The effects of coffee on the heart, sleep and inflammation

Do you have palpitations? You should stop drinking coffee. Are you stressed? Stop drinking coffee. Can’t sleep? No more coffee after lunch!

When it comes to coffee, everyone has their own little anecdote or little stratagem to reduce their consumption in order to sleep better, be less stressed or reduce/prevent the risk of possible (future) cardiovascular problems. So how do we separate fact from fiction? Here’s what the science says.

Read also: Heartburn, palpitations, mortality: coffee is innocent

Is coffee good or bad for your health? What the studies say

The health benefits of coffee are undeniable, as long as you don’t overdo it!

Coffee and inflammation

Several studies have looked at the impact of coffee consumption on inflammation (1). One of them gathered data from more than 22,000 people on both biomarkers of inflammation (C-peptide, C-reactive protein, insulin growth factors, certain hormones and interleukins) and others associated with anti-inflammatory effects (sex hormones and other anti-inflammatory hormones).

Their results confirm the anti-inflammatory effect of coffee (more precisely caffeine). In people who consumed four or more cups, markers of inflammation decreased and those associated with anti-inflammatory effects increased, compared to non-drinkers (2).

Read also: A natural anti-inflammatory in your little black

Cardiovascular benefits…to a certain point

Contrary to popular belief that coffee increases cardiovascular risk, several large epidemiological studies suggest the opposite. One of them, conducted over 15 years on 27,321 women aged 55 to 69, indicates that those who drink one to three cups of coffee per day see their risk of death from cardiovascular disease reduced by 24%compared to those who drink little or no coffee. This protection could be explained by the richness of coffee in antioxidants, compounds which fight the inflammation responsible for cardiovascular pathologies (3). In these studies, it is often a question of statistical associations and not of proven cause and effect links, but the convergence of the data argues for a protective effect at moderate doses.

Coffee and cardiac arrhythmia

Other recent work suggests that coffee protects the heart: drinking coffee could reduce the risk of atrial fibrillation (AF), a heart arrhythmia that affects one in three people during their lifetime. This is shown by a clinical trial carried out on 200 patients in Australia, the United States and Canada. For six months, half of the participants consumed at least one cup of coffee daily, while the others avoided all caffeine. Result: a 39% reduction in risk of recurrence of AF in coffee drinkers (4). Several hypotheses could explain it: coffee stimulates physical activity, acts as a diuretic – reducing blood pressure – and contains beneficial anti-inflammatory compounds.

Negative effects at high doses

Knowing this, should we still drown ourselves in coffee? Not really: beyond three cups, the risk no longer decreases and it would even tend to increase. For example, a recent study grouped together the food (and therefore coffee) consumption habits of more than 347,000 individuals (5). Small drinkers (one to three cups) would be better protected than abstainers, while heavy drinkers (more than six cups) have a slightly higher risk. A little extra from this study, the investigators studied the impact of certain genes which would predispose to a privileged metabolism of coffee. In people with these genes, the risk is not reduced for heavy consumption.

Read also: Should we prescribe coffee after a heart attack?

Mixed effects on sleep

According to a recent systematic review of scientific literature, coffee promotes latent sleep, reduces the time and quality of sleep, and deteriorates one’s perception of it even if one has slept well (6). Nocturnal electroencephalograms reveal measurable disturbances up to six hours after consumption. The effects vary depending on several parameters such as genetics or age: older people are more sensitive to it than younger people.

Scientists explain these harmful effects by two mechanisms: the disruption of the production of melatonin (the sleep hormone) and that of the neurotransmission of adenosine, a neurotransmitter essential for falling asleep.

Sleeping well is essential to maintaining good health. If you have trouble sleeping or poor quality sleep, avoid coffee after 4 p.m. to go to bed at 10 p.m..

Read also: Coffee for mom, excess weight for baby?

In practice: how to adjust your consumption?

Several pragmatic advice can emerge from these studies on the effects of coffee on health.

• If you don’t drink coffeethere is no reason to start (except in certain pathologies where it could be useful or if you want to increase your sporting performance). The health effects (among others, anti-inflammatory and antioxidant) that it provides can be provided by other foods.
• If you consume one to three cups of coffee per dayyou can continue, there is apparently no risk at this level of consumption, only benefits.
• If you consume four to six cups of coffee per day, you can continue (if all is well with your sleep), knowing that the beneficial effects seem to plateau beyond four cups.
• If you consume more than six cups per dayit seems preferable to reduce your consumption in order to benefit from the beneficial effects without the relative risks associated with cardiovascular incidents. Try varying it with other drinks like tea (which contains less caffeine) or herbal teas.

How to make good coffee? Read: How to choose and prepare coffee

Special cases:

• in cases of hypertension, coffee consumption seems to play such a minimal role that reducing it would have no impact on cardiovascular events (7);
• in case of sleep problems, banish coffee within six hours before bedtime. (8).

Read also: 3 cups of coffee a day to live longer?