 Malnutrition is a major global health problem. Poor diet has been linked to a range of chronic diseases and even deaths. Obesity has nearly tripled around the world in recent decades, while undernutrition remains a serious concern. So how can governments improve the nutrition and health of their people? Stable isotope techniques can help. They provide important data to determine nutrition trends and design better interventions. Isotopes are variations of elements that differ in mass. With specialized equipment, isotopes can be tracked in the body because of their different weight and provide precise information on the nutritional status of a person. Deuterium, an isotope of hydrogen, can help measure the body's composition of fat mass and fat free mass. This stable isotope can also provide an objective measurement of whether infants are being exclusively breastfed. Stable isotopes can also be used to determine the amount of Vitamin A stored in the body and tell if important minerals like iron or zinc are being effectively absorbed and used. These techniques help to check if efforts to improve diet and physical activity in the population are actually working. So that policymakers can plan better actions such as stricter controls on unhealthy ingredients or programs to enrich food with key vitamins and minerals.