Scientific Nutrition Update 23: Coffee

This episode is all about one of my favorite drugs, coffee.  Coffee is one of the most commonly consumed mind altering substances, full of a huge number of compounds with various health effects.  Coffee seems to have pretty incredible health benefits, and seems quite safe.  This is one you are going to want to share with the coffee consumers in your life.


For today’s episode we are going to talk about coffee, that beautiful elixir that has helped me write my book, sit through boring committee meetings, and pull many all-nighters.  This episode does include some pretty cool, but somewhat complex science and is somewhat longer so buckle up. Back in episode 19 we discussed caffeine, and this might tangentially connect to that, but we are primarily focused on coffee as a compound as a whole.  Coffee is one of those common foods that has really surprising benefits in a huge number of health domains. These are my favorite kind of thing, because it isn’t some esoteric mushroom, or extract from some rare plant, it is a common and frequently used substance.


Let’s look at one of the diseases I have spent the most time studying type 2 diabetes.  Six out of 9 large scale studies have found that coffee consumption reduces the risk of developing type 2 diabetes.  However, some of the people in this study are drinking crazy amounts of coffee. One study found that those who drank 7 cups of coffee per day had a 50% lower risk relative to those who drink 2 cups or less a day.  The 7 cups a day caught my attention because that is a ton of coffee. Then I read another one which found that men who drank 10 cups or more per day had a 55% lower risk, while women who drank ten cups a day had a 79% lower risk than those that drank two cups a day or less.  However, the most convincing study to me was a twin study that found that those who consumed 7 cups per day had a 35% lower risk than those that consumed two or less. Overall it seems quite large coffee consumption may reduce the risk of type 2 diabetes, but it may require drinking a lot of coffee.  Oddly enough large amounts of coffee consumption are associated with raised levels of insulin while consuming, which is surprising consider what we just established, so the full mechanism here requires some more explanation. There are several proposed mechanisms, including impaired glucose absorption from the intestine, increase in magnesium consumption, inhibition of glucose 6 phosphate, and even possibly weight loss (though I am not convinced about that one because coffee consumption is normally either not associated with, or weakly associated with BMI)


There have also been several studies which have seemed to suggest that coffee consumption may reduce the risk of developing Parkinson’s disease.  There have been both case-control studies and large prospective studies that all seem to show coffee consumption is inversely associated with Parkinson’s disease.  This effect seems to show up more often in men than women, and doesn’t seem to show up in all of the cohort studies you would expect. The Nurse’s Health study actually found that more 6 cups of day seemed to increase the risk in postmenopausal women who used estrogen, but it was inversely correlated with risk for women who had not used postmenopausal estrogen.  This suggests the overall mechanism here may be quite complex, sex-modulated, and involve estrogen. It may be because estrogen inhibits an enzyme that breaks down the caffeine in coffee.


Now we move on to the liver, which is one of my organs that has received its fair share of abuse from $2 Thursdays at Ribco and my own fishbowls and love for reposado tequila.  There is some evidence that coffee may help the liver. Coffee consumption has been found to be inversely correlated with markers of liver injury. There is an issue here though, and that is that liver damage such as cirrhosis inhibits caffeine metabolism which is done in the liver, so there is a chance the effect goes the other way here.  Namely that people with liver damage, drink less coffee, because the caffeine is not metabolized as well. However, it is important to note that coffee consumption is associated with a lower risk of dying from cirrhosis suggesting it may have some benefit to the liver.


Even better coffee consumption seems to be negatively associated with all-cause mortality, suggesting that coffee as a whole may reduce the risk of death.  All-cause mortality is a tool I use for compounds like this with mixed effects to determine whether or not they have a net benefit. Coffee seems to pass this test.  


This may also be because coffee is rich in antioxidants and as such can help reduce free radicals and oxidative damage in the body.  This is generally a good thing for health, though I do have a tendency to think many Internet Health Experts overstate their potential utility.


Now there are some potential health risks associated with coffee consumption that need to be discussed first.  First and foremost is the risk of cardiovascular disease. Case control studies have suggested that coffee consumption may increase the risk of heart disease.  However, this effect does not seem to hold in prospective cohort studies so I am hesitant to overinterpret those studies. Even more telling seems to be that many of the studies that suggest a danger seem to come from boiled coffee instead of filtered coffee, so I would seriously recommend filtering your coffee.  The mechanism for this potential increase may be due to the fact that boiled coffee seems to increase plasma cholesterol concentration, while filtered coffee seems not to have that same effect. It is also important to remember that caffeine can acutely raise blood pressure, though maybe not chronically. It also may impair the absorption of some minerals like calcium and zinc.  It is also important to remember it is addictive and does induce withdrawal headaches.


Also a note on cancer, since California is now saying that coffee needs to come with a warning, some case control studies seem to suggest that coffee can increase the risk of cancer, this does not seem to hold in large prospective cohort studies.  


There is also some somewhat obvious evidence that coffee consumption, especially late in the day can interfere with sleep.  So do be cognizant of that risk.


Overall coffee seems to be a useful compound for health, reducing the risk of type 2 diabetes,

Liver disease, and parkinson’s disease.  There is a slight chance it may contribute to cardiovascular disease but I think that risk is relatively small.  Plus it is a useful antioxidant. Overall, I think coffee seems to be almost completely safe and actually beneficial for health.


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