Stronger coffee brew ups total cholesterol

The seventh survey using data from the Tromsø Study (Tromsø7) revealed an association between coffee consumption and increased serum total cholesterol (S-TC) levels among adults and the elderly, with brewing method influencing this association.

This link between coffee intake and elevated S-TC levels has been attributed to the diterpene (ie, cafestol and kahweol) in coffee, and the brewing method has been identified as an essential factor affecting the diterpene content. [J R Soc Med 1996;89:618-623; J Agric Food Chem 1995;43:2167-2172]

“The more unfiltered the brewing method is, the higher [the diterpene content is] in the finished brew,” said the researchers. “[Our] main finding … was that espresso was associated with increased S-TC, [which was] stronger for men compared with women.”

Using the missing indicator method, men who consumed 3–5 cups of espresso daily had significantly increased S-TC than those reporting zero consumption (β, 0.16 mmol/L; p_{linear trend}<0.001). In women, the increase in S-TC among espresso (3–5 cups daily) vs non-espresso consumers was borderline significant (β, 0.09 mmol/L; p_{linear trend}=0.052). [Open Heart 2022;9:e001946]

The weaker association in women may have been driven be a couple of non-physiologic factors. For one, serving cups for women could have been smaller, the researchers noted. Women may also be taking espresso-based coffee (eg, from capsules, machines, mocha pots) instead of actual espresso.

“[There may also be] fewer women drinking larger quantities of coffee, [hence the] nonsignificant results,” they continued. Indeed, in the complete case analysis, women fell short by a cup when compared against men's mean daily coffee intake of almost 5 cups.

Boiled/plunger, filtered coffee

Compared with participants who did not take boiled/plunger coffee, those who had ≥6 cups daily had increased S-TC (β, 0.23 mmol/L [men] and β, 0.30 mmol/L [women]; p_{linear trend}<0.001 for both). For filtered coffee (≥6 cups/day), the S-TC elevation was only seen in women (β, 0.11 mmol/L; p_{linear trend}=0.003).

Filtered coffee has lower diterpene content than boiled/plunger coffee hence the watered-down effect in this subgroup. The filter paper may have played a role, potentially due to its high fat permeability. [Food Res Int 2017;100:798-803; Food Res Int 2018;108:280-285] “The porosity of filter paper and particle size of ground roasted coffee were determining factors in obtaining filter coffee brews with lower diterpene contents. The variation in diterpene concentrations passing through the filter paper may [have driven] the variance in results,” the researchers explained.

Should coffee be struck off the menu?

“Because of high coffee consumption, even small health effects can have considerable health consequences,” said the researchers. Coffee consumption has been integrated into the 2021 ESC* guidelines on cardiovascular disease prevention in clinical practice, but there was no exhaustive discussion on the effect of espresso consumption. [Eur Heart J 2021;42:3227-3337]

The current analysis involving 21,083 participants (n=11,074 [women] and 10,009 [men]; mean age 56.4 years) reinforces existing literature reflecting trends on coffee and cholesterol associations and builds on previous data based on the Tromsø study that have shown similar results. [Br Med J 1985;290:893-895; BMJ 1988;297:1103-1104]

It would still be best to dig deeper to ascertain what drives the association between espresso and elevated S-TC levels, the researchers stressed. For boiled/plunger coffee, the findings may be generalizable as these align with evidence dating back to the ‘80s. [N Engl J Med 1983;308:1454-1457; BMJ 1984;288:1960; N Engl J Med 1989;321:1432-1437] “[Our findings] support previous health recommendations to reduce boiled/plunger coffee intake because of its capabilities to increase S-TC.”

The investigators recommended randomized trials to validate these data. They suggested looking into other contributing factors, such as brewing methods, types of coffee beans, roasting degrees, coffee particle sizes, cup sizes, and even filter paper. “The goal should be to explore whether there is a reliable dose-response curve to diterpene intake and raise in S-TC, and whether there are sex differences,” they concluded.