Coffee first entered human lives and veins over 600 years ago.

Now we consume an average of almost two kilos per person each year – sometimes with very specific preferences about blends and preparation methods. How much you drink is influenced by genes acting on your brain’s reward system and caffeine metabolism.

Coffee can raise your blood pressure in the short term, especially if you don’t usually drink it or if you already have high blood pressure.

But this doesn’t mean you need to cut out coffee if you have high blood pressure or are concerned about your heart health. Moderation is key.

So how does coffee affect your blood pressure? And if yours is high, how much is OK to drink?

Read more: Health Check: four reasons to have another cup of coffee

Blood pressure is the force blood exerts on artery walls when your heart pumps. It’s measured by two numbers:

the first and biggest number is systolic blood pressure, which is the force generated when your heart contracts and pushes blood out around your body

the lower number, diastolic blood pressure, is the force when your heart relaxes and fills back up with blood.

Normal blood pressure is defined as systolic blood pressure of less than 120 millimeters of mercury (mm Hg) and diastolic blood pressure of less than 80 mm Hg.

Once your numbers consistently reach 140/90 or more, blood pressure is considered high. This is also called hypertension.

Knowing........

© The Conversation