Written by: Sandeep Ravindran, Ph.D. | Issue # 64 | 2017
- In a new study, researchers conducted a systematic review and meta-analysis of previous research on the relationship between milk consumption and cognitive disorders.
- The researchers analyzed seven articles published between 2006 and 2015 and found that higher milk intake was significantly associated with a decreased risk of cognitive disorders.
- The study could not rule out the influence of other confounding factors on the association between milk intake and cognitive disorders, and follow-up prospective studies are needed to further explore this association.
Increased age brings with it a greater risk of cognitive decline and disorders such as dementia and Alzheimer’s disease. The lack of effective treatments for these cognitive disorders has spurred the search for factors that can prevent or slow cognitive decline. One of the factors that has attracted a lot of interest is nutrition, and it turns out many of the things we eat or drink could play a role in preventing cognitive decline [1-4].
Given the widespread popularity of milk and its many beneficial health effects, several recent studies have investigated the association between milk intake and cognitive disorders [5-11]. However, so far these studies have come to contradictory conclusions. Some studies report that an increased risk of cognitive disorders is significantly associated with a lower intake of milk [5-8]. Other studies do not find this inverse association [9-11].
A new study tries to resolve these contradictory findings by conducting a systematic review and meta-analysis of previous observational studies that investigated the relationship between milk consumption and the risk of cognitive disorders . The study was conducted by Lei Wu of the Chinese People’s Liberation Army General Hospital and Dali Sun of the Houston Methodist Research Institute and expanded on a 2010 systematic review that showed an inverse association between dairy intake and cognitive functioning . The new study finds that higher milk intake is significantly associated with a decreased risk of cognitive disorders.
The researchers searched the Pubmed and Embase databases for observational studies that reported the association between milk consumption and cognitive disorders or cognitive decline. They identified seven articles published between 2006 and 2015 that fit the selection criteria for their analysis. The sample size of the studies ranged from 601 to 4809, for a total of 10,941 healthy participants.
The combined analysis of all seven studies showed that higher milk intake was significantly associated with a decreased risk of cognitive disorders and Alzheimer’s disease. The risk of cognitive disorders was reduced by 28% at the highest level of milk consumption compared with the lowest level of milk consumption.
The researchers note that these results were based on a limited number of studies and that there was significant heterogeneity in the association between milk intake and cognitive disorders. They conducted subgroup analyses based on factors such as race, gender, and type of dairy intake, and found that none of these explained the heterogeneity in their pooled analysis.
Although the study did not explore the mechanisms underlying milk’s preventive effects on cognitive disorders, the researchers suggest that they could be a result of milk’s beneficial effects on type 2 diabetes, hypertension, and obesity, all of which are associated with an increased risk of age-related cognitive impairment [14-16]. Another possible explanation is that the effects are due to some of the nutritional components of dairy, such as calcium and vitamin B12, which are known to have some effects on cognition .
Previous studies have also indicated that full-fat and low-fat dairy products could have different effects on cognitive function [18,19]. This wasn’t something the meta-analysis addressed, as the studies it evaluated did not describe the fat content of the milk. The researchers suggest that follow-up studies could investigate the role of high-fat or low-fat dairy on cognitive decline.
The researchers conclude that their systematic review and meta-analysis of previous observational studies showed an inverse association between milk consumption and cognitive disorders. However, due to the limitations of the study design, the meta-analysis was unable to rule out the influence of other confounding factors on the association between milk intake and cognitive disorders. The researchers suggest that large follow-up prospective studies are needed to further explore this association.
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