Fish oil benefits for men encompass a range of potential health effects, from cardiovascular support to possible improvements in mental wellbeing and reproductive health. Derived from oily fish such as salmon, mackerel, and sardines, fish oil is rich in omega-3 polyunsaturated fatty acids—particularly EPA and DHA—which play vital roles in cellular function, inflammation regulation, and brain health. Whilst the NHS recommends obtaining omega-3s primarily through dietary sources, supplementation may be considered when intake is insufficient. Understanding the evidence base, appropriate dosages, and safety considerations is essential for men considering fish oil as part of their health strategy.

What Is Fish Oil and How Does It Work?

Fish oil is a dietary supplement derived from the tissues of oily fish, including mackerel, herring, sardines, and salmon. It is particularly valued for its high concentration of omega-3 polyunsaturated fatty acids, primarily eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These essential fatty acids cannot be synthesised efficiently by the human body and must therefore be obtained through diet or supplementation.

The therapeutic effects of fish oil are mediated through several biological mechanisms. EPA and DHA are incorporated into cell membranes throughout the body, where they influence membrane fluidity and cellular signalling pathways. These omega-3 fatty acids serve as precursors for specialised pro-resolving mediators (SPMs), including resolvins and protectins, which help regulate inflammatory responses. Unlike omega-6 fatty acids—which tend to promote inflammation when consumed in excess—omega-3s from fish oil generally exert anti-inflammatory effects by competing for the same enzymatic pathways.

Fish oil also affects cardiovascular function by modulating lipid metabolism, reducing triglyceride synthesis in the liver, and potentially improving endothelial function. The omega-3 fatty acids influence gene expression through interactions with transcription factors, affecting the production of proteins involved in lipid metabolism and inflammation. Additionally, DHA is a major structural component of neuronal cell membranes and the retina, contributing to normal brain and visual function.

In the UK, fish oil supplements are widely available as over-the-counter products in various formulations, including standard triglyceride form, ethyl esters, and re-esterified triglycerides. It's important to distinguish between these supplements and prescription-only omega-3-acid ethyl esters (such as Omacor), which are licensed by the MHRA as medicines for specific conditions like hypertriglyceridaemia.

The NHS recommends consuming at least two portions of fish weekly, including one portion of oily fish, as part of a balanced diet to obtain adequate omega-3 fatty acids naturally. The Food Standards Agency (FSA) advises that adult men can safely consume up to four portions of oily fish weekly, though certain species (shark, swordfish, and marlin) should be limited to one portion per week due to potential mercury content. Fish body oils differ from cod liver oil, which contains vitamins A and D; excessive intake of cod liver oil may lead to vitamin A toxicity.

Effects on Testosterone and Male Fertility

The relationship between fish oil supplementation and male reproductive health has attracted considerable research interest, though the evidence base remains evolving. Some observational studies have suggested associations between higher omega-3 intake and improved semen parameters, whilst the effects on testosterone levels are less clearly established.

Potential effects on fertility parameters include:

• Sperm quality: Several studies have reported that men with higher dietary or supplemental omega-3 intake may demonstrate improved sperm morphology (shape), motility (movement), and concentration. The proposed mechanism involves omega-3 incorporation into sperm cell membranes, potentially enhancing membrane fluidity and function.

• Testicular function: Animal research suggests omega-3 fatty acids may support testicular health by reducing oxidative stress and inflammation, though human data remain limited.

• Testosterone levels: There is no consistent evidence that fish oil supplementation significantly increases testosterone levels in healthy men. Some small studies have reported modest changes, but these findings have not been reliably replicated in larger trials.

It is important to emphasise that whilst these associations are biologically plausible, there is no official link definitively established between fish oil supplementation and clinically meaningful improvements in male fertility or testosterone production. The evidence is largely observational or derived from small interventional studies with methodological limitations.

Men experiencing fertility concerns should consult their GP after one year of trying to conceive (or sooner if there are known risk factors). NICE guidance (CG156) recommends comprehensive assessment including semen analysis, and lifestyle modifications such as maintaining a healthy weight, avoiding excessive alcohol, stopping smoking, and eating a balanced diet. Other modifiable factors include avoiding anabolic steroids, excessive heat exposure to the testicles, and certain medications that may affect fertility.

Fish oil may form part of a broader nutritional approach, but should not replace evidence-based fertility investigations or treatments. Men taking anticoagulant or antiplatelet medications should exercise particular caution, as omega-3 supplementation may potentially prolong bleeding time. Those on such medications should discuss fish oil supplementation with their healthcare provider before starting.

Mental Health and Cognitive Function Benefits

Omega-3 fatty acids, particularly DHA, play crucial structural and functional roles in the central nervous system, comprising approximately 40% of brain polyunsaturated fatty acids. This has prompted extensive research into fish oil's potential benefits for mental health and cognitive function in men across different life stages.

Depression and mood disorders: Systematic reviews and meta-analyses suggest that omega-3 supplementation, particularly formulations higher in EPA, may provide modest benefits as an adjunctive treatment for depression. The proposed mechanisms include anti-inflammatory effects, modulation of neurotransmitter systems, and improved neuronal membrane function. However, the evidence is not sufficiently robust for omega-3 supplements to be recommended as a standalone treatment. NICE guidance on depression (NG222) emphasises psychological therapies and antidepressant medications as first-line treatments, with lifestyle interventions including diet playing a supportive role. NICE does not recommend omega-3 supplements as a routine treatment for depression.

Cognitive function and dementia prevention: Observational studies have associated higher fish consumption with reduced risk of cognitive decline and dementia in older adults. However, randomised controlled trials of fish oil supplementation in cognitively healthy older people have generally not demonstrated significant benefits in preventing cognitive decline. The evidence is more promising for individuals with very mild cognitive impairment, though further research is needed. NICE guidance (NG97) does not recommend omega-3 supplements for preventing or treating dementia.

Anxiety and stress: Some preliminary evidence suggests omega-3 supplementation may help reduce symptoms of anxiety, potentially through anti-inflammatory pathways and effects on the hypothalamic-pituitary-adrenal (HPA) axis. However, the evidence base remains limited.

Key considerations for men include:

• Fish oil should complement, not replace, evidence-based mental health treatments

• Men experiencing persistent low mood, anxiety, or cognitive concerns should consult their GP

• Men with suicidal thoughts or acute mental health crises should seek urgent help via NHS 111, their GP, local crisis team, 999, or A&E

• Adequate omega-3 intake throughout life may support long-term brain health, though supplementation in later life shows less consistent benefits

Men should be aware that whilst fish oil is generally well-tolerated, it is not a substitute for professional mental health assessment and treatment when clinically indicated.

Recommended Dosage and How to Take Fish Oil Safely

Determining the appropriate fish oil dosage depends on individual health status, dietary omega-3 intake, and specific health goals. UK guidance emphasises obtaining omega-3 fatty acids primarily through diet, with supplementation considered when dietary intake is insufficient.

General recommendations:

• Dietary approach: The NHS recommends at least two portions (approximately 280g) of fish weekly, including one portion of oily fish (such as salmon, mackerel, sardines, or trout).

• Supplementation dosage: For general health maintenance, typical fish oil supplements provide 250–500mg of combined EPA and DHA daily. Higher doses (1,000–3,000mg daily) have been used in some studies investigating specific health outcomes, but should only be taken under healthcare professional guidance. Doses above 3g daily should generally be avoided without medical supervision.

• Therapeutic doses: Prescription-only omega-3-acid ethyl esters (such as Omacor) are MHRA-licensed medicines primarily for treating hypertriglyceridaemia. These require medical supervision and should not be confused with over-the-counter supplements.

Safety considerations and potential adverse effects:

• Common side effects: Fishy aftertaste, mild gastrointestinal disturbance (nausea, loose stools), and belching. Taking supplements with meals or using enteric-coated formulations may reduce these effects.

• Bleeding risk: Omega-3 supplementation may potentially prolong bleeding time. Men taking anticoagulants (warfarin, DOACs) or antiplatelet medications (aspirin, clopidogrel) should consult their GP before starting fish oil supplements and may require monitoring.

• Cardiovascular considerations: High-dose prescription omega-3 preparations have been associated with a small increased risk of atrial fibrillation in some clinical trials. Additionally, some omega-3 formulations may increase LDL cholesterol in certain individuals.

• Quality and purity: Choose supplements from reputable UK or EU manufacturers that test for contaminants such as mercury, PCBs, and dioxins in accordance with FSA guidance.

When to seek medical advice:

• Before starting supplementation if you have a bleeding disorder or take anticoagulant medications

• If you experience persistent gastrointestinal symptoms or allergic reactions

• If you have diabetes, as very high doses may slightly affect glycaemic control

• If you have a history of atrial fibrillation or significant cardiovascular disease

• Before using fish oil alongside other supplements or herbal medicines

Men with fish or shellfish allergies should exercise caution, though most fish oil supplements contain minimal allergenic protein. Algae-based omega-3 supplements provide a suitable alternative for those following plant-based diets or with fish allergies. Always inform your GP and pharmacist about all supplements you are taking to ensure safe and appropriate use alongside any prescribed medications.

Suspected adverse reactions to fish oil supplements can be reported through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk or the Yellow Card app).

Frequently Asked Questions