The study was published recently in the journal Prostaglandins, Leukotrienes and Essential Fatty Acids. The research hailed from the Cooper Institute in Texas and from universities in Iowa, California, Texas and South Dakota.
The research was structured as an observational study using data from 13,912 patients who had undergone a comprehensive examination at the Cooper Institute. The institute is a research facility founded by Dr Kenneth Cooper, whose 1968 book Aerobics helped transform how Americans saw exercise and its role in supporting health.
As part of their examinations the participants underwent a maximal treadmill test as well as comprehensive blood tests.
Healthy study population
Of the almost 14,000 subjects about twice as many were men as women. Their ages ranged from a low of 20 up to 80 years of age, with an average of about 50 years. Most of the subjects were in good health, with healthy measures of BMI and resting heart rate. More of the men than women were current smokers, but the overall numbers were low in both cases (11% for the men and 3% for the women).
Most of the subjects fell into the 4% to 8% Omega-3 Index range, with a small number falling below 4% and even smaller number have a measurement greater than 8%. This higher level is considered the threshold for achieving the greatest health benefits from Omega-3s.
Comparing this sample to what omega-3s testing firm Omega Quant has found in its studies shows that the Cooper Institute subjects scored slightly higher on average Omega-3 Index than does the typical American. Omega Quant was founded by Dr William S. Harris, PhD, of the Sanford School of Medicine at the University of South Dakota. Harris, who is also cofounder of the Omega-3 Index, is also one of the current authors of the present study. Harris now heads the Fatty Acid Research Institute, based in Sioux Falls, SD.
More omega-3s helps subjects recover heart rate faster
After performing the maximal treadmill test as part of their comprehensive examinations, the Cooper Institute subjects had their heart rates measured at 1-minute, 3-minute and 5-minute intervals. The researchers found a distinct correlation between faster heart rate recovery (HHR) at the 1-minute and 3-minute intervals and higher Omega-3 Indexes. By 5 minutes the differences between the groups had become negligible.
That might be partly attributable to the overall good health of the study population. The subjects had resting heart rates of about 60 for the men and 63 for the women. Although resting heart rates can vary due to genetic factors, generally the lower the resting heart rate the healthier or better trained the individual. Most heart rate charts show that 72 to 76 beats for minute is about average for 50-year-old Americans. It might be expected that a less healthy cohort would include more individuals who would take longer than 5 minutes to recover their resting heart rate after a maximal aerobic exercise test.
“A direct relationship between HRR and O3I values was observed in both men and women, with a steeper gradient in women. These findings suggest a potential cardioprotective mechanism for n-3 PUFA,” the authors concluded.
Mechanism still unclear
Harris said the precise mechanism by which EPA and DHA have these effects in the heart has not been fully elucidated. But years of longitudinal studies and short term observational studies like this one show unequivocally that it’s there.
“You could say that this study shows that a higher Omega-3 Index makes the heart light on its feet. It’s tuned properly, and is not sluggish in its response,” he said.
Harris said research has shown that omega-3s have important effects in the membranes of cells, helping to forestall the formation of ‘rafts’ in the membranes where bioactive proteins gather instead of being dispersed in the cell where they are available to perform their functions. Is that the reason for the effects observed in this study? That’s not entirely clear, Harris said.
However it is worth noting, Harris said, that the researchers were able to observe any effect at all, given the overall good health of the population. Many omega-3 studies have focused on subjects who are already experiencing heart problems, which brings along a host of confounding factors, such as background statin use.
“This is definitely a healthy population. It’s hard to see these benefits in that situation, so maybe it’s remarkable that we saw anything in people who are as healthy as these people seem to be,” he said.
Source: Prostaglandins, Leukotrienes and Essential Fatty Acids
2020 Dec;163:102206. doi: 10.1016/j.plefa.2020.102206. Epub 2020 Nov 13
Higher omega-3 index is associated with more rapid heart rate recovery in healthy men and women
Authors: Farrell SW, et al.