Over the years, researchers and health care providers have debated how drinking coffee affects health. 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.
Health Effects of Drinking Coffee:
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.
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.