By James Odhiambo
Achieng is healthy now, but six years ago, aged 8, she had the farming sickness that research now shows is causing fatigue, aching, poor concentration, poor development, and disease for up to a fifth of Western Kenyans. The cure for Achieng was a coincidence: her father and brother abandoned synthetic fertiliser for other reasons, but the change cured Achieng and transformed their farm’s yields.
The illness Achieng had was a form of malnutrition, caused not by too little food, but by food grown in ruined soils missing key nutrients humans need to be healthy. The culprit is fertiliser.
“We had always used fertiliser, which we got on the government’s subsidised scheme. But the fertiliser was of such poor quality that we finally started making compost in an effort to improve our yields,” said Achieng’s father. “We saw the results from the second season in our yields, but also in Achieng’s health,” he said.
What they had inadvertently done was make the change that scientific research now shows is causing malnutrition for up to a fifth of Western Kenyans through magnesium deficiency. Testing foods in Tanzania and Western Kenya, the research found that the foods in Western were so low in magnesium, which is essential to human health, that a standard diet in the region was leading to magnesium deficiencies for up to a fifth of Western Kenyans, compared with only 1 per cent of Tanzanians
“Effectively, the overuse of fertiliser in Western Kenya and poor soil care has moved through to human health, and is making farming families sick,” said Jenny Luesby, a farming expert and analyst with FarmBizAfrica.
For Achieng, the journey was miserable. Her days were marked by constant tiredness, illness and slow growth. She struggled to stay awake in class and was visibly stunted compared to other children her age. Her mother tried feeding her more, took her to the local clinic, and even sought traditional remedies. Nothing worked. The idea that her daughter’s symptoms were due to nutrient-poor food never crossed her mind. “We thought maybe it was illness or something spiritual,” she recalls. “But we didn’t know the food had lost its power.”
However, the research in 2019, which compared food and soil samples from counties in Western Kenya with those from Kilimanjaro, Tanzania, had proven exactly that, and the contrast was stark.
Tanzanian maize contained 2,000 mg/kg of magnesium—nearly double the 941 mg/kg found in Kenyan maize. Leafy vegetables in Kilimanjaro had 8,985 mg/kg of magnesium, compared to only 5,489 mg/kg in Kenya. The study revealed that the food in Western Kenya, although calorically sufficient, was failing to deliver the minerals necessary for children’s physical and cognitive health and development. It was a farming issue that was driving a public health crisis.
The result was that when Achieng eat maize, it was empty of vital nutrients that children eating maize in Tanzania were still getting, causing stunted growth, learning delays, chronic fatigue, and vulnerability to a wide range of illnesses, including diabetes and heart disease.
The magnesium hole in Western Kenyan food
For Achieng, the story had a happy ending. The arrival of more subsidised fertiliser made up largely of sand saw her father and brother move to producing their own compost. They began digging compost into their soil, and later adding manure. Within two seasons, they were harvesting healthier vegetables, more vibrant maize, and seeing a dramatic improvement in Achieng’s health. Her energy returned. She could concentrate in school. She began smiling again.
Dr. Diana Menya, a public health researcher at Moi University and co-author of the magnesium study, believes stories like Achieng’s are exactly why the research matters. “We always say we need more food, but the truth is, we need better food—food that feeds growth, energy, and intelligence. And that begins with the soil.”
Even where fertiliser is at full strength, it can provide a fast boost to yields, but leaves the soil short on other nutrients and makes it steadily more acidic. Over time, the soil is so damaged that for the heaviest fertiliser users, in Western Kenya and the Rift Valley, farming sickness is now becoming widespread.
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The researchers recommended urgent national action five years ago:, calling for region-specific soil nutrient mapping, an overhaul of food composition databases, and moves to integrate mineral restoration into national fertiliser strategies. They emphasised that magnesium deficiency must be treated as a front-line health challenge in the fight against malnutrition.
Achieng now dreams of becoming a nurse. She understands the pain of unexplained illness and the power of a solution grounded not in pills or clinics, but in knowledge—knowledge that her family did not have, but which it tripped over totally by coincidence.