Malnutrition is not caused only by a lack of food; access to clean and safe water also plays a critical role in determining whether children can properly absorb the nutrients they need to grow and stay healthy. When water is unsafe for drinking, cooking or washing, it can trigger a harmful cycle of illness and undernutrition that prevents the body from using food effectively. This connection between water, disease and nutrition is central to understanding and addressing hunger.
Unsafe water can expose people to a range of serious waterborne diseases, including diarrhea, cholera, typhoid fever, intestinal parasites and other gastrointestinal infections. These illnesses are especially common in communities where sanitation systems are weak and hygiene practices are limited. Since roughly one in four people worldwide still lack reliable access to safe water, millions remain at risk of repeated illness that can directly undermine their health and nutritional status.
Water is essential for digestion and nutrient absorption, but when it is contaminated, it can instead make people sick and interfere with the body’s ability to benefit from food. Illnesses such as diarrhea can rapidly deplete the body of fluids, electrolytes and vital nutrients, even when a child has eaten enough. In young children, especially those under five, this can quickly become dangerous because they are in a critical stage of growth and have fewer reserves to cope with nutrient loss. Diarrhea is a major driver of child malnutrition and remains one of the leading causes of illness and death among young children globally.
Illness and malnutrition reinforce one another in a dangerous cycle. A child who becomes sick may lose nutrients, eat less and become malnourished. Once malnourished, the child’s immune system weakens, making them more vulnerable to further infections. If they continue to consume unsafe water or live in poor sanitation conditions, the cycle repeats and their health can deteriorate further each time. Repeated episodes of illness can also lead to chronic malnutrition, or stunting, which can result in long-term physical and developmental consequences.
Illness contributes to malnutrition in several ways. In addition to causing the body to lose nutrients through vomiting or diarrhea, sickness often reduces appetite, meaning children may eat very little for days at a time. This leads to lower intake of calories, vitamins and minerals needed for growth and recovery. When such illnesses occur repeatedly because of unsafe water and poor hygiene, the risk of long-term nutritional damage becomes much higher.
At the same time, malnutrition itself makes illness more likely and more severe. The body needs adequate vitamins, minerals and protein to build and maintain a strong immune system. Nutrients such as vitamin A, zinc, iron and protein are essential for immune function and recovery. When children or adults are malnourished, their bodies are less able to produce the immune cells and antibodies needed to fight infection. This means common illnesses like diarrhea or respiratory infections can last longer, become more severe and be harder to recover from.
Malnourished individuals also struggle more during recovery because healing requires energy, protein and micronutrients. Without these reserves, the body may remain weak even after the immediate illness has passed, increasing the risk of relapse or new infections. If the person continues to be exposed to unsafe water, this can lead to repeated sickness, prolonged weakness and, in severe cases, life-threatening complications.
Young children are especially vulnerable to this cycle because their bodies are growing rapidly and need more nutrients relative to their size. Even short periods of poor nutrient intake or absorption can have lasting effects on their development. Their immune systems are also still developing, making it harder for them to fight infections. In many communities, children are more exposed to harmful bacteria and parasites because they play in environments where sanitation is poor. The first 1,000 days of life, from pregnancy to a child’s second birthday, are particularly critical, as illness and malnutrition during this period can seriously affect brain development and physical growth.
Access to clean water is therefore one of the most powerful tools for preventing malnutrition. When communities have reliable safe water, sanitation and hygiene services, rates of diarrhea and other infections fall significantly, improving children’s ability to stay healthy and absorb nutrients. Safe drinking water systems, protected wells and boreholes, household water treatment and storage, sanitation facilities such as latrines, and hygiene education including handwashing with soap are all essential measures that help break the cycle of illness and malnutrition.
By improving water, sanitation and hygiene conditions, organisations such as Action Against Hunger help children avoid preventable diseases and give them a better chance to benefit fully from the food they eat. This makes clear that tackling malnutrition requires not only food assistance, but also strong investment in clean water and public health systems that protect children from recurring illness.
