Over the years, researchers and health care providers have debated how drinking coffee affects health. Scientists have uncovered some fascinating data on how coffee–specifically, caffeinated coffee–affects the brain. Is your morning cup of java bad for you?
Previous research from the UK found that coffee drinkers are less prone to liver cancer. Now, scientific evidence suggests that people who drink coffee also lower their risk from colorectal cancer. On the other hand, a reader suggests that coffee may increase the risk for osteoporosis. Some researchers confirm that drinking coffee may lead to bone loss.
How Drinking Coffee Affects the Brain:
Researchers in Portugal were curious about the increased alertness coffee drinkers claim (Frontiers in Behavioral Neuroscience, June 28, 2023). Does drinking coffee really affect the brain, they wondered, or is it the pleasure of a tasty hot beverage? They collected functional MRIs from 47 young adults before and half an hour after a cup of coffee. While in the machine, the subjects were encouraged to let their minds wander. (This is an important detail.) The comparison of fMRI results from these people showed reduced connectivity to the posterior Default Mode Network after drinking coffee. The Default Mode Network links parts of the brain that are most active when we are doing self-reflection, planning, visualizing or daydreaming. Instead, areas of the visual and executive control network were more fully active following coffee consumption.
Was it coffee, or caffeine alone, that had this effect? The investigators recruited an additional 36 young adults willing to spend two sessions in an MRI machine. These volunteers got hot water with caffeine dissolved in it between their sessions. No flavor, no pleasant associations, no additional phytocompounds. And they too had decreased connectivity in the posterior DMN during the second section. It was not clear that caffeine alone was as effective at preparing people for action as a delicious cup of coffee, though.
Health Effects of Drinking Coffee:
Reduced Risk of Neurodegenerative Diseases:
Your cup of joe might benefit your brain in some unexpected ways. Not only does it help you pay attention, drinking unsweetened caffeinated coffee day after day can lower the risk for Parkinson disease and dementia, including Alzheimer disease.
Researchers analyzed data from nearly 205,000 participants in the UK Biobank (American Journal of Clinical Nutrition, Oct, 2024). They classified the volunteers on the basis of non-coffee drinkers, those consuming 1 cup a day or less, those drinking 1 to 2 cups, 2 to 3 cups and those consuming 3 or more cups daily. Over about nine years, some of these people developed neurodegenerative diseases.
Compared to those not consuming coffee, those who drank the most unsweetened caffeinated coffee had a 25% lower likelihood of being diagnosed with Alzheimer disease, a 29% lower risk of Parkinson disease and a 33% lower chance of dying from either of these conditions. People drinking sugar-sweetened or artificially-sweetened coffee did not experience those benefits. The study did not address the presence or absence of milk or creamer.
Colon and Rectal Cancer:
Epidemiological research has suggested that coffee drinkers with colorectal cancer had improved survival rates compared to those who abstain. A new study in JAMA Oncology followed more than 1100 individuals diagnosed with advanced or metastatic colorectal cancer (JAMA Oncology, online, Sept. 17, 2020). Data were collected from 2005 to 2018.
In summary, this prospective observational study confirmed the earlier results. Coffee drinkers have a lower risk of disease progression and death. There was a dose response curve, meaning that the more coffee people drank, the better the outcome. It didn’t matter whether the coffee was decaf or regular.
Liver Cancer:
The British scientists studying liver cancer did a systematic review of data from 26 observational studies with more than 2 million participants (Kennedy et al, BMJ Open, May, 2017). Those who normally drank two cups of coffee a day were about 35 percent less likely to develop liver cancer (hepatocellular carcinoma).
Regular or Decaf?
As with the recent research on colorectal cancer, it did not seem to matter whether the coffee was decaf or high test. Consequently, the apparent protective effect comes not from the caffeine but from some other component of coffee. Coffee is rich in antioxidant compounds, and some of them have anticancer activity.
This study included only observational studies, not clinical trials. Consequently, the researchers don’t claim that drinking coffee protects people from liver cancer. Nonetheless, the association suggests that your morning cup (or two) won’t do your liver damage.
Coffee and Diabetes Risk:
These studies are not the first to indicate that drinking coffee may have health benefits. Years ago, we received this question:
Q. My father and uncle both have diabetes. As a result, I would like to reduce my risk of developing this disease. I’ve heard that drinking coffee can help. Is there any evidence behind this claim?
Here is our answer:
A. Several epidemiological studies have demonstrated an association between drinking coffee and a reduced risk of developing type 2 diabetes (Smith et al, Diabetes Care, Nov. 2006; van Dam et al, Diabetes Care, Feb. 2006).
Despite the epidemiology, do not count on coffee alone to protect you. In most cases, regular exercise and weight control are far more likely to help you avoid type 2 diabetes.
Downsides of Drinking Coffee:
Q. You’ve written about the health benefits of coffee, but I think you’ve missed an important downside. My mother, mother-in-law and sister were all coffee drinkers. All three lived past 80 and all three lost at least 4 inches in height.
My mother was 5’5″ in her youth and was about 5’1” before her death. What’s more, my mother-in-law was 5’2″ in her youth and 4’10” before she died. Although my sister was 5’9″ as a young woman, she is currently 5’4″ at age 81.
I do not drink coffee. While I drank black tea in the first three decades of my life, I switched to herb tea in the last four decades.
I am currently 70 years old and have lost almost two inches in height. I remain convinced that coffee increases bone loss worse than tea.
Bone Loss in Coffee Drinkers:
A. You may well be right. Green tea drinkers are less likely to develop osteoporosis (Nutrients, Dec. 26, 2021). Coffee drinkers, on the other hand, may be at greater risk of osteoporosis and fractures (Osteoporosis International, April 15, 2022 and June 2022).
These associations are intriguing but inconclusive. The benefits are clear: People who drink coffee have less type 2 diabetes and a lower risk of stroke, heart failure, cancer and dementia. A recent analysis of UK Biobank data shows that coffee drinkers live longer (Annals of Internal Medicine, May 30, 2022).
Other Downsides from Coffee:
Other research shows that drinking coffee has some adverse effects as well as health benefits. A review of 94 studies found that even people with high blood pressure or heart rhythm abnormalities can safely consume moderate amounts of coffee (Chrysant, Expert Review of Cardiovascular Therapy, March 2017).
However, Israeli investigators report that people who drink coffee are more susceptible to rheumatoid arthritis and type 1 diabetes (Sharif et al, Autoimmunity Reviews, online May 4, 2017). In addition, they found that coffee interferes with the effectiveness of methotrexate for treating rheumatoid arthritis and inhibits absorption of levothyroxine for Hashimoto’s disease.
Can You Quit Drinking Coffee Without Suffering Withdrawal?
If you decide the risks of coffee are too great, you’ll want to stop. Coffee lovers know that if they have to give up caffeine suddenly because of surgery or some other interruption in the daily schedule, they will probably suffer symptoms of withdrawal. The most common is headache. But fatigue, irritability and trouble concentrating are also frequent.
A study published in the Journal of Psychopharmacology (Feb. 2023) discovered that drinking good quality decaffeinated coffee can reduce caffeine withdrawal symptoms. The authors recruited 61 heavy coffee drinkers and asked them to stop drinking coffee for 24 hours. That precipitated withdrawal symptoms, including intense coffee cravings, drowsiness, fatigue and decreased motivation.
For the study, the researchers randomly assigned the volunteers to one of three groups. The control group drank water. One group got decaf coffee but were told it was regular coffee. The last group got decaf and were told it was decaffeinated. Surprisingly, caffeine withdrawal symptoms decreased for both groups drinking coffee even though it was decaf. Those who believed they were getting regular coffee had the least withdrawal symptoms. However, even those who knew they were drinking decaf got significant protection.
