~ Annie Bothma, Elite Athlete, IOPN Performance Sports Nutritionist (EQF Level 7. Masters), Running & Strength Coach
Nutrition isn’t just about getting enough vitamins and minerals—it’s about understanding how these nutrients work together. Some nutrients enhance each other’s benefits, creating synergies that amplify their effects, while others compete, limiting absorption and effectiveness. For athletes, these nutrient interactions can play a critical role in optimizing recovery, performance, and long-term health.
For example, vitamin D enhances calcium absorption, a synergy that’s essential for strong bones and effective muscle contraction. On the other hand, calcium and iron compete for absorption, making careful timing of supplementation crucial for athletes who often require higher iron intake. Similarly, while vitamin C can boost iron absorption, excess zinc can disrupt copper and iron balance.
In this post, we’ll explore the most important nutrient interactions that affect athletes, how to leverage positive pairings, and how to avoid competitive absorption issues. By taking a strategic approach to your diet and supplementation, you can ensure your body is performing at its best.
Positive Nutrient Interactions: Working in Synergy
Some nutrients enhance each other's absorption and effectiveness, creating powerful synergies that support optimal health, recovery, and athletic performance.
Vitamin D and Calcium
How They Work Together: Vitamin D promotes calcium absorption in the intestines and helps direct calcium to the bones and teeth. Without adequate vitamin D, calcium absorption decreases, potentially leading to bone loss or fractures.
Why It Matters for Athletes: Athletes rely on strong bones to handle the repetitive impact of training and competition. Ensuring optimal levels of both nutrients supports skeletal strength and muscle function.
Taking Action: Pair calcium-rich foods (like dairy or leafy greens) with vitamin D sources (like fatty fish, fortified foods, or supplements) for maximum benefits.
Vitamin C and Iron
How They Work Together: Vitamin C enhances the absorption of non-heme iron (from plant-based foods) by converting it into a more bioavailable form.
Why It Matters for Athletes: Iron is essential for oxygen transport and energy production. Athletes, particularly females and endurance athletes, often have higher iron needs, making this interaction critical.
Taking Action: Add a vitamin C-rich food (like citrus or strawberries) to your iron-containing meals (like spinach or lentils) to improve absorption.
Vitamin D and Magnesium
How They Work Together: Magnesium activates vitamin D by converting it into its biologically active form. Without sufficient magnesium, vitamin D metabolism is impaired.
Why It Matters for Athletes: Both magnesium and vitamin D are critical for muscle contraction, recovery, and bone health.
Taking Action: Incorporate foods high in magnesium such as nuts, seeds, and whole grains into your diet, while also making sure to maintain adequate levels of vitamin D through exposure to sunlight, dietary sources, and supplements if necessary.
Sodium and Potassium
How They Work Together: These electrolytes regulate fluid balance, nerve transmission, and muscle contractions. Sodium draws water into cells, while potassium helps balance this effect by preventing excess fluid retention.
Why It Matters for Athletes: Proper sodium and potassium balance prevents dehydration, cramping, and fatigue, especially during endurance events.
Taking Action: Balance sodium intake (through electrolyte drinks or salty snacks) with potassium-rich foods like bananas, avocados, and sweet potatoes.
Omega-3 Fatty Acids and Vitamin E
How They Work Together: Omega-3s reduce inflammation, but their unsaturated nature makes them prone to oxidation. Vitamin E acts as an antioxidant, protecting omega-3s from damage.
Why It Matters for Athletes: This pairing supports recovery, reduces inflammation, and promotes cardiovascular health.
Taking Action: Pair omega-3 sources like salmon or flaxseeds with vitamin E-rich foods like almonds or sunflower seeds for optimal benefits.
Competitive Nutrient Interactions: Avoiding Absorption Issues
Certain nutrients compete for absorption in the body, meaning excessive intake of one can limit the effectiveness of another, which is especially important for athletes relying on precise nutrient balance for performance.
Zinc and Iron (and Copper)
The Competition: Zinc, iron, and copper share the same absorption pathways. Excessive intake of one can block the others, leading to deficiencies.
Why It Matters for Athletes: Over-supplementing zinc for immune health can inadvertently reduce copper or iron absorption, leading to anemia or fatigue.
Taking Action: If feasible, opt for food sources over supplements. Excellent sources include such as lean meats (iron and zinc) and nuts (copper) to prevent interference.
Calcium and Iron
The Competition: Calcium can inhibit the absorption of iron when consumed together in significant amounts, particularly non-heme iron from plant sources.
Why It Matters for Athletes: Athletes, especially females, often need supplemental iron due to increased losses from sweat, menstruation, and impact-based exercise. Timing iron intake away from calcium is crucial.
Taking Action: Take iron supplements or eat iron-rich meals away from calcium-rich foods or supplements. Pair iron with vitamin C to enhance absorption.
Test, Don’t Guess: Addressing Deficiencies with a Strategic Approach
If a nutrient deficiency is identified, it’s important to carefully consider the underlying factors and the most effective intervention. A common first step is the “food first” approach—prioritizing the inclusion of nutrient-rich foods in the diet. For example, boosting iron intake with lean meats alongside fresh fruits and vegetables to provide sufficient vitamin C for optimal absorption.
However, food alone isn’t always sufficient, especially if the deficiency requires more of the nutrient than the diet can realistically provide. In such cases, supplementation may be necessary. For example:
Iron Deficiency: A vegetarian athlete with low iron levels might require a daily iron supplement to complement plant-based iron sources. Pairing iron with vitamin C-rich foods, such as citrus fruits or bell peppers, can further enhance absorption. Iron supplements should ideally be taken in the morning an hour away from any foods coffee or tea.
Vitamin D Deficiency: Low blood levels of vitamin D often require sustained supplementation for 4–12 weeks to reach optimal levels. Regular sun exposure, fortified foods, or supplements can help maintain these levels long-term. Adequate dietary fat is needed for optimal vitamin D absorption.
Calcium for Low Bone Density or Vegan Athletes: Athletes with low bone density or those excluding dairy products from their diet (e.g., vegans) should aim to meet the recommended intake of 1,000 mg of calcium per day, ideally split into two 500 mg doses for better absorption. Plant-based calcium sources include fortified plant milks, tofu, almonds, and leafy greens. If dietary calcium remains insufficient, supplementation may be necessary to support bone health and reduce the risk of stress fractures.
Read More: Food First but Not Always Food Only: Recommendations for Using Dietary Supplements in Sport
Table 1: Key vitamins and minerals for athletes of importance to haematology, bone health and immune function, their Recommended Daily Intake (RDI) by sex, the blood reference range for healthy adults (18–50 years) and their common food sources
Nutrient | RDI (Male) | RDI (Female) | Blood Reference Range | Common Food Sources |
Vitamin C | 90 mg | 75 mg | 4–14 mg/L | Citrus (oranges, kiwi, lemon, grapefruit), bell peppers, cruciferous vegetables (broccoli, Brussels sprouts) |
Vitamin D | 15 µg | 15 µg | >50 nmol/L | Salmon, tuna fish, sardines, beef liver, egg yolk, milk |
Vitamin B12 | 2.4 µg | 2.4 µg | 140–1000 pmol/L | Fish, liver, red meat, eggs, poultry, milk, cheese, yoghurt |
Vitamin B9 (Folate) | 400 µg | 400 µg | >7 nmol/L | Leafy green vegetables (spinach, asparagus, Brussels sprouts), beans, peanuts, liver, fish, eggs |
Iron | 8 mg | 18 mg | 30–300 µg/L (ferritin) | Red meat, chicken, leafy green vegetables (spinach, bok choy), nuts, seeds |
Calcium | 1000 mg | 1000 mg | 210–260 mmol/L | Milk, cheese, yoghurt, soybeans, leafy green vegetables (spinach, bok choy), almonds |
Zinc | 14 mg | 8 mg | 9–16 µmol/L | Shellfish, beef, chicken, legumes, nuts, seeds |
Source: Peeling P, Sim M, McKay AKA. Considerations for the Consumption of Vitamin and Mineral Supplements in Athlete Populations. Sports Med. 2023 Dec;53(Suppl 1):15-24. doi: 10.1007/s40279-023-01875-4. Epub 2023 Jun 26. PMID: 37358750; PMCID: PMC10721676.
While supplementation can be effective, it’s not without challenges. Some athletes experience gastrointestinal discomfort with supplements like iron, and there’s always a risk of contamination in unregulated products. To minimize these risks, opt for batch-tested supplements and consult with a professional to ensure safe and effective use.
Addressing deficiencies is a process that takes time, often requiring several weeks or months to correct. With a well-planned strategy, athletes can restore optimal nutrient levels, improving performance, recovery, and overall health.
Read More: SPORT NUTRITION SUPPLEMENT SERIES
Conclusion: Optimizing Nutrition with Smart Pairings
Nutrient interactions are complex but incredibly important for athletes aiming to perform at their best. Synergies like vitamin D and calcium or vitamin C and iron can amplify benefits, while competitive interactions, such as calcium and iron, highlight the need for careful timing and planning.
If you’re experiencing fatigue, slow recovery, or other signs of a potential nutrient deficiency, the first step is to test, not guess. A blood test can uncover specific deficiencies, enabling a targeted approach to addressing the issue—whether through dietary adjustments, supplementation, or both.
By understanding these nutrient relationships and taking a personalized approach, you can unlock your body’s full potential. Prioritize balanced nutrition, smart supplementation, and professional guidance to ensure your nutrition plan works as hard as you do.
Contact me at anniesathletes@gmail.com for personalized guidance on diet and supplements to address deficiencies and optimize your health!
References
Peeling P, Sim M, McKay AKA. Considerations for the Consumption of Vitamin and Mineral Supplements in Athlete Populations. Sports Med. 2023 Dec;53(Suppl 1):15-24. doi: 10.1007/s40279-023-01875-4. Epub 2023 Jun 26. PMID: 37358750; PMCID: PMC10721676.
Giustina, A., Bilezikian, J.P., Adler, R.A., et al. (2024). Consensus Statement on Vitamin D Status Assessment and Supplementation: Whys, Whens, and Hows. Endocrine Reviews, 45(5), 625-654. doi: 10.1210/endrev/bnae009. PMID: 38676447.
Close GL, Kasper AM, Walsh NP, Maughan RJ. "Food First but Not Always Food Only": Recommendations for Using Dietary Supplements in Sport. Int J Sport Nutr Exerc Metab. 2022 Mar 12;32(5):371-386. doi: 10.1123/ijsnem.2021-0335. PMID: 35279015.
Jeukendrup, A., & Gleeson, M. (2019). Sport Nutrition (3rd ed.). Human Kinetics.
Sale, C., & Elliott-Sale, K. J. (2019). Nutrition and athlete bone health. Sports Medicine, 49(Suppl 2), 139–151. https://doi.org/10.1007/s40279-019-01161-2. PMID: 31691899.
Walsh, N. P. (2019). Nutrition and athlete immune health: New perspectives on an old paradigm. Sports Medicine, 49(Suppl 2), 153–168. https://doi.org/10.1007/s40279-019-01160-3. PMID: 31691927.
Maughan, R. J., Burke, L. M., & Dvorak, J. (2018). IOC consensus statement: Dietary supplements and the high-performance athlete. British Journal of Sports Medicine, 52(7), 439–455. https://doi.org/10.1136/bjsports-2018-099027. PMID: 29540367.
Rogerson, D. (2017). Vegan diets: Practical advice for athletes and exercisers. Journal of the International Society of Sports Nutrition, 14, 36. https://doi.org/10.1186/s12970-017-0192-9. PMID: 29151871.
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