expenditure from physical activity, while the nut group showed a significant increase in basal metabolic rate (+5%, ~100 kcal).
Looking at the individual data presented in figure 2 above, I have to wonder what characteristics predicted the BMR response to the interventions. Two participants in the nut group showed an astonishing 20% increase in BMR, whereas two participants in the fruit group showed a 20% reduction and two others showed a 20% increase. Why? If anything, it certainly speaks to the notion of individuality when discussing dietary changes.
Liver fat and blood biomarkers
There were no changes in the liver fat content in either group, nor were there changes in visceral fat, subcutaneous fat, and intramuscular thigh fat. There were also no changes in blood lipids, except that the nut group showed a trend for reduction in total cholesterol. The fruit group did show a significant reduction in HbA1c, as well as a significant increase in fasting insulin. However, these changes were small enough to not be of clinical concern (e.g. fasting insulin increased by ~ 1 pmol/L, from 7.73 to 8.81 pmol/L).
Nuts supply a considerable amount of vitamin E, whereas fruit supplies many different carotenoids. Yet, there were no changes in serum carotenoid status in either group except for a significant reduction in beta-carotene in the nut group. As for vitamin E, alpha-tocopherol showed a significant increase in the fruit group and trend for reduction in the nut group, while gamma-tocopherol showed a trend for increase in the nut group.
Splurge on fruit or nuts and not much will change
There are several limitations to the current study, with the most notable being the small sample size of only healthy, normal-weight, physically active (12,000 steps/day) individuals. As such, we are constrained to this type of person when making inferences. That being said, the conclusion is pretty straight forward. Binge on a ton of nuts or fruit every day for 2 months and not much will change.
I really want to emphasize this point for everyone who still has a bone to pick with fructose. Eating roughly 2 lbs of fruit daily for 2 months did not significantly affect liver fat or blood lipids, despite leading to a 3-fold increase in daily fructose consumption. These findings support the largest meta-analysis to date that found no uniquely detrimental impact of fructose on blood lipids when compared to other carbohydrates.
I’m sure there are plenty of reasons for why no effect was observed. One could argue the dose was too low (25 g) or that the mode of delivery was unrealistic (~2 lbs of fruit), but these only serve to support the notion that fruit shouldn’t be discounted because of its sugar content. And yes, clearly the study participants are another reason for the findings. I have previously written about how physical activity, both as exercise and walking daily, offset the negative effects of giant sugar boluses.
The takeaway is simple, if you are a healthy and active individual, then enjoy your fruit and nuts.