For some people, consuming lots of coffee each day can be bad for their hearts, for others 3 cups a day may be good for their hearts, it depends on their genetic make-up.

According to a study published in the Journal of the American Medical Association (JAMA), 4,000 people were monitored in Costa Rica by researchers from the University of Toronto, Canada. 2,014 of them had had a heart attack (non-fatal) during the period 1994-2004. The others had not had a heart attack during that period.

If your genetic profile means your body breaks down caffeine slowly, your chances of suffering a heart attack are 64% higher.

The researchers wanted to find out whether caffeine alone may be associated with cardiovascular disease risks, as opposed to other chemicals present in coffee.

Depending on your genetic profile, controlling the action of cytochrome (CYP1A2), an enzyme which metabolises caffeine, can vary. CYP1A2 must be activated in order to break down (metabolise) the caffeine. People with a slow variation of a gene are slower at activating CYP1A2.

The volunteers were asked about their coffee consumption. They also underwent genetic tests to determine which variation of the gene they had, slow or fast.

They found that those carrying the slow form of the gene had:

— 36% higher risk of heart attack if they drank 2-3 cups of coffee a day (compared to people who only drank up to one cup and had the slow form of the gene)

— 64% higher risk of heart attack if they drank 4 or more cups of coffee a day

The risk was clearer for people under 50.

Surprisingly, those who had the fast gene actually lowered their heart attack risk if they consumed up to 3 cups of coffee a day.

If you just drink one cup of coffee a day your risk of heart attack is not altered, whether you have the slow or fast gene, according to this study. The researchers stressed that other lifestyle factors influence your risk of heart attack much more than coffee, such as smoking, what you eat and how much exercise you do.

So, if this study is anything to go by, it is perhaps better to stick to one cup a day until you know what your genetic profile is.

Written by: Christian Nordqvist
Editor: Medical News Today