How Caffeine and Alcohol Affect Your Blood Pressure

Ask someone what they can do to address high blood pressure (aka hypertension), and the first answer is nearly always something like “cut back on salt”. We dietitians also like to teach people about foods you can add that can help (that’s the DASH approach). But rarely do I hear talk of alcohol and caffeine.

The bottom line is simple: Drink too much alcohol and high blood pressure is just one of numerous health consequences you risk. And while caffeine can increase blood pressure for 1-3 hours, in moderation it’s not considered a cause of hypertension or a concern in terms of overall cardiovascular health.

How much is too much? Here’s what the blood pressure guidelines say:

Caffeine

Good news coffee lovers, a moderate amount of caffeine is fine, as long as:

It’s not in the hour or so before you measure your blood pressure.
Your hypertension is controlled. (If it’s not, and lifestyle habits don’t help, for goodness sakes, talk to your doctor about medication. There are plenty of affordable options with few side effects.)

While coffee might raise your blood pressure briefly, long term use of caffeine isn’t thought to cause or worsen hypertension or cardiovascular disease in general, according to the American College of Cardiology (ACC) blood pressure guideline (with more details on the actual studies here). The Canadian hypertension guidelines hardly mention it, except to remind us not to measure BP after caffeine intake.

In fact, as you’ve likely heard in the news, some studies suggest that coffee and other sources of caffeine may be beneficial in some ways, although those kind of studies can’t prove cause and effect.

So how much is too much? The American College of Cardiology blood pressure guideline says to generally limit to less than 300mg a day, while Health Canada goes with 400mg for adults, except women who are breastfeeding or may become pregnant: 300mg.

How does that compare to your morning brew? Coffee ranges from 76 to 179mg per 8-oz cup, depending on the way it’s prepared. Tea is 30-50mg. You can find coffee details and other sources here, including pop and various kinds of chocolate.

So somewhere in the neighbourhood of two 8-oz cups of coffee leaves room for a bit more caffeine from other sources. Keep in mind that an medium cup of coffee at Tim Horton’s is 15oz. The travel mug on my desk right now is 20oz. So you might have two “cups” in your cup, if you know what I mean.

What happens if you get more than that? Health Canada tells us that “some sensitive individuals experience side effects such as insomnia, headaches, irritability and nervousness.” While none of those are directly related to heart disease, lack of sleep and emotional stress can be underlying drivers.

A meta-analysis (study of studies) where the median coffee intake was 5 cups a day showed a small increase in blood pressure: 2.4/1.2 mm Hg, although hypertension guidelines out of the UK comment that the small sample size and short duration of trials do not provide sufficient evidence to infer long-term effects of caffeine consumption.

(And a heavy intake of unfiltered coffee can raise cholesterol. More on that here.)

Truly, I’m not losing much sleep over it (haha pun), but if you want to be on the conservative side, two or so cups a day appear to be fine, ideally by about lunchtime so you don’t disrupt your sleep.

If you feel you should cut back, do so gradually to minimize withdrawal symptoms, and experiment with replacement beverages, like various flavours of tea, to see if you can find something similarly comforting and energizing.

Alcohol

While alcohol in moderation has long been thought to be associated with fewer heart problems, the effect was never so strong or consistent as to make drinking a recommendation, especially given the known risks, from accidents to cancer.

If you do drink, in terms of blood pressure, Hypertension Canada suggests limiting alcohol to ≤2 “drinks” per day and ≤14 per week for men, ≤9 for women.

In early 2023, the Canadian Centre for Substance Use and Addiction (CCSA) released more conservative guidance around alcohol and health, which suggested no more than two drinks a week for low-risk drinking, citing hypertension as one of the conditions adversely affected by alcohol, even at low levels of consumption.

As with coffee, alcoholic beverages sometimes come in larger sizes than the standards referenced in the guidelines. A standard “drink” is approximately:

5 oz (148 mL) of 12% wine
12 oz (355 mL, a standard can or bottle) of 5% beer
1.5 oz (44 mL) of 80 proof (40%) spirits
Psst… that’s more than two standard drinks.

A bottle of wine is 750 mL, or about 5 standard drinks, so if you’re regularly splitting one with a friend, at least one of you is drinking too much, at least in terms of blood pressure. In my experience, restaurants and bars routinely serve wine in 6-9 oz portions. A pint glass of beer is 16-20 oz.

So again, you might be into your second “drink” while you think you’re still enjoying your first. Order a second and you’ll be over the recommended amount.

If you feel you should cut back, here are 11 ways to curb your drinking. And if you find you need more help than this, reach out to your doctor.

Okay, hopefully I didn’t just ruin your weekend! As with most things on my blog, the theme is moderation and enjoyment. Any questions, let me know.