It could be your best shot at a productive day.
Coffee offers a bevy of health perks, from boosting brain function and reducing inflammation to improving heart health and supporting metabolism.
Unfortunately, your morning brew can also affect how your body absorbs certain supplements, possibly making them less effective and triggering irritating side effects.
About 66% of US adults drink coffee every day, while roughly 74% take a dietary supplement — so there’s bound to be some potentially problematic overlap.
These are the five supplements you may want to think twice about washing down with coffee.
Iron
“Iron is the most clearly affected by coffee,” Dr. Karan Rajan — chief of science at Throne Science, a gut health tech company — told The Post about the popular supplement.
Coffee is packed with polyphenols, which are powerful antioxidants that protect against oxidative stress and fight inflammation.
Chlorogenic acids are a major group of polyphenols in coffee — they add to its flavor and health benefits.
Rajan noted that polyphenols like chlorogenic acid can bind to non-heme iron in the digestive tract, making it harder for the body to absorb.
“This matters most for people who are iron-deficient, menstruating, pregnant or plant-based,” Rajan said.
“Practical advice would be: If you’re taking iron, do it at least one to two hours away from coffee. Vitamin C can help offset the inhibition caused by iron.”
Zinc
“Coffee can modestly reduce zinc absorption, again due to polyphenols binding minerals,” Rajan said.
“The effect is dose- and timing-dependent and usually small for people eating a zinc-adequate diet.”
Foods high in zinc include oysters, red meat, poultry, shellfish, cashews, almonds, pumpkin and hemp seeds, lentils, chickpeas, beans, whole grains, dairy, eggs and fortified cereals.
Those supplementing with zinc for deficiency or immune support may benefit from taking it separately from coffee, Rajan said.
Calcium
“Coffee has a small inhibitory effect on calcium absorption, mainly due to caffeine increasing urinary calcium loss rather than blocking absorption outright,” Rajan explained.
Research has estimated that about 5 milligrams of calcium are lost per cup of coffee.
“For most people with adequate calcium intake, this is negligible,” Rajan said.
“If someone relies heavily on supplements for bone health, spacing calcium away from coffee is sensible, but it’s not a major concern for the general population.”
Magnesium
Coffee doesn’t strongly block magnesium absorption, Rajan said, but caffeine does increase urine output.
This mild diuretic effect can lead to magnesium loss, particularly with high caffeine intake.
“For simplicity, magnesium is often better taken later in the day, but coffee isn’t a hard ‘no,’ ” Rajan said.
Separately, mixing magnesium citrate or sulfate with coffee can cause diarrhea or stomach cramps because these forms of magnesium and caffeine have laxative effects.
B vitamins
“Most B vitamins are not meaningfully blocked by coffee,” Rajan said. “However, caffeine can increase urinary excretion of some B vitamins (notably B1).”
B vitamins are water-soluble, meaning that they dissolve in water and excess amounts are flushed out through urine.
Vitamin B1, or thiamine, turns carbs into energy and supports healthy nerve, muscle and heart function.
Rajan said caffeine’s diuretic effect doesn’t matter much unless the person is consuming a small amount of B1 or a lot of caffeine.
“From a practicality standpoint, B vitamins can still be taken with coffee without major concern,” Rajan added.
