Which varieties of plants should medical gardeners grow to create the best medicine cabinet?
The food we eat can also be our medicine. From the tips of the shoots and stamens to the leaves, fruits and roots, plants are packed with phytochemicals that deter animals from eating them and protect them from disease. These phytochemicals can also be extremely beneficial to us both as a source of nutrients for general health and as medicines. Unfortunately, today's fruits and vegetables bear very little resemblance to traditional fruit and vegetables of the middle ages. Plants have undergone years of cross breeding and selection to create varieties that are bigger and tastier. Plants often naturally double up the sets of chromosomes in a cell with the only effect being to be to make the fruits and leaves bigger. It is now common policy to multiply the sets of chromosomes to create bigger fruits and vegetables in plants. Strawberries are a good example, the original wild strawberries are smaller with a much more concentrated flavour than the large commercial strawberries that can have as many as ten sets of chromosomes in a cell. The other disadvantage of hundreds of years of cross breeding is that the plants no longer contain many of the beneficial phytochemicals. Phytochemicals are often bitter and so plants have been cross bred to reduce the bitterness. Some important phytochemicals give a very dark purple/black colour to vegetables and have been cross bred out for aesthetic reasons, so if there is a choice of purple over green, go purple, think red cabbage, purple potatoes and black carrots. Colour isn't everything though as many phytochemicals are colourless.
If gardeners are to create truly medical gardens, it may not be enough to go organic, they may need to go organic and also go back to the older traditional varieties of plants. Fortunately there is a dedicated community of scientists, biologists, ecologists and gardeners working together to preserve traditional varieties of many fruits and vegetables and to identify those that have the best quality and quantity of phytochemicals. One of the most researched vegetables is the carrot and there is even an online world carrot museum dedicated to this humble vegetable.
Here we summarise three studies that show how the phytochemical levels in asparagus, wheat and broccoli can vary greatly by variety and cultivation methods.
1. Green asparagus.
Study carried out by a Spanish group showed that Huetor-Tajar asparagus contained eight different saponins as compared to commercial hybrids of asparagus that only contained the protodioscin saponin. The total concentration of saponins was also much higher in the Huetor-Tajar asparagus shoots.
2. Black, red, brown and white rice.
A French group studied the levels of phytochemicals in different types of rice grown in the Carmague area of France. Black rice contained the widest range of phytochemicals, with the main chemicals being anthocyanins followed by flavones, flavenols, gamma oryzanols and low levels of carotenoids. Red rice also contained a good range of phytochemicals but in different concentrations with procyanidins being the most abundant followed by carotenoids and gamma oryzanol. Brown rice and white rice had the lowest levels and lowest number of types of phytochemicals.
3. Sprouting Broccoli
Sprouting broccoli is grown in the winter and harvested in the spring and is different from green broccoli that is grown in the summer. A study carried out by a group in Ireland has looked at the effect of variety and crop management on phytochemicals in broccoli. The group found that phytochemical content was higher in white sprouting broccoli and in more mature plants than in a green broccoli variety.
So where should the medical gardener start? Reading Jo Robinson's 'Eating on the Wild Side' would be a good place. Robinson has spent decades researching plant nutrition and phytochemicals so she's done most of the mental leg work and gives good pointers as to which varieties a gardener should grow.
1. Vazquez-Castilla et al. Optimization of a method for the profiling and quanitification of saponins in different green asparagus genotypes. J. Agric Food Chem. Jul 2013.
2. Pereira-Caro et al. Phytochemical profiles of black, red, brown and white rice from the Camargue region of France. J Agric Food Chem. Aug 2013.
3. Reilly et al. Potential of cultivar and crop management to affect phytochemical content in winter-grown sprouting broccoli (Brassica oleracea L var italica). J Sci Food Agric. Jan 2014.