Sunday, September 27, 2015

Should you drink your coffee filtered?

Coffee is one of the most widely consumed beverages in the world. Arguably a key reason for this is that coffee has psychoactive properties that we may be hardwired to value, even if subconsciously. For example, it increases alertness; possibly a fitness-enhancing effect in our evolutionary past. Here the term “fitness” in “fitness-enhancing effect” means “reproductive success”, and does not mean having great athletic ability or having shredded abs.

The two most common sources of coffee beans, which are roasted and ground prior to brewing, are the widely favored Coffea arabica, and the "robusta" form Coffea canephora. The arabica form accounts for 80 percent or so of world consumption. The graph below, from a study by Bonita and colleagues (), shows the per capita consumption of coffee in various countries. As you can see, Scandinavian countries are big consumers.

Most people probably drink filtered coffee. However, there are many unfiltered coffee preparation methods that are also widely used. Greek coffee, Turkish coffee, coffee prepared with a French press, and “cowboy coffee” are all unfiltered.

In the photo below (from:, illustrating cowboy coffee, note that the coffee pot is placed near but not over the fire.

What is “cowboy coffee”? This method of preparation has many variations. A simple one involves mixing ground coffee with hot water, and then keeping the coffee simmering on very low fire for a while. It is called cowboy coffee due to its association with coffee drank by cowboys around a campfire.

After brewed, coffee tends to rise and spill out of the pot if heated at a high temperature. To avoid this, one should turn off the fire just prior to the coffee boiling, heat the coffee in a pot on very low fire, or heat the coffee by placing the pot near but not too close to a campfire. The same is generally true for tea.

With cowboy coffee you need significantly less coffee per measure of water, and the coffee ends up with a stronger flavor – if prepared properly. You also keep two key oily components of the coffee, namely the diterpenes known as kahweol and cafestol; its polyphenols, most notably chlorogenic acid; and some of the coffee particles.

Both kahweol and cafestol seem to be associated with reduction in certain types of cancer in humans, and show strong anti-cancer effects in rats (). The same seems to be generally true for chlorogenic acid (). The coffee particles, if ingested, would probably be treated as indigestible fiber and promote colon health. This is usually the fate of indigestible and partially digestible plant matter.

Why is filtered coffee often recommended? Well, unfiltered coffee is believed to promote heart disease. But that is not primarily due to any strong association having been found between unfiltered coffee consumption and heart disease. In fact, the absence of evidence in favor of this hypothesis in long-term studies is rather conspicuous ().

The belief that unfiltered coffee can promote heart disease is due to evidence showing that consumption of 4 cups per day of unfiltered coffee raises total cholesterol by up to 10 mg/dl ().

Only diehard proponents of the lipid hypothesis would look at total cholesterol increase as a marker of heart disease, in part because total cholesterol may increase due to an increase in HDL cholesterol – a much more reliable marker, but of protection against heart disease, particularly within certain ranges. And yes, unfiltered coffee consumption is associated with an increase in HDL cholesterol ().

Moreover, some of the metabolites of caffeine, 1-methyxanthine and 1-methyluric acid, appear to help prevent LDL oxidation; caffeine metabolites also seem to have potent anti-inflammatory properties ().

Some research provides evidence of the importance of moderation in coffee consumption as an important factor in its relationship with health. In this respect, coffee is like almost anything that can be ingested, including water – the dose makes the poison. In a study of 40,000 post-menopausal women in the US reviewed by Bonita and colleagues (), the hazard ratio of death attributed to heart disease was 0.76 for consumption of 1–3 cups/day, 0.81 for 4–5 cups/day, and 0.87 for ≥6 cups/day. Interestingly, the same study reported that the hazard ratio for death from other inflammatory diseases was 0.72 for consumption of 1–3 cups/day, 0.67 for 4–5 cups/day, and 0.68 for ≥6 cups/day.

Frequently you hear about the possible connection between coffee consumption and gastritis. The most widely cited study I could find that looked into this link found no association between coffee consumption and reflux-associated gastritis ().

By the way, if you have gastritis, you should consider getting tested for Helicobacter pylori (), especially if you like eating raw fish.

Stress and coffee consumption may have similar effects in those who test positive for Helicobacter pylori (see, e.g., ). In those individuals, past research has found a link between: (a) stress, coffee consumption, and other purported “stomach irritants”; and (b) exacerbation of gastritis symptoms, stomach ulcers, and stomach cancer.

This discussion on gastritis is largely unrelated to the issue of drinking unfiltered coffee. It is unclear based on the past studies that I reviewed whether coffee filtration has anything to do with any possible connection between coffee consumption and exacerbation of gastritis symptoms caused by other factors.

As a side note, it is important to keep in mind that the acidity of coffee is nowhere near the acidic of gastric acid, which the stomach is uniquely designed to handle.

I may be wrong, but from what I can see, if you drink coffee regularly and it causes no problems for you, drinking unfiltered coffee is not a bad idea at all.


Gretchen said...

I have GERD, and coffee is definitely one of the triggers, along with chocolate and fat. It's not the caffeine, because decaf has the same effect.

Studies have shown that coffee increases the secretion of acid.

Tests for Helicobacter were negative, but I have a hiatal hernia and no LES.

Acid is fine as long as it stays in the stomach. It's when it gets up into the esophagus that it causes problems.

Because there are a lot of variables, I think finding out what works for your individual physiology/dietary preferences is as important as formal studies of coffee, especially when the results of the studies don't agree.

I still drink coffee (espresso), but I limit the amount per day.

Bill said...

I've seen some of those data on coffee lipids, their impact on total cholesterol, and the complete reversal within a few days of withdrawing the coffee lipids. It's really pretty interesting.

That said, French press & espresso are my favorites.

Marty said...

Interesting. Coffee consumption seems to correlate with lower rates of liver disease, as well as Parkinson's, Alzheimer's and Type 2 diabetes. But I thought unfiltered coffee tended to significantly raise liver enzyme levels ( And coffee with or without filtering increased homocysteine ( Are either of these potentially more concerning than an increase in total cholesterol?

I'd sure love to go back to drinking French press coffee or better yet, Turkish coffee.

Anonymous said...


Since you're interested in cortisol, perhaps you might benefit from studying coffee's impact on cortisol. I believe the impact is quite large. I would love to read your thoughts on the matter.

Perhaps coffee is not our friend.



Ned Kock said...

The cowboy coffee preparation is much closer to espresso (many people’s favorite) than most of the filtered variations, but without the crema.

Ned Kock said...

Hi Marty. Very often you see different short- and long-term effects in response to dietary and lifestyle changes. The post discussed mostly long-term effects.

Ned Kock said...

Hi Mark. Well, based on anecdotal evidence, too much coffee seems to mess up one’s cortisol levels.

Ned Kock said...

The quote below, from the 1996 study by Urgert and colleagues on liver enzymes, illustrates my point regarding short- and long-term effects:

... short term intake of boiled coffee5 or preparations rich in cafestol and kahweol raise the serum concentration of alanine aminotransferase. However, lifelong consumers of boiled coffee in Norway did not have higher alanine aminotransferase concentrations than matched lifelong consumers of filtered coffee ...

Gretchen said...

I use a filter with my espresso, not because of a concern with coffee ingredients but to avoid coffee sludge. I cut up regular coffee filters to fit.

I don't agree that espresso is close to cowboy coffee, which is boiled. Some of the harmful components of coffee are extracted only with long processing and high temperature.

Espresso doesn't boil the water, you usually stop it when it's been extracted for a short time (and it's very concentrated), and the later-extracted bitter compounds are left behind.

I don't know where on these curves the cafestol etc, are.

Ugur Gundogmus said...

Hi Ned.

Just a clarification: There is no such thing as Greek coffee. This type of coffee is called Turkish coffee.

(Ultra nationalist Greek people use the term Greek coffee to create confusion)

It`s like "Turkish Delight". I saw some Greek delight signs in some pastry shops in Toronto which sounds so desperate.

David Isaak said...

It's not really clear what short-term elevation of liver enzymes really indicate anyway, except that the liver is busy. Medical science, in its wisdom, has decided it is an index of liver damage, but that's far from clear. Niacin has any number of benefits, but bumps up liver enzymes.

I view elevated liver enzymes sort of the way I view sweating: It means one thing if you are exercising, and another if you have the flu.

In any case, I am fond of chocolate-covered espresso beans, so I hope that consuming the grounds is beneficial.

Matthew @ Lasik said...

Not bad!

Finn Felton said...

Filtered coffee is one of the best type of coffee you have ever drunk this is only because it contains the real ingredients that is formed after a good brewing session.

Finn Felton

Kopi Luwak

Anonymous said...

Makers of Aeropress claim the best temperature for preparing coffee is 80C, and that whole coffee should have such temperature. Doesn't it mean more coffee oils are saved? The cost is that you have to use more coffee (up to 2x compared to 15 bar, 92C pressure maker) per the same volume of end product than those made with higher temperatures.

This by the way matches the recommendations for preparing tea, with some green varieties having even lower 70C temperatures recommended.

Anonymous said...

Would the Keurig coffee brewing method be considered "unfiltered" or "filtered"? In other words, would that K-cup method be worse for you than a drip-filter method?

Anand Aggarwal said...
This comment has been removed by a blog administrator.
Anonymous said...

The Turks should give Greeks back all the land they stole from them and then they'll stop calling it Greek coffee. Not to mention all the ancient Greek temples along the western turkish coast

Ivor Goodbody said...

Hi Ned

Another splendid article, thanks.

I note the Urgert article "Levels of the Cholesterol-Elevating Diterpenes Cafestol and Kahweol in Various Coffee Brews" says espresso contained less than half the diterpenes of Scandi, French-press or Turkish/Greek coffee. Also brewing strength "increased diterpenes in boiled, French press and espresso but not Turkish/Greek coffee."

Of interest, Turkish/Greek coffee is credited with heart-HEALTHY effects here:

"Consumption of a boiled Greek type of coffee is associated with improved endothelial function: The Ikaria Study"

though closer scrutiny of the subjects' health markers does not inspire great confidence in daily consumption of this type of coffee:

"The study included a sample of 71 men and 71 women from Ikaria, out of 673 Ikarians over the age of 65 who are permanent residents of the island. 80 percent had high blood pressure, 23 percent had diabetes, 73 percent had high cholesterol, 17 percent were active smokers, and 22 percent had a history of cardiovascular disease."

The study included a sample of 71 men and 71 women from Ikaria, out of 673 Ikarians over the age of 65 who are permanent residents of the island. 80 percent had high blood pressure, 23 percent had diabetes, 73 percent had high cholesterol, 17 percent were active smokers, and 22 percent had a history of cardiovascular disease."

I certainly think the headlines touting it as "the key to longevity" are seriously overstretching the study's data and conclusions, which only point to one advantageous measure relative to other types of coffee.

Full disclosure: I have flip-flopped over coffee because I'm none too keen on the taste of filtered as compared to espresso. I've sometimes abstained altogether for long periods. But the evidence seems broadly in favour, so my current intake is 2 espressos a day from my home machine. I will soon experiment with Aeropress, to see if I can combine the taste of espresso with the cholesterol-neutral effect of filtered.

Wishing you lifelong health