Nutritional deficiencies are a risk for any severely restricted diet, and in 2008 there was a report of two cases of sudden cardiac arrest in children who had been on the ketogenic diet for three years. Impairments in cardiac function may be due to deficiency in the mineral selenium from following the diet. Support from a dietician or nutritionist may be required to help ensure that these and other potential nutrient deficiencies are addressed. Ketosis is the accumulation of ketone bodies or ketones in the blood. Ketosis occurs in healthy people during fasting and strenuous exercise.