Coffee is a ubiquitous product in our everyday life. For many, coffee is essential to getting through the day. Not surprisingly, coffee is known to increase attention, memory, and other cognitive measures in the short-term (1). Caffeine also has acute physiological effects, leading to short-term high blood pressure and increased heart rate. But what, if any, are the long-term health effects of coffee beyond the stimulatory boom that we crave?
Many studies over the years have tried to answer that question. One of the first large-scale studies was the Honolulu Longitudinal Heart Study. It examined many factors in over 8000 Japanese men residing in Hawaii from 1965 to 1968. Specifically, the study investigated the association between cardiac event outcomes and lifestyle factors like smoking and drinking, including an item for coffee. A 1986 study following up with the data found that–although the effect size was small– there was a statistically significant impact of higher coffee consumption on total serum cholesterol (2), both of which are well-established risk factors of coronary heart disease risk, especially in men (3,4). These studies had to use a model that took into account the correlation between smoking and coffee consumption. This effect was not present for caffeinated tea and cola, control sources of caffeine.
In 1991, a prospective cohort study confirmed this finding, showing that coffee can be a risk factor in raising total cholesterol (5).The researchers randomly split sixty-four healthy volunteers into three groups. One group drank six cups of non-filtered coffee daily, one group drank six cups of filtered coffee, and one group did not drink any coffee. Non-filtered coffee drinking was positively correlated with higher low-density lipoprotein (LDL) levels. They concluded some LDL-raising factor is responsible. In 1995, scientists identified a component in coffee called diterpenes that are a causative agent of higher serum cholesterol (6). These can easily be filtered out. So does boiled-and-unfiltered coffee consumption lead to high cholesterol?
Not necessarily. Many of these studies were admittedly small case-control studies and looked at cholesterol without considering other effects that also influence coronary heart disease (CHD) risk at the population level. A recent 2015 population study found lower incidence of CHD events in those who drank coffee than those who didn’t (7). Specifically, the graph was a U-shape, with a declining risk until the greater than five cups per day segment had a higher risk than three to five cups per day segment. Scientists today know there are positive effects of moderate coffee consumption on long-term CHD risk (8), perhaps due to antioxidants or other components or associated lifestyle factors that go along with moderate coffee consumption. This means three to five cups a day is ideal, with more or less consumption leading to higher risk within the population. A 2014 meta-analysis confirmed a whopping 16% reduction in total mortality in the population associated with four cups per day, where four was the ideal number (9).
Drinking coffee probably won’t make up for other unhealthy habits. But there is little reason to stop moderate consumption as long as it is filtered. Working from home can be tough. Whether you’re a morning person or all hours, hopefully coffee can be a source of cardiovascular health in a time of stress.
Written by: Ben Lieberman
Edited by: Akshay Govindan
Illustrated by: Eugenia Yoh