By Stepha McMullin and Katja Kehlenbec
Today is World Health Day, and the spotlight is shining on the worrisome upsurge of high blood pressure cases, which can lead to heart disease and stroke.
The World Agroforestry Centre (Icraf) believes the widespread cultivation of trees on farms will form part of the solution to hypertension and other chronic diseases.
In 2008, 40 per cent of adults aged 25 and over had raised blood pressure, says the World Health Organisation (WHO). In recent guidelines aimed at arresting this trend, WHO says adults should limit their daily intake of sodium to less than 2,000mg – equivalent to 5g of salt, and simultaneously raise their intake of potassium to 3,510mg or more daily. WHO adds: “Currently, most people consume too much sodium and not enough potassium.”
Salty foods to cut back on include soy sauce, cured meats and salty chips; this is generally well known. But apart from bananas, which contain around 420mg of potassium in a medium-sized fruit, potassium-rich foods are poorly understood. Yet there is a whole array of tree-nuts and fruits that are rich in potassium and a host of other nutrients, too.
For instance, a 100g serving (about two handfuls) of cashew nuts has 600mg of potassium; macadamia nuts 360mg, and pistachio nuts around 1000mg. Besides potassium, nuts are rich in unsaturated fats that help lower cholesterol, vitamins E and B, and important minerals like zinc, copper, and magnesium.
Many fruits also pack a potassium punch. A medium cup of orange juice has around 450mg of potassium, and 10 dates have around 550mg. A single 5g tablespoon of cocoa powder or dark chocolate is packed with 125mg of potassium. Fruits are also well known for their vitamin, mineral and trace element content. Baobab fruit, with 1,700mg of potassium per 100g powder, has amazingly high vitamin C content, up to 10-times higher than oranges. The first requisite to widespread good nutrition is to make healthy food accessible and affordable.
Many nut and fruit trees can be successfully integrated into farming landscapes, and grown in city backyards and even public spaces. Farmers in tropical and sub-tropical climates have a wider range of tree species to choose from.
The forest is another source of highly nutritious tree products. ICRAF has since the 1980s worked with national partners and farmers to domesticate traditionally important farmer-selected species, so these can be grown on farms. Tree domestication both protects forests from over-exploitation, and brings important nourishment closer to people. Today, bush mango (Irvingia gabonensis) and African plum (Dacryodes edulis) trees are being grown on smallholder farms in West Africa, following successful domestication. Baobab is undergoing domestication research by Icraf and partners, as is the marula tree.
According to the Food and Agriculture Organisation, the highest incidence of chronic malnourishment is found in sub-Saharan Africa, with East Africa recording the lowest fruit consumption anywhere in the world. Stepping up the cultivation of useful trees in rural and urban landscapes will bring health-related rewards. What’s more, agroforestry has been shown to improve farmer’s well being through the improvement of farm productivity, income, and livelihood resilience.
Dr Stepha McMullin and Dr Katja Kehlenbeck are research scientists in the Tree Diversity, Domestication and Delivery programme of the World Agroforestry Centre in Nairobi
