The purpose of this study is to investigate whether fish oil containing free fatty acids affects people's susceptibility to viral infections such as colds, influenza, and COVID-19, as well as the course of these illnesses. Omega Cold is purified fish oil with 2% added free fatty acids, making it similar in that respect to less-purified fish oils. Participants aged 18-80 in generally good health will be recruited through Matís' consumer mailing list and social media advertisements. A total of 400 participants are planned: 100 in the winter of 2025-2026 and 300 in the winter of 2026-2027. Participants will be randomly assigned to two equal groups. One group will take Omega Cold orally twice a day for four months, while the other receives a placebo (vegetable oil) taken in the same way. They will not be asked to change any other habits. All participants will report weekly on their health and any cold or flu symptoms during the time they take the oil, using short questionnaires. The study is scheduled to begin in December 2025, when the oil will be sent to participants.

The purpose of the Omega Cold fish oil study is to determine whether fish oil enriched with free fatty acids affects people's susceptibility to viral infections, such as colds, flu or COVID, and the illnesses caused by such infections.

Free fatty acids are present in untreated fish oil. However, the fish oil most commonly on the market today has been purified of free fatty acids. Omega Cold fish oil is purified fish oil with added free fatty acids in 2% concentration. This study is the first step in investigating whether fish oil with free fatty acids affects how often people get sick from viral infections, and whether consuming the fish oil affects the progression of the illness.

Participants in the study are recruited by sending an email to Matís' consumer list and through advertisements on social media. The conditions for participation are to be between the ages of 18-80 and in generally good health. The aim is for 400 people to participate in the study - 100 in the winter of 2025 - 2026 and 300 in the winter of 2026 - 2027.

The participants will be divided into two equal groups. One group will receive Omega Cold fish oil to take twice a day for four months. The other group is a placebo group and will receive vegetable oil to take in the same way. Participants will not be asked to change anything else in their consumption or behavior. All participants will be asked to record information about their health with regard to cold and flu symptoms weekly during the time they take the oil using short questionnaires.

Inclusion Criteria: To be in general good health, be between 18 to 80 years of age and be willing and able to take fish oil orally.

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Exclusion Criteria: Younger than 18 years and older than 80 years.

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