Influence of Fish Consumption and ω-3 Supplementation on the ω-3 Index of Young Adults: A 2 × 2 Factorial Randomized Controlled Trial (YouFish Study)

James E McMullan; Rohith Ajaya Kumar; Alison J Yeates; Philip J Allsopp; Maria S Mulhern; Edwin van Wijngaarden; J J Strain; Emeir M McSorley

doi:10.1016/j.tjnut.2025.10.010

Influence of Fish Consumption and ω-3 Supplementation on the ω-3 Index of Young Adults: A 2 × 2 Factorial Randomized Controlled Trial (YouFish Study)

James E McMullan, Rohith Ajaya Kumar, Alison J Yeates, Philip J Allsopp, Maria S Mulhern, Edwin van Wijngaarden, J J Strain, Emeir M McSorley

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Abstract

BACKGROUND: The omega-3 (n-3) index (O3I), reflecting the percentage of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in erythrocyte membranes, is associated with reduced risk of cardiovascular disease (CVD). United Kingdom dietary guidelines recommend 2 portions of fish/week (280 g/wk) or supplementation of ∼500 mg EPA + DHA/d for non/low-fish consumers; however, the impact of these recommendations on the O3I is unclear.

OBJECTIVES: The aim of this study was to explore the influence of the current guidance for fish consumption and ω-3 supplementation on the O3I among young adults.

METHODS: Healthy adults aged 18-30 y (n = 40) with low-fish intake and O3I <6% were randomly assigned to receive either 2 fish (1 portion oily fish and 1 portion white fish) or 2 nonfish meals per week as well as a daily 700 mg EPA+DHA supplement capsule or placebo capsule for 8-wk in a 2×2 factorial design. The effects on lipid profiles and high-sensitivity C-reactive protein (hs-CRP) were also examined.

RESULTS: Consumption of 2 portions of fish/week and ω-3 supplementation resulted in a significant mean % increase in O3I of 2.27% ± 0.82% and 2.03% ± 0.88%, respectively. Both interventions also significantly increased total erythrocyte n-3 polyunsaturated fatty acids (n-3 PUFAs) (+3.11% ± 1.79% and +2.00% ± 1.24%) and lowered total n-6 PUFAs (-1.94% ± 1.65% and -2.60% ± 1.16%) (all false discovery rate P < 0.05). There were no significant effects on blood lipids or hs-CRP.

CONCLUSIONS: In support of current dietary guidelines for fish consumption and ω-3 intake, 2 portions of fish/week or ω-3 supplementation are effective strategies for increasing the O3I. These findings support the efficacy of current public health recommendations for fish consumption and ω-3 intake as early dietary interventions to reduce CVD risk through increasing the O3I among young adults. This trial was registered at www.

CLINICALTRIALS: gov as NCT06729229.

Original language	English
Pages (from-to)	4345-4355
Number of pages	11
Journal	The Journal of nutrition
Volume	155
Issue number	12
Early online date	11 Oct 2025
DOIs	https://doi.org/10.1016/j.tjnut.2025.10.010
Publication status	Published (in print/issue) - Dec 2025

Bibliographical note

Publisher Copyright:
© 2025 The Author(s)

Data Access Statement

Data described in the manuscripts, code book, and analytic code will be made available on request pending.

Funding

JEM is a PhD Student funded by Department for the Economy scholarship, Ulster University. EPAX Norway provided the supplements and Lir Native Seafood and Scran, Coleraine provided the fish used within the intervention. Only the named authors had input to the study design, data interpretation, and study conclusions.

Keywords

Omega 3 polyunsaturated fatty acids
omega 3 supplementation
fish consumption
cardiovascular disease
young adults
omega 3 PUFAs

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1016/j.tjnut.2025.10.010

1-s2.0-S0022316625006297-mainProof, 2.46 MBLicence: CC BY

Cite this

McMullan, J. E., Kumar, R. A., Yeates, A. J., Allsopp, P. J., Mulhern, M. S., Wijngaarden, E. V., Strain, J. J., & McSorley, E. M. (2025). Influence of Fish Consumption and ω-3 Supplementation on the ω-3 Index of Young Adults: A 2 × 2 Factorial Randomized Controlled Trial (YouFish Study). The Journal of nutrition, 155(12), 4345-4355. https://doi.org/10.1016/j.tjnut.2025.10.010

@article{bf234745925048c4b559242074168c38,

title = "Influence of Fish Consumption and ω-3 Supplementation on the ω-3 Index of Young Adults: A 2 × 2 Factorial Randomized Controlled Trial (YouFish Study)",

abstract = "BACKGROUND: The omega-3 (n-3) index (O3I), reflecting the percentage of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in erythrocyte membranes, is associated with reduced risk of cardiovascular disease (CVD). United Kingdom dietary guidelines recommend 2 portions of fish/week (280 g/wk) or supplementation of ∼500 mg EPA + DHA/d for non/low-fish consumers; however, the impact of these recommendations on the O3I is unclear.OBJECTIVES: The aim of this study was to explore the influence of the current guidance for fish consumption and ω-3 supplementation on the O3I among young adults.METHODS: Healthy adults aged 18-30 y (n = 40) with low-fish intake and O3I <6\% were randomly assigned to receive either 2 fish (1 portion oily fish and 1 portion white fish) or 2 nonfish meals per week as well as a daily 700 mg EPA+DHA supplement capsule or placebo capsule for 8-wk in a 2×2 factorial design. The effects on lipid profiles and high-sensitivity C-reactive protein (hs-CRP) were also examined.RESULTS: Consumption of 2 portions of fish/week and ω-3 supplementation resulted in a significant mean \% increase in O3I of 2.27\% ± 0.82\% and 2.03\% ± 0.88\%, respectively. Both interventions also significantly increased total erythrocyte n-3 polyunsaturated fatty acids (n-3 PUFAs) (+3.11\% ± 1.79\% and +2.00\% ± 1.24\%) and lowered total n-6 PUFAs (-1.94\% ± 1.65\% and -2.60\% ± 1.16\%) (all false discovery rate P < 0.05). There were no significant effects on blood lipids or hs-CRP.CONCLUSIONS: In support of current dietary guidelines for fish consumption and ω-3 intake, 2 portions of fish/week or ω-3 supplementation are effective strategies for increasing the O3I. These findings support the efficacy of current public health recommendations for fish consumption and ω-3 intake as early dietary interventions to reduce CVD risk through increasing the O3I among young adults. This trial was registered at www.CLINICALTRIALS: gov as NCT06729229.",

keywords = "Omega 3 polyunsaturated fatty acids, omega 3 supplementation, fish consumption, cardiovascular disease, young adults, omega 3 PUFAs",

author = "McMullan, \{James E\} and Kumar, \{Rohith Ajaya\} and Yeates, \{Alison J\} and Allsopp, \{Philip J\} and Mulhern, \{Maria S\} and Wijngaarden, \{Edwin van\} and Strain, \{J J\} and McSorley, \{Emeir M\}",

note = "Publisher Copyright: {\textcopyright} 2025 The Author(s)",

year = "2025",

month = dec,

doi = "10.1016/j.tjnut.2025.10.010",

language = "English",

volume = "155",

pages = "4345--4355",

journal = "The Journal of nutrition",

issn = "0022-3166",

publisher = "Elsevier BV",

number = "12",

}

McMullan, JE, Kumar, RA, Yeates, AJ , Allsopp, PJ , Mulhern, MS, Wijngaarden, EV, Strain, JJ & McSorley, EM 2025, 'Influence of Fish Consumption and ω-3 Supplementation on the ω-3 Index of Young Adults: A 2 × 2 Factorial Randomized Controlled Trial (YouFish Study)', The Journal of nutrition, vol. 155, no. 12, pp. 4345-4355. https://doi.org/10.1016/j.tjnut.2025.10.010

TY - JOUR

T1 - Influence of Fish Consumption and ω-3 Supplementation on the ω-3 Index of Young Adults

T2 - A 2 × 2 Factorial Randomized Controlled Trial (YouFish Study)

AU - McMullan, James E

AU - Kumar, Rohith Ajaya

AU - Yeates, Alison J

AU - Allsopp, Philip J

AU - Mulhern, Maria S

AU - Wijngaarden, Edwin van

AU - Strain, J J

AU - McSorley, Emeir M

PY - 2025/12

Y1 - 2025/12

N2 - BACKGROUND: The omega-3 (n-3) index (O3I), reflecting the percentage of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in erythrocyte membranes, is associated with reduced risk of cardiovascular disease (CVD). United Kingdom dietary guidelines recommend 2 portions of fish/week (280 g/wk) or supplementation of ∼500 mg EPA + DHA/d for non/low-fish consumers; however, the impact of these recommendations on the O3I is unclear.OBJECTIVES: The aim of this study was to explore the influence of the current guidance for fish consumption and ω-3 supplementation on the O3I among young adults.METHODS: Healthy adults aged 18-30 y (n = 40) with low-fish intake and O3I <6% were randomly assigned to receive either 2 fish (1 portion oily fish and 1 portion white fish) or 2 nonfish meals per week as well as a daily 700 mg EPA+DHA supplement capsule or placebo capsule for 8-wk in a 2×2 factorial design. The effects on lipid profiles and high-sensitivity C-reactive protein (hs-CRP) were also examined.RESULTS: Consumption of 2 portions of fish/week and ω-3 supplementation resulted in a significant mean % increase in O3I of 2.27% ± 0.82% and 2.03% ± 0.88%, respectively. Both interventions also significantly increased total erythrocyte n-3 polyunsaturated fatty acids (n-3 PUFAs) (+3.11% ± 1.79% and +2.00% ± 1.24%) and lowered total n-6 PUFAs (-1.94% ± 1.65% and -2.60% ± 1.16%) (all false discovery rate P < 0.05). There were no significant effects on blood lipids or hs-CRP.CONCLUSIONS: In support of current dietary guidelines for fish consumption and ω-3 intake, 2 portions of fish/week or ω-3 supplementation are effective strategies for increasing the O3I. These findings support the efficacy of current public health recommendations for fish consumption and ω-3 intake as early dietary interventions to reduce CVD risk through increasing the O3I among young adults. This trial was registered at www.CLINICALTRIALS: gov as NCT06729229.

AB - BACKGROUND: The omega-3 (n-3) index (O3I), reflecting the percentage of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in erythrocyte membranes, is associated with reduced risk of cardiovascular disease (CVD). United Kingdom dietary guidelines recommend 2 portions of fish/week (280 g/wk) or supplementation of ∼500 mg EPA + DHA/d for non/low-fish consumers; however, the impact of these recommendations on the O3I is unclear.OBJECTIVES: The aim of this study was to explore the influence of the current guidance for fish consumption and ω-3 supplementation on the O3I among young adults.METHODS: Healthy adults aged 18-30 y (n = 40) with low-fish intake and O3I <6% were randomly assigned to receive either 2 fish (1 portion oily fish and 1 portion white fish) or 2 nonfish meals per week as well as a daily 700 mg EPA+DHA supplement capsule or placebo capsule for 8-wk in a 2×2 factorial design. The effects on lipid profiles and high-sensitivity C-reactive protein (hs-CRP) were also examined.RESULTS: Consumption of 2 portions of fish/week and ω-3 supplementation resulted in a significant mean % increase in O3I of 2.27% ± 0.82% and 2.03% ± 0.88%, respectively. Both interventions also significantly increased total erythrocyte n-3 polyunsaturated fatty acids (n-3 PUFAs) (+3.11% ± 1.79% and +2.00% ± 1.24%) and lowered total n-6 PUFAs (-1.94% ± 1.65% and -2.60% ± 1.16%) (all false discovery rate P < 0.05). There were no significant effects on blood lipids or hs-CRP.CONCLUSIONS: In support of current dietary guidelines for fish consumption and ω-3 intake, 2 portions of fish/week or ω-3 supplementation are effective strategies for increasing the O3I. These findings support the efficacy of current public health recommendations for fish consumption and ω-3 intake as early dietary interventions to reduce CVD risk through increasing the O3I among young adults. This trial was registered at www.CLINICALTRIALS: gov as NCT06729229.

KW - Omega 3 polyunsaturated fatty acids

KW - omega 3 supplementation

KW - fish consumption

KW - cardiovascular disease

KW - young adults

KW - omega 3 PUFAs

UR - https://pure.ulster.ac.uk/en/publications/bf234745-9250-48c4-b559-242074168c38

UR - https://www.scopus.com/pages/publications/105020691026

U2 - 10.1016/j.tjnut.2025.10.010

DO - 10.1016/j.tjnut.2025.10.010

M3 - Article

C2 - 41082976

SN - 0022-3166

VL - 155

SP - 4345

EP - 4355

JO - The Journal of nutrition

JF - The Journal of nutrition

IS - 12

ER -

Influence of Fish Consumption and ω-3 Supplementation on the ω-3 Index of Young Adults: A 2 × 2 Factorial Randomized Controlled Trial (YouFish Study)

Abstract

Bibliographical note

Data Access Statement

Funding

Keywords

UN SDGs

Access to Document

Other files and links

Fingerprint

Fish consumption & polyunsaturated fatty acids (PUFAs) across the lifecycle: implications for cardiometabolic health and ageing

Cite this

Influence of Fish Consumption and ω-3 Supplementation on the ω-3 Index of Young Adults: A 2 × 2 Factorial Randomized Controlled Trial (YouFish Study)

Abstract

Bibliographical note

Data Access Statement

Funding

Keywords

UN SDGs

Access to Document

Other files and links

Fingerprint

Student theses

Fish consumption & polyunsaturated fatty acids (PUFAs) across the lifecycle: implications for cardiometabolic health and ageing

Cite this