What is the optimal combination of fruits and vegetables for a healthy diet?
The results of a new observational study confirm most of the current dietary recommendations on fruits and vegetables. Consuming 5 servings of fruits and vegetables daily has been associated with a lower risk of death from cancer, cardiovascular disease, or respiratory disease. Starchy vegetables and fruit juices, however, did not appear to help reduce the risk.
For many decades, nutritionists have recommended a balanced diet to provide the body with the proper nutrients to maintain good health. The main elements of this diet are vegetables, fruits, cereals, proteins and dairy products.
A recent study by researchers at the Harvard School of Public Health in Boston provides additional evidence for current dietary recommendations. This study finds that consuming at least 2 servings of fruit and 3 servings of vegetables daily can reduce the risk of disease-related death and death from all causes. The study is published in Circulation, a scientific journal of the American Heart Association (AHA).
Information collected over 30 years
The researchers collected self-reported dietary information in two large cohort studies: the Nurses’ Health Study (NHS) and the Health Professionals Follow-Up Study (HPFS). The NHS cohort included registered nurses aged 30 to 55, while the HPFS cohort included men aged 40 to 75 working in a health profession.
These studies included follow-ups with participants every 2 to 4 years to accumulate dietary information over a period of about 30 years. The researchers excluded participants with heart disease, cancer or diabetes, still combining data from 66,719 women and 42,016 men.
They also incorporated data from 26 other studies involving a total of 1.9 million participants. They looked at the relationship between fruit and vegetable consumption and death rates. The high number of participants and the ongoing longitudinal evaluations provided the team with a large collection of data for analysis.
5 servings of fruits and vegetables reduce the risk of death from any cause
The results of the study showed that increased consumption of fruits and vegetables is associated with a lower risk of death. Including deaths from cancer, heart disease or respiratory disease. Additionally, the researchers found that the risk of death was lowest at a threshold of 5 combined servings, beyond which there was no apparent risk benefit.
These results highlight the nutritional value of these foods. For example, eating more fruits and vegetables increases potassium intake and antioxidant activity, which are linked to lower blood pressure and improved lung function, respectively.
As the data is entirely self-reported, there may be discrepancies between actual intakes and reported intakes. Participants with higher intakes, in particular, may have tended to overestimate the number of servings they consumed. This margin of error can blur the defined threshold of 5 portions. The study authors therefore acknowledge that slightly higher servings (up to 10) could also lead to a lower risk.
The best fruits and vegetables for your health
This study also goes beyond current guidelines by distinguishing between specific groups of fruits and vegetables.
The researchers observed trends in lower risk of death for leafy green vegetables and foods high in vitamin C and beta-carotene. Fruits and vegetables that fall into these categories include spinach, kale, carrots, and citrus fruits.
Conversely, they did not identify trends for fruit juices or starchy vegetables, such as potatoes and peas. One of the possible reasons for the latter is the prevalence of canned foods. The canning process can rob starchy vegetables of their antioxidant properties.
Whole fruit instead of fruit juice
Compared to whole fruit, the liquid form of juices may cause blood glucose and insulin levels to rise more quickly, which may increase the risk of disease. Unlike existing guidelines, which include canned foods and juices among recommended foods and beverages, this study calls for further research into the health effects of these items.
Maintaining support for the recommendation of 5 servings of fruits and vegetables per day
There is plenty of evidence that points to the benefits of a balanced diet that contains plenty of fruits and vegetables. These findings are also consistent with findings from similar observational studies on associations between fruit and vegetable consumption and disease.
The results of this study are in line with the general dietary recommendations in force, which recommend eating at least 5 servings of fruit and vegetables per day. In addition, it provides additional insight into the specifics and benefits of fruit and vegetable consumption.