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News Article

Five is good 10 is better?


Systematic review finds benefits for intakes up to 800 g of fruit and vegetables

Ten servings a day of fruit and vegetables is better for you than 5 suggests a systematic review carried out by UK scientists. They found that eating 10 servings or 800 g of fruit and vegetables lowers risk of death by 31% compared with eating less than 40 g a day, whereas eating 5 portions or 400 g reduces risk of death by 27% compared to less than 40 g per day. The study also showed an association of fruit and vegetable intake and cancer risk that had not been observed before. The message is 5-a-day is good but 10 might be better. The study is published in International Journal of Epidemiology.

Fruit and vegetable consumption: guidance and reality

Around the world, guidance about the amount of fruit and vegetables individuals should eat varies from 400 g/day recommended by WHO and in England, to 500 g/day in Sweden, to 600 g/day in Denmark, 650–750 g/day in Norway, and 640–800 g/day in the USA, according to the researchers. But what the optimal intake is, is still unclear, say the study authors, led by Aune Dagfinn from Imperial College London.

Guidelines are good but actual intakes often do not reach the recommneded amounts. Fruit and vegetable intake is about 310 g in the UK where the guidance is 400 g. Across Europe, it ranges from 192 to 824 g. Nine of fourteen countries consumed <400 g, according to a review by Tennant et al in 2014.

The study

Dagfinn and colleagues considered 95 cohort studies of fruit and vegetable intake and deaths from all causes, heart diseases, strokes, and cancer in populations worldwide. They analysed particular fruit and vegetable groups and examined the effects of intakes of <40 g, 200 g, 400 g, 600 g and 800 g. This review is the biggest of its kind so far, including twice as many studies as the previous one by Wang Xia and colleagues which concluded there was no benefit above intakes of 400 g per day.

Dagfinn and colleagues found that the lowest heart disease, stroke and cardiovascular mortality risks occurred at intakes of 800 g versus less than 40 g. However, the steepest change occurred for intakes up to 400 g. For cancer the lowest mortality risk seemed to be around intakes of 600 g and further increases in intake didn't result in any lower risks. The study also showed associations between certain fruits and vegetables and certain diseases, but the authors stress more work is needed.

The findings suggest that 5-a-day campaigns shouldn’t be regarded as a guidance for maximum intake but as a minimum. The authors say: ”Our meta-analysis provides further support for public health recommendations and interventions to increase fruit and vegetable intake for prevention of cardiovascular disease, cancer and premature mortality.” Whether recommendations are changed based on this study is open to question because aside from the evidence, policymakers will be considering what goal people can be motivated to reach.

Other evidence

The flaw in this type of study is that it only shows associations, it doesn’t prove that eating more fruit and vegetables helps any of these diseases and there may be factors that haven’t been taken into account. However it may be the best evidence we have at present. There are few interventional studies for fruit and vegetable intake where people randomly receive particular diets (see “Further Reading for some examples). A recent Cochrane review examined interventions that provided fruit and vegetables or dietary advice to eat more fruit and vegetables. However the trials it reviewed were all short term and monitored cardiovascular risk factors but not clinical outcomes (i.e. disease itself). Its conclusions suggested that dietary advice might improve risk factors for cardiovascular disease but more studies are needed.

Dagfinn and colleagues' paper:

Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality–a systematic review and dose-response meta-analysis of prospective studies. Dagfinn Aune, Edward Giovannucci, Paolo Boffetta, Lars T. Fadnes, NaNa Keum, Teresa Norat, Darren C. Greenwood, Elio Riboli, Lars J. Vatten, Serena Tonstad. Int J Epidemiol dyw319. DOI:https://doi.org/10.1093/ije/dyw319

 

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