This is a guest post from Michelle Fitzpatrick of Happy Paleo Kids.  Michelle has worked with special needs children and their families for over 13 years to promote development and mental health. She adopted a “Paleo Diet ” to lose weight after baby number 3, and quickly saw that the benefits of eating nutrient-rich, plant-and-animal-based foods would benefit her entire family. After applying the Paleo Philosophy to her family, she felt compelled to find a way to bring the science behind how food impacts child development to the masses. Follow her blog  or keep up to date on Facebook , Twitter , and Instagram .
Yes! It’s summer! School is out, the sun is shining, and the kids are… glued to the iPad? I hope not. Summer is time for busy kids to catch up on things they don’t have time for during the school year (like play ). Most importantly, it is a time when days are long and the sun shines bright.
Our bodies are dependent on the sun to function properly. Paleolithic children basked in the sun’s rays, which regulate vitamin D production, brain chemistry, and circadian rhythms (sleep cycles). Today’s kids spend little time outdoors in comparison. Meals and leisure activities often take place inside, with the average 8-18-year-old  spending about 7 hours per day in front of a screen (eek!).
Sun is a commodity that is free (tell that to your friends that say the paleo lifestyle is expensive!), ample in summer (I know, this depends on where you live), and provides a wealth of health benefits. This summer is a great time for your family to create a habit of getting as much sun time as possible. A habit to carry out through the school year and beyond.
Vitamin D Production
About 90% of the body’s vitamin D is produced by the body when sunlight hits the skin. Vitamin D  plays a crucial role throughout the body. It helps metabolize and absorb calcium and other minerals (including zinc, magnesium, iron, and phosphate). It influences proteins that trigger gene expression (that is, turn genes on and off) and has a profound impact on the production of feel-good brain chemicals, such as beta-endorphins and serotonin. It modulates cell growth, neuromuscular function, immune function, and helps reduce inflammation.
Vitamin D is an important compound for kids’ developing bodies. Significant vitamin D deficiency prenatally through the first few months of life can lead to rickets , a disease that is characterized by soft, weak bones and poor motor development. In rats, developmental vitamin D deprivation leads to altered brain structure and function (with altered brain cell growth and “differentiation”)  , impaired attention and impulsivity.    
Scientists have not yet examined vitamin D and cognitive performance in healthy developing children. However, there is undisputed evidence that low vitamin D levels are associated with decreased cognitive functioning in adults and increased risk for dementia and Alzheimers in the elderly.   The pattern correlating cognitive deficiencies with low vitamin D likely continues down into childhood (now if only the research would catch up).
Children with ADHD  , autism  , and depression have been found to have lower blood levels of vitamin D than their typically developing peers. Researchers  don’t yet understand the nature of the relationship between vitamin D and ADHD or autism – are low serum levels of D triggering the expression of genes for these behaviors? Is there a disruption to the biosynthetic process of converting UVB rays into the vitamin D in these children? Time will tell. Intervention studies have not yet been conducted, but it’s possible that exposure to sunlight decreases behaviors associated with those disorders by increasing blood levels of vitamin D serum.
Circadian Rhythm Regulation
Sunlight is necessary to regulate our circadian rhythms (that is, our “internal clock” which determines our sleep/wake cycle). During evolutionary times, being active and awake during nighttime meant an increased chance of being eaten by a mountain lion or falling off a cliff. It was in our best interest to sleep during hours of darkness in order to decrease such risk. Modern amenities have lead to a decreased risk of harm at night, but they have also led to serious disruption of our circadian rhythms.
The American Association of Pediatrics recommends  that children sleep about 9-13 hours per night (depending on age). Sleep is a time when hormones and macronutrients go to work in the body so that bones, muscles, and organs can grow. The brain consolidates memories, processes emotions, produces important neurotransmitters in preparation of the day to come, and oxidative stress  due to environmental toxins are detoxified.
But a 2004 national survey  found that the average kid’s Z’s are falling short.
A 2013 study found that children who increase their daily sleep by one hour had improved emotion regulation, decreased impulsivity, and improved attention and behavior.   Restricted sleep has the opposite effect: decreased attention, memory (short and long term), academic performance, as well as difficulty with decision making, behavioral outbursts, depression and anxiety.    
Exposure to sunlight influences the production of serotonin, a chemical messenger in the brain (neurotransmitter) used to regulate mood and emotion (this is in part due to increased vitamin D and in part due to well balanced circadian rhythms). Researchers believe that serotonin plays an important role in brain development, as children actually have higher levels of serotonin than adults. Increased levels of serotonin  is related to feelings of well-being, joy and happiness in children, whereas low levels of serotonin are related to impulsivity, aggression, depression, anxiety and other developmental problems.  
More Time Outdoors
When kids are outdoors they are less likely to be sedentary. Outside there are infinite ways to get moving, including walking, playing basketball, or climbing at the playground. And if your kids aren’t being active they are still interacting with their environment in ways that are more beneficial to their development than if they are in front of a screen. Playing in the sandbox is great for sensory integration , and playing in the dirt can help improve their immune system. Simply going outside to read or eat a snack can be advantageous. Researchers have found that just hearing sounds and seeing sites of nature can have a positive, calming effect.  
Now put down the device on which you are reading this (after you go over and bookmark Happy Paleo Kids , of course 🙂 ) and take your kids to the park (or schedule an evening walk with friends or SOMETHING). Go!
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Duan, X., Jia, F., & Jiang, H. (2013). Relationship between vitamin D and autism spectrum disorder. CPJC: 15(8). 
Gruber, R., et al. (2012). Impact of sleep extension and restriction on children’s emotional lability and impulsivity. Pediatrics. 130(5). 
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9. Astill, Rebecca G., Kristiaan B. Van Der Heijden, Marinus H. Van IJzendoorn, and Eus JW Van Someren. (2012) Sleep, cognition, and behavioral problems in school-age children: A century of research meta-analyzed. Psychological Bulletin: 138(6).