Not too long ago I wrote a post compiling the latest studies and reviews on the intake of vegetables and fruits and health, especially aimed at trying to find out the evidence on the ideal amount of this food group. From the data it could be deduced that there was strong and clear evidence of an increasing positive relationship for an intake of up to three servings per day. From that amount and up to five daily servings, the favorable relationship continued to exist, but it was less clear and its growth was also much less pronounced. And at that time I couldn’t find any solid evidence that eating more than 5 servings of fruit and vegetables a day was especially beneficial.
However, from some sources it is often insisted that dietary recommendations in this regard should suggest “at least” five servings of vegetables and fruit. Something with which I do not agree too much, considering the results that I summarized in that post and that showed that there is no solid data to make claims about health beyond five daily servings. In addition, as I also explained in that post, I also did not find evidence to prioritize fruit over vegetables, something that is also often done in some guidelines.
To complete all this information, just a few days ago a new meta-analysis on the subject was published, analyzing the relationship between the amount of vegetables and fruits in the diet and various types of mortality. This is the research “Fruit and Vegetable Intake and Mortality: Results From 2 Prospective Cohort Studies of US Men and Women and a Meta-Analysis of 26 Cohort Studies” (2021), a work published in the journal of the American Heart Association and that it is especially relevant because it is based on a huge amount of data (26 observational studies that followed almost two million people for several decades) and because it bears the signature of some of the first swords in the area of nutrition at the School of Health Harvard Public.
First of all, it should be clarified that in this study a serving refers to an amount of 80 grams of food, considerably less than the 140-150 grams per serving that is usually considered in Spain.
Well, let’s see the results, first of all visually. The following figure shows the dose response based on the calculated curves, which show the relationship between the amount ingested and various types of mortality (click to enlarge):
The first row of graphs shows the results on the total intake of vegetables and fruits, the second row on the intake of fruits and the third row on the intake of vegetables. In each of them, the approximate values at which the curves reach their minimum values can be appreciated quite well with the naked eye. But in any case, in the table-summary of the original document the authors explain it clearly:
“Higher fruit and vegetable intake was associated with lower overall and cause-specific mortality (…). The lowest risk of mortality was observed for approximately 5 servings per day, but above that amount the risk did not decrease further The mortality risk reduction thresholds were 2 daily servings for fruit intake and 3 daily servings for vegetable intake.”
And they also detail it in the abstract:
“Higher intakes of most fruit and vegetable subgroups were associated with lower mortality, with the exception of starchy foods such as peas and corn. Intake of fruit juices and potatoes was not associated with overall mortality and for specific reasons. (…) the risk reduction leveled off at about 5 servings of fruit and vegetables per day. These findings support current dietary recommendations to increase the intake of fruits and vegetables, but not fruit juices and potatoes.
In other words, the lowest mortality values were reached at around five daily servings of vegetables and fruits, distributed as 2 of fruits and 3 of vegetables, without detecting significant improvements at higher amounts. Five 80-gram servings, which would equal 400 grams in total or about three “Spanish” servings. In addition, vegetables achieve lower mortality values at higher amounts than fruits, so it seems that vegetables should be prioritized over fruits.
In short, I think that the conclusions of this study continue to confirm to a large extent the conclusions of the post I wrote: there is solid evidence to recommend a minimum of 3 “Spanish rations” (of 140 grams each) daily, some evidence to suggest going up to 5, but we don’t know what happens beyond that. Other recent large reviews, looking at other relevant health indicators, come to similar results and show the same “benefit ceiling” between 3-5 servings (1, 2, 3, 4).
Some data that should be taken into account when formalizing dietary recommendations, I think.