5 min read
While it might be tempting to take all your vitamins simultaneously, health experts warn that this practice may hinder the effectiveness of your supplements. Certain vitamins and minerals can compete for absorption, which diminishes their effectiveness and may even lead to side effects such as stomach upset, constipation, or diarrhea.
Conversely, some vitamins and minerals enhance one another’s absorption, improving their bioavailability. For instance, vitamin D aids calcium absorption, while vitamin C optimizes iron utilization. To truly reap the benefits of your supplements (and ensure you invest wisely), it’s crucial to understand which combinations to avoid and which ones to embrace.
Timing is also crucial, especially concerning meals. “Some [supplements] are best absorbed with food, while others need to be on an empty stomach,” shares Amy Margulies, R.D.N., a registered dietitian and owner of The Rebellius RD. “Some combinations can interfere with each other or with medications.”
In severe cases, improper combinations of supplements can lead to long-term nutritional deficiencies or vitamin toxicity, warns Brynna Connor, M.D., a board-certified family medicine physician.
This doesn’t mean you need to avoid supplements altogether; however, knowing which vitamin and mineral combinations to steer clear of can help shield you from unfavorable side effects while optimizing your wellness regimen.
Nutrient combinations to avoid
Keep these combinations in mind when planning your supplement routine.
Iron and calcium
Calcium can hinder iron absorption in the gut. If your levels of both are low, you may still take them, provided you space them out appropriately.
What to do: Consume iron at least two hours before or after taking calcium supplements.
Calcium is best absorbed in smaller doses (500 milligrams or less), spread throughout the day, suggests Lamees Hamdan, M.D., an integrative medical practitioner. While calcium citrate can be taken with or without food, calcium carbonate should ideally be taken with meals since it relies on stomach acid for maximum absorption.
Iron and zinc
Research indicates that iron and zinc compete for the same absorption pathways in the gut. “Taking a high-dose iron supplement and zinc at the same time—especially on an empty stomach—may hinder zinc absorption,” Margulies explains.
What to do: For optimal absorption, it’s usually best to take iron on an empty stomach and to separate it from zinc. While there’s no strict guideline on timing, waiting two hours between the two is a sensible practice.
Copper and zinc
If you are taking zinc supplements, keep in mind that high doses of zinc may inhibit copper absorption, which could lead to copper deficiency over time. Consuming copper-rich foods such as shellfish, seeds, nuts, and organ meats may help mitigate this effect, but it’s wise to monitor your levels regularly.
What to do: If you need to take both copper and zinc, try to space them out. Experts recommend waiting about two hours between taking the two. Both can be safely consumed on an empty stomach. “You could take zinc in the morning before breakfast and copper before lunch or dinner, as long as you haven’t eaten within the previous few hours,” advises Margulies.
Vitamin B12 and Vitamin C
Because vitamin C creates an acidic environment in the stomach, some research indicates that large doses can potentially degrade vitamin B12 before it is fully utilized. However, for most people, typical doses of vitamin C and B12 are unlikely to pose significant concerns when taken together. While some studies suggest this interaction, the evidence is not strong and conclusive. Nevertheless, it’s an important consideration.
What to do: When uncertain, Dr. Connor advises taking them in alphabetical order—start with vitamin B12 and wait at least two hours before taking vitamin C. You can pair vitamin B12 with a light breakfast, but taking it on an empty stomach is also acceptable.
The best vitamin combinations
Some vitamins and minerals work well in tandem, enhancing each other’s effects. While it’s essential to meet your nutritional requirements primarily through your diet, if supplementation is necessary, consider these effective pairings:
- Vitamin C + iron: Vitamin C improves iron absorption, especially from plant sources like beans and lentils. “This combination is excellent for preventing iron deficiency and boosting energy,” explains Margulies.
- Vitamin D + Vitamin K2: These vitamins work synergistically to optimize calcium delivery and support bone health, according to Dr. Hamdan.
- Vitamin A + iron: This pairing is especially powerful for individuals dealing with anemia.
What about multivitamins?
Given that certain vitamins and minerals can inhibit each other’s absorption, you might wonder about the safety of multivitamins that combine multiple vitamins in one pill.
“Multivitamins are carefully crafted with smaller, balanced doses that minimize competition among nutrients,” explains Margulies. These lower doses help reduce interactions that may occur from taking larger amounts of nutrients, ensuring that they can coexist without largely diminishing effectiveness or causing negative effects.
However, whether these smaller doses are effective can vary based on individual dietary needs and habits. For those with nutrient deficiencies or increased requirements due to health conditions, lifestyle, or age, the levels in a multivitamin may not meet their needs. Conversely, for individuals with a balanced diet, multivitamins can serve as a safety net, filling minor gaps in nutrition without the risk of excessive intake of any single nutrient. Ultimately, the effectiveness of multivitamins hinges on how well they complement a person’s overall nutrient intake.
The bottom line on pairing vitamins
Before introducing any new supplements to your regimen, it is essential to consult with your healthcare provider. This step is crucial to avoid potential interactions with existing medications, particularly blood pressure, thyroid medications, and anticoagulants, cautions Dr. Connor. “Establishing a consistent routine when taking your vitamins and minerals is beneficial,” she advises. “Once you learn how to space them properly, taking them at the same time each day can enhance absorption and adherence.”
Laura Iu, R.D., is a registered dietitian nutritionist, certified intuitive eating counselor, yoga guide, and owner of Laura Iu Nutrition, a private practice in New York City. She earned her Bachelor of Science in Nutrition and Dietetics from New York University and completed her internship in dietetics at Weill Cornell & Columbia Medical Center of New York-Presbyterian Hospital. She went on to work in New York City’s top hospitals, including Mount Sinai Hospital and NYU Langone Health. Laura believes that true health encompasses physical, emotional, and mental wellbeing rather than being measured by external factors like shape or size.
