Should I Take Fish Oil or Magnesium for Better Health?

November 14, 2025 •

4 min read

According to the National Institutes of Health, many people in the US do not meet the recommended daily intake of magnesium through diet alone, and many also fail to consume sufficient omega-3 fatty acids, which are found in fish oil. This makes supplements a popular option, but for specific wellness goals, the question of whether you should take fish oil or magnesium requires a deeper look.

Quick Summary

This article explores the distinct benefits of fish oil and magnesium supplements for different health goals, including heart function, anxiety, sleep, and inflammation. It contrasts their primary roles, helping individuals choose the right supplement based on personal needs.

Key Points

Choose Based on Goals: Prioritize fish oil for heart health, inflammation, and cognitive support, while favoring magnesium for anxiety, stress relief, sleep quality, and muscle relaxation.
Different Functions: Fish oil provides essential omega-3 fatty acids for cellular and anti-inflammatory support, whereas magnesium is a mineral vital for over 300 biochemical processes, including nerve and muscle function.
Consider the Combo: Taking both supplements can offer synergistic benefits for heart and brain health, though it's important to monitor potential interactions, especially with blood pressure.
Check Quality and Forms: Opt for third-party tested supplements. For fish oil, prefer the triglyceride form; for magnesium, choose a form like glycinate for better sleep or citrate for digestion.
Consult a Professional: It is essential to speak with a healthcare provider before starting any new supplement, particularly if you have health conditions or take other medications, to ensure safety and proper dosing.
Timing Matters: For best results, take fish oil with a meal containing fats, and consider taking magnesium in the evening to aid relaxation and sleep.

Understanding the Core Differences

Fish oil and magnesium are fundamentally different supplements, each serving distinct purposes in the body. Fish oil is a source of omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are healthy fats essential for cellular function that the body cannot produce on its own. Magnesium, on the other hand, is a mineral critical for over 300 biochemical reactions, from muscle and nerve function to blood pressure regulation and protein synthesis. The choice often comes down to your primary health concerns and what your body needs most.

The Case for Fish Oil (Omega-3s)

Fish oil is widely recognized for its cardiovascular and anti-inflammatory properties. The omega-3s, EPA and DHA, help reduce inflammation throughout the body, which is a key factor in many chronic diseases.

Heart Health: Fish oil can help lower high triglyceride levels, modestly reduce blood pressure, and decrease the risk of plaque buildup in arteries, supporting overall heart function.
Brain and Mental Health: Omega-3s are crucial for brain cell structure and function. Supplementation has been linked to improved cognitive function and mood regulation, with some studies showing benefits for anxiety and depression, particularly with higher EPA content.
Joint Health: Due to its potent anti-inflammatory effects, fish oil may help reduce joint pain and stiffness associated with conditions like rheumatoid arthritis.

The Case for Magnesium

Magnesium is often dubbed the "relaxation mineral" for its calming effects on the nervous system. It plays a crucial role in regulating neurotransmitters, like GABA, which promotes calmness and rest.

Anxiety and Stress Management: Adequate magnesium levels help regulate stress hormones and calm the nervous system. Low magnesium is linked to increased anxiety, so supplementing can aid in stress management and reduce anxious feelings.
Improved Sleep: Magnesium's ability to promote relaxation makes it a popular supplement for improving sleep quality. Forms like magnesium glycinate are particularly noted for their calming properties and are often taken in the evening.
Muscle and Nerve Function: Magnesium is essential for proper muscle contraction and relaxation, helping to prevent muscle cramps and spasms. This makes it a valuable supplement for athletes or those with restless leg syndrome.
Migraine Prevention: Some research suggests that magnesium deficiency may be a risk factor for migraines, and supplementation could help reduce their frequency.

Fish Oil vs. Magnesium: A Comparative Look

To decide between fish oil and magnesium, consider your specific health goals. This table offers a side-by-side comparison to help clarify the choice.


Feature	Fish Oil (Omega-3s)	Magnesium
Primary Function	Anti-inflammatory, structural fat for cells, heart health	Mineral for biochemical reactions, relaxation, muscle function
Best for...	Heart health (triglycerides, blood pressure), brain function, inflammation, joint pain	Anxiety, stress, sleep issues, muscle cramps, migraines
Timing	Best with a meal containing fat for absorption	Evening for relaxation/sleep, with food to prevent GI upset
Potential Side Effects	Fishy burps, mild digestive issues; high doses can cause blood thinning	Mild diarrhea, nausea; excess amounts can affect heart rhythm
Key Interaction	Can interact with blood thinners and blood pressure medication	Can interfere with certain antibiotics and thyroid medication
Best Form	Triglyceride form for better absorption	Glycinate for sleep/anxiety, Citrate for digestive health

When to Consider Both

For many, the answer isn't choosing one over the other but using them synergistically. Fish oil and magnesium have complementary actions, particularly concerning brain health, inflammation, and cardiovascular support. For instance, magnesium supports nerve and muscle function, while fish oil helps manage inflammation, making them a powerful combination for stress management and muscle recovery. Similarly, both nutrients contribute to cardiovascular health by regulating blood pressure and vessel health, though spacing out high doses may be necessary to avoid excessively low blood pressure. A balanced diet rich in both nutrients is ideal, but supplements can fill gaps. A healthcare professional can help you determine if taking both is right for you, especially if you have underlying conditions or take medication.

Sourcing and Safety Considerations

Regardless of your choice, supplement quality is paramount. When purchasing fish oil, look for third-party testing seals (like IFOS or GOED) to ensure purity and freedom from contaminants. For magnesium, ensure the product lists the elemental magnesium content, as different forms have varying absorption rates and elemental concentrations. Always start with a low dose and increase gradually to assess tolerance, particularly with magnesium due to its potential laxative effect. Before beginning any new supplement regimen, especially if you have existing health issues or take medication, it is crucial to consult a healthcare provider. They can provide personalized advice based on your complete health picture and specific needs.

Conclusion: Making Your Decision

Deciding between fish oil and magnesium depends on your primary health goals. If your focus is on cardiovascular health, joint inflammation, or cognitive function, fish oil may be the more direct option. If your priority is stress reduction, improved sleep, or muscle relaxation, magnesium is likely the better choice. However, as these two nutrients often work together to support overall well-being, taking them in combination is also a valid and potentially more effective strategy for holistic health. Always consult with a healthcare professional to personalize your supplement plan and ensure safety. For more in-depth, authoritative information on a wide range of dietary supplements, consider exploring the resources offered by the National Institutes of Health: Office of Dietary Supplements.(https://ods.od.nih.gov/factsheets/WYNTK-Consumer/)

Frequently Asked Questions

Yes, it is generally safe to take fish oil and magnesium at the same time. Many people benefit from their complementary effects on heart and brain health. However, if you are on blood pressure medication, consult your doctor, as both can have a mild blood pressure-lowering effect.

Both can help with anxiety, but they work differently. Magnesium is known as a relaxant that calms the nervous system by regulating neurotransmitters like GABA. High doses of fish oil (EPA) have also shown benefits for anxiety by reducing inflammation. Many find a combination effective, but magnesium's calming effect is more direct.

Magnesium is generally considered more effective for improving sleep quality due to its role in calming the nervous system and regulating neurotransmitters involved in sleep. Forms like magnesium glycinate are particularly recommended for this purpose, and are best taken in the evening.

Fish oil provides essential omega-3 fatty acids, which are healthy fats that combat inflammation and support brain cell structure. Magnesium is a mineral that acts as a cofactor in hundreds of biochemical reactions, with primary roles in nerve relaxation, muscle function, and energy production.

Individually, both can modestly lower blood pressure. While the risk of a significant drop is theoretical and rare, it's wise to consult a healthcare provider before combining them, especially if you already have low blood pressure or are on medication.

For relaxation and improved sleep, magnesium glycinate is a highly recommended and well-tolerated form. Magnesium citrate is another absorbable option, but is more commonly used for digestive health.

Side effects are usually mild. Fish oil can cause fishy burps, nausea, or mild digestive upset. High doses can increase bleeding risk. Magnesium can cause diarrhea, especially in certain forms or dosages. Always monitor your body's reaction and start with a low dose.