science

Which Vitamins Should You Avoid Taking Together? A Simple Guide to Staying Safe

Dr. Carla Montrond Correia ND, CNS

Medically Reviewed by

Dr. Carla Montrond Correia ND, CNS

5 min read

Vitamins can be very good for your health. But to ensure you’re getting the maximum benefit from them, there are certain combinations to avoid.

Which Combinations of Vitamins Should You Avoid?

Vitamins and supplements can be great for your health, especially when they’re addressing nutrient deficiencies in your diet. But some vitamins should not be taken together, lest their impact be weakened or side effects occur. Let’s take a look at some combinations to avoid.

Calcium and vitamin D

Calcium and vitamin D are both hugely important for bone health, and optimal vitamin D levels are necessary to increase your body’s ability to absorb calcium. So, it’s only natural that some believe taking calcium and vitamin D together is a good idea. However, a 2019 study has raised some eyebrows by suggesting that taking vitamin D and calcium supplements together can lead to cardiovascular issues. However, that study was inconclusive and the results couldn’t be replicated. Other lifestyle factors can play a role in cardiovascular issues, including excessive sedentary time and lack of nutrient-dense foods in diet, including omega-3s, fiber, fruits and vegetables, and lean protein.

Calcium and iron

Calcium is crucial for bone health, while iron is essential for carrying oxygen from your lungs to the rest of your body. If you’re deficient in either, supplements can be helpful. Calcium can be taken with a meal, and iron should ideally be taken on an empty stomach. A note about iron supplementation: You should only take iron supplements after consulting with a doctor, since taking too much iron can be toxic.

As it turns out, you should also avoid taking calcium and iron together. Studies show that calcium can disrupt iron absorption. To ensure optimal absorption, take them apart from one another.

Vitamin B9 and vitamin B12

Vitamins B9 and B12 are both part of the B-complex family and can be taken together. Both can be taken either with or without food. However, high levels of B9 (a.k.a. folic acid, methylfolate, or folate) above 1000 mcg can mask a B12 deficiency. Keep your medical professional informed of any supplements you take so it can be incorporated into your lab value interpretations.

Copper and zinc

If you’re thinking about combining copper and zinc, keep this word in mind: balance. Taking an extremely high dose of zinc can interfere with your body’s ability to absorb copper; indeed, studies show that taking too much zinc can result in a reduction in copper stores. On the other hand, per this study, zinc absorption isn’t much affected by increased copper intake. It remains to be seen, though, whether increased copper intake affects zinc absorption when zinc levels are already low. Care/of’s zinc supplement is blended with copper compounds for mineral balance, preventing possible mineral depletions. Because taking minerals on an empty stomach can sometimes cause digestive discomfort, it’s recommended to take this supplement with food.

Magnesium and calcium

Magnesium and calcium both play an important role in supporting healthy bones. However, studies have found that calcium competes with magnesium for intestinal absorption – and this is especially so if your calcium intake is significantly higher than your magnesium intake. What matters is the ratio. If the gut has more magnesium than it has calcium, the magnesium will be absorbed; if there is a much higher amount of calcium in the gut, then the magnesium will not be absorbed. A study published by the BJM Open journal found that the right ratio of calcium to magnesium is about 1.7:1. When using magnesium and calcium supplements, you have to be careful to keep the ratio right, or else your body will absorb neither properly. Talk to a doctor about the right approach for you.

Fish oil & ginkgo biloba

Ginkgo and fish oil can both be used to thin the blood – and, as such, can become a problem for people already on blood thinning medication. Both supplements also support healthy blood flow, and ginkgo does so in part by increasing nitric oxide levels. If you’re not concerned about blood thinning properties, you can take these supplements together; just be sure to do so with food. You should talk to a medical professional about what will work best for you.

Vitamins C and B12

Vitamin C and vitamin B12 supplements can both be good for you. However, one study has shown that taking high doses of vitamin C might reduce the available vitamin B12 in your body. Results of others studies have been somewhat mixed, however. Another study found no correlation between high vitamin C levels and low serum B12. Still, to ensure optimal absorption, you may consider keeping your vitamin C supplement dose below the 2,000mg upper limit. Both of the vitamins can be taken any time of day, with or without food.

Vitamins K and E

According to this study, taking high doses of vitamin E can disrupt the body’s absorption of vitamin K. Since vitamin K is essential to blood clotting, failure to absorb adequate vitamin K in the system can lead to a number of health risks, including the chance of bleeding issues. The doses are what matter most. Taking the Care/of multivitamin poses no issues because the doses of each vitamin have been expertly calibrated. Since vitamin K and vitamin E are both fat-soluble vitamins, you’ll ideally take them with food, which helps absorption.

Key takeaways

While a vitamin and supplement routine can be good for you, it’s important to know what you’re putting into your system and how various supplements interact with one another. To ensure optimal absorption and maximum health benefit, some supplement combinations should be avoided. As always, you should discuss your supplement routine with a medical professional who can evaluate your nutrient levels and point you in the right direction.

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