I saw a couple of people in the low carb world tweet about this week’s study. It was published on December 18th, 2020 in the journal Age and Ageing and it was called “Consumption of dietary nuts in midlife and risk of cognitive impairment in late-life: the Singapore Chinese Health Study” (Ref 1).
The study is one of those nutritional epidemiology studies with which we're familiar. The study also emanates from a well-established population study, which we're used to seeing. Large scale new population studies are rare. Most papers like this one are just re-examinations of data from long standing studies.
This paper uses the Singapore Chinese Health study data. Data from 16,737 participants were analysed. Participants came from two major Chinese dialect groups – the Hokkiens and the Cantonese – who originally came from Fujian and Guangdong provinces in China, respectively.
This population study goes back a long way. A food frequency questionnaire (FFQ) was completed at baseline, which was between 1993-1998. At that time, participants were, on average 53.5 years old (age range at recruitment was 45-74). Women accounted for 59% of participants. Cognitive function was tested using the Singapore Modified Mini-Mental State Examination (SM-MMSE). This was conducted during the third follow-up visit (2014–2016), when participants were 61–96 years old (mean age=73.2 years).
Dietary intake was assessed using a 165-item FFQ at baseline. The paper noted that one of the limitations of the study was “the consumption of nuts was only assessed once at baseline and time-varying changes during the follow-up could not be measured.” This means that cognitive ability in 2014-2016 was evaluated for its association with recalled nut intake in 1993-1998. (You may like to read that sentence again). Nut intake included "combination of peanuts and tree nuts as a single item from 16 mixed food dishes in the FFQ and did not distinguish by types of nuts." Peanuts are legumes, but they were included in the definition of nuts. A serving was defined as 1-ounce (28g).
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