As people grow old, the small proteins called cytokines released by cells, once crucial to fight off infections, can become dysregulated and pathological, promoting a wide range of chronic and age-related diseases, explained researchers in the Archives of Gerontology and Geriatrics.
Scientists funded by the Thailand Research Fund studied the anti-inflammatory benefits of star fruits (Averrhoa carambola L.), what they call “undervalued as a healthy functional food,” to see if it can reverse immunosenescence (the aging of the immune system).
Citing an earlier study about the fruit’s chemical constituents and nutritional values, star fruit’s saponins, alkaloids, flavonoid C-glycosides, tannin, and ascorbic acid have been observed to have anti-inflammatory properties.
“A further benefit of ascorbic acid is its ability to decrease the osmotic fragility of erythrocytes from oxidative stress,” the report said, citing a study from 2004.
Selecting the participants
Observation was conducted in Thailand, and the research participants came from an elderly community in Chiang Mai province.
There were 40 approved participants, 20 men and 20 women, aged between 54 and 87 years. Participants were required to be non-smokers and capable of performing “basic daily activities independently and [lived] on their own,” the report said. Participants were screened for inclusion six weeks prior to the study by a physician using hospital records and a physical examination.
In addition, their regular activities, such as diet and behavioral aspects, were controlled prior and during the study period. Taking supplementary multi-vitamins was part of the control.
The study design was divided into two periods: The first two week control period was when the participants went on with their daily life, under observation, without the consumption of star fruit, and the second period was four weeks with star fruit juice consumption, made out of locally bought fruits juiced using a blender, consumed immediately after breakfast and dinner each day.
Measuring cytokine secretion and six-minute walks
The pro-inflammatory cytokines measured for the study were tumor necrosis factor-alpha (TNF-a), Interleukin 23 (IL-23), and interleukin-2 (IL-2), as well as the chemical compound nitric oxide, all of which have been observed to affect vascular impairment, cancer, and other inflammatory responses.
In addition, the participants’ distance during 6-minute walk was also measured to assess physical capacity. The cytokine levels and walking distances were evaluated three times: At week zero and two for the controls, and week six, after four weeks of star fruit juice consumption.
Data from the 29 participants who completed the study indicated that star fruit juice consumption was associated with reductions of some pro-inflammatory markers such as TNF-a, nitric oxide, and IL-23. “This study supports the claim that star fruit consumption can alter the oxidative stress levels in elderly individuals,” the researchers wrote.
The researchers also noted that there was “interesting results showing a significant correlation between the [six-minute walking distance test], TNF-a, and [nitric oxide].”
The participants finished off the study period walking on an average distance of 424.3 m in six minutes, as opposed to the average 348.2 m and 353.1 m in week zero and two.
The researchers contend that the positive correlation of the six-minute walking distance and nitric oxide can be explained by the effects of vasodilatation, which helps increase the flow of blood in the muscle and affects walking tolerance.
However, they also wrote that the negative correlation between the six-minute walking distance and TNF-a “is an unclear mechanism, possibly because of the down regulation from antioxidant vitamin C on the TNF-a releasing system, or the up regulation at the pro-inflammatory cytokine gene expression process, which must be confirmed by further study.”
Source: Archives of Gerontology and Geriatrics
Published online, doi:10.1016/j.archger.2015.12.001
"Consumption of star fruit juice on pro-inflammatory markers and walking distance in the community dwelling elderly"
Authors: J. Leelarungrayub, J. Laskin, R. Bloomer, D. Pinkaew