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Gardening and health

Campaigns, such as the Government-backed five-a-day, are encouraging people to increase their consumption of fruit and vegetables; 400g per day is the recommended daily amount, with vegetables providing more benefits than fruit. But, due to a desire to market the health benefits of fruit and veg in a positive manner, they are unwilling to publicise the significant link between a diet lacking fruit and vegetables and an increased risk of contracting cancer or cardiovascular disease (CVD). Despite huge efforts in this area, the National Statistics study for the Department for Environment, Food and Rural Affairs (DEFRA) revealed that fruit and vegetable consumption fell by 1.6% in 2003/2004.

The fact is that two out of three people in the UK will die from CVD or cancer. The major cause of these and many other diseases is the production of super oxide radicals and other reactive oxygen species (ROSs) due to inefficient respiration. Experiments suggest that without controlling these ROSs, life could not exist. However, the body has evolved many strategies to limit the damage of these ROSs with the result that death is slowed - a process we call ageing. The major way the body removes these ROSs is by using antioxidants to neutralise them. Cancer and CVD are natural consequences of the ageing process and eventually everyone would contract these diseases. However, ensuring that the body is not limited in its ability to make and use antioxidants can result in delaying their appearance to the point where death results from other causes often at ‘a ripe old age’.

The body obtains antioxidants from two sources. Those that are present in the diet and those that it makes. In evolutionary terms diet can not be guaranteed, and so the most important group of antioxidants are those we make. These are proteins that can be made from any diet able to sustain life and ensure we have a high chance of surviving long enough to reproduce - the driving force behind evolution. As a consequence people often have few health problems well into their 40's despite the quality of their diet. But it is at this point that age-related conditions start to appear. There is little we can do to influence this source of antioxidants except to ensure an adequate diet, which even the worst UK diets tend to supply, although, in recent years much concern has been expressed over the lack of the antioxidant cofactor selenium. Selenium, although not essential for life, has been shown to be involved in slowing many aspects of the ageing process including the onset of cancer and CVD. It is rarely present in UK soils but is present in manure and manure-based fertilisers, making these essential soil additives when growing fruit and veg.

The best strategy for attempting to extend one's life well past the point where evolution would really think reproduction is a bad idea, is to fill our bodies with antioxidants from the diet. And the best sources are fruit and vegetables. Unlike animals, which can move when they encounter stress, plants cannot and so have evolved a host of biochemical pathways, which animal's lack, to synthesise protective compounds. By eating fruit and vegetables we take these compounds into our bodies with the result that we enjoy their protective effects. Science is now discovering that some of these compounds have other unexpected properties. An example is glucosinolates, a class of compounds found in cruciferous vegetables (e.g. brassicas). There is increasing evidence that some of these compounds may not only protect against cancer, but actively slow the growth and in some cases kill cancer cells.

The option of taking an antioxidant-containing pill is attractive to many people, although science remains divided on the effectiveness of such supplements. Pills also lack the variety of protective compounds in fruit and vegetables. For example, a supplement company a few years ago started to include lutein in their multivitamin pill. Lutein helps slow age-related deterioration of vision. If you take this brand of multivitamin, the question is, "Where did you get your lutein from before they included it in this supplement?" And if you take a different brand, "Where do you get your lutein from now?" Green vegetables have always been a good source of lutein. Additionally, you will not find glucosinolates in any multivitamin supplement either. The fact is that science is still only scratching the surface when it comes to understanding the potential health benefits of many plant compounds, and the only way to ensure you take advantage of these benefits is to eat a wide range of different fruit and vegetables; variety is not only the spice of life - it is the key to life.

Home-grown fruit and vegetables may also hold an advantage in terms of conferred health benefits. Commercial growers are skilled at maximising yields and quality by reducing the stress load on their crops. Gardeners however, often refrains from using pesticides and artificial fertilisers with the aim of producing a more ‘natural’ product. This has the effect of forcing the plant to cope with the stresses it encounters using its natural biochemical defences. Many gardeners know that to maximise the odour of many plants, which often have therapeutic properties, you ‘grow them hard’.

Secondly, a major tenet of the five-a-day campaign is variety - every crop may confer slightly different health benefits. This can be taken a step further in that different varieties can confer different health benefits; coloured carrots being a prime example.

Unfortunately, many food retailers do not offer such variety, but gardeners, often with an eye for the unusual, can take full benefit by growing their own.

Finally, many government recommendations are concerned with removing the causes of cancer and CVD. These include giving up smoking, increased exercise and a reduction in your level of stress - a major cause of high blood pressure and consequently CVD. Many gardeners find their plot a welcome break from the pressures of the outside world, making gardening a major health benefit.

To summarise, cancer and cardiovascular disease are natural consequences of ageing due to damage by reactive oxygen species. By eating a diet rich in fruit and vegetables we can bolster our natural defences against ageing and reduce our risk of contracting these diseases.