The researchers, affiliated with the School of Health Sciences at the University of South Australia, argued that it is significant because it hints at lutein’s role in chronic disease prevention.
“The hypothesis that lutein might increase physical activity is novel. Therefore, while 135 studies were identified that had measured both lutein status and physical activity, only 17 of them formally tested whether there was a relationship between the two,” they wrote in their report, published this week in the open-access journal Nutrients.
The big question remaining is what the mechanism is—are higher lutein levels triggered by increased physical activity? Or is having a high lutein level simply indicative of more physically active people, who tend to eat more fruits and vegetables than those less physically active?
Because most studies included in the review were cross-sectional, the authors argued that it may be a case of ‘people-who-eat-healthy-also-work-out-more.’
“However, the preliminary evidence from the trial in rats and a double-blind randomized controlled trial in humans suggests that lutein status influences physical activity,” they added.
They were referring to a 2014 Japanese study which found that rats given lutein-fortified milk had an increased voluntary run distance, and another from the same year by Australian researchers (the same team that compiled this current systematic review) which found that 19 older adult participants who took lutein had increased physical activity, reduced sedentary time compared to the 20 who took a placebo.
The two studies were the only ones that specifically explored a correlation between lutein and physical activity, while all the other studies analyzed only had physical activity levels as a secondary outcome.
To this, the authors wrote that “the lack of formal assessment and/or discussion of associations between lutein status and physical activity in studies that had measured relevant outcomes is indicative of the novelty of the hypothesis that lutein status might influence physical activity.”
“If increasing lutein status, or possibly also the status of other carotenoids, is able to increase physical activity, this might be useful for improving physical activity to mitigate the risk of chronic disease,” they added. “However, large-scale RCTs are required to confirm effects on physical activity and any associated health benefits.”
Published online, https://doi.org/10.3390/nu10091186
Lutein Intake and Blood Lutein Concentration Are Positively Associated with Physical Activity in Adults: A Systematic Review
Authors: Madeline C. Cooke, et al