I have just eaten a delicious conference pear weighing about 180g. I do not normally weigh snacks, but the recently reported health benefits of eating more fruit and vegetables has inspired me to dig out the scales.
A study published last month showed that, as expected, people who eat fruit and vegetables regularly cut their risk of dying from several diseases such as stroke, cancer and heart disease. Generally, the higher the intake of fruit and vegetables, the lower the risk.
Here’s the new bit, according to the paper in the International Journal of Epidemiology, the optimum intake was about 800g per day. Since 80g counts as one serving — roughly one small banana or pear, or three heaped tablespoons of cooked veg — this equates to 10 portions. Given that two out of three Britons struggle to hit the recommended target of five a day, the news that we should now be aiming for 10 was greeted with incredulity.
Researchers from Norway, the UK and US pooled data from 95 separate studies, involving a total of about 2m people. Each of those studies had one thing in common: they asked participants about their dietary intake and measured health outcomes, such as rates of cancer, stroke or heart disease.
A meta-analysis of that pooled data suggested that, compared with eating no fruits and vegetables, overall health outcomes improve with every 200g increment, up to 800g (up to 600g for those with cancer). Unsurprisingly, few people manage to eat more than 800g, meaning that scientists are unable to reliably investigate the benefits of higher intakes (which, I assume, accrue mainly to toilet-roll manufacturers).
Even so, modest amounts seem to make a difference. Eating 200g of fresh produce (about two-and-a-half portions) appeared to cut the risk of cardiovascular disease by 13 per cent; the risk of dying from cancer by 4 per cent; and the risk of premature death by 15 per cent.
Upping daily intakes to 800g brings even better news: a 28 per cent reduction in risk of cardiovascular disease; a 13 per cent reduction in total cancer risk; and a 31 per cent cut in the risk of premature death. Dr Dagfinn Aune from Imperial College’s School of Public Health, who led the analysis, estimated that about 7.8m deaths worldwide per year could be prevented if people ate 10 a day.
What to eat?
Some fruits and vegetables seemed especially protective for certain conditions. Those wanting to fend off early death, particularly from stroke or heart disease, could add the following to their plates: apples, pears, citrus fruits, spinach, lettuce, chicory, and cruciferous vegetables such as broccoli, cabbage and cauliflower. For cancer, the researchers suggested a possible benefit from green and yellow vegetables, such as peppers and green beans and, again, cruciferous vegetables.
This study shows a correlation rather than causation. The researchers have not proved that dining on fresh produce fends off death and disease; it could be that people who eat more healthily also exercise more and are less likely to smoke, with these confounding behaviours really responsible for their rude health. The fact, however, that incrementally higher intakes were associated with incrementally lower risks, though, adds weight to the idea that a healthy diet plays a role.
Other research points to mechanisms by which fruits and vegetables work their therapeutic magic. They are known to reduce cholesterol and blood pressure, and to contain antioxidants that help to repair DNA damage. This last factor is thought to have a bearing on cancer risk. Tumours usually begin with rogue cells whose growth can’t be kept in check.
Dr Aune said that, even though further research was needed to pin down the details, “a high intake of fruit and vegetables holds tremendous health benefits, and we should try to increase their intake in our diet”.
Whole plant foods beat processed versions such as smoothies, which can be high in sugar. Nutritional supplements are no substitute; Dr Aune said there was no evidence they cut the risk of disease.
Headlines might have suggested otherwise but the new paper, persuasive though it is, did not prompt a change in the official five-a-day message. This is pragmatic: those already managing five are health-conscious and self-motivated enough to raise their cruciferous-munching ambitions without official haranguing. Those who are not yet heeding the message would risk becoming disheartened at the sudden shifting of the nutritional goalposts.
Anyway, back to the scales. With each pear clocking in at nearly 200g, I did fleetingly wonder whether I could tick off my 800g with three more ripe beauties from the fruit bowl, currently sitting atop two wrinkly apples and an unappealing banana. Alas not — the biggest benefits come from eating a variety of fruits and vegetables, with their corresponding panoply of nutrients. My ugly fruit friends: your time has come.
根据《国际流行病学杂志》(International Journal of Epidemiology)的这篇文章，新的发现是，最优摄入量是每天约800克。由于80克算一份——差不多是一根小香蕉或小个儿梨子，或满满3大汤匙煮熟的蔬菜——800克相当于10份。鉴于三分之二的英国人连每天5份的推荐摄入量都难以达到，每天应该争取吃10份的消息让人觉得匪夷所思。
每天摄入量达到800克会带来更好的消息：心血管疾病风险减少28%；总体癌症风险降低13%；早亡风险降低31%。牵头这项研究的帝国理工学院(Imperial College)公共卫生学院(School of Public Health)的达芬?奥纳(Dagfinn Aune)博士估计，如果每天吃10份水果和蔬菜，那么全世界每年的死亡人数有望减少约780万。