It has been established that the consumption of fruits and vegetables is important in reducing the risk of mortality from illnesses such as cardiovascular disease, but results between different studies have lacked consistency when it comes to the ideal amount to be consumed.
Different countries recommend different amounts to be consumed by the public. For example, while the US government have advocated consuming five portions of fruits and vegetables every day, the Australian government recommend eating five portions of vegetables and two portions of fruits.
A study that was published in the Journal of Epidemiology and Community Health earlier in the year suggested that people should be eating seven portions of fruits and vegetables every day. These findings conflict with new research, however, conducted by a team of researchers based in China and the US.
Five portions or seven?
The American Cancer Society recommend including fruits and vegetables in every meal and for snacks.
The team performed a meta-analysis of 16 cohort studies, examining the data of 833,234 participants - which included 56,423 deaths - and adjusted the findings to take into account differences in study design and data quality.
After bias was minimized in this manner, the researchers found that a higher consumption of fruits and vegetables was associated with a significantly lower risk of death from all causes, and in particular cardiovascular disease.
There was a 5% average reduction in the risk of death from all causes and a 4% reduction in the risk of death from cardiovascular disease for each additional daily portion of fruit and vegetables that was consumed.
In contrast with the study published in the Journal of Epidemiology and Community Health, however, the researchers noted that after five servings of fruits and vegetables, additional portions did not affect the risk of death in any significant way.
The authors also did not see higher consumption of fruits and vegetables having much of an effect on reducing the risk of cancer. The authors say that, in light of this, "the adverse effects of obesity, physical inactivity, smoking, and high alcohol intakes on cancer mortality should be further emphasized."
Results 'support current recommendations'
The authors say that further studies will need to look more closely at specific types of cancer and the role of different groups of fruits and vegetables in affecting mortality for different causes. They also write that further studies are needed to confirm their finding of a five-a-day threshold in reducing mortality.
This is in part due to limitations in their analysis. Their findings may have been influenced by imprecise measuring of consumption due to reliance on food frequency questionnaires in most of the studies utilized.
As well as this, the cohort studies did not take into account other dietary factors such as the consumption of saturated fat or processed meat, which may have also had an impact on mortality rates.
At present, the American Cancer Society (ACS) recommend that adults eat at least 2.5 cups (5 portions) of fruits and vegetables every day, placing an emphasis on variety and the importance of whole fruits and vegetables, such as drinking pure fruit juice rather than drinks from concentrate.
The ideal amount of fruits and vegetables to be consumed daily may still be very much up for debate, but, according to the authors, "the results support current recommendations to increase consumption of fruits and vegetables to promote health and longevity."
Recently, Medical News Today reported on a study that suggested a vegan, low-carbohydrate diet could reduce the risk of heart disease.