Parents considering giving their children dietary supplements in place of healthy balanced meals are being warned to think again.

Weight loss company Isagenix has sparked controversy by marketing meal replacement shakes and soups for children as young as four, and daily cleanse products for 12 year olds.

According to its website children can "enjoy" meal replacement shakes and soups from the age of four.

Isagenix also stocks a multi-vitamin for children, which was advertised as having 16 essential vitamins to "promote healthy development of cartilage, bones and teeth, and support healthy metabolism and immunity".

Head of Obesity and Diabetes Research at Auckland University, Professor Peter Shepherd, said he's never seen dietary supplements marketed so aggressively towards children.

He said it is not advisable to have children using such products without medical supervision.