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Diet, children and brain function

Obesity steals youth and happiness

There is no greater risk to the current and future health of young children or teenagers than obesity. The two major factors that predispose young people to obesity are a lack of sleep and the consumption of calorie-dense, fat-enriched foods. Sleep deprivation, prolonged wakefulness and a high-fat diet all lead to increased insulin resistance and reduced insulin secretion and poor growth. A fat-enriched diet can impair the actions of leptin, a hormone that regulates food intake, and stress hormones to correctly act within the brain. Changes in how these chemicals affect the brain may constitute the early warning signs of a disturbed energy balance leading toward obesity.

The adequacy of nutrition during the early formative years may have long-term consequences on the brain. Because shrinkage of the brain actually begins in young adulthood, any insidious influence of diet could begin early and progress over a period of many decades. Clearly, diet is influential on brain growth and function throughout the entire lifespan.

Obesity is not just an American problem. A recent study of 1229 European, Polynesian and Asian children aged 5-11 years, after controlling for differences in sex, age, and socioeconomic status (SES), determined that Asian children were more likely to have excess body fat than European children. The odds of being overweight increased with age and decreased with SES. Not surprisingly, there were three very familiar lifestyle risk factors related to likelihood of obesity: low physical activity, skipping breakfast, and insufficient sleep on schooldays. What was surprising in this study was the discovery of factors that had no influence on whether these kids were obese, such as participation in organized sports, availability of school lunches and fast food or sugary drink consumption. A study of over 59,000 children and teenagers in Europe consistently indicated that eating breakfast was protective against becoming obese and reducing one body mass index (BMI). Furthermore, across all of these investigations, boys seemed to benefit more than girls from eating breakfast.

Still, how strong is the evidence for not skipping breakfast? A systematic review forty-one published studies between 1950 and 2008 examined the potential benefits of breakfast on cognitive performance in well-nourished children and nutritionally at-risk or stunted children. The results indicate that eating breakfast is more beneficial than skipping breakfast, but this effect is more apparent in children whose nutritional status is already compromised.

Most parents want to also know whether it matters what is eaten for breakfast. Sadly, there is still too little information available that compares breakfast content, precluding making any accurate recommendations for the size and composition of the optimal breakfast for children's brain function. A few studies suggest that public school breakfast programs can have positive effects on academic performance, but these findings are confounded by the fact that these programs also increase school attendance.

What is known about the content of a good breakfast on the brain as children grow? Without doubt, the quality of breakfast positively affects the cognitive functioning of well-nourished children, so let's focus upon them. 290 children underwent studies to determine whether the content of their breakfast affected the amount of gray matter in their brain or their IQ. Breakfast types were divided into rice or bread-based foods, or both. The children who ate rice for breakfast had significantly enlarged gray matter volumes in several brain regions critical for language and thinking. The children who ate bread also exhibited some significant increases in both gray and white matter volumes in at least one brain region related to abstract thinking. The results were complicated and it's difficult to draw specific conclusions, however, these studies demonstrate that what children eat for breakfast does affect how their brain grows.

Every parent is aware that diet can affect the behavior of children and adolescents. Most often, we hear how the beneficial effect of their diet results mainly from the correction of poor nutritional choices. For example, thiamin treatment reverses aggressiveness in thiamin-deficient adolescents who consume too much alcohol or too little lean meats and fish. It was once thought that too much sugar or certain food additives induced hyperactivity, but these effects have never been confirmed by more careful scientific investigations.

Overall, the published evidence suggests that good dietary habits are the best way to ensure optimal brain performance. No solid evidence exists that additional benefit can be gained from acute dietary manipulations such as taking specific vitamins, minerals or herbals in the absence of a true deficiency. For example, there is increasing evidence that a deficiency of vitamin C and zinc in the diet can adversely affect the physical and mental development of children. In general, nutrition should be the main vehicle for providing all essential nutrients; however, supplementation should not yet be ignored as a valid support for the development of the brain.

© Gary L.Wenk, Ph.D., author of Your Brain on Food (Oxford, 2010)