I was brewing some Vietnamese coffee with a new phin and I noticed some extra oil floating on top of the coffee. It wasn’t usually there, likely because I normally use the Aeropress – which has a paper filter – and it reminded me that some people say paper filtered coffee can actually be more healthy. So, how do filters affect our favorite brew?

Coffee releases compounds, “diterpenes”, which are removed with paper or cloth filters. They have a mildly bitter taste and are linked with mixed health effects. The research is still not conclusive.

Some of the health effects are raising cholesterol, and lowering lipoprotein(a). Higher levels of lipoprotein(a) has been linked with increased risk of heart attacks. To muddy the waters even further, diterpenes seem to have antimicrobial and anti-inflammatory effects, which appear to be positive.

In short, it appears that unfiltered coffee may have added costs and benefits, but the evidence is far from clear.

The main takeaway for you would be that coffee with paper or cloth filters will remove some bitterness, while mesh/metal or no filter will result in the full flavor of coffee. As well, the oils may help the coffee to have a slightly fuller body, giving it a more full mouth-feel.

What kinds of filters are there?

Cloth

Also called “coffee socks”, you can buy cloth-based filters that look a little bit like one of those cloth skull caps they put on babies (such as this one; not an affiliate link). It’s shaped much like the conical paper filters, but made of “natural fibers”, most likely cotton. They are reusable, but according to the brand, Hario, they suggest boiling them for 10 minutes in water to remove the oils and coffee debris.

Bleached Paper & Unbleached Paper

Both bleached and unbleached come in the options of either cone-type, which stack easier and take up less space, or basket-type, which are likely what comes to mind when you think “American Diner”.

Bleaching them doesn’t seem to make a massive difference or add any benefit, other than fulfilling people’s expectations of a “clean” or “new” aesthetic.

In case you’re wondering, there are two methods for bleaching, each focusing on a different chemical in the process:

• Chlorine
• Oxygen

Oxygen is widely considered to be the superior method of bleaching, so if you insist on buying bleached filters, that’s your best bet. Personally, I suggest getting unbleached when you have the option, as the bleach doesn’t help anyone at any step. I honestly don’t know why they continue to do it and couldn’t find a source for it.

Mesh & Metal

I’m distinguishing mesh filters from metal slightly, as mesh filters are the extremely fine mesh made from nylon or stainless steel. The non-mesh, metal filter that immediately springs to mind is the Vietnamese Phin, which uses a sort of “press” to hold the grinds together and stop them from falling through the holes.

They’re reusable, easier to wash than cloth, and durable. They can, however, let through small amounts of coffee dust through in the process, which is generally why I’m not as big of a fan of them. I’m fussy sometimes, I know.

When using them, you generally want a medium or coarser grind level, or you’ll end up with a bunch of sludge at the bottom of your brew.

Do they affect flavor?

Cloth

Some sources said that cloth filters produce a lighter, sweeter coffee when compared to metal filters. They may mute some flavors a little due to absorbing some of the oils and other elements during the brewing process. It will also result in a clearer cup. If you like ‘em sweeter, this may be for you.

Bleached Paper & Unbleached Paper

People will swear – swear to god – that they can taste the difference between bleached and unbleached paper filters. This appears to be false.

If you don’t believe me, rinse both a bleached and unbleached filter, remove the water, then make a coffee. Have a friend provide you with a (double-)blind taste test. $20 bucks says you can’t tell the difference. The amount of bleach is miniscule.

That being said, we don’t encourage you to use bleached paper, as it seems the worst option available.

As for “paper vs no paper”, paper filters will remove some of the oils, which add more bitter flavors to the brew, so yeah, there will be a difference in flavor that seems like it might be comparable to cloth filters. There is a chance that the cloth fibers will absorb more than the paper, so it’s possible that paper will make it only modestly less bitter as a result of straining out the diterpenes

Mesh & Metal

Since these kinds only filter out the gross materials of the coffee – aka the grinds – they will allow all flavors to filter through. That means the oils which are normally filtered out will be present, making for the full coffee flavor to be present.

Yes, this means they will likely be a little more bitter than what the other filters produce, but it will be as though you didn’t use any filter at all.

Are filters good for you? What do they do?

While coffee is being brewed, the filter traps oily substances called diterpenes. There are two main kinds:

• Cafestol
• Kahweol

I don’t know how to pronounce those, but these are the oil spots you will notice floating on the top of your unfiltered coffee. Apparently, they will block receptors in your intestines that regulate the amount of cholesterol in your blood, which can result in a higher blood cholesterol level.

Let’s start with the bad; one study in Nutrition (volume 29, Issue 7-8, July-Aug 2013, pages 977-981) found results that the title of the article aptly describe:

“Paper-filtered coffee increases cholesterol and inflammation biomarkers independent of roasting degree”

“What kind of cholesterol?”, you may ask. It’s LDL, aka ‘bad’ cholesterol. Other sources found that if you drank unfiltered coffee, your cholesterol would increase by 6-8 percent over a four week period… if you drank five cups of unfiltered a day.

Put simply: paper filters catch these oily substances and thus prevent your cholesterol from going up.

But before you start worrying too much about your heart health, know this: the book Coffee: A Comprehensive Guide to the Bean, The Beverage, and the Industry (2013) showed that people who drink up to 3 cups of coffee a day had actually decreased rates of heart attacks and strokes – and these were American populations with less-than-optimal dietary and exercise habits.

More than anything, coffee seems protective against heart attack, stroke, and even certain cancers (liver in specific). So even if it does raise your cholesterol, it seems to beneficially affect heart health. Strangely, they also pointed out that spontaneous heart attacks and other heart conditions didn’t have a relationship with drinking coffee – if under 4 cups a day.

In general, filters only change one main factor – the diterpenes. In the past, doctors used to all believe that fat = unhealthy, but we know that isn’t true today. In fact, there was a long-standing misinformation campaign perpetrated by the sugar industry that was blaming ill health effects all on fat. So the belief that paper-filtered coffee is healthier than unfiltered coffee may just be a artifact of outdated beliefs.

Which has more caffeine?

Well, as I’ve mentioned in another post, that largely has to do with the level of the surface area, time spent brewing, and water flow speed. Paper filters seem to slightly reduce the amount of caffeine when compared to French presses, percolated (i.e. Moka pot), and boiled coffee (e.g.Turkish/Greek style).

This may all come down to the amount of time spent brewing and the surface area, so filters that give you more control could allow for higher caffeine, if that’s what you want.

Which are the most environmentally friendly?

Well, between the filters, the reusable ones are more environment-friendly. Some are more convenient than others, such as the Aeropress. However, if you’re worried about drinking the oils, then you’ll likely have to use the least environmentally friendly ones, aka paper.

The upside to paper, however, is that it is typically made with biodegradable materials. If you’re going to go this route and you have a home garden or compost, you can simply chuck it onto your compost heap and gain some extra fertilizer.

I suggest using an unbleached filter for that since multiple sources suggested it, but… failed to elaborate as to why. Once again, bleaching doesn’t help anyone in the process, so everyone might as well stop supporting it.

But hey, you do you.

Which filter should you use?

Honestly, this is mainly a personal choice. If you are ok with the slightly bitter flavors that are normally filtered out, then you could skip filters altogether through using a Moka pot, french press, Vietnamese phin, or other filter-less methods.

Personally, even after writing this article, I don’t find myself partial to any particular form of filter. My morning cup is normally made with an Aeropress, and I’ll probably stick with that so long as it’s convenient.

One final note that I find amusing: there’s a massive debate between bleached and unbleached paper filters. Personally, I vote we all skip that entire argument and go with cloth or metal filters. The main question is whether you want the slightly bitter flavors of unfiltered coffee, or the potential health benefits that come with drinking the natural oils.

Stay tuned for later posts because I want to dive deeper into the health effects soon.