Do we need 7 portions of fruit & Veg?
Post date: 02-Apr-2014 13:25:02
After being asked by the local newspaper for a comment on some research, I was left feeling slightly misrepresented and the beauty of having my own website is that I can now present a more accurate picture of my own thoughts on the research.
The newspaper report was based on a new study by Oyebode et al, that has attracted plenty of interest from the nation’s media this week. The study reviewed evidence from the Health Survey of England and used information on more than 65,000 randomly selected adults that were interviewed and then remained part of the study sample for an average of 7.7 years.
It was an observational cohort study that was able to look at correlations between different factors but while appropriate, this design is limited in its ability to account for every confounding factor or to establish direct cause and effect. Despite this it is an important study due to its large size, relatively robust data collection methods and the fact that most previous cohort studies have used selected populations that are not as representative of a mass population as this study used.
The study found that people who ate seven or more portions of fruit and veg a day had a 42% reduced risk of death compared to those who ate less than one portion, and it is this headline that has been used to represent the study and at times supported the common narrative of “conflicting advice” that is often enough for some to use as an excuse for not making healthy choices. The claim of conflicting advice is based on the difference between the findings of this study and the well known recommendation of five portions of fruit and vegetables a day.
In reality the 5-a-day message, used in the UK since 2003, is really at least 5-a-day, although a glance at the current NHS information doesn’t promote this message too clearly. This new study does not at any point suggest that 5-a-day is insufficient, it simply reinforces the concept that additional benefits are conveyed for every portion of fruit and veg that are consumed. Figure 1 below shows some of the main findings and it can be seen that although there is a 42% relative reduction in the likelihood of early death for those consuming seven or more portions of fruit and veg, those consuming between 3 and 5 portions have a 29% decreased risk of death when compared to those that consume no fruit and vegetables.
Fig 1: This table summarises the main effects of fruit and vegetable consumption on risk of death, expressed as percentage decreases. The upper row contains figures where deaths in year 1 are excluded as it is suggested these people may have been ill prior to the study and also may have had their intake of fruit and veg altered due to poor health. Both issues may interfere with the datasets.
Problems with the study
This study does provide further evidence of the benefits of eating fruit and vegetables; however, the assessments of dietary consumption were based on only one self-recall measurement over 24 hours, which may not be representative of a person's usual diet and weekly fluctuations and doesn’t take into account changes in diet over time.
Any cohort study has to try and take account of confounding factors and this study tried to account for age, sex, smoking status, social class, education, body mass index (BMI), level of physical activity and alcohol consumption. Other factors that were not accounted for, and could have additional impact could be a history of smoking, exercise levels and income.
The replacement value of fruit and veg in the diet was also not examined as many people that eat more fruit and veg may also be consuming less fat, more fibre and less sugary snacks and drinks. While this suggests that the mechanism of the protective effect is less clear it doesn’t detract from the main correlation between meeting the guidelines on 5-a-day and mortality rates. Other studies that have examined fat and fibre alongside fruit and veg have suggested that this is not a concern in terms of any undue influence on findings (Leenders et al, 2013)
Fruit versus Veg
Interestingly the study makes a clear distinction between the protective effect of consuming more vegetables and that of more fruit. It found that vegetables continued to offer an increased benefit to mortality rates as consumption levels increased whereas fruit did not convey this benefit beyond three portions a day. There was also no significant relationship between consumption of fruit and cancer or CVD risk whereas vegetables on their own did have a beneficial effect on the development of these conditions. Additionally, the researchers found that frozen or canned fruit was associated with increased mortality (it was worse) but identified that this may have been more linked to socioeconomic status and the multiple confounding factors that come with this. It is also not helpful that both frozen and canned are counted as one item in the data collection as there are distinct differences in the sugar levels of these products which may be more interested to use in the analysis.Current Guidelines
In the search for a consensus of advice, it is worth taking a look at the guidelines of other countries; France and Germany mirror the 5-a-day message, the USA has no minimum in favour of “...more matters”, and Australia promote the 2+5 message (2 fruit + 5 veg). In terms of how many people are meeting the guidelines, in the US around 25% of people are consuming 5 or more fruit and veg (Heo et al, 2011) and in 2010, 25% of men and 27% of women in England consumed the recommended five or more portions of fruit and vegetables daily while the corresponding figure of 5-15 year old boys was 19% and 5-15 year old girls 20% (HSCIC, 2012). In addition, household purchases of fruit are falling in the UK and in 2010 were 11.6% lower than in 2007 (HSCIC, 2012) while purchases of vegetables are 2.9% lower over the same timeframe. Attempts have been made to increase consumption in children and combined fruit and veg intake was seen to improve when children were offered fruit and veg in school but these changes were not translated to the child's home setting (Teeman et al, 2010) suggesting that more work is needed in supporting healthy lifestyle choices across the lifespans.
Take away points
This study suggests that the more fruit and veg that we consume, the less likely we are to die of cancer, CVD or indeed any cause. The study suggests that any amount of fruit and veg is good for you, and the more you consume the bigger the effect is right up to 7 portions a day. It also suggests that there is a difference between fruit and veg with veg having a greater positive effect than fruit, suggesting that moving forward we might be better using the Australian guidelines of 2+5.
The issue is not necessarily about simple education and information as many people know about the key guidelines. Eating more fruit and veg is most commonly cited as the most important factor in eating a healthy diet (NOO, 2011) and when asked if they had a healthy diet, children and young people are most likely to comment on the amount of fruit and veg that they consume.
This study found that 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 and other studies have found that fruit and veg intake is inversely proportional to income (Thompson, 2008) and socioeconomic status. So for us, as a population we need to consider a range of initiatives that will work on an individual and community level making it easier for all people to make healthy choices and see the same benefits for all.
So to address my misrepresentation in the local paper, I think this research is helpful in providing further evidence of the importance of eating fruit and veg, and in supporting the argument that we should be reducing the amount of highly processed, high sugar foods in favour of more natural produce. It is clearly a challenge to encourage more people to eat more healthily but the fact that only a quarter of people are achieving 5 a day should not mean that we avoid promoting the message that "more is better". The challenge remains the same and it will only be met with a concerted effort that involves individual education and support, community level initiatives and government support.
References and Further Reading
Bélanger, M., Poirier, M., Jbilou, J., & Scarborough, P. (2014). Modelling the impact of compliance with dietary recommendations on cancer and cardiovascular disease mortality in Canada. Public health, 128(3), 222-230.[abstract]
Darmon, N., & Drewnowski, A. (2008). Does social class predict diet quality?. The American journal of clinical nutrition, 87(5), 1107-1117.[full text]
Dauchet, L., Amouyel, P., Hercberg, S., & Dallongeville, J. (2006). Fruit and vegetable consumption and risk of coronary heart disease: a meta-analysis of cohort studies. The Journal of nutrition, 136(10), 2588-2593.[full text]
Featherstone, G., Sims, D., & Sharp, C. (2011). Qualitative Impact Evaluation of the Food for Life Partnership Programme. National Foundation for Education Research.[full text]
Heo, M., Kim, R. S., Wylie-Rosett, J., Allison, D. B., Heymsfield, S. B., & Faith, M. S. (2011). Inverse association between fruit and vegetable intake and BMI even after controlling for demographic, socioeconomic and lifestyle factors. Obesity facts, 4(6), 449-455.[full text]
HSCIC (The Health and Social Care Information Centre) (2012) Statistics on obesity, physical activity and diet: England, 2012 [full text]
Jebb, S. A., Aveyard, P. N., & Hawkes, C. (2013). The evolution of policy and actions to tackle obesity in England. Obesity Reviews, 14(S2), 42-59.[full text]
Leenders, M., Sluijs, I., Ros, M. M., Boshuizen, H. C., Siersema, P. D., Ferrari, P., ... & Bueno-de-Mesquita, H. B. (2013). Fruit and Vegetable Consumption and Mortality European Prospective Investigation Into Cancer and Nutrition. American journal of epidemiology, 178(4), 590-602.[abstract]
Muraki, I., Imamura, F., Manson, J. E., Hu, F. B., Willett, W. C., van Dam, R. M., & Sun, Q. (2013). Fruit consumption and risk of type 2 diabetes: results from three prospective longitudinal cohort studies. BMJ: British Medical Journal, 347. [full text]
NOO (2011) Knowledge and attitudes towards healthy eating and physical activity:what the data tell us [full text]
Oyebode O, Gordon-Dseagu, Walker A, Mindell JS. (2014) Fruit and vegetable consumption and all-cause, cancer and CVD mortality: analysis of Health Survey for England data. Journal of Epidemiology and Community Health.[full text]
Teeman, D., Ransley, J., Lynch, S., White, K., Scott, E., Waldman, J., Cade, J., Benton, T., Thomas, J.,
Shamsan, Y. and Stoddart, S. (2010). The Third Evaluation of the School Fruit and Vegetable Scheme: Executive Summary. London: Department of Health. [online]. Available: http://www.nfer.ac.uk/publications/SFRZ01
Thompson J. ‘Diet and healthy eating’. Chapter 5 In: Craig R, Shelton N, eds. (2008) Health Survey for England 2007. Knowledge, attitudes and behaviours. London: NHS Information Centre: 107–48.[full text]