Supplements You Shouldn’t Take With Your Coffee

Your morning cup can impact how well some supplements absorb — here’s which ones to space out and which don’t matter.

If you’re a daily coffee drinker, you probably don’t think much about what your morning cup does beyond providing that beloved jolt. At this point, it’s just another part of the routine. But caffeine is a stimulant, and certain compounds in coffee interact with some of the other nutrients you ingest — like certain supplements.

That’s not to say washing down your multivitamin with coffee is dangerous. Coffee can make it harder for your body to absorb certain nutrients, stopping you from receiving the full intended benefit of the supplement you’re taking. In some cases, simply putting a little time between your coffee and your supplements may be enough to avoid problems.

What You Should Know About Coffee and Absorption

There are hundreds of compounds in coffee, but two worth paying attention to when it comes to nutrient absorption are polyphenols — antioxidants also found in fruits and veggies — and caffeine. Certain polyphenols, including chlorogenic acids, can bind to iron during digestion, making it harder for your body to absorb the mineral. Caffeine, meanwhile, can increase the amount of certain minerals, like calcium, you excrete through urine. “Research suggests that consuming approximately 1–2 cups of coffee may increase urinary calcium excretion by a few milligrams per cup,” says Caroline Thomason Bunn, RD, CDCES. That doesn’t mean you’re flushing your supplements down the toilet, but it can slightly affect how much of those nutrients your body retains.

“Research suggests that consuming approximately 1–2 cups of coffee may increase urinary calcium excretion by a few milligrams per cup.”

-Caroline Thomason Bunn, RD, CDCES.

The mild acidity of coffee is sometimes cited as another reason it interferes with supplement absorption. However, there’s little evidence that’s true, and in fact, stomach acid helps your body absorb certain minerals, including iron and calcium. 

Going Deeper: The Supplements

Understand that the supplements listed below interact with coffee in their own specific way, so what’s true for iron isn’t true for calcium. Some research is stronger for certain supplements than others, too, so it’s important not to lose sight of the big picture: Drinking coffee doesn’t completely negate the effects of any supplement, and it’s a relatively safe beverage to consume with some serious benefits. 

That said, we also provide practical takeaways you can start implementing immediately to potentially reduce the negative cross-over effects of taking coffee with certain supplements. Speaking of, those supplements are:

Iron

Iron is essential for producing red blood cells, transporting oxygen throughout the body, and supporting healthy hormone production. There’s also a significant amount of evidence that drinking coffee can interfere with how much iron your body absorbs. One study of 34 iron-deficient women found that taking an iron supplement with coffee reduced absorption by 54% compared to taking it with water. When the women consumed coffee with breakfast, iron absorption dropped by 66%.

Your best bet: “Iron supplements are generally best absorbed on an empty stomach, ideally 30 to 60 minutes before eating or about 2 hours after a meal. Iron can cause nausea, abdominal discomfort, constipation and other GI side effects. If you experience these symptoms, taking iron with a small amount of food is a reasonable alternative,” shares Bunn.

Calcium

Calcium is vital for healthy bones, teeth, and muscles, and adults need between 1,000 and 1,200 milligrams daily. You can get it from dairy, leafy green vegetables, and supplements. What you should know is that coffee can slightly affect how much calcium your body absorbs and retains. One study associated higher caffeine intake with increased calcium excretion through urine.

Your best bet: The effect is small enough that most people don’t need to worry about separating their calcium supplements from their coffee. Instead, focus on meeting your daily calcium needs through food and, if necessary, supplementation. Researchers estimate that an additional 40 milligrams of calcium — about a one-third cup of cow’s milk — could offset the effects of each 6-ounce serving of coffee.

Magnesium

Magnesium is an essential mineral that helps convert food into cellular energy, supports muscle contractions, and calms the nervous system to help you sleep — and your body doesn’t make it on its own. You get it through foods like dark leafy greens and seeds. Supplements are a popular option for taking magnesium, but know that, similar to calcium, magnesium excretion through urine can temporarily increase on days you have at least two servings of caffeine. Small, short-term studies have also found that caffeine can reduce the percentage of magnesium reabsorbed by the kidneys, although the long-term implications for magnesium status remain unclear.

Your best bet: The evidence doesn’t establish that moderate coffee consumption meaningfully depletes magnesium or that you need to separate magnesium supplements from coffee. Focus on meeting your daily magnesium needs through food, and consider supplementation when appropriate.

Zinc

Zinc supports immune function, wound healing, and the production of DNA and proteins. There’s some research suggesting that coffee may interfere with zinc absorption. One study from 1975 found that several foods, including dairy products and brown bread, reduced zinc absorption in healthy volunteers. The researchers also observed that coffee appeared to inhibit zinc absorption, though they didn’t quantify the effect in their published abstract.

Your best bet: There’s no established recommendation to separate coffee and zinc supplements by a specific amount of time. If you want to take a precautionary approach, you could take your supplement an hour or two apart from coffee, but this isn’t a proven requirement. Follow your supplement’s instructions, and if zinc causes nausea, try taking it with food.

B Vitamins

B vitamins play important roles in energy production, red blood cell formation, and nervous system function. There’s some evidence that coffee consumption may affect your body’s B-vitamin levels, though it’s unclear whether it interferes with absorption. One study of more than 10,000 adults found that people drinking at least four cups of coffee daily had 11.7% lower folate (B9), 14.1% lower vitamin B6, and 5.5% lower riboflavin (B2) concentrations in their blood compared with non-coffee drinkers. Researchers speculated that coffee could increase the amount of excess B vitamins excreted through urine.

Your best bet: There’s no established need to separate B-vitamin supplements from coffee. If you regularly take a B-complex supplement, focus on following the recommended dosage rather than worrying about timing.

Multivitamins

About one-third of American adults take a multivitamin, which typically contains a mix of essential vitamins and minerals. Whether coffee interferes with absorption depends on what’s inside. Multivitamins containing iron are the biggest concern, since coffee’s polyphenols can substantially reduce how much iron your body absorbs. According to the National Institutes of Health, multivitamins formulated for women commonly contain 18 milligrams of iron, whereas those designed for men or older adults often contain little or no iron.

Your best bet: Check the label. If your multivitamin contains iron, consider taking it at a different time than your coffee. Otherwise, there’s little evidence that you need to separate a standard multivitamin from your morning cup.

The Takeaway

If you’re taking an iron supplement or a multivitamin containing iron, for optimal absorption,  wait 1 to 2 hours after your morning coffee. For other supplements, including calcium, magnesium, and B vitamins, there’s less evidence that timing makes a meaningful difference. If you’re taking prescription medications, check with your doctor or pharmacist about potential interactions with coffee, as some medications have specific timing requirements.

Bottom Line

Yes, coffee can interfere with how your body absorbs and retains certain nutrients, but the degree varies. The evidence is strongest for iron, while caffeine’s effects on calcium balance are well-documented but relatively small. Claims about coffee interfering with magnesium, zinc, and B-vitamin supplements are less conclusive. Ultimately, there’s no reason to overhaul your entire supplement routine to accommodate your coffee habit, though a few small timing adjustments may help you get more out of certain supplements.

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