Whether it’s a long black the moment your eyes open or a takeaway latte from your favourite cafe, for the vast majority of us, the day doesn’t properly begin without coffee. Between juggling work, family and full calendars, it’s often the small ritual that gets us going.
But according to experts, pairing supplements with your morning brew may not always be the best idea, particularly when it comes to how well certain vitamins and minerals are absorbed.
“Caffeine has shown to reduce the absorption of minerals like iron, calcium, vitamin D, and B group vitamins,” explains Accredited Practising Dietitian, Zoe Brain. “This is because the naturally occurring polyphenols and tannins found in coffee bind to vitamins and minerals in the gut, making it harder for them to absorb.”
It can also act as a mild diuretic, meaning it makes you need to go to the bathroom more frequently, which matters when you’re relying on supplements to correct or prevent deficiencies. “Caffeine can also have a diuretic effect by increasing urinary losses of some minerals,” Zoe says, which is an issue for nutrients that are already water-soluble.
If you’re taking supplements to support energy, bone density or iron levels – particularly during menstruation, pregnancy or perimenopause – these interactions can add up.
Supplements best taken away from coffee
Iron
Iron is the nutrient most affected by your morning cappuccino. “Coffee is rich in polyphenols, which can bind to iron, especially non-heme iron, which is the type found in plant foods and many supplements,” Zoe explains.
“Think of it like this: iron is like tiny metal filings, and coffee is like a magnet. When they meet, the magnet pulls the filings together into a heavy clump. Once it’s clumped up, it’s too bulky to pass through the intestinal wall and into the bloodstream.”
This matters particularly for those with heavy periods, and women who are pregnant or following vegetarian or vegan diets.
Vitamin D
Vitamin D is essential for bone strength, immune health and mood regulation. While coffee doesn’t completely block absorption, it may interfere with how the body uses it.
“Coffee doesn’t block vitamin D from being absorbed. Instead, it may slightly affect how well your body uses it,” Zoe says. “A simple way to picture it is like coffee turning down the ‘volume’ on vitamin D’s message in some bone cells.”
Taking vitamin D with food is key. “Vitamin D is essential for bone health, and it’s best absorbed when you take it with a meal that contains some healthy fat, for example, avocado, olive oil, eggs, or fatty fish like salmon.”
B-group vitamins
B-group vitamins play a central role in energy production, stress response and nervous system function. While coffee doesn’t stop them from being absorbed outright, it can increase losses.
“They are water-soluble, so having a lot of caffeine may increase the amount of B vitamins lost in your urine,” Zoe explains.
Spacing them away from coffee, and taking them with food, may help maximise their benefit.
Calcium
Calcium supports bones, muscles and nerve function. Its interaction with coffee is more subtle but still worth noting.
“Caffeine doesn’t block calcium absorption like it can with iron, but it may make you lose a little more calcium in your urine a few hours after you drink it,” Zoe says.
Rather than relying solely on supplements, she recommends a food-first approach. “Aim to get your calcium throughout the day from foods like low-fat dairy, tofu, tinned salmon with bones, and leafy greens to maximise the absorption.”
Supplements less affected by coffee
The good news? Not all supplements clash with caffeine. Fish oil, probiotics and collagen are generally considered safe to take with coffee, as they don’t appear to have significant absorption issues when consumed together.
Simple ways to improve absorption
“I recommend waiting at least one hour between drinking coffee and taking B-vitamins, calcium or vitamin D supplements,” she says, although for iron, more distance is needed. “For those treating low ferritin or iron deficiency, leave at least two.”
Pairing nutrients can further improve absorption. “Pairing iron with vitamin C can significantly boost absorption,” Zoe says, noting that vitamin C both converts iron into a more absorbable form and protects it from inhibitors like caffeine.
Do you need coffee, or are you lacking something?
If coffee feels essential just to get through the day, it may be worth asking why. “Most of the time needing coffee to function may be more about sleep quality and quantity, stress, dehydration, or not eating enough, especially in the morning, rather than a single nutrient deficiency,” Zoe says.
That said, ongoing fatigue shouldn’t be dismissed. “If fatigue is persistent, it’s sensible for women to check for common deficiencies, particularly ferritin and vitamin B12.”
And while it can be tempting to go to the pharmacy and grab something off the shelf, a conversation with your GP or dietitian can help ensure supplements – and coffee – are working with your body, not against it.
