Coffee and Nutrient Absorption: What You Need to Know

• Coffee can hinder the absorption of iron, calcium, magnesium, and several vitamins.
• It’s advisable to wait at least one hour after drinking coffee before taking supplements to improve nutrient uptake.
• Consult your healthcare provider before adding supplements—some people may not need them at all.

If you depend on coffee to kickstart your mornings, you’re definitely not alone. For many, that first cup (or two) is a daily ritual—whether it accompanies breakfast, fuels a workout, or simply perks you up right after waking. But if you’re also in the habit of taking vitamins or minerals, you might want to consider how coffee could affect how your body absorbs those nutrients.

Caffeine, along with polyphenols and coffee’s mild diuretic effect, can interfere with the utilization of certain vitamins and minerals. As Philip Ngo, Pharm.D. points out, “For example, caffeine can slow down iron absorption and also influence nutrients through its diuretic properties.”

We reached out to pharmacists to gain insight into the effects of coffee on nutrient absorption—and to explore how you can optimize your supplement intake.

1. Iron

Iron is crucial for growth and hormone production, yet it’s often deficient in many people’s diets. Your healthcare provider might have recommended iron supplements. However, Bo Wang, M.D., Pharm.D. warns, “Consuming coffee with an iron supplement or fortified cereal can reduce iron absorption.” In fact, studies suggest that drinking coffee can lower absorption by up to 54%, especially when paired with breakfast.

This issue stems not from caffeine itself, but from chlorogenic acid, a polyphenol present in coffee and tea that inhibits the absorption of non-heme iron found in plant foods. Elise Kim, Pharm.D., notes that these polyphenols could affect how our gut absorbs iron.

To improve iron absorption, Wang suggests separating it from your coffee by at least an hour and considering pairing it with vitamin C-rich foods like oranges or lemons.

2. Vitamin D

Vitamin D is tricky to get through diet alone, as it’s not prevalent in many foods—our bodies mainly produce it from sunlight. Kim mentions that “some research indicates caffeine might reduce vitamin D receptors, potentially lowering vitamin D levels.” A 2021 study linked higher caffeine intake to lower circulating vitamin D, although more investigation is needed.

For maximum benefit, Ngo advises spacing vitamin D supplements about an hour apart from coffee. Since vitamin D is fat-soluble, taking it with a meal that includes healthy fats will enhance absorption.

3. B Vitamins

This group of water-soluble vitamins—which includes B1, B2, B7, B9, and B12—is essential for energy production and nerve function. However, “caffeine’s mild diuretic effect may lead to increased excretion of these vitamins, especially with higher caffeine consumption,” explains Kim. Studies have shown that coffee drinkers tend to have lower levels of circulating B vitamins due to these losses.

Wang recommends avoiding taking supplements with coffee or tea. If you can, wait an hour. Water-soluble vitamins like B and C may take better when taken after meals.

4. Magnesium

Magnesium is vital for various bodily functions, including blood sugar control and sleep quality. Many people don’t get enough through diet alone. Kim points out that “caffeine can lead to increased loss of calcium and magnesium through urine.”

If you’re using magnesium supplements for better sleep, it’s wise to steer clear of caffeine in the evening. Caffeine can disrupt sleep and diminish magnesium’s effectiveness.

5. Calcium

Similar to magnesium, caffeine may impede calcium absorption. Kim observes, “While the clinical impact isn’t fully understood, studies indicate participants consuming caffeine excreted 77% more calcium in urine than those taking a placebo.”

Adding milk to your coffee may help mitigate calcium loss. Also, consider spacing calcium supplements at least an hour after coffee—or two hours before—for optimal absorption.

Our Expert Take

Coffee does affect how your body absorbs some nutrients, but with just a few timing adjustments, you can improve nutrient uptake. If you miss the window and take supplements with coffee, you’ll probably still absorb some of the nutrients.

And despite what you might hear from wellness influencers, not everyone requires supplements. “Supplements should complement your diet,” reiterates Ngo. “If you’re generally healthy and eat a balanced diet, spending on supplements might not be necessary unless you’re genuinely deficient.” Speaking with a healthcare provider and possibly undergoing lab tests can give insight into what’s right for you.