Children usually need only small amounts of B6 in their daily diet. The Food and Nutrition Board of the National Institutes of Medicine established Recommended Daily Allowances, or RDAs, for a number of vitamins, including B6. For children aged 1 to 3 years, the RDA is 0.5 mg per day. Children ages 4 through 8 need 0.6 mg daily, and children ages 9 through 13 need 1 mg.

Research suggests that children with autism don't process B6 well from foods and may benefit from supplements. In 1985 the journal "Biological Psychiatry" reported that giving unspecified large doses of B6 and magnesium to autistic children resulted in improved language skills and behavior, but a 2002 review was unable to find studies that verified this result. More research is needed to verify the effect of B6 on children with autism. Don't give your autistic child B6 without your pediatrician's okay.

Some children with Attention Deficit Hyperactivity Disorder, or ADHD, may benefit from B6 supplements as well. A French study in 2006, in which 40 children diagnosed with ADHD were given B6 and magnesium supplements for eight weeks, showed improvement in the behavior of the children given the supplements after just two weeks. The children took magnesium along with the B6 because magnesium neutralizes some of the possible negative side effects of B6. In the study, the children were given 0.6 mg of B6 for every kilogram of their body weight, along with 6 mg of magnesium for every kilogram of body weight. If your child has ADHD, consult with your physician before adding B6.

High doses of B6 can lead to pain and nerve damage. Don't give your child B6 supplements without your doctor's approval. For children, good sources of B6 include fortified cereals, bananas, chicken, turkey and potatoes. A medium baked potato has about 0.7 mg of B6, while a medium banana has 0.43 mg.