By Hugo Francisco de SouzaReviewed by Susha Cheriyedath, M.Sc.Jun 16 2024

In a recent study published in the journal Progress in Lipid Research, researchers updated the Omega-3 Index map from its first iteration in 2016. They collated available Omega-3 polyunsaturated fatty acids (N3 PUFAs) data from studies since 1999, comprising 328 studies of 342,864 participants from 48 countries globally. They found that while most countries depicted improvements in their N3 PUFA status, more than 90% of this data was obtained from only European and North American subjects.

Alarmingly, 75% of countries do not have data on N3 PUFA levels, and of those that do, most presented low to deficient levels of Omega-3 Index (O3I), highlighting the need for substantial and urgent global intervention.

Study: Omega-3 world map: 2024 update. Image Credit: Ground Picture / Shutterstock

What is the Omega-3 Index, and why is it essential to public health?

Omega-3 fatty acids are a class of polyunsaturated fatty acids (omega-3 polyunsaturated fatty acids [N3 PUFAs]) essential to optimal human physiology. Comprised of three main types, namely α-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), these nutrients cannot be synthesized by mammals (including humans) and are derived exclusively from diet (predominantly fish oils or marine organism-derived supplements).

A growing body of research has revealed that EPA and DHA are associated with decreased risk of all-cause mortality, cardiovascular diseases (CVDs), and preterm birth. High blood levels of these N3 PUFAs have also been shown to improve normal immune system function, brain development, eye health, and memory function, particularly in older individuals. In 2004, the Omega-2 Index (O3I) was first proposed. The metric consisted of the sum of EPA+DHA taken as a percentage (%) of total fatty acids (FA) in RBCs and was hypothesized as an estimate of subsequent coronary heart disease risk.

"At that time, and based on data then available, an O3I of >8% was proposed as a healthy or optimal target for reducing risk. O3I values of 4%–8% were considered "intermediate," and an O3I <4% was associated with the highest risk."

Intensive research over the following two decades substantiated this hypothesis, making studies into the O3I status of the global population imperative. The first review to elucidate the global O3I status was by Stark et al. in 2016, wherein the team synthesized published data from 1980 to 2014 from both observational and interventional studies to produce a 'world map' of the metric and its derivatives. The map used a color-based estimate of the global O3I status, dividing the globe into four colors to represent O3I levels from <4% (red), 4%-6% (yellow), 6%-8% (orange), and >8% (green).

Encouragingly, growing public interest in the health benefits of O3I over the past decade has produced substantial literature on the metric, prompting the need for an update on the original world map.

About the study

In the present study, researchers aim to collate data between 1999 and 2023 to update Stark et al.'s original O3I world map to reflect the current scenario of global N3 status. Data for the study was obtained from two scientific repositories, PubMed and the Global Organization for EPA and DHA Omega-3 s (GOED) Clinical Study Database (CSD), perused between May and October 2023. The literature search included observational studies (OS) and randomized controlled trials (RCTs) with inclusion criteria accepting original, full-length research reports published in English and excluding reviews and meta-analyses.

Data extracted from included studies was categorized into PTL, PPL, PPC, RBC, and WB based on each study's fraction of blood analyses. The reported EPA and DHA levels were subsequently converted into O3I as the universal metric. Wherever multiple studies were included for a particular country, a weighted mean of their reported O3I values was used.

Consistent with the 2016 map, the mean O3I of each country was categorized as desirable (>8%, green), moderate (>6% to 8%, yellow), low (>4% to 6%, orange), or very low (≤4%, red).

Study findings and conclusions

Of the 666 studies initially identified during the database search, only 328 met the study inclusion criteria and were included in the current review. Surprisingly, 92% of the participant's data were of individuals from Europe and North America, with significant data gaps in most other regions, particularly developing and underdeveloped countries. Compared with the original world map, the current world map includes Mexico, Malaysia, Austria, Switzerland, Poland, Egypt, Saudi Arabia, and the Palestinian Territories. In contrast, Chile, Tanzania, Kenya, Papua New Guinea, Central Russia, and Eastern and Northern Provinces of Russia do not have records from the period under investigation and were removed from the updated world map.

"O3I changes from the previous to the current map include 1) USA, Canada, Italy, Turkey, UK, Ireland, and Greece moving from red to orange, 2) France, Spain and New Zealand moving from orange to yellow, 3) and Finland and Iceland moving from yellow to green."

Encouragingly, with Nigeria as the only exception, almost all countries that presented a change in their O3I status showed improvements in their O3I records. Unfortunately, Egypt (2.1%), Iran (2.41%), the Palestine Territories (2.56%), Brazil (3.44%), Guatemala (3.43%), and India (3.63%) were significantly lower than the healthy threshold for O3I. This trend can be observed even in developed countries such as Austria, the Netherlands, and Ireland.

"Many countries still have virtually no population data on the O3I. This has not changed significantly since the 2016 n3 map. Most of Africa, Central and South America, South-East Asia, the Middle East and many countries in Eastern Europe do not yet have reported data on blood FA levels. Even if all countries are included in both maps, regardless of when the blood was taken, 76% of the countries of the world still have essentially no information on this important health measure."

In summary, the present report highlights the need for two urgent public health interventions – increased and improved screening of citizens' blood N3 PUFA levels and interventions aimed at increasing these levels via dietary improvements and supplements where necessary.

"It has been estimated that a low seafood intake (which would be reflected in a low O3I) is the fourth most important dietary factor contributing to death from cardiovascular disease in the USA [387], and this relationship is likely to be true worldwide. Our data are consistent with this observation as the O3I was in the low to very low category in most countries around the world (where data are available). National health agencies around the world should make efforts to assess the n3 status of their populations, and based on those data, strive to improve the O3I in order to reduce risk for many of the chronic diseases plaguing the modern world."

Journal reference:

Schuchardt, J. P., Beinhorn, P., Hu, X. F., Chan, H. M., Roke, K., Bernasconi, A., Hahn, A., Sala-Vila, A., Stark, K. D., & Harris, W. S. (2024). Omega-3 world map: 2024 update. In Progress in Lipid Research (p. 101286). Elsevier BV, DOI – 10.1016/j.plipres.2024.101286, https://www.sciencedirect.com/science/article/pii/S0163782724000195