The study, released Monday evening in the Journal of Epidemiology and Community Health, found that at any point over that period, people who ate seven or more portions of fruits and vegetables dropped their risk of death from cancer by 25 percent and from cardiovascular disease by 31 percent.
Consumption of vegetables and salad proved to have a greater "protective effect" than eating fresh fruit, and consuming canned fruits actually increased the statistical risk of death, according to the researchers at University College London. Fruit juices had no effect at all.
More remarkably, the researchers said they were able to quantify the health benefits per portion of fruits and vegetables consumed. One to three portions daily reduced the chance of death from any cause by 14 percent, three to five portions had a 29 percent impact, five to seven portions dropped the chances by 36 percent and seven or more portions produced a 42 percent decline in the risk of death. The benefits appeared to tail off at that level.
The study concluded that each daily portion of fresh vegetables reduced the overall risk of death by 16 percent. For salad, the benefit was 13 percent, and for fresh fruit it was 4 percent.
A news release issued by the university said the study is the first to quantify health benefits per-portion. In the study, however, the researchers were cautious to make clear that "this study has found a strong association, but not necessarily a causal relationship" between fresh fruit and vegetable intake and declining mortality. "There are additional unmeasured confounders not included in the analyses, including other aspects of diet. Total energy intake and salt consumption were not measured, and assessment of fat intake was not made in most years, and were therefore not included in these analyses," the authors wrote.
They also noted that the results are based on people's own reports of their eating habits, rather than observed data.
Nevertheless, the findings appear to provide strong support for increased consumption of vegetables and fruits that governments around the world, as well as the World Health Organization, have promoted for years.
“We all know that eating fruit and vegetables is healthy, but the size of the effect is staggering,” Oyinlola Oyebode, the study's lead researcher, said in a prepared statement.
The results take into account sex, age, cigarette smoking, social class, Body Mass Index, education, physical activity and alcohol intake. They did not count deaths that occurred within a year of the food survey. The researchers also noted that fruit and vegetable consumption is inversely related to household income.