sharing here as well!

Coffee for women?

The general verdict seems to be clear, that coffee is generally good for you. Take this huge meta-analysis for example.

But interestingly the study also warns (from the credo tldr) pregnant women and women at risk of bone fractures should be careful.

The "pregnant case" seems straightforward enough, but what about the "risk of bone fracture" case? When should we not drink coffee?

I'd be interested to delve into this!

Coffee dripper: Plastic vs Ceramic?

[tldr: Plastic keeps brewing water slightly hotter, but not enough to make a perceptible difference in taste. Instead (all other things equal), you can vary taste profile by varying grind amoung and ground size.]

I use a ceramic dripper.

Contrastingly, my friend uses a plastic dripper. He says "plastic drippers have better heat properties".

Basically (the argument goes): with plastic drippers, the water stays hotter (and so improves bean extraction). Conversely, ceramic drippers drain more heat from water (and the relatively colder water leads to poorer extraction).

However, my friend is also worried about micro-plastics leaking into the coffee.

So, is plastic really better (for taste profile) than ceramic – and worth potentially ingesting micro-plastics?

We can try and answer this, in two parts.

(We won't look at the risks of micro-plastics here!)

Firstly, do plastic drippers help keep the water hotter? (And by how much?)

The answer is yes, they do – but only by around 2-3° celsius.

These two (very cool) home-experiments (by a reddit user and a coffee roaster coffee roaster) present some data.

The two setups are slightly different, but in short I think we can say:

Using a plastic dripper, the water remains hotter (by around 2-3° celsius) as it brews the coffee – compared with using a ceramic dripper.

So for example, if you start with 96° celsius water:

• Using plastic dripper: the end brew may be around 90° celsius.

• Using ceramic dripper: the end brew may be around 87-88° celsius.

• (And glass is somewhere in between.)

This seems like quite a small difference.

Secondly, does the temperature difference affect the brew taste profile?

The short answer: no, it doesn't seem so. That is, for small temperature differences – e.g. between a 87° vs 93° celsius range.

And so, small 2-3° temperature differences, resulting from using plastic vs ceramic drippers, probably won't (perceptibly) matter.

In this study, researchers:

• Varied water temperature (87° vs 90° vs 93°) – and other variables i.e. coffee ground amount, ground size, and brew time – to achieve different levels of total dissolved solids (TDS) (1.00% vs 1.25% vs 1.50%) and percent extraction (PE) (16% vs 20% vs 24%) of the final brew. (The same drip brewer was used.)

• Then asked a panel (of 12 trained individuals) to smell and taste the brews – and evaluate them – based on the Coffee Taster’s Flavor Wheel attributes. (The serving temperature of the brews were the same.)

• Finally, analysed the responses. The result? Differences in TDS levels and (less so) PE levels affected the panel's evaluation of the brews; but differences in brew temperature did not. E.g. panellists thought brews with higher TDS were more "ashy", "citrus" tasting, "bitter", etc. – vs brews with lower TDS. (See Image 2 below.)

(TDS is basically how much coffee solubles are in the final brew. PE is basically the percent of coffee extracted from the beans/grounds.)

An obvious question: doesn't water temperature affect TDS and PE?

Of course, the answer is "yes". (And the study above summarises other studies that investigate larger temperature differences.)

But with such small differences (e.g. 87° vs 93° celsius, or 2°-3° difference caused by dripper material) – it doesn't look like you can easily predict TDS and PE levels.

Instead, it seems to me (base on Image 3 below, from the study) easier to get desired TDS and PE levels you like, by varying coffee ground amount/mass and ground size.

Conclusion?

So:

• If you're worried about micro-plastics, it seems to me that using a ceramic dripper would be fine – and it won't lead to lower quality brews.

• And rule of thumb (see Image 4), all other things equal:

  • If you want stronger coffee (higher TDS), use more coffee grounds.

  • If you want more bitter coffee (higher PE), use finer coffee grounds.

Coffee and Cancer

Cancer is all too prevalent, and is of course a leading cause of death. My family is no exception.

Does drinking coffee reduce cancer risk?

This umbrella review of "coffee consumption and health" finds drinking coffee seems to lower cancer risk.

The umbrella review highlighted results from this meta-analysis of 40 cohort studies, that found that drinking coffee is associated with an 18% lower risk of (any) cancer.

(Note: this is 18% lower "relative risk", not lower "absolute risk".)

But not for all cancer types, unfortunately.

Drinking coffee is associated with lower risk of: melanoma, leukaemia, and prostate, endometrial, oral, non-melanoma skin, liver, and lung cancers.

(A caveat: among smokers, those who drink more coffee seem to have higher mortality risks.)

But (sadly) there is no association between coffee consumption and: lymphoma, glioma, or gastric, colorectal, colon, rectal, ovarian, thyroid, breast, pancreatic, oesophageal, and laryngeal cancers.

Still – plus points for coffee!