Linseed oil was chosen for its alpha-linoleic acid (ALA) content, a type of omega-3 fatty acid found in plants. The researchers based their study on the hypothesis that the consumption of different types of fat evokes different rates of fat metabolism.
“We and other groups have investigated fat metabolism in humans and rodents and concluded that ALA [with diacylglycerol] has the potential to increase fat oxidation compared with conventional triacylglycerol (which mainly occurs as oleic acid and linoleic acid),” the researchers wrote in their report, published in the December 2017 edition of the journal Nutrition Research.
One area this current study sought to elucidate, which the research team’s past trials on ALA have not done, is to compare the effect of ALA + diacylglycerol on fat metabolism to a conventional ALA with similar fatty acid composition.
Study design
The trial was a randomized, double-blind, cross-over study, where participants had to consume both ALA with diacylglycerol or ALA with triacylglycerol with similar fatty acid compositions over eight weeks. To measure the main outcome, which is dietary fat oxidation, the researchers analyzed 13CO2 recovery in participants’ breaths.
A total of 17 participants aged 35 – 57, ranging from normal to moderately obese, were recruited in Tokyo, Japan. One group received diacylglycerol oil intervention for the first four weeks, while the other received the triacylglycerol oil during the same time period.
After the first four weeks are up, participants go through a four week-long washout period before starting another four weeks taking the other ALA oil type.
Oils were manufactured by Japanese food company Kao Corporation, which also funded the study. Both oils derived from linseed oil. They were delivered in similar packaging and created to look and smell similar so both participants and study personnel could not tell the difference.
Participants were asked to consume 2.5 g of their assigned oil per day at any time of day and add the test oil to any food they like.
Results
Body weight, fat mass, fat-free mass, BMI, and body measurements did not differ significantly between treatments. Nor were glucose, insulin, and total ketone body levels.
However, the researchers found that visceral fat area, or excess adipose tissue accumulation in the abdominal area, was significantly lower after four weeks of ALA with diacylglycerol consumption compared to the other oil.
“Accumulation of visceral fat area is more closely associated with metabolic risk factors than BMI or subcutaneous fat,” the researchers wrote. “Thus, assessment of visceral fat area is the best predictor of adverse metabolic consequences.”
Additionally, analysis of 13CO2 recovery rate revealed that participants had higher fat oxidation after consuming ALA with diacylglycerol compared to the triacylglycerol oil.
“This present study demonstrated significantly greater [post-meal] dietary fat oxidation following 4-week ALA diacylglycerol consumption in normal and moderately obese men and women compared to ALA with triacylglycerol,” they wrote.
“Further studies with larger sample sizes that include premenopausal women and other races are necessary to establish a more general observation.”
Source: Nutrition Research
Published online ahead of print, https://doi.org/10.1016/j.nutres.2017.10.012
Consumption of alpha-linolenic acid-enriched diacylglycerol induces increase in dietary fat oxidation compared with alpha-linolenic acid-enriched triacylglycerol: A randomized, double-blind trial
Authors: Yasutoshi Ando, Shinichiro Saito, Hirona Miura, Noriko Osaki, Yoshihisa Katsuragi