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|How the Standard American Diet (SAD) affects the brain (Part Two)||05/26/16|
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Last weekend I spoke to a conference of psychiatrists about Culinary Medicine. They were amazingly receptive and had a great response to the lecture. Those in behavioral medicine are very interested in understanding how food and lifestyle can impact our mood and mental health, and at the Goldring Center for Culinary Medicine we have a number of psychiatrists pursuing our certification in Culinary Medicine.
Those of you who have been following Dr. Gourmet for a while know that I believe in having quality evidence - preferably from controlled trials - before being able to make a claim about a particular intervention. While there is not a great deal of direct research that links poor diet to increased depression or mental health issues, there's more than enough indirect evidence for you to want to watch these three things:
Obesity, metabolic syndrome, and diabetes are all a function of abnormal processing of glucose. When blood sugars are chronically high, our bodies churn out insulin in an effort to cope with the excess glucose. The excess insulin levels induce a pro-inflammatory state. 1 This leads to overproduction of reactive oxygen species and thus to oxidative stress. This pro-inflammatory state has been shown to cause disruptions in how the brain processes neurologic impulses. The hippocampus (the brain's memory formation and processing center) is particularly susceptible to high blood sugars, and wide swings in blood glucose can lead to a decrease in its volume and structure. 2
Similarly, patients with diabetes have an increased risk of Alzheimer's Disease. The higher insulin levels seen in diabetics appear to impair our ability to clear amyloid beta proteins from the body, a pathologic feature of Alzheimer's Disease. 3
Amyloid beta proteins are the main component of the plaques in the brain typifying Alzheimer's Disease, and impaired signaling between brain cells is linked to accelerated brain aging, which includes damage to small blood vessels. Such changes have been shown on MRI in patients with Alzheimer's, and these lesions, along with other structural changes, have been found to occur at higher rates in diabetic vs. non-diabetic populations. 4 This is supported by research that shows poorer cognitive scores in Type 2 diabetics without dementia. 5
To help you reduce the risk of diabetes and metabolic syndrome, follow a Mediterranean diet plan. Here's our guide to understanding a Mediterranean-style diet.
Fat is not the enemy, but for folks who do eat too much fat and fewer quality fats there has been a link with memory loss, especially in those consuming higher levels of saturated fats. This includes functions involving memory, speed, and cognitive flexibility in both the short term and the long term. 6 In one study of men, a high fat diet was linked to significantly decreased attention scores. 7 In another study, high saturated fat intake was linked to decline in memory, processing speed, and attention measures over a six year period. 8
The key is to consume less saturated fat (not none) and higher proportions of omega -3 fatty acids. Omega-3s play a key role in the function of the nervous system, and for those who already had Alzheimer's, taking omega-3 fatty acid supplements (as opposed to a placebo) were found to slow cognitive and functional decline over a 12 month period. 9 The recommended ratio of omega-3 to omega-6 fatty acid intake for an optimal diet is 1.6:1 (think of it as 1.6 teaspoons of omega-3s to 1 teaspoon of omega-6s). Unfortunately the standard American diet contains 14 to 25 times more omega-6 fatty acids than omega-3 fatty acids. 10
Here are some great recipes that can help you increase your consumption of great quality fats:
Oxidative stress caused by the inflammatory process plays a role in age-related memory disorders like Alzheimer's Disease. A substance known as brain-derived neurotrophic factor (BDNF) is critical for brain cell creation, ability to change over time, and regeneration. Positive associations have been seen between omega-3 fatty acid and antioxidant consumption and BDNF production. 11
For example, berries have antioxidant and anti-inflammatory benefits, and higher consumption is linked to increased signaling in the brain, mediating memory. 12 In a small study of elderly men and women with early memory decline, drinking blueberry juice on a daily basis was shown to significantly improve memory function and reduce symptoms of depression. 13 In another study, consuming more strawberries and blueberries was associated with a slower progression of cognitive decline in older women. 14
Tree nuts are a good source of antioxidants that decrease inflammation, and 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. 15
Walnuts have 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. 16
Here are some of my favorite recipes using nuts:
There have been a number of studies that link fast food and processed food consumption with depression. The best quality study was performed in Spain with about 9,000 participants. That research showed that people with the highest consumption of processed foods had almost a 50% increased risk of depression. 17 Those with a higher Mediterranean Diet score have been shown to have a higher physical quality of life as well as a better emotional quality of life (although the mental health association was not as strong). 18
In a study of children, those kids consuming fast food on a daily basis were almost twice as likely to experience depression and to experience feelings of worthlessness and anxiety. 19
There are other links including micronutrient levels such as iron (linked with cognitive decline) and turmeric (shown to reduce memory decline in animal models) as well as magnesium, zinc, and artificial food coloring (linked with ADHD).
These four: reducing blood sugar by following a diet low in simple sugars and high in fiber, increasing the quality of fats in your diet, getting more antioxidants, and stopping consumption of highly processed food - can make a huge difference in your mood and memory now and your risk of memory loss as you grow older.
Timothy S. Harlan, MD, FACP
1. Roriz-Filho et al. "(Pre)diabetes, brain aging, and cognition." Diabetes and the Nervous System 2009;1792(5):432-443
2. Kerti et al., "Higher glucose levels associated with lower memory and reduced hippocampal microstructure." Neurology 2013;81:1746-52
3. Roriz-Filho et al. "(Pre)diabetes, brain aging, and cognition." Diabetes and the Nervous System 2009;1792(5):432-443.
4. Akisaki et al. "Cognitive dysfunction associates with white matter hyperintensities and subcortical atrophy on magnetic resonance imaging of the elderly diabetes mellitus Japanese elderly diabetes intervention trial (J-EDIT)." Diabetes Metabolism Research and Review 2006; 22:376–384.
5. Geijselaers et al. "Glucose regulation, cognition, and brain MRI in type 2 diabetes: a systematic review." Lancet Diabetes Endocrinology 2015; 3:75-89.
6. Barnard et al. "Saturated and trans fats and dementia: a systemic review." Neurobiology of Aging 2014; 35(2): S65–S73.urated and trans fats and dementia: a systemic review." Neurobiology of Aging 2014; 35(2): S65–S73.
7. Edwards et al. "Short-term consumption of a high-fat diet impairs whole-body efﬁciency and cognitive function insedentary men." The FASEB Journal. March 2011, Vol 25.
8. Morris et al. "Dietary fat intake and 6-year cognitive change in an older biracial community population." Neurology 2004;62(9):1573-9.
9. 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.
10. NIH Meeting on the Essentiality of and Recommended Dietary Intakes (RDIs), 1999
11. 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.
12. 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.
13. Krikorian, Robert, et al. "Blueberry Supplementation Improves Memory in Older Adults." Journal of Agricultural and Food Chemistry 2010;58(7): 3996-4000.
14. Devore, Elizabeth E., et al. "Dietary intakes of berries and flavonoids in relation to cognitive decline." Ann Neur 2012;72(1): 135-143.
15. Pribis, Peter, et al. "Effects of walnut consumption on cognitive performance in young adults."British Journal of Nutrition 2012;107(9): 1393-1401.
16. 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.
17. Sanchez-Villegas, et al Fast-food and commercial baked goods consumption and the risk of depression Public Health Nutrition: 15(3), 424–432
18. Sanchez-Villegas, et al, Adherence to the Mediterranean diet and quality of life in the SUN Project European Journal of Clinical Nutrition (2012) 66,360–368; doi:10.1038/ejcn.2011.146; published online 17 August 2011
19. Zahedi, H, et al, Association between junk food consumption and mental health in a national sample of Iranian children and adolescents: The CASPIAN-IV study, Nutrition 2014; 30 (11-12): 1391-1397).