Millions of children with autism could unknowingly be suffering key vitamin deficiencies, research today suggested. 

Studies have long shown those with the condition are five times more likely to be picky eaters and have a fear of new foods than typically developing youngsters.

But little is still known about the impact of such diets.

Now, scientists from Singapore believe almost 40 per cent of autistic children could be deficient in vitamin D and iron. 

The researchers, who assessed the dietary habits of over 240 children, also found more than 15 per cent with an iron deficiency had developed anemia—when the body lacks enough healthy red blood cells to carry adequate oxygen to tissues. 

Experts, who labelled the findings important, urged officials to consider implementing routine nutrition checks for children with autism. 

Writing in the journal Nutrients, they said: 'Vitamin D and iron deficiencies were commonly detected in this study population of children with autism. 

'Identifying the presence of such deficiencies and pursuing appropriate treatment for these can result in improvements in the overall health and development in these children.'

In the study, researchers discovered 36.5 per cent of the children, who were aged four on average, were deficient in vitamin D and 37.7 per cent had an iron deficiency.

Over a follow up of four years, they also found that age was a factor for low iron levels.

Every additional month of age increased a child's odds of developing vitamin D deficiency by four per cent.

Older children were more likely to present with iron deficiency anemia. 

But among the picky eaters, 'there was also no association between age and iron deficiency', the researchers from the National University Hospital, Singapore, said. 

'These findings could be related to the common use of formula milk when younger, which is fortified with nutrients including iron, thereby protecting against nutritional deficiencies.'

They acknowledged, however, the study did have limitations, including its small size. 

'As it was based on children whose caregivers agreed for blood investigations to be performed, these parents could have been more concerned regarding their child’s dietary habits,' they added. 

'This could have motivated them to proceed with blood investigations.'

If left untreated, vitamin D deficiencies can trigger more serious health issues including bone deformities like rickets.

Other side effects of low vitamin D include muscle pain, bone pain, pins-and-needles in the hands or feet and weakness.

Typically, the NHS says in summer months we should get all the vitamin D we need from sunshine, but in winter months some people need supplements.

Meanwhile, it should be possible to get enough iron through a balanced diet, but some people with low iron need tablets like ferrous fumarate.

Symptoms of low iron also include fatigue, shortness of breath, paler skin than usual and headaches.

It comes as US research earlier this week suggested autism diagnoses in young girls may be flying under the radar because their symptoms are milder than boys.

The findings have prompted concern that girls are missing out on key treatment and therapy that is leaving them prone to other health issues later on.

In England, the number of children seeking help for suspected autism has spiralled to an all-time high in Covid's wake.  

According to latest NHS figures, almost 130,000 under 18s in England were still awaiting an assessment in December 2024—a six-fold increase on the 20,000 logged in December 2019.

Experts have long warned that young people are facing an 'invisible crisis', with a system that has repeatedly failed to keep pace with rising demand.

Autism is not a disease and people have it from the moment they are born, although it may not be spotted until childhood and sometimes much later.

It exists on a spectrum. Some people will be able to lead fully functioning lives with no additional help. Others may need full-time assistance.