A recent study conducted in the United Kingdom looked at the impact that fruit and vegetable consumption has on overall risk of death, as well as risk of cancer and cardiovascular disease. Importantly, this study also looks at the impact of fruits and vegetables separately, to see which is associated with the greatest reduction of risk. It also examines the impact of specific types of vegetables and fruits. Moreover, this study has the advantage of looking at a nationally representative population, and can take into account the impact of fruits and vegetables independently of other factors such as class and physical activity.
A number of studies have shown positive health impacts of fruits and vegetables, but many of these examine individuals like physicians and nurses, who are likely to be health conscious. Recently, concerns have been raised about studies that do not use a nationally representative population, which reflects the composition of a population as a whole. This could be because the amount and types of vegetables and fruits may differ in individuals who are more health-conscious, or because other lifestyle factors of a group that is more health-conscious than the general population could affect the impact of fruits and vegetables. A major advantage of this study is that it includes 65,226 individuals from a nationally representative sample in the United Kingdom. With so many participants, it is possible to statistically control for a wide range of other factors that could be associated with fruit and vegetable consumption. In analyzing this data the researchers were able to control for age, sex, social class, education, body mass index, alcohol consumption, and physical activity.
The participants in this study were adults above the age of 35, and the majority of them began the study between 2001 and 2008.When they entered the study, each participant was interviewed about their food consumption habits, as well as a number of demographic questions and information about their health behaviors. Additionally, some medical measurements were taken and blood was collected. The dietary questions asked about all vegetables, as well as about salads separately. Fruit was broken by type, into fresh, dried, canned/frozen, and fruit juice/smoothies.
At the time this analysis was done, there were 4,399 deaths in this group of participants (6.7 percent of the total). Of these, 1,398 were due to cancer and 1,554 were due to cardiovascular disease. Other characteristics of interest in this population are that the average age of participants was 57, 56 percent were female, 21 percent were current smokers, and 48 percent had never smoked.
As for fruits and vegetables, the average number of portions of fruit was 2.3 per day, and 1.5 portions of vegetables per day. Those individuals who consumed more fruits and vegetables were more likely to be older, more likely to be women, and more likely to hold a degree, as well as being less likely to smoke. Those who ate more vegetables and fruits were also more likely to have increased physical activity. However, when the researchers examined the impact of fruit and vegetable consumption, they statistically took these factors into account, in order to attempt to separate out the unique contribution of fruit and vegetable consumption on risk of overall death, as well as risk of death from cancer and cardiovascular disease.
When they conducted the analysis on the impact of fruits and vegetables, the researchers found that individuals who ate more than seven servings of fruits and vegetables a day had a 45 percent lower risk of death than those who ate less than one portion a day, even when levels of physical activity were taken into account. There was a 25 percent reduction in risk of cancer, and a 31 percent reduction in risk of cardiovascular disease.
Turning to the relative contribution of fruits compared to vegetables, this study showed that vegetable consumption had a greater health benefit than fruit consumption. The consumers of three or more servings of fruit per day had a 14 to 16 percent lower risk of death, while those individuals who consumed three or more servings of vegetables had a 32 percent lower risk of death. While higher vegetable consumption was significantly associated with a lower risk of death from cancer (24 percent) and cardiovascular disease (22 percent), the association of fruit with deaths from these causes was not statistically significant.
When they looked more closely at the types of fruit and vegetable consumed, the researchers examined the decrease in risk of death for each portion of the food eaten per day. A portion of vegetables was associated with a 16 percent reduction in risk, and a portion of salad was associated with a 14 percent reduction in risk. A portion of fresh fruit showed a 6 percent reduction in risk of death, while a portion of dried fruit showed a 12 percent reduction of risk. Interestingly, for each portion of canned/frozen fruit, there was a17 percent increase in risk of death. Since the data collection did not distinguish between frozen and canned foods, it is not clear which of these is most responsible for this increased risk. The researchers propose that this increased risk may be due to the higher sugar content in canned fruits, or it may be due to other unmeasured factors related to having less access to fresh groceries.
Lastly, the researchers noted that although the majority of adults in the study knew that they were recommended to eat more than five servings of fruits and vegetables a day, the average number of vegetables and fruits consumed per day was only 3.8 servings. They also noted that even among individuals who perceived their diet as “very healthy”, over 50 percent ate less than five portions of fruits and vegetables a day. In light of all of these findings, the researchers suggested that policy makers need to consider broader initiatives to promote fruit and vegetable consumption. They also suggest that instead of lumping together fruits and vegetables, vegetable and salad consumption in particular should be encouraged.
Oyebode O, Gordon-Dseagu V, Walker A, et al. Fruit and vegetable consumption and all-cause, cancer and CVD mortality: analysis of Health Survey for England data. Journal of Epidemiol Community Health. (2014). DOI: 10.1136/jech-2013-203500