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I'm talking about the classic paper tea bags (sold empty) that you can buy and then put whatever you want in; sometimes different sizes are available for cups vs teapots, etc. Yes, I do realise most "pre-filled" tea bags like Lipton have bags made from roughly the same material, but I don't know if those don't filter out nutrients too.

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    Hi Valikojan, there is no worldwide consent on what is an "important nutrient". To make your question answerable, you would have to identify the exact nutrient in which you are interested (or more than one, but the list should be short enough to be answerable). Else your question would have to be closed. We have a bit more info on which questions about nutrition we accept - cooking.stackexchange.com/tags/nutrient-composition/info.
    – rumtscho ♦
    Mar 9 at 17:00
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    Well, tea is not food. You don't drink it for his nutritional value.
    – Candid Moe
    Mar 9 at 17:02
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    Many people drink tea for some sort of health benefit @CandidMoe, antioxidants, etc. Food is defined as any liquid or solid that's consumed for taste or nutritional value, so tea is food.
    – GdD
    Mar 9 at 17:14
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    There's some sort of cultural barrier here, because (from a UK perspective) I have no idea what " the classic paper tea bags (sold empty) " are
    – AakashM
    Mar 10 at 10:09
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    @rumtscho: Do we really want a separate question like this for every possible nutrient in tea, when all(?) of them can be covered by a single answer? As GdD says, they're all microscopic, unless there's some kind of tea where you want bits of stuff floating in it, not just what can infuse into the liquid.
    – Peter Cordes
    Mar 10 at 10:41

2 Answers 2

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Nutrients are microscopic, the pores in tea bags are far too large to act as a filter. However, tea bags will absorb a very small amount of liquid, and in that liquid there will nutrients, sugars, colors, volatile compounds and other things in suspension. So, the bag is going to absorb some of the tea, but the amount is negligible.

That doesn't mean that everything will get out of the bag, though. Even though the pores in the material are too big to trap nutrients the material is going to impede water circulation. Also, when the leaves expand they tend to get constricted by the bag, which further reduces flow. If you stir the bag around or squeeze it you'll often see darker water coming out of it, which demonstrates this effect. The upshot is that the material isn't filtering vitamins and minerals, but the slower circulation means some tea is going to be left inside the bag, and therefore nutrients along with it. Stirring the bag around a bit helps to a certain extent.

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    Well, some substances like active coal can absorb "microscopic" substances, e.g. toxins. The pore size is a different category than the chemical properties of a filter. A correlation exists because filter materials work best if the fluid to be filtered passes by a lot of surface area on the way through, which is helped by small pores. But the pores can, I think, be much larger than the molecules a chemical filter, e.g. made of charcoal, absorbs.
    – Peter - Reinstate Monica
    Mar 11 at 6:59
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    Peter makes a very important point here. For a visual demonstration of why your assumption does not hold: Make some hibiscus tea, steeping for maybe two minutes. It will be pink, due to natural dyestuff from the hibiscus that gets dissolved in the water. Now take the teabag out and press it with your fingers (or if you prefer, lay it in a second vessel and cut it, not squeezing out anything extra from the plant). The liquid coming out will be a deep red-pink, much darker than the tea in your mug. The teabag holds back a lot of dye molecules that are dissolved in the water inside it.
    – rumtscho ♦
    Mar 12 at 11:50
  • That effect is due to the leaves being compacted in the bag, which restricts water flow @rumtscho. The bag material isn't filtering the dyes, it's just slowing the extraction process. I take your point though, it's worth calling that out, so I'll edit.
    – GdD
    Mar 12 at 13:49
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Paper filters such as tea bags, exclude at a size of 1 to 1000 microns, nutrient vitamins and minerals in foods and drink are measured in nano sizes for consumptions. Unless you are dealing with a unique or bulk formulation a paper filter should not limit the vitamin and mineral passage from one location to another.

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    Or, put in other words, filters remove suspended particles. Nutrients, however, are dissolved compounds that cannot be removed mechanically.
    – cmaster - reinstate monica
    Mar 11 at 23:26
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    @cmaster-reinstatemonica As I mentioned in the comments to the question, the reasoning about all nutrients being dissolved is faulty. When you make tea without a teabag, you also consume plant matter that is suspended, not dissolved, in the water. And the teabag surface has its own chemical properties on a microscopic level. A credible answer would have to consider whether there exists a vitamin that is likely to adhere to paper instead of staying in solution.
    – rumtscho ♦
    Mar 12 at 9:07
  • @rumtscho The answer has been rebranded to ask about "vitamins and minerals", and none of these fall into the category of suspended particles. And when you ask the wikipedia for nutrients, you find that it says: "Essential nutrients for animals are the energy sources, some of the amino acids that are combined to create proteins, a subset of fatty acids, vitamins and certain minerals." Again, none of these classify as suspended particles. Finally, teabag fibers are generally cellulose, a polymerized sugar. If that did bind to a nutrient, the nutrient would already be bound within the plant.
    – cmaster - reinstate monica
    Mar 12 at 9:31
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    @cmaster-reinstatemonica PLL wrote a great explanation why suspended particles matter. To the second point: the microstructure of cellulose in paper bags is entirely different than the microstructure of cellulose in cells, which changes a lot what stays where. And, imagine a water-soluble molecule X which has a strong affinity for cellulose, but does not form indestructible bonds with it. Some X gets out from the plant matter and is dissolved in the tea. Out of this dissolved X, a lot now clings to the bag, and only very little gets into the tea that is consumed.
    – rumtscho ♦
    Mar 12 at 11:41
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    @cmaster-reinstatemonica It's pretty much certain that cellulose from tea bags interacts differently with the compounds than cellulose from the plant cells, for pretty much the same reason that cellulose in bramble thorns through which I run interacts differently with my sweater than cellulose from the papers on my desk on which I lean my elbows. Only it happens on the microscopic level. When we talk about physical effects, structure is the major factor, and should always be considered.
    – rumtscho ♦
    Mar 12 at 13:14

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