One of the most controversial topics when it comes to sugar consumption is juice. I am still not sure what to believe in. Here I am not talking about the obvious: sodas and artificial drinks are, for me, bad for you by default. No. I am talking about fruit and vegetable juices, and in particular 100% fruit and vegetable juices.

When I look into the subject, I can’t always tell if people are talking about juice you can buy or juice you can make yourself. For instance, the NHS recommendation is for no more than 150ml of juice or smoothie a day, but when they mention that even the unsweetened ones have lots of sugar, it makes me wonder if they are not talking about commercially-available ones. In a policy statement issued by the American Academy of Pediatrics, the authors recommend in between4 ounces (118 ml) and 1 cup (250 ml) a day, depending on age. This explicitly includes juice that you can buy, though the recommendation is for 100% fruit juice only.

A study published in volume 38 of “Nutrition” in 2017 showed that consuming 100% orange juice every day was not detrimental to the subjects’ weight loss efforts. The study was conducted on 78 obese patients with comparable BMIs and body fat percentages. All of them were put on individualised reduced calorie diets, but half of them were given 100% orange juice as a snack twice a day (250 ml for each snack, so 500 ml a day), the second half would have a calorie-equivalent snack from “food groups” (p. 14), whatever that may be. The results showed no significant difference between the weight loss registered by either half of the subjects (though the group not drinking the juice had a slightly greater reduction in weight, BMI, and waist circumference), leading the scientists to conclude that the consumption of 100% orange juice does not hinder weight loss efforts. In fact, there was an improvement in biochemical biomarkers in the subjects who drank the juice daily.

I do have one question that the study did not address: what was the calorie-equivalent snack of the other half of the subjects? For instance, if they were to eat a rice waffle – low in calories, but also low in nutrients and highly processed – it would hardly be a surprise that those foods do not have a positive effect on blood sugar levels or cholesterol or anything else. A more interesting question to answer would have been if the group not getting juice were to eat the fruit instead. Would the results have been the same? Would the juice group still have shown improved blood sugar, cholesterol and insulin levels? Or would eating the fruit have proven to yield better results for the weight loss and health improvement efforts?

The authors of the study give an approximate answer as to calorie count influencing weight loss, as they have shown that reducing the calories in the subjects’ diets did have a positive impact, no matter what the calories were made of. This, however, was by all means not a tremendous find. I think this is something that anyone would expect to happen. But there is no attempt to answer whether fruit juice is worse or better for the body than eating the fruit itself.

I also have a bit of a problem with the premise of the study, namely that studying the effects of a reduced-calorie diet, with or without orange juice, can say anything about whether orange juice consumption is linked to weight gain. Here is the objective of the study, as summarised in the abstract:

“Assumptions have linked orange juice (OJ) consumption with weight gain and adverse effects on health due to its sugar content; however, epidemiologic studies have not shown increased risk for overweight or obesity with the consumption of 100% OJ. The aim of this study was to verify whether the combination of a reduced-calorie diet (RCD) and 100% OJ contribute to weight loss, promote changes in glucose and lipid metabolism, and improve diet quality in obese individuals.”

The authors say that there was a lack of studies in the areas of OJ and weight loss, which might have helped them get funding for it (including from the company providing the orange juice for the study), but my question still stands: how does that say anything about orange juice and weight gain? Saying that orange juice does not hinder weight loss in reduced calorie diets is not the same thing as saying that orange juice is not linked to weight gain. While both statements may be true, they are not linked from a logical point of view, and the study does nothing to address the latter. I feel that, in order to prove that orange juice does not contribute to weight gain, you shouldn’t study it in connection to a diet aimed at weight loss, it should be studied in connection with normal eating habits, by which I mean letting people eat what they normally eat, while some can have orange juice and the others cannot. Otherwise, it is impossible to tell whether these results only apply to obese people, only to people on a reduced calorie diet, or anyone, irrespective of their body weight and diet.

At the end of the article, the authors say that the amount of orange juice given to the participants, although greater than the 8 ounces recommended by the Dietary Guidelines for Americans, “does not seem detrimental”. This is another sophism. The fact that a given amount is not detrimental for obese people on a diet does not also mean that it will not be detrimental for people with a healthy weight. Compared to the poorer diet that participants had before the study, the 16 ounces of orange juice may have been a tremendous improvement anyway. This should not be considered, or even just implied, to be a new guideline that can be applied to everyone and anyone.

I do agree that the study is a step forwards, as it is important to show that orange juice does not hinder a weight loss programme for obese people. It is of even more consequence that the consumption of orange juice can have positive effects on biochemical biomarkers for them. But the study is a small step forwards. What is needed is to also show whether orange juice is beneficial outside a weight loss programme as well; whether fruit in juice form is better, worse or the same as eating the fruit itself; whether it is just orange juice that is beneficial, or any other 100% fruit or vegetable juice. No, one study need not answer every question there is, but it would have been nice to acknowledge this at the end and make recommendations for further studies. Instead, the only limitations that the authors acknowledge are the midterm follow-up of those drinking orange juice and the lack of blindness of participants. No recommendations for future research are made. And this is why I lament the faulty logic and the context of the study. Had I seen more openness about the limitations of both the study itself and the implications it has on the larger context of fruit juice consumption and its links to obesity, I might have had a better opinion of it. But as it stands, the study is not a great contribution to either science or everyday life.