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Endurance sports demand a lot from the body. Whether you’re training for a triathlon, cycling event, marathon or long-distance running challenge, your body needs the right nutrients to support energy production, muscle function, recovery and overall health.
At NUTRiD Personalised Sport Nutrition, we believe that performance starts with the right foundation. Sports nutrition is about more than carbohydrates and hydration during training. Your everyday nutritional habits also matter.
Here are five supplements worth understanding as part of a well-planned nutrition strategy: magnesium bisglycinate, vitamin D3, iron bisglycinate, krill oil and fish oil.
1. Magnesium Bisglycinate – Supporting Muscle Function and Recovery
Magnesium is an essential mineral involved in hundreds of processes in the human body. It contributes to normal muscle and nerve function, energy metabolism and the maintenance of normal bones.
For endurance athletes, adequate magnesium intake is particularly important because training increases the body’s overall nutritional demands. However, more magnesium does not automatically mean better performance.
Why consider magnesium bisglycinate?
Magnesium bisglycinate is a form of magnesium bound to the amino acid glycine. It is often chosen for its tolerability and suitability for daily supplementation.
Potential benefits include:
- Supporting normal muscle and nerve function.
- Contributing to normal energy-yielding metabolism.
- Helping maintain electrolyte balance.
- Supporting normal psychological function and reducing tiredness and fatigue when magnesium intake is inadequate.
Magnesium supplementation is most useful when dietary intake is insufficient or a deficiency exists. It is not a guaranteed solution for muscle cramps, which can have several causes.
NUTRiD tip: Combine a balanced diet with an appropriate magnesium intake. Check the amount of elemental magnesium in your supplement rather than relying only on the total compound weight.
2. Vitamin D3 – Supporting Bones, Muscles and Immune Function
Vitamin D plays an important role in calcium absorption, bone health and normal muscle function. It also contributes to the normal function of the immune system.
Athletes who train indoors, spend limited time in sunlight, cover most of their skin or have low vitamin D levels may be more likely to benefit from supplementation.
Vitamin D3, also known as cholecalciferol, is a commonly used form of vitamin D.
Why is vitamin D relevant to athletes?
- It contributes to normal calcium absorption and utilisation.
- It supports the maintenance of normal bones and teeth.
- It contributes to normal muscle function.
- It supports the normal function of the immune system.
Maintaining adequate vitamin D levels is important for general health, but taking additional vitamin D when levels are already sufficient has not consistently been shown to improve athletic performance.
NUTRiD tip: Consider your sun exposure, diet and individual requirements when choosing a vitamin D3 supplement. A blood test can help identify low levels. Avoid excessive doses, as vitamin D can accumulate in the body.
3. Iron Bisglycinate – Supporting Oxygen Transport and Endurance
Iron is particularly important for endurance athletes because it is needed to produce haemoglobin, the protein in red blood cells that transports oxygen throughout the body.
Iron also contributes to normal energy metabolism and helps reduce tiredness and fatigue when iron intake is inadequate.
Low iron stores can be a concern for endurance athletes, particularly female athletes, athletes with heavy menstrual losses, frequent blood donors and those following restrictive or predominantly plant-based diets.
Iron bisglycinate is a chelated form of iron in which iron is bound to glycine. It is often used as an alternative to conventional iron salts and may be better tolerated by some people.
Why does iron matter for endurance performance?
- It contributes to normal oxygen transport in the body.
- It supports normal red blood cell and haemoglobin formation.
- It contributes to normal energy-yielding metabolism.
- It helps reduce tiredness and fatigue when iron status is inadequate.
Iron supplementation is not something every athlete needs. Excess iron can be harmful, and unexplained fatigue should not automatically be treated with an iron supplement.
NUTRiD tip: If you experience persistent fatigue or an unexpected drop in performance, discuss iron testing with a healthcare professional. Depending on your situation, testing may include haemoglobin, ferritin and other relevant markers. Supplementation should be guided by the results and appropriate medical advice.
4. Krill Oil – A Marine Source of Omega-3 Fatty Acids
Krill oil is extracted from small marine crustaceans and provides the omega-3 fatty acids EPA and DHA. It also naturally contains phospholipids and, depending on the product, astaxanthin.
EPA and DHA contribute to normal heart function when consumed in a combined daily amount of 250 mg. DHA also contributes to the maintenance of normal brain function and vision at an intake of 250 mg per day.
Krill oil is sometimes selected because its omega-3 fatty acids are partly present in phospholipid form. However, this does not mean that krill oil is universally superior to fish oil for athletic performance or recovery.
Why consider krill oil?
- It provides EPA and DHA omega-3 fatty acids.
- It offers an alternative marine source of omega-3s.
- Some products contain astaxanthin, a naturally occurring antioxidant.
- It may suit people who prefer krill oil to conventional fish oil.
Evidence that krill oil specifically improves endurance performance or speeds up recovery remains limited.
NUTRiD tip: Compare the actual EPA and DHA content per serving, not simply the total milligrams of krill oil. Check the source and quality of the product, and consider potential shellfish allergies before use.
5. Fish Oil – A Practical Source of EPA and DHA
Fish oil is one of the most widely used sources of long-chain omega-3 fatty acids. EPA and DHA are involved in normal physiological processes, including cell membrane function.
For athletes, fish oil can be a practical option when oily fish is rarely included in the diet.
Potential reasons to consider fish oil:
- Providing EPA and DHA when dietary intake is low.
- Supporting normal heart function at an appropriate combined EPA and DHA intake.
- Providing DHA, which contributes to the maintenance of normal brain function and vision at an adequate intake.
Omega-3 fatty acids are also studied for their potential effects on inflammation, muscle soreness and recovery. However, research findings vary, and fish oil should not be presented as a proven performance enhancer.
For most people, eating oily fish regularly can be an effective way to obtain omega-3 fatty acids. Supplementation may be useful when dietary intake is insufficient or when recommended by a healthcare professional.
NUTRiD tip: Choose a product with clearly stated EPA and DHA amounts, appropriate quality testing and suitable storage instructions. Fish oil and krill oil overlap in their main nutritional purpose, so taking both may not be necessary.
How to Choose the Right Supplements for Your Training
Not every athlete needs all five supplements. Your requirements depend on your diet, training load, health, lifestyle and individual nutritional status.
| Supplement | Main nutritional role |
|---|---|
| Magnesium bisglycinate | Muscle and nerve function, energy metabolism |
| Vitamin D3 | Bone health, muscle function, immune function |
| Iron bisglycinate | Haemoglobin formation and oxygen transport |
| Krill oil | Source of EPA and DHA omega-3s |
| Fish oil | Source of EPA and DHA omega-3s |
A personalised approach is more useful than taking every supplement simply because it is popular among athletes.
Start with a varied diet, sufficient energy intake, appropriate carbohydrate and protein intake, hydration and quality sleep. Supplements should complement these fundamentals, not replace them.
The NUTRiD Philosophy: Personalised Nutrition for Better Training
At NUTRiD Personalised Sport Nutrition, our focus is on helping athletes make informed choices about their nutrition.
For endurance athletes, a well-designed strategy includes more than what you consume before, during and after training. It also considers everyday nutritional needs and whether particular supplements are appropriate for the individual.
Magnesium, vitamin D3, iron and omega-3 fatty acids each have specific roles in the body. The key is knowing what you need, why you need it and how to use it responsibly.
Train with purpose. Fuel with knowledge. Supplement with a plan.
Disclaimer: This article is for general educational purposes and is not medical advice. Supplements are not a substitute for a balanced diet. Iron and high-dose vitamin D supplementation should be guided by individual needs and appropriate professional advice.
