Is one large weekly dose of omega-3 more effective than smaller daily doses?

By Stephen Daniells contact

- Last updated on GMT

Image: © iStockPhoto / Kagenmi
Image: © iStockPhoto / Kagenmi

Related tags: Omega-3 fatty acid, Epa

A big weekly dose of omega-3s may lead to greater omega-3 deposits in body tissues than smaller daily doses, says a new study from Australia.

Writing in Nutrients​, researchers from Deakin University reported that 23% of the large weekly ‘spike’ dose was deposited compared to only 15% of the daily doses in lab rats. This “unexpected” result was contrary to the researchers’ original hypothesis.

“The results from this animal study provide a suitable platform for future human studies aimed at developing substantiated evidence for advising consumers on the most efficient way to increase their n-3 LC-PUFA status,” ​they wrote.

“These findings suggest that a large dose of n-3 LC-PUFA once per week is more effective in increasing whole body n-3 LC-PUFA content compared to a smaller dose delivered daily.

“This observation, if validated in humans, could have remarkable effects on the possible development of more effective and sustainable utilization strategies of these limited and metabolically important nutrients, currently derived primarily from the dwindling oceanic fish stocks.”

Interesting, but conflicting data... 

Commenting on the study’s findings Harry Rice, PhD, VP of regulatory & scientific affairs for the Global Organization for EPA and DHA Omega-3s (GOED), told us: "The results of this research are very interesting because they suggest that the pattern of n-3 LCPUFA consumption affects omega-3 status. The results, however, conflict with a recent study in humans that was conducted for a similar purpose. In that study from Browning et al., 2014​, over the course of 12 months, daily delivery (versus 2 times per week) of fish oil resulted in a higher omega-3 status.

"As is often the case, further research is needed, particularly since the results could ultimately have an impact on public health recommendations." 

Study details

Samaneh Ghasemifard, Andrew Sinclair and their co-workers used six-week old male Sprague-Dawley rats and randomly assigned them to receive a ‘constant’ daily supplements (0.7% of fish oil in their diet), a single weekly dose (4.9% of the same fish oil once per week), or no fish oil (control) for six weeks.

Results showed that over 70% of the omega-3s (EPA, DPA, & DHA) were catabolized (beta-oxidized) with deposition accounting for less than 25%.

The daily supplementation regime was associated with significantly greater catabolism (84% of the dose), compared with the weekly doses (75% of the dose), said the researchers. There was also a preference towards beta-oxidation of EPA versus DPA and DHA in both groups.

“It has been reported using Wistar rats that EPA-CoA was a good substrate for mitochondrial carnitine acyl-transferase-I and DHA was a poor substrate for both mitochondrial and peroxisomal beta-oxidation, which could explain the high rate of beta-oxidation for EPA,”​ explained the researchers.

On the other hand, a greater proportion of the omega-3s were deposited in the weekly dose group, compared with the daily dose group.

“While the dietary intake of n-3 LC-PUFA provided by the two diets were similar, but not identical, there were some differences between treatments that might be independent of the difference in dietary intake,” ​they wrote. “For example, the DPA concentration in liver and muscle was significantly greater in the Spike treatment than in the Constant treatment, despite the dietary DPA intake being significantly greater for the Constant treatment.

“This has no obvious explanation, but reveals that metabolic processing of dietary n-3 LC-PUFA is more complex than simply looking at dietary intake values or tissue levels.”

Statistically significant but is it biologically relevant?

Michael McBurney, PhD, VP Science, Communication & Advocacy – DSM Nutritional Products, had a different interpretation of the data, however, and said that while the digestibility data (displayed in Table 3 in the journal article) may be statistically significant it is not biologically relevant.

"Virtually, all the fat was absorbed (not excreted in feces),"​ Dr McBurney told NutraIngredients-USA. "There were no differences in where fat was deposited (as shown in Tables 4 & 5). Table 6 does find some differences in where EPA and DHA are found. Most important observation is that increasing intake increases body content, but that's no surprise. The only place showing a statistical difference between constant and spike is whole body.

"Unfortunately, the researchers do not exactly describe beta-oxidation,"​ he added. "However, their deposition data seems to be calculated from body composition analysis. Presumably they are using differences in intake vs loss (accumulation) to calculate oxidation and in vivo enzyme activity. If that is the case, then beta-oxidation and in vivo enzyme activity measurements would include all the errors associated with every other measurement, which would undermine the accuracy of the values. More importantly, one can use labeled fatty acids to measure oxidation. They did not."

“Given the limitations of the data and the unanswered questions, I’d be cautious about taking anything from this rat study that would change current supplementation habits for consumers.”

Source: Nutrients
2015, Volume 7, Number 7, Pages 5628-5645, doi:10.3390/nu7075241
“What Is the Most Effective Way of Increasing the Bioavailability of Dietary Long Chain Omega-3 Fatty Acids—Daily vs. Weekly Administration of Fish Oil?”
Authors: S. Ghasemifard,  A.J. Sinclair,  G. Kaur,  P. Lewandowski, G.M. Turchini

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