The Paper of the Month for April is 'Emerging evidence on selenoneine and its public health relevance in coastal populations: a review and case study of dietary Se among Inuit populations in the Canadian Arctic'. The blog is written by authors Matthew Little, Pierre Ayotte and Mélanie Lemire. The paper is published in Nutrition Research Reviews and is free to access for one month.

There are numerous essential vitamins and minerals that play crucial roles in maintaining our health and wellbeing. Among these, selenium stands out as a lesser known yet exceedingly important micronutrient. Found naturally in certain foods, and also available as a dietary supplement, selenium is incorporated into selenoproteins that play numerous roles in the body, from supporting the immune system to protecting against oxidative stress.

It is often remarked that there is a “narrow range between essentiality and toxicity”(1) of dietary selenium. Yet, this perspective overlooks the diversity of dietary selenium species and their related toxicity. We believe it is important that health scientists, nutritionists, and the public be made aware that not all selenium species are equivalent.

Selenoneine is a selenium compound that was initially identified in the blood of bluefin tuna and has subsequently been shown to be present in various animals of marine origin, including multiple species of fish, dolphins, sea turtles, and seabirds. Selenoneine has also been identified in red blood cells of human populations whose diet comprises large amounts of marine foods, including in Japan. Working in collaboration with Nunavimmiut (Indigenous Inuit living in Nunavik, Québec, Canada who consume large amounts of locally harvested marine foods), our research team found that selenoneine accounted for up to 92% of selenium in red blood cells in this population(2). Mattaaq (skin and underlying fat) derived from beluga whales – considered a delicacy by Inuit – is the richest source of selenoneine in the Inuit diet(3).

While research on selenoneine is nascent, interest in this compound has been growing in recent years. Selenoneine has strong antioxidant activity and may play a role in the protection and function of the central nervous system. It has also been shown to detoxify methylmercury through demethylation(4). This function is of particular interest to Inuit populations who are exposed to elevated levels of methylmercury due to its bioaccumulation and biomagnification in fish and marine mammals that comprise important dietary staples(5).

An important observation of research to date is that selenoneine does not contribute to selenoprotein synthesis and appears less toxic than other forms of selenium. Thus, individuals consuming a high percentage of selenium as selenoneine may not experience the same detrimental health effects as populations consuming elevated amounts of other selenium species(6). Conversely, those same individuals may need to ensure they have other dietary sources of selenium to safeguard adequate selenoprotein synthesis and activity, although this doesn’t appear to be a concern among Inuit populations in North America.

In our recent article published in Nutrition Research Reviews, we assert that the persistent failure to disaggregate selenium species in dietary guidelines and communications about selenium is problematic and may lead to unnecessary concern about selenosis among Inuit and other populations who consume high amounts of selenium as selenoneine from marine food sources. Additionally, research on selenium and its health effects must distinguish between selenium species in dietary intake and biological (e.g., blood and urine) samples. Our review therefore underscores the need to ensure appropriate risk assessments and public health nutrition strategies on selenium that account for the various biological functions, health impacts, and toxicity of selenium species.

References:

1. Hays SM, Macey K, Nong A, Aylward LL. Biomonitoring Equivalents for selenium. Regulatory Toxicology and Pharmacology. 2014 Oct 1;70(1):333–9.

2. Achouba A, Dumas P, Ouellet N, Little M, Lemire M, Ayotte P. Selenoneine is a major selenium species in beluga skin and red blood cells of Inuit from Nunavik. Chemosphere. 2019 Aug;229:549–58.

3. Little M, Achouba A, Dumas P, Ouellet N, Ayotte P, Lemire M. Determinants of selenoneine concentration in red blood cells of Inuit from Nunavik (Northern Québec, Canada). Environment International. 2019 Jun;127:243–52.

4. Yamashita M, Yamashita Y, Suzuki T, Kani Y, Mizusawa N, Imamura S, et al. Selenoneine, a novel selenium-containing compound, mediates detoxification mechanisms against methylmercury accumulation and toxicity in zebrafish embryo. Marine Biotechnology. 2013;15(5):559–70.

5. Lemire M, Kwan M, Laouan-Sidi AE, Muckle G, Pirkle C, Ayotte P, et al. Local country food sources of methylmercury, selenium and omega-3 fatty acids in Nunavik, Northern Quebec. Science of the Total Environment. 2015;509–510:248–59.

6. Drobyshev E, Schwerdtle T. Toxic or beneficial? What is the role of food-relevant selenium species selenoneine? Lebensmittelchemie. 2023 Jun 1;77(S2):S2-146.