You need magnesium for forming DNA and proteins, creating strong bones and keeping your nerves and muscles, including the heart, functioning properly. Men need at least 420 milligrams per day, and women need at least 320 milligrams per day for good health. Tea is one source of magnesium, but it isn't typically high in the mineral.
Magnesium in Tea
Tea does contain magnesium, but you'd have to drink quite a bit to get a significant amount. For a food to be considered high in a nutrient, it should have 10 percent of the daily value per serving. According to a study published in the Journal of Toxicology in 2013, drinking 4 cups of brewed tea provides 5 percent of the DV for magnesium.
Type of Tea
It doesn't necessarily matter which type of tea you drink when it comes to magnesium content. A study published in the European Chemical Bulletin in November 2012 found that all of the black teas, green teas, herbal teas and fruit teas tested by the researchers had about the same magnesium content, which was about 1 gram per kilogram of tea leaves. A tea bag contains roughly 2 grams of tea, which translates to about 2 milligrams of magnesium per bag, or less than 1 percent of your daily needs.
True teas, including green, white and black teas, contain oxalates, which can interfere with magnesium absorption. Unless you choose decaffeinated versions, these teas also contain caffeine, which can increase the amount of magnesium that leaves the body in your urine.
Better Sources of Magnesium
Many people don't drink enough tea to significantly impact magnesium levels either due to its magnesium content or the effect of the oxalates and caffeine it can contain. Foods high in magnesium include most nuts, fortified breakfast cereals, whole grains, green leafy vegetables, avocado, bananas, edamame, beans and lentils, low-fat yogurt, dark chocolate, dried fruits, pollock, mackerel and tuna.