Updated: Jul 21
In the continuation of our last discussion on "consuming fruit juices", I bring to you an analysis of a brand new study on the "effect of a fruit-rich diet on liver biomarkers...". It studied impact of fruit consumption in excess of four servings per day i.e (≈300gms of fruit per day) on liver enzymes, steatosis (fat deposition in liver), insulin resistance, waist circumference etc in patients who had NAFLD (non-alcoholic fatty liver disease).
This is a fascinating study because in the past, we've had multiple studies but often those studies were confounded by other factors which were not accounted for such as difference in weight, caloric intake, vegetable intake, physical activity during the study, so you're never sure how much of an impact fruit alone had on the outcome. In contrast, this study does a good job of eliminating other factors as best as it could. Let's jump into the key takeaways:
Participants were divided into two groups : intervention group (FRD) were put on a fruit-rich diet (> 4 servings/day) whereas control group was put on a low fruit diet (< 2 servings/day)
At the end of six months, FRD group had significantly higher level of TG (triglycerides), BMI, waist circumference, liver enzymes (ALT, AST, ALP, GGT) and low HDL compared to baseline level, whereas all these parameters improved in control group compared to baseline levels.
FRD group also developed higher degree of insulin resistance, higher blood glucose and insulin compared to control group.
Frequency of severe and moderate steatosis (liver-fat deposition) was significantly higher in FRD group. FRD group also had a large liver at the end of the study compared to that of control group.
After adjusting for physical activity, BMI, and caloric intake, no significant difference was observed in the results. It means that the outcome is more likely to be due to increased fruit intake.
Grade of steatosis pre and post study
Liver size pre and post study
Now, before you start drawing over-arching conclusions and begin to stress about your fruit intake, let's also look at what this study DOESN'T show or prove:
Fruit is inherently bad irrespective of existing metabolic health
Fruit, in excess of four servings per day, causes NAFLD
Fruit, in excess of four servings per day, causes insulin resistance
In other words, this study cannot be extrapolated to healthy people. The participants in this study had pre-existing NAFLD since 3.53 years on an average. This study doesn't prove or suggest that fruit in any quantity is bad for healthy people.
Nonetheless, findings of this study are applicable to a large number of people who have liver disease, diabetes or insulin resistance. Sadly, majority of people fall in that bucket.
Mechanism behind these outcomes has to do with fructose in fruit. "Fruit consumption may play a more important role in the accumulation of fats in the liver in FRD group due to the lipogenic potential of fructose which can downregulate the fatty acids oxidation compared to the glucose. There is an evidence that fructose leads to a greater increase in liver fat content than glucose".
If you have liver disease, diabetes or other comorbidities and/or are trying to lose weight, limit your fruit intake to less than three servings/day.
Besides restricting fruit, focus on improving your lifestyle. We have much stronger evidence than this study that exercise is a very powerful remedy against modern chronic disease including NAFLD.
Cut your alcohol intake to zero.
If you are healthy, you don't need to restrict fruit because of it's potential benefits provided you don't consume processed foods, sugary smoothies in the name of fruit. Three to five servings are probably a sweet spot.
There may be a genetic component that decides how much fruit can you safely tolerate. To find that out, track your biomarkers like uric acid, liver enzymes, insulin resistance. That's the approach I follow with my clients and for myself.
Fruit is a very heterogenous group of food. Different fruit may vastly differ in the amount of fructose they contain. Refer below image for reference. As you may notice, dried fruit is very very high in sugar (hence fructose) and should be avoided by those with pre-existing metabolic health issues.
Image taken from Peter Attia Website