Several nurseries have had to change their menus after a study revealed many had little understanding of children's nutritional needs.
Pre-school children have specific nutritional requirements
The day-care centres in East Sussex were assessed by Trading Standards, who found many were offering inappropriate food for one to four-year-olds.
A week's worth of meals from ten nurseries were analysed by a paediatric dietician for nutritional content.
The results showed that only 20% excelled in their provision of meals.
The survey showed all nurseries failed to meet the requirement for iron and that three nurseries appeared to be providing menus based on adult healthy eating principles.
Children under four have different nutritional requirements to older children and adults.
All the nurseries surveyed committed themselves to improving the diet offered to children.
The changes range from altering snacks and switching to more nutritionally suitable products to completely altering menus and the range of foods on offer.
An East Sussex County Council spokesperson said: "Trading Standards officers are confident that all the participating nurseries should now know what constitutes good nutrition for the under five age group."
Councillor Bob Tidy, cabinet member for community services said it had been an "educational experience" for the nurseries which had to "change their thinking" about healthy eating for under fives.
He said: "Some of the nurseries also have the added difficulty of having to accommodate the demands of parents, who often have very specific viewpoints of what they will and will not allow their children to consume and their own perceptions of healthy eating which may not be appropriate for children of this age group."