Caffeine rush? To avoid CVD, six coffees a day upper limit, study says

14 May 2019 --- Consuming six or more coffees a day may increase the risk of heart disease by up to 22 percent, according to a study from the University of South Australia (UniSA). Published in The American Journal of Clinical Nutrition, the study marks the first time an upper limit has been placed on safe coffee consumption in relation to cardiovascular health. The researchers note that more research on the matter is warranted to determine whether other aspects of health are affected by coffee consumption and also to determine the varied individual responses to caffeine.

“In nutrition, we would typically expect to see a threshold above which intakes are no longer beneficial. For coffee the threshold appears to be relatively high,” Elina Hypponen, Professor in Nutritional and Genetic Epidemiology and Director of the Australian Centre for Precision Health, UniSA Cancer Research Institute, tells NutritionInsight. 

“In order to maintain a healthy heart and a healthy blood pressure, people must limit their coffees to fewer than six cups a day – based on our data, six was the tipping point where caffeine started to negatively affect cardiovascular risk,” she notes.

How much coffee do six cups exactly translate to is however relatively unclear. “The data which was used in our study did not exactly specify how large is a ‘cup,’ and there is a possibility that this has meant different things to different people. A standard measure of cup is 2.5dl, and hence, if we take this as a threshold, the upper limit would be about 1.5 liters of coffee per day,” she explains.

According to the World Health Organization (WHO), in Australia, one in six people are affected by cardiovascular disease (CVD), with one person dying from the disease every 12 minutes. Additionally, CVD may be the leading cause of death, yet it is one of the most preventable, WHO data shows.

Elina Hypponen, Professor in Nutritional and Genetic Epidemiology and Director of the Australian Centre for Precision Health, UniSA Cancer Research InstituteInvestigating the association of long-term coffee consumption and cardiovascular disease, the UniSA researchers, including Hyppönen and Dr. Ang Zhou, say their research confirms the point at which excess caffeine can cause high blood pressure. 

“Coffee is the most commonly consumed stimulant in the world – it wakes us up, boosts our energy and helps us focus – but people are always asking ‘How much caffeine is too much?’,” Hyppönen says.

Most people would agree that if you drink a lot of coffee, you might feel jittery, irritable or perhaps even nauseous, she says. This is because the caffeine helps the body work faster and harder, but it is also likely to suggest that it may have reached its limit for the time being. “We also know that the risk of CVD increases with high blood pressure, a known consequence of excess caffeine consumption.”

The researchers used UK Biobank data of 347,077 participants aged 37-73 years and explored the ability of the caffeine-metabolizing gene (CYP1A2) to better process caffeine, identifying increased risks of cardiovascular disease in line with coffee consumption and genetic variations.

Hyppönen says that despite carriers of the fast-processing gene variation being four times quicker at metabolizing caffeine, the research does not support the belief that these people could safely consume more caffeine, more frequently, without detrimental health effects.

“An estimated three billion cups of coffee are enjoyed every day around the world,” Hyppönen says. “Knowing the limits of what’s good for you and what’s not, is imperative. As with many things, it’s all about moderation; overindulge and your health will pay for it.”

Hyppönen notes that people tend to naturally limit their coffee intakes in response to unpleasant sensations. “We are all different and if the body is sending us signals indicating that the personal limit has been reached, it is important to follow those signals.”

However she says, it was reassuring to see that the level of intake associated with an increased cardiovascular risk was relatively high, and in the studied population, about 2 percent women and 3 percent of men drank over six cups of coffee each day. However, as is typical for dietary intakes or indeed any lifestyle habits in general, the best practice appears to be that of sticking to moderation, she notes.

What’s next?
More work is needed to establish the full range of health benefits and risks associated with coffee consumption, according to Hyppönen. Higher coffee intakes have been shown to increase sympathetic nervous system activity and blood pressure, and in layman’s terms, excessive coffee intake can make your heart work harder. 

“CVD is clearly just one aspect of health which may be affected by coffee consumption, and we need to work to establish the health effects of coffee also more broadly. More work is also needed to establish individual differences in the responses to coffee consumption,” Hyppönen concludes.

The positive side of coffee
The morning staple loved around the world is however also linked to several beneficial health outcomes, according to emerging science. Certain compounds found in coffee, called phenylindanes, may hinder two protein fragments responsible for Alzheimer’s and Parkinson’s from clumping, therefore potentially aiding in the prevention of these diseases, researchers from the Krembil Brain Institute have found. In addition, certain coffee compounds may inhibit the growth of prostate cancer, according to a new pilot study, carried out on drug-resistant cancer cells in cell culture and in a mouse model. 

Cold brew coffee has seen a surge in new product development, finding popularity among many health-conscious consumers, however, a recent Jefferson University study found hot brewed coffee to be the better option. The pH levels are similar, however hot brewed coffee is richer in antioxidants compared to cold brew, which makes it healthier.

By Kristiana Lalou