Is it better not to take iron and calcium together?
For healthy people without medication, strictly separating intake is probably unnecessary, as long-term research shows no deterioration in iron levels. If you use thyroid medication or antibiotics, spacing them throughout the day is important.
Calcium inhibits the absorption of non-haem iron in the gut, and this has been demonstrated in humans. Non-haem iron is found in plant-based foods and most iron supplements. The effect is short-term: if you take calcium and iron at the same time, your gut absorbs less iron than if you take them separately.
For healthy people who are not on medication, that short-term effect is probably not important. Long-term research shows that people who consistently take more calcium still maintain normal iron levels. Blood markers such as haemoglobin and ferritin do not worsen. The gut appears to adapt over time. Strictly separating the two is therefore probably unnecessary for healthy people. Haem iron, from meat, fish and poultry, is well absorbed regardless and is largely unaffected by calcium.
Vitamin C does the opposite: it strongly improves the absorption of non-haem iron and can even cancel out the inhibitory effect of calcium. A glass of orange juice with an iron-rich plant-based meal is more useful than worrying about when you take your calcium supplement. When reading an iron supplement label, look for the words 'ferrous sulfate' and check the number of milligrams of elemental iron per tablet: that figure is what matters, not the total tablet size.
There are two situations in which the combination is clinically relevant. Do you use thyroid medication (levothyroxine)? Both calcium and ferrous sulfate can bind the medication in the gut, meaning you absorb noticeably less of it. This interaction has been found to be clinically significant in research. Discuss with your doctor how to space your intake throughout the day. The same applies to fluoroquinolone antibiotics, such as ciprofloxacin: iron and calcium supplements reduce the absorption of this type of antibiotic. In both cases, do not take supplements and medication at the same time, and discuss the timing with your doctor or pharmacist.
All claims are based on the supplied abstracts (PMID 21462112, 6940487, 28153426, 1749294, 29484538). The effect in healthy people without medication is based on short- and long-term human studies; the medication risk is based on clinical studies and case reports.
How much iron do you need per day?
For healthy adults without a deficiency, 1 to 2 mg of iron per day through food is sufficient. When a deficiency or anaemia is confirmed, requirements are much higher; discuss that with your doctor.
Which form of iron is best absorbed?
Haem iron from meat, fish and poultry is absorbed best. If you choose a supplement, divalent iron (ferrous sulfate) works better than trivalent iron, but have your iron status checked first because too much iron is harmful.
Is too much zinc harmful?
Too much zinc is certainly harmful: as an adult, stay below 25 mg of elemental zinc per day (EFSA limit) and be cautious with high-dose zinc supplements, because even moderate over-supplementation can disrupt copper balance.
How much magnesium do you need per day?
Research suggests that your body reaches balance at around 165 mg per day, but official recommendations are higher and there is considerable individual variation. In any case, make sure you get enough magnesium-rich foods, as a large part of the population falls short.
How much calcium do I need per day, and can too much be harmful?
Calcium requirements range from 800 mg (young children) to 1500 mg per day (older adults, teenagers, postmenopausal women). Up to 2000 mg per day is safe for most people; aim to get calcium from food wherever possible.
Are calcium supplements bad for your heart?
Calcium supplements may be associated with an increased heart risk, but not all studies confirm this. Ideally, obtain calcium from your diet, and discuss with your doctor whether a supplement is truly necessary for you.