As well as worrying about what's missing from children's diets, there are concerns about what's being added to their food. There have been consistent suggestions that too much sugary, highly coloured, highly flavoured junk food leaves children in no fit state to learn.
The Food Commission believes that certain additives and preservatives can trigger behavioural problems. It has called for them to be withdrawn.
Kath Dalmeny, the commission's policy officer, says that parents and teachers have been making these connections between diet and behaviour for years - but an official response, or even a rigorous testing of the evidence, is still needed.
"Nobody has really taken it seriously enough and parental concerns are dismissed as just making a fuss." she says. But she adds that there has been evidence from a study of three-year-olds on the Isle of Wight that demonstrated that a number of artificial colourings could be linked to mood changes and temper tantrums.
However, this research, which made headlines last year, is far from accepted as "proof". The Food Standards Agency dismisses the research as being insufficiently objective and overly dependent on the anecdotal observations of parents.
Now the agency is commissioning its own research study due to begin early this year. A spokesperson says there needs to be evidence to support the theory.
What is more surprising, says the FSA, is the way that the debate about E-numbers so often ignores the much clearer evidence of an impact on behaviour of natural products such as sugar and caffeine. According to the agency, a 50mg bar of chocolate and an 80mg fizzy drink contains more caffeine than a cup of coffee. If young children were fed copious cups of coffee we wouldn't be surprised if they started to become over-excited or complain of headaches and have difficulties with sleep.
"No adult who drinks coffee every morning to wake up would say that caffeine has no effect. So if they give even higher levels of caffeine to their children, plus the energy rush from all the sugar, should they be looking at the E-numbers to explain their children's behaviour?" the agency asks.