Diet and attention deficit hyperactivity disorder
For some children, diet is suspected of playing a role in the multiple behavioral and cognitive symptoms of attention deficit hyperactivity disorder (ADHD). Concerns have focused on food additives, blood sugar regulation, food allergies and intolerances, and vitamin, mineral and fatty acid deficiencies.
Food coloring and additives
Pediatrician Benjamin Feingold claimed a link between artificial dyes, preservatives, and ADHD in the 1970s. He proposed the Feingold diet as a solution, which eliminates certain processed foods and food additives as well as certain fruits and vegetables.
In September 2007, research financed by Britain’s Food Standards Agency and published online by the British medical journal The Lancet presented evidence that a mix of additives commonly found in children’s foods increases the mean level of hyperactivity.
The team of researchers concluded that "the finding lends strong support for the case that food additives exacerbate hyperactive behaviors (inattention, impulsivity and overactivity) at least into middle childhood." That study examined the effect of artificial colors and a sodium benzoate preservative, and found both to be problematic for some children. Further studies are needed to find out whether there are other additives that could have a similar effect, and it is unclear whether some disturbances can also occur in mood and concentration in some adults. In the February 2008 issue of its publication, AAP Grand Rounds, the American Academy of Pediatrics concluded that a low-additive diet is a valid intervention for children with ADHD:
Although quite complicated, this was a carefully conducted study in which the investigators went to great lengths to eliminate bias and to rigorously measure outcomes. The results are hard to follow and somewhat inconsistent. For many of the assessments there were small but statistically significant differences of measured behaviors in children who consumed the food additives compared with those who did not. In each case increased hyperactive behaviors were associated with consuming the additives. For those comparisons in which no statistically significant differences were found, there was a trend for more hyperactive behaviors associated with the food additive drink in virtually every assessment. Thus, the overall findings of the study are clear and require that even we skeptics, who have long doubted parental claims of the effects of various foods on the behavior of their children, admit we might have been wrong.
Several other recent studies have renewed interest in whether certain foods and additives might affect particular symptoms in a subset of children with ADHD.
As of mid-2009, the consensus on a sensible approach to nutrition for children with ADHD is the same recommended for all children: eat a diet that emphasizes fruits and vegetables, whole grains, healthful unsaturated fats, and good sources of protein; go easy on unhealthy saturated and trans fats, rapidly digested carbohydrates, and fast food; and balance healthy eating with plenty of physical activity. (Emphasis added) 
As yet there is no consensus about how such additives might contribute to ADHD symptoms in children. In a recent well-designed study in Britain, the investigators found a mild but significant increase in hyperactivity in both age[clarification needed] groups of children—across the board, regardless of baseline hyperactivity levels—during the weeks when they consumed drinks containing artificial colors. This study concluded that the additives might explain about 10% of the behavioral difference between a child with ADHD and one without the disorder.
An earlier meta-analysis conducted at Columbia University and Harvard University suggests that removing these agents from the diets of children with ADHD would be about one-third to one-half as effective as treatment with methylphenidate (Ritalin).
Authors of both of these studies cautioned that only a minority of children are particularly vulnerable to the effects of artificial additives. They also pointed out that determining which children are susceptible is difficult, though not impossible.
The European Food Safety Authority (EFSA) reviewed the literature on the association between food additives and hyperactivity and concluded that there is only limited evidence of an association between the intake of additives and activity and attention and then only in some children studied. They further indicated that the effects reported in the study were not consistent for the two age groups and for the two food additive mixtures used in the study. Others have suggested a trial of removing additives from the diet for children with ADHD as it is harmless and might be helpful.
As of March 2011, the FDA was evaluating the scientific evidence of a link between dyes and ADHD; a preliminary analysis found there was no link.
According to the Food Standards Agency, the food regulatory agency in the UK, food manufacturers are encouraged to voluntarily phase out the use of most artificial food colors by the end of 2009. Sunset yellow FCF (E110), quinoline yellow (E104), carmoisine (E122), allura red (E129), tartrazine (E102) and ponceau 4R (E124) are collectively called the "Southampton six". The European Food Safety Authority ruled that any food products containing the contentious colors must display warning labels on their packaging by 2010.
A number of studies have found that sucrose (sugar) has no effect on behavior and in particular it does not exacerbate the symptoms of children diagnosed with ADHD. One study demonstrated the impact of expectancy effects in parents' perceptions of their children's hyperactivity after consuming sugar. In this study, parents who were told their child had ingested a high concentration of sugar in drink form (even though the drink was actually flavored with aspartame), reported their child as being more active, inattentive and resistant to parental demands. This was in comparison to the group who were told (accurately) that their child had ingested no sugar.
Omega-3 fatty acids
Some research suggests that children with ADHD may have low blood levels of essential omega-3 fatty acids. However, it is unknown if decreased blood levels of omega-3 fatty acids can cause or exacerbate ADHD or whether lower blood levels of omega-3 fatty acids associated with ADHD are caused by an underlying mechanism. Fish oils appear to reduce ADHD-related symptoms in some children. A double blind study has showed "medium to strong treatment effects of omega 3 fatty acids on symptoms of ADHD" after administering amounts around 1 gram for three to six months. Several other studies showed similar effects, especially of Omega 3 fatty acids with Zinc and Magnesium. A recent longitudinal study that examined the effect of omega-3 in an animal model of ADHD found gender-specific changes in all ADHD-symptoms. Thus though it is increasingly documented in clinical studies that omega 3 fatty acids provide a safe way to treat ADHD-symptoms the mechanism of the effect may interact with several other factors such as gender.
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