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“7 a day fruit and veg 'saves lives’” reports BBC News, while The Daily Telegraph states that “10 portions of fruit and vegetables per day” is best.
The headlines have been prompted by the results of a UK-based study that used information on more than 65,000 randomly selected adults who were participating in the Health Survey for England.
This is an ongoing health survey that looks at health and lifestyle factors such as fruit and vegetable consumption. The researchers followed up participants for an average of 7.7 years after their initial participation.
The researchers found that eating fruit and vegetables was associated with a lower risk of death from any cause, looking especially at deaths as a result of cardiovascular disease and cancer. The higher a person's intake of fruit and vegetables, the greater the protective effects seemed to be.
People who ate seven or more portions a day had a 33% reduced risk of death compared with people who ate less than one portion.
This study provides further evidence of the benefits of eating fruit and vegetables. However, the study does carry limitations, with the most pertinent being that there could have been other factors (confounders) responsible for the associations seen. These could include smoking history, exercise levels and income.
Much of the media’s reporting implies that this study contradicts the official Department of Health advice about eating five portions of fruit and vegetables a day. It should be stressed that the advice in full was to eat at least five portions a day. The “5 a day” target was always meant to be a minimum target to hit, rather than the maximum.
Where did the story come from?
The study was carried out by researchers from University College London. This study was unfunded, but used information for the Health Survey for England, which was funded by the Department of Health and the Health and Social Care Information Centre. In the interests of transparency, it should be made clear that the Behind the Headlines team are employed by the Health and Social Care Information Centre.
The study was published in the peer-reviewed Journal of Epidemiology and Community Health. This article is open-access, meaning that it can be accessed for free from the journal’s website.
The results of this study were reported accurately by the UK media. However, they all reported figures for all causes of mortality, excluding any deaths that occurred in the first year of the study.
This meant that the risk of death they reported (42%) was reduced by a greater extent than when these people were included in the analysis (33%).
What kind of research was this?
This was a cohort study that aimed to assess if fruit and vegetable consumption in a group of people representative of the UK population was linked to:
- death from any cause
- death due to cancer
- death due to cardiovascular disease
A cohort study is the ideal study design to answer this question. However, this study design is limited by the fact that other confounders could have been responsible for the associations seen.
In the study, people who consumed more fruit and vegetables were generally older, less likely to smoke, more likely to be women, be of a higher social class and have a higher standard of education.
In addition, the proportion of people who were vigorously active increased as more portions of fruit and vegetables were consumed.
Although the researchers tried to adjust for these factors in their analyses, these differences may influence the association seen.
What did the research involve?
The researchers used information on 65,226 adults who were aged 35 years or older, who responded to the Health Survey for England.
Participants were visited by an interviewer who asked about fruit and vegetable consumption on the previous day. They were asked about their consumption of:
- vegetables
- fresh, canned and frozen fruit
- salad
- pulses
- dried fruit
- fruit juices/smoothies
- dishes made mainly from fruit or vegetables
Responses were coded into portion sizes. A maximum of one portion of pulses, one of fruit juice or a smoothie and one of dried fruit contributed to total daily portions of fruit and vegetables.
The researchers looked at mortality (death) records over 7.7 years (on average), to see if participants had died – and if they had, what they had died of.
The researchers compared the risk of death for people eating less than one portion to people eating more than one portion.
The researchers adjusted their analysis for the following confounders:
- age
- sex
- smoking status
- social class
- education
- body mass index (BMI)
- level of physical activity
- alcohol consumption
What were the basic results?
During the 7.7 years (on average) follow-up period, 6.7% of participants died (equivalent to 4,399 deaths).
Eating one or more portion of fruit and vegetables was associated with a significantly reduced risk of death from any cause compared to eating less than one portion. The risk of death from any cause decreased as portions of fruit and vegetables increased.
People consuming seven or more portions a day had the lowest risk of death from any cause, with a 33% reduced risk (hazard ratio [HR] 0.67, 95% confidence interval [CI] 0.58 to 0.78), compared to those who ate less than one portion a day (a portion was defined as 80g).
Eating three or more portions of fruit and vegetables was associated with a significantly reduced risk of death from cancer and death from cardiovascular disease. Risk of death from cancer was 25% lower in participants eating between five and seven portions, and seven portions or more (HR 0.75, 95% CI 0.62 to 0.91 for 5 to <7 portions; HR 0.75, 95% CI 0.59 to 0.96 for 7 or more portions). Risk of death from cardiovascular disease was lowest in people eating seven or more portions, with a 31% reduced risk (HR 0.69, 95% CI 0.53 to 0.88).
When fruit and vegetable consumption was analysed separately, the risk of death from any cause was lowest in people eating three to less than four portions of fruit per day (HR 0.84, 95% CI 0.76 to 0.93) and three or more portions of vegetables per day (HR 0.68, 95% CI 0.58 to 0.79).
Eating vegetables was associated with greater reductions in risk of death than eating the same number of fruit portions.
The researchers also looked at the type of fruit and vegetable consumption and found that consumption of vegetables, salad, fresh fruit and dried fruit were associated with decreased risk of death from any cause. However, consumption of frozen or canned fruit was associated with an increased risk of death.
How did the researchers interpret the results?
The researchers conclude that they found “a strong inverse association between fruit and vegetable consumption and all-cause mortality”. They go on to say that “fruit and vegetable consumption was significantly associated with reductions in cancer and [cardiovascular disease] mortality, with increasing benefits being seen with up to more than seven portions of fruit and vegetables daily for the latter [vegetables]. Consuming vegetables appeared to be significantly better than consuming similar quantities of fruit. When different types of fruit and vegetables were examined separately, increased consumption of vegetables, salad, fresh and dried fruit showed significant associations with lower mortality. However, frozen/canned fruit consumption was associated with a higher risk of mortality”.
Conclusion
This UK-based study found that eating fruit and vegetables was associated with a lower risk of death from any cause, and deaths from cardiovascular disease and cancer. The higher the intake of fruit and vegetables, the greater the protective effects seemed to be.
People who ate seven or more portions a day had a 33% reduced risk of death from any cause, a 25% reduced risk of death from cancer and a 31% reduced risk of death from cardiovascular disease, compared with people who ate less than one portion per day.
The researchers found that vegetables may lower risk more so than fruit. Consumption of vegetables, salad, fresh fruit and dried fruit were associated with decreased risk of death from any cause, although consumption of frozen or canned fruit was associated with an increased risk of death.
This study provides further evidence of the benefits of eating fruit and vegetables; however, it is based on only one diet measurement over 24 hours, which may not be representative of a person's usual diet and does not take into account changes in diet over time.
This study is limited by the possibility that other factors (confounders) could have been responsible for the associations seen. In the study, people who consumed more fruit and vegetables were generally older, less likely to smoke, more likely to be women, be of a higher social class and have a higher standard of education.
Despite reporting to the contrary, the results of this study do not go against the current “5 a day” message. This is a minimum recommended level. When it comes to fruit and vegetables, as long as you watch your calorie and sugar intake it is very much the case of “the more the merrier”.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.
Links to the headlines
Seven-a-day fruit and veg 'saves lives'. BBC News, April 1 2014
Healthy diet means 10 portions of fruit and vegetables per day, not five. The Daily Telegraph, April 1 2014
Forget five a day: You need SEVEN portions of fresh fruit and veg per day to live longer, says new research. The Independent, April 1 2014
Are you getting your seven-a-day? Experts say we need more helpings of fruit and veg. Daily Mirror, April 1 2014
Fruit and vegetable intake: five a day may not be enough, scientists say. The Guardian, April 1 2014
Forget five a day, we should eat SEVEN a day for a long life: Eating more portions of fruit and veg can cut risk of dying prematurely by 42%. Daily Mail, April 1 2014
Diet that adds years to life: Seven fruit and veg a day halves risk of an early death. Daily Express, April 1 2014
Have you had your ten-a-day? Five-a-day ‘not enough’ – and doubts over canned fruit too. Metro, March 31 2014
Links to the science
Oyebode O, Gordon-Dseagu, Walker A, Mindell JS. Fruit and vegetable consumption and all-cause, cancer and CVD mortality: analysis of Health Survey for England data. Journal of Epidemiology and Community Health. Published online March 31 2014
