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How the Standard American Diet (SAD) affects the brain (Part 2)

Part One | Part Two

a fast food hamburger meal with french fries

Good Fats (Omega-3s) vs. Bad Fats (Omega-6s)

There are 2 essential fatty acids we must obtain from our diet because our bodies cannot synthesize them:

1. alpha-linolenic acid (ALA): an omega-3 fatty acid and 
2. linoleic acid: an omega-6 fatty acid

Omega-3s play an essential role in the function of the nervous system, including: cognitive development, neuroplasticity (the ability of the brain to create new neural pathways), synaptogenesis (the creation of new synapses, or the connections between brain cells), and synaptic transmission (the actual transmission of signals between synapses). There are two types of omega-3 fatty acids: EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). These are "good" fats found in cold water fatty fish sources such as salmon, tuna, and trout. Omega 3 fatty acid supplementation was found to slow cognitive and functional decline over a 12 month period in subjects with Alzheimer's Disease when compared to placebo.11 Observational studies also show a positive correlation between fish intake and DHA plasma concentrations in healthy older adults and better cognitive health.12 

Omega-3s and fish consumption during pregnancy has also been associated with improved mental health scores in the women's children. Research in children up to 8 years of age has shown that 2 or more servings of fish per week in pregnant women led to lower inattentive and hyperactivity scores in those children.13 In fact, taking omega-3 supplements is believed to be beneficial for ADHD, depression, and bipolar disorder, and has also shown beneficial effects for mild cognitive impairment. Lower blood levels of these essential fatty acids have been associated with ADHD.14 

While also "essential" for health, like omega-3 fatty acids, omega-6 fatty acids tend to cause health problems when their levels are too high. omega-6s play a role in programmed cell death (a normal process) and so tend to promote inflammation. Omega-6 fats are often found in processed foods that use soybean oil. 

The recommended ratio of omega-3 to omega-6 fatty acid intake for an optimal diet is ideally 1.6:1, but 1:1 is a good goal. Unfortunately the standard American diet contains 14 to 25 times more omega-6 fatty acids than omega-3 fatty acids.15

Bad Fats Good Fats
Trans fats (hydrogenated oils)
Packaged and processed foods (high in omega-6)
Foods high in omega-3s:
Cold water fish: salmon, tuna, trout; Flax seed, chia seed; olive oil; walnuts

Preservatives/Artificial Food Coloring and the Link to ADHD

In our media saturated society, kids are vulnerable targets for food advertisements featuring brightly colored, sugar-laden cereals like Trix and Fruity Pebbles. Many of these attractive food items are chock full of artificial food coloring and preservatives.16 

Stevens et al.'s compilation of 35 years' worth of studies on dietary sensitivities and associated ADHD symptoms in children and adolescents, published in the journal Clinical Pediatrics, highlights examples of randomized controlled trials in which children and adolescents were fed elimination diets without artificial food coloring (AFCs) and then given diets with AFCs added back.17  

The studies found that in those children who had already been diagnosed with moderate to severe ADHD, consuming AFCs worsened their symptoms. Those children who did not have ADHD also were less attentive and showed increased hyperactivity. In a randomized, double-blinded, placebo-controlled, crossover trial examining the effects of AFCs or the preservative sodium benzoate (or both) in the diet of 3 year olds and 8 or 9 year olds that lasted 7 weeks, those who consumed over 85% of the premixed drinks containing either or both additives showed a statistically significant increase in hyperactivity symptoms as measured on a global hyperactivity assessment scale.18 

Food additives have been linked to numerous adverse health effects. Studies in humans have shown an increase in the tendency to develop allergic reactions, greater hyperactivity and inattentive behaviors, and sleep disturbances including taking longer to fall asleep.

Micronutrients and Neurocognition

Iron is an essential mineral involved in making red blood cells, which are crucial for oxygen transport. It is needed for cell growth and healthy immune function. In the brain, it is an essential component of brain myelination (the process of forming myelin sheaths around certain brain cells which allow nerve impulses to travel more quickly), energy metabolism, and the creation and metabolism of certain neurotransmitters, including dopamine, serotonin, GABA (gamma-aminobutyric acid), and glutamate.19 

In seven studies, iron supplementation appeared to improve memory and intellectual ability in healthy, pre-menopausal women between 12 and 55 years of age, regardless of whether the participant had mild or severe iron deficiency.20 

Studies have shown that children and adolescents who have been diagnosed with ADHD tend to have low serum iron and ferritin levels. Lower serum iron levels have also been found in patients with anxiety, depression, and schizophrenia. In children with low serum ferritin, taking 80 mg/day of iron supplements has been shown to reduce ADHD symptoms about as well as taking stimulants, with few side effects other than mild stomach or intestinal problems. Over the course of the study, their ADHD symptoms improved in line with their serum ferritin levels.21

Recommended daily allowance (RDA) for iron depends on age, gender, and special conditions (see table below). In general, 18 mg/day is recommended. Foods made from enriched flour (bread, pasta, pancakes, etc.) can add a significant amount of iron over the course of a day. Spinach is probably the first food you think of when you think of good iron sources, but iron is found in many other vegetables as well, including broccoli, chard, collards, asparagus, Jerusalem artichokes, baked potato with skin, snap peas, pumpkin, mushrooms, tomato products, and whole grains. Meal replacement drinks (such as Instant Breakfast, etc.) also have a significant amount of iron. While the iron from supplements is not as well absorbed as that from food, supplements are needed when people have true iron deficiency.

Sources of Iron mg / svg %DV
Fortified cereals 18 100%
White beans, canned, 1 cup 8 44%
Beef liver, pan fried, 3 ounces 5 28%
Lentils, boiled and drained, 1/2 cup 3 17%
Spinach, boiled and drained, 1/2 cup 3 17%
Tofu, firm, 1/2 cup 3 17%
Beef, braised bottom round, trimmed, 3 ounces 2 11%
Tomatoes, canned, stewed, 1/2 cup 2 11%
Chicken, roasted, meat and skin, 3 ounces 1 6%

Zinc supplementation has been studied in treating and alleviating symptoms of ADHD, but the evidence, whether zinc is used by itself or along with stimulant medications, is conflicted.22 We just do not have enough information to recommend for or against zinc supplementation in treating ADHD, but it's certainly smart to make sure that those with ADHD are getting enough minerals in their diet. (Discuss this with your doctor.)

Antioxidants from berries and walnuts and their effects on cognitive health

The brain is more susceptible to oxidative stress than any other organ. Oxidative stress, along with inflammation, plays a role in aging and age-related cognitive disorders like Alzheimer's Disease. Brain-derived neurotrophic factor (BDNF) plays an important role in brain cells' creation, ability to change over time, and regeneration. Positive associations have been seen between omega-3 fatty acid and flavanol intake and BDNF production.23

Berry fruits have strong antioxidant and anti-inflammatory benefits. They contain anthocyanins, a type of plant compound which has antioxidant and anti-inflammatory properties. Anthocyanins have been associated with increased signaling in the brain, mediating memory, and facilitating the body's ability to make use of circulating glucose.24

In a small study of elderly men and women (average age 76) with early memory decline (including general forgetfulness as well as forgetting things they had planned to do later), drinking blueberry juice on a daily basis for 12 weeks was shown to significantly improve memory function - and it helped reduce symptoms of depression.25

In a large scale study of participants older than 70, consuming more strawberries and blueberries was associated with a slower progression of cognitive decline in older women.26

Tree nuts are a good source of essential nutrients and contain a variety of substances that decrease inflammation and reduce oxidative stress.27 Walnuts in particular contain a number of potentially neuroprotective compounds like vitamin E, folate, melatonin, several types of antioxidants, and significant amounts of omega-3 fatty acid. A randomized cross-over trial of over 200 healthy male and female college-age students showed that their verbal reasoning scores improved after adding walnuts to their diet for eight weeks.28

Walnuts have also been shown to have the highest level of antioxidant capacity as compared to other nuts. The PREDIMED-NAVARRA trial showed that when nuts were added to a Mediterranean diet, there was a 78% lower risk of having low levels of plasma BDNF (brain derived neurotrophic factor).29

Curcumin - an Indian spice and its beneficial effects for neurocognition

Curcumin is an antioxidant compound found in turmeric, which is traditionally used in Indian cooking. It is the yellow pigment present in turmeric and shows promising potential as a neuroprotective agent. There is substantial in-vitro data indicating that curcumin has antioxidant and anti-inflammatory properties, and studies in animal models of Alzheimer's Disease indicate that curcumin may help decrease the growth of amyloid plaques that are typical of Alzheimer's. Several clinical trials are currently underway to examine this potential specifically in Alzheimer's Disease patients.30, 31


The current Standard American Diet is not only impairing our physical functioning, it impairs the functioning of our brains. Be mindful of eating whole, unprocessed foods like vegetables, fruits, legumes, nuts, and complex carbohydrates, along with good fats like omega-3s. Eating whole foods also helps us obtain micronutrients and antioxidants from our diet to optimize our brain function and slow neurocognitive decline.


1. When possible, choose whole foods. 

2. Aim for a "rainbow colored" plate with ample fruits & vegetables.

3. Avoid omega 6 fatty acids, trans fats, and food additives whenever you can, as these impair both short term and long term brain health.

4. Omega-3 fatty acids are good sources of fats with anti-inflammatory effects. They can be found in fatty fish like salmon, tuna, and trout, and in walnuts and olive oil. Omega-3s boost cognitive function and improve mood, so aim for at least 3 servings a week.

5. Stock up on nuts and berries. Buy berries fresh when they are in season or buy frozen berries for their antioxidant effects. Nut butters are delicious, filling and healthy.

6. The buddy system is not only fun but helps you be mindful of how much you are eating or exercising. Recruit a friend to break bread with or to exercise with.


11. Shinto et al. "A randomized placebo-controlled pilot trial of omega-3 fatty acids and alpha lipoic acid in Alzheimer's disease." Journal of Alzheimer's Disease. 2014;38(1):111-20.

12. Morris MC, Evans DA, Bienias JL et al. "Consumption of fish and n-3 fatty acids and risk of incident Alzheimer's disease." Arch Neurol. 2003; 7: 940-6

13. Sagiv et al. "Prenatal Exposure to Mercury and Fish Consumption During Pregnancy and Attention-Deficit/Hyperactivity Disorder-Related Behavior in Children." Arch Pediatr Adolesc Med. 2012;166(12):1123-1131.

14. Bloch M, Qawasmi A. "Omega 3 Fatty Acid Supplementation for the treatment of children with ADHD symptomatology: systemic review and meta-analysis." Journal of American Academy of Child & Adolescent Psychiatry, October 2011, 51; 10, 991-9.

15. NIH Meeting on the Essentiality of and Recommended Dietary Intakes (RDIs), 1999

16. Kaliebe and Krishna. "Trix Are For Kids!" American Academy of Child and Adolescent Psychiatry. May-June 2013. Vol. 44, Issue 3.

17. Stevens et al. "Dietary Sensitivities and ADHD Symptoms: Thirty-Five Years of Research." Clinical Pediatrics 2011;50(4):279-293

18. McCann et al. "Food additives and hyperactive behaviour in 3-year-old and 8/9-year-old children in the community: a randomised, double-blinded, placebo-controlled trial." Lancet 2007; 370: 1560-67

19. Resnick. "Iron and mechanisms of emotional behavior." J Nutr Biochemistry. 2014;25(11):1101-1107.

20. Lomagno et al. "Increasing iron and zinc in pre-menopausal women and its effects on mood and cognition: a systematic review." Nutrients. 2014 Nov 14;6(11):5117-41.

21. Konofal et al. "Iron Deficiency in Children with ADHD." Arch Ped Adolesc Med. 2004;158(12):1113-1115.

22. DiGirolamo et al. "Randomized trial of the effect of zinc supplementation on the mental health of school-age children in Guatemala." The American Journal of Clinical Nutrition. Nov 2010; 92(5): 1241-1250.

23. Arnold et al. "Zinc for Attention-Deficit/Hyperactivity Disorder: Placebo-Controlled Double-Blind Pilot Trial Alone and Combined with Amphetamine ." Journal of Child and Adolescent Psychopharmacology. Nov 2011; 21(1): 1-19.

24. Sánchez-Villegas, Almudena, et al. "The effect of the Mediterranean diet on plasma brain-derived neurotrophic factor (BDNF) levels: the PREDIMED-NAVARRA randomized trial." Nutritional neuroscience 2011;14(5): 195-201.

25. Joseph, James A., Barbara Shukitt-Hale, and Lauren M. Willis. "Grape juice, berries, and walnuts affect brain aging and behavior." The Journal of Nutrition 2009;139(9): 1813S-1817S.

26. Krikorian, Robert, et al. "Blueberry Supplementation Improves Memory in Older Adults." Journal of Agricultural and Food Chemistry 2010;58(7): 3996-4000.

27. Devore, Elizabeth E., et al. "Dietary intakes of berries and flavonoids in relation to cognitive decline." Ann Neur 2012;72(1): 135-143.

28. Pribis, Peter, et al. "Effects of walnut consumption on cognitive performance in young adults." British Journal of Nutrition 2012;107(9): 1393-1401.

29. Sánchez-Villegas, Almudena, et al. "The effect of the Mediterranean diet on plasma brain-derived neurotrophic factor (BDNF) levels: the PREDIMED-NAVARRA randomized trial." Nutritional Neuroscience 2011;14(5): 195-201.

30. Brondino N, Re S, Boldrini A, et al. Curcumin as a Therapeutic Agent in Dementia: A Mini Systematic Review of Human Studies. The Scientific World Journal 2014;2014:174-282. 

31. Ringman JM, Frautschy SA, Cole GM, Masterman DL, Cummings JL. A Potential Role of the Curry Spice Curcumin in Alzheimer's Disease. Current Alzheimer Research 2005;2(2):131-136.

Timothy S. Harlan, M.D.
Dr. Gourmet