Energy and Protein Intake of Alzheimer's Disease Patients Compared to Cognitively Normal Controls: Systematic Review

J Am Med Dir Assoc. 2019 Jan;20(1):14-21. doi: 10.1016/j.jamda.2018.06.019. Epub 2018 Aug 9.


Objectives: Protein and energy malnutrition and unintended weight loss are frequently reported in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD). Possible underlying mechanisms include increased energy expenditure, altered uptake of nutrients, a reduced nutritional intake, or a combination of these 3. We aimed at systematically reviewing the literature to examine potential differences in energy and protein intake in patients with MCI and AD compared to controls as a possible mechanism for unintended weight loss.

Design: Systematic review and meta-analysis.

Setting: PubMed and Cochrane Electronic databases were searched from inception to September 2017 for case control studies.

Participants: Patients with MCI or AD compared to cognitive healthy controls, all adhering to a Western dietary pattern.

Measurements: Energy and protein intake.

Results: The search resulted in 7 articles on patients with AD versus controls, and none on patients with MCI. Four articles found no differences in energy and protein intakes, 1 found higher intakes in patients with AD, and 1 article found lower intakes in patients with AD compared to controls. One article reported on intakes, but did not test differences. A meta-analysis of the results indicated no difference between patients with AD and controls in energy [-8 kcal/d, 95% confidence interval (CI): -97, 81; P = .85], or protein intake (2 g/d, 95% CI: -4, 9; P = .47). However, heterogeneity was high (I2 > 70%), and study methodology was generally poor or moderate.

Conclusion: Contrary to frequently reported unintended weight loss, our systematic review does not provide evidence for a lower energy or protein intake in patients with AD compared to controls. High heterogeneity of the results as well as of participant characteristics, setting, and study methods was observed. High-quality studies are needed to study energy and protein intake as a possible mechanism for unintended weight loss and malnutrition in both patients with MCI and AD.

Keywords: Older adults; malnutrition; mild cognitive impairment.

Publication types

  • Research Support, Non-U.S. Gov't
  • Systematic Review

MeSH terms

  • Alzheimer Disease / complications*
  • Cognitive Dysfunction / complications*
  • Dietary Proteins / administration & dosage*
  • Energy Intake*
  • Humans
  • Protein-Energy Malnutrition / diet therapy*
  • Protein-Energy Malnutrition / etiology*


  • Dietary Proteins