The absorption of a vitamin or mineral is required before the body can use it. Iron and calcium are two minerals which can be "tied up" by compounds in tea, keeping them from being absorbed. To keep minerals and tea from interfering with each other, take them separately. There's no need to remove any of them from your diet, as being mindful about the timing of each is enough to guarantee absorption of each.
Look to see if your tea is regular or herbal tea. Teas are divided into two families. Tea made from leaves that come from the Camellia sinensis are regular "tea": green, black, white and oolong teas. All containing caffeine unless decaffeinated, tea sourced from these leaves touts some notable health benefits with possible roles in boosting the immune system, inhibiting the formation of tumor cells, detoxifying, and fighting against infection. The compounds responsible are flavenoids and catechins – both types of polyphenols. Phytates and polyphenols might sound familiar for their reputation as antioxidants, but the power of the compounds does not stop there. They also have the capacity to "grab" or "bind" substances that really should be kept around in the body – specifically, calcium and iron. Teas that are classified as "herbal" (such as Rooibos tea) have much lower concentrations of interfering compounds and should not be of concern.
Consume iron supplements two hours after or before drinking tea. Iron found in tablets, whether alone or as a multivitamin, will not mix with tea. The "tannins" in the tea need to be kept away from supplements, but not for long. Iron deficiency, a condition called anemia, can lead to weakness, fatigue, dizziness, irritability, and shortness of breath or depression. An anemic body automatically absorbs more iron than one that doesn't need it as badly, while being iron overloaded decreases the amount of iron absorbed. Separating the dosage into two daily servings instead of one, both apart from tannin-containing teas, will help to maximize absorption.
Take calcium two hours before or after drinking tea. Calcium, important for muscle contraction, nerve conduction, and blood clotting, should be consumed at around 1,000 milligrams a day for most adults with about 200 milligrams more for women over 51. Since 8 ounces of milk or yogurt has a minimum of 300 milligrams, while calcium fortified drinks (orange juice, soymilk) have about 200-300 milligrams per cup, it only takes a few good sources to meet the recommended amounts. For those who are especially worried about their bone health or developing osteoperosis, taking a supplement can act as a safeguard. Again, tannins and phytates can interfere with absorption, so tablets should be taken a couple of hours before.
You might notice that calcium comes most often in pills with 500 milligrams. This is another one that should be taken a couple of times a day to enhance absorption. Complicating the picture is the inconvenience that calcium interferes with iron absorption as well. Professionals from Oregon State University suggest taking iron and calcium two hours away from each other as well.