Written by Greg Arnold, DC, CSCS. Older adults with mild cognitive impairment significantly improved their learning memory scores after 6 weeks of a low carbohydrate diet  compared to those on a high carbohydrate diet.  

Alzheimer’s disease, the most common form of dementia among older adults, is a significant contributor to the $100 billion annual cost of dementia to the healthcare system (1).  In addition to the 5 million Americans with Alzheimer’s disease, an additional 5.4 million Americans have cognitive impairment without dementia (2), totaling more than 10 million Americans with at least some form of cognitive impairment (3).

While research has started to show that antioxidants like vitamin E may help maintain cognitive health (4), another focus involves obesity, since disturbances in blood sugar control and insulin levels “is a fundamental factor contributing to neurodegeneration” (5). In addition, type 2 diabetes increases the risk for dementia (6) and having high insulin levels may increase the risk for Alzheimer Disease by as much as 39% (7).

As a result, researchers are seeking ways to improve blood sugar control and maintain healthy insulin levels for mental health. One such option may be to follow a strict low-carbohydrate diet. A 2012 study (8), involved 23 older adults (10 men, 13 women) aged 64 to 79 with mild cognitive impairment (as confirmed using the Clinical Dementia Rating Scale (9)). They were assigned to either a high carbohydrate diet (50% of total calories) or a very low carbohydrate diet (5-10% of total calories) for 6 weeks. Total carbohydrate intake was the only nutrient that was monitored. Subjects were allowed to consume all the protein and fat they wished.

The focus on carbohydrate intake was designed to induce a condition called ketosis in the low carbohydrate group, whereby the body starts burning fat for energy (10) and leads to the presence of ketones in the urine (11). Throughout the study, researchers provided dietary education and counseling and maintained weekly contact with each subject.

After 6 weeks, those in the low-carbohydrate group averaged 34 grams of carbohydrate per day (compared to 197 grams in the high-carbohydrate group). The low-carbohydrate group had a significant improvement in their learning memory as assessed with the Verbal Paired Associate Learning Test (12). Specifically, those in the low-carbohydrate group had a 31.6% improvement in their score (12 to 15.8) compared to an 11% increase in the high-carbohydrate group (10 to 11.1) (p < 0.01).

The following changes were also noted between the two groups:

Low--carbHigh-carbp-value
Weight (kilograms)8.4% decrease
(84 to 77)
2.5% increase
(79 to 81)
< 0.0001
Waist Circumference (centimeters)9.1% decrease
(99 to 90)
2.1% increase
(93 to 95)
< 0.0001
Fasting glucose (milligrams/deciliter)9.5% decrease
(95 to 86)
1.1% decrease
(97 to 96)
0.009
Fasting insulin (microUnits/mL)29.6% decrease
(16.9 to 11.9)
0.6% increase
(14.4 to 14.5)
0.005

When attempting to explain the results in the low-carbohydrate group, the researchers suggested the benefits “may be attributable in part to correction of [high insulin levels], other mechanisms associated with ketosis such as reduced inflammation and enhanced energy metabolism also may have contributed to improved [mental] function.”

For the researchers, “These findings indicate that very low carbohydrate consumption, even in the short term, can improve memory function in older adults with increased risk for Alzheimer’s disease” though they admit “Further investigation of this intervention is warranted to evaluate its preventive potential and mechanisms of action in the context of early neurodegeneration.”

Source: Krikorian, Robert, Marcelle D. Shidler, Krista Dangelo, Sarah C. Couch, Stephen C. Benoit, and Deborah J. Clegg. “Dietary ketosis enhances memory in mild cognitive impairment.” Neurobiology of aging 33, no. 2 (2012): 425-e19.

© 2012 Elsevier Inc. All rights reserved.

Posted April 25, 2016.

Greg Arnold is a Chiropractic Physician practicing in Hauppauge, NY.  You can contact Dr. Arnold directly by emailing him at PitchingDoc@msn.com or visiting his web site at www.PitchingDoc.com.

References:

  1. “NIH-supported study finds U.S. dementia care costs as high as $215 billion in 2010” posted on the National Institute of Aging website April 4, 2013
  2. “Prevalence of Alzheimer’s Disease” posted on the National Institute of Aging website
  3. Blassman PL. Prevalence of Cognitive Impairment without Dementia in the United States. Ann Intern Med. 2008 March 18; 148(6): 427–434
  4. Mangialasche F.  Tocopherols and tocotrienols plasma levels are associated with cognitive impairment.  Neurobiol Aging 2012.  Printed online ahead of print December 11, 2011
  5. Craft, S. Insulin resistance syndrome and Alzheimer’s disease: Ageand obesity related effect on memory, amyloid, and inflammation. Neurobiol. Aging 2005;26S, S65–S69
  6. Biessels, G.J., Kappelle, L.J., 2005. Increased risk of Alzheimer’s disease in type II diabetes. Biochem. Soc. Trans 2004; 33, 1041–1044
  7. Luchsinger, J.A., Ming-Xiu, T., Shea, S., Mayeux, R.. Hyperinsulinemia and risk of Alzheimer’s disease. Neurology 2044; 63, 1187–1192
  8. Krikorian R. Dietary ketosis enhances memory in mild cognitive impairment. Neurobiol Aging. 2012 Feb;33(2):425.e19-27
  9. Hughes, C.P., Berg, L., Danziger, W.L., Coben, L.A., Martin, R.L., 1982. A new clinical scale for the staging of dementia. Br. J Psychiatry 1982; 140:566–572
  10. “Ketosis: What is Ketosis” posted on Medical News Today October 1, 2015
  11. Westman, E.C., Feinman, R.D., Mavropoulos, J.C., Vernon, M.C., Volek, J.S., Wortman, J.A., Yancy, W.S., Phinney, S.D.   Low-carbohydrate nutrition and metabolism. Am. J. Clin. Nutr 2007; 86: 276–284
  12. Krikorian, R., 1996. Independence of verbal and spatial paired associate learning. Brain Cogn. 32, 219–223.