 Aluminum is the third most abundant element on earth and may not be good for our brain, something we learned studying foundry workers exposed to high levels. Though the role of aluminum in the development of brain disease, like Alzheimer's, is controversial, to be prudent, the steps should probably be taken to lessen human exposure to this metal. There are a number of aluminum-containing drugs on the market, like anti-acids, which have the highest level. Though aluminum compounds can also be added to processed foods, with anti-caking agents and pancake mix, melting agents in American cheese, meat binders, gravy thickeners, rising agents, and some baking powders, and dye binders and candy. So it's probably better to stick to unprocessed natural foods. However, if you cook those natural foods in an aluminum pot, a significant amount can leach into the food compared to cooking in stainless steel. If you do the same thing with tea, though, you get a few milligrams of aluminum, regardless of what type of pot you use, suggesting the aluminum is in the tea itself. And indeed, back in the 1950s, it was noticed that tea plants tend to suck up aluminum from the soil. But like anything, it's the dose that makes the poison. According to the World Health Organization, the provisional totable weekly intake, our best guess at a safety limit for aluminum, is 2 milligrams per healthy kilogram of body weight per week, which is nearly a milligram per pound. So someone who's around 150 pounds probably shouldn't ingest more than 20 milligrams of aluminum per day. Up to a fifth of intake may come from beverages, so what we drink probably shouldn't contribute more than about 4 milligrams a day, which is the amount found in about 5 cups of green, black, or Oolong tea. So should we not drink more than 5 cups a tea a day? Well, it's not what we either drink, it's what we absorb. If you just measured how much aluminum was in tea, it would seem as though a couple of cups could double our aluminum intake for the day. But if you measure the level of aluminum in people's bodies after they drink tea, it doesn't go up. This suggests that the bioavailability of aluminum in tea is low, possibly because mostly extractable aluminum in brewed tea is strongly bound to these large-fitted nutrients that are not easily absorbed from the gastrointestinal tract, so it just passes right through. Our intestines get flushed away without actually getting inside of our body. Even more than 90% of the aluminum in tea is bound up. What about studies like this showing a large spike in aluminum excretion through our urine after drinking tea compared to water? The only way for something to get from our mouth to our bladder is to first be absorbed into our bloodstream. But they weren't comparing the same quantity of tea and water. They had the study subjects chugged down like 8.5 cups of tea, or just drink water at their leisure. So the tea drinkers peed a lot more, period. So the aluminum content was no different really tea versus water, suggesting that gross aluminum absorption from tea is unlikely, and that only little aluminum is potentially available for absorption. So though as few as 4 cups of tea could provide 100% of one's daily aluminum limit, the percentage available for absorption in the intestine may be less than 10%. Therefore it's unlikely that moderate amounts of tea drinking can have any harmful effects on humans. However, that's for people with normal aluminum excretion. For example, tea may not be a good beverage for children with kidney failure, since they can't get rid of aluminum as efficiently. For most people though, tea shouldn't be a problem, though if you drink tea out of a can, buy undented cans, as the aluminum-indented cans can leach into the liquid, boosting aluminum levels by a factor of 8 sitting on store shelves for a year.