Myth revealed: does drinking coffee help you stay healthy?

Some like hot coffee, some like iced coffee, and some don't like coffee at all. Until recently, it was suggested that if you want to stay healthy, you'd better quit coffee.

You don't have to think about quitting coffee. Because a systematic summary of the results--the strongest measure of scientific evidence--suggests that most of the evidence so far is in favor of coffee drinking. Coffee consumption was associated with lower rates of premature death, type 2 diabetes and certain cancers.

However, some people need to pay attention to their coffee intake. High coffee intake is associated with an increased incidence of stomach cancer and exacerbates heart disease.

A systematic review of the findings suggests that most of the evidence supports coffee consumption.

Coffee and Life

Coffee drinkers live longer. A review of 20 studies involving 970,000 participants found that regular coffee drinkers had a 14 percent lower risk of premature death (from any cause) than those who drank less coffee. Even drinking 1-2 cups of coffee a day reduced the risk by 8%. Those who drank two to four cups of decaf coffee a day also had a 14 percent lower relative risk of premature death than those who drank no coffee.

Coffee and Liver Cancer

Coffee drinkers, especially men, have a lower risk of liver cancer. This is important because liver cancer is one of the six most common cancers in the world and has a higher incidence in men. The results of six studies showed that each additional cup of coffee consumed reduced the relative risk of liver cancer by 14 percent, depending on the number of cups consumed per day.

Studies have shown that natural ingredients in coffee, including coffee bean alcohol and caffeinol, have anti-cancer and anti-inflammatory effects. Coffee up-regulates anti-toxic biochemical processes in the liver, protecting the body from toxic substances such as aflatoxins and other carcinogens.

type II diabetes

Coffee drinkers had lower rates of type 2 diabetes. According to 28 studies involving more than 1 million adults, people who drank three or more cups of coffee a day had a 21 percent lower relative risk of developing type 2 diabetes than those who drank no or very little coffee. For those who drank six or more cups a day, the risk was reduced by 33 percent.

Interestingly, both regular and decaffeinated coffee drinkers had a lower risk. Drinking one cup of regular coffee a day reduced the relative risk of diabetes by 9%, and drinking decaffeinated coffee reduced the risk by 6%.

Many organizations have a soft spot for decaf coffee.

The active ingredients in coffee can help alleviate oxidative stress, an imbalance between free radicals and antioxidants. Coffee contains chlorogenic acid, which has been shown to boost glucose metabolism and insulin sensitivity, caffeic acid, which improves muscle use of blood sugar, and immune system and anti-inflammatory ingredients.

Coffee and prostate cancer

Coffee drinkers have a lower risk of prostate cancer. Thirteen studies of more than 530,000 men showed that men who drank the most coffee had a 10 percent lower relative risk of prostate cancer than those who drank the least. For every two more cups of coffee a day, men had an additional 2.5 percent lower risk.

However, when different grades of prostate cancer were taken into account, coffee showed no protective effect against high-grade or advanced prostate cancer.

Next, let's talk about why you need to pay attention to coffee intake.

Coffee and Lung Cancer

You need to watch your total coffee intake to reduce your risk of lung cancer. Studies of more than 10,000 adults found that the highest coffee intakes had a 27 percent higher relative risk of lung cancer. Every two extra cups of coffee a day increased lung cancer risk by 11%. There were only two studies of decaffeinated coffee, but the findings were the opposite: heavy decaffeinated coffee consumption was associated with a 34 percent lower risk.

Coffee research comes from population-based observational studies that focus on finding associations rather than causes.

Coffee and pregnancy

Drinking more than one or two cups of coffee a day during pregnancy may not be as risky as originally thought, but it's worth noting.

The most likely reason for previous studies showing a link between coffee and miscarriage and other adverse pregnancy outcomes is that those studies were poorly designed, especially in cases of low birth weight and birth defects. Some of the risk of miscarriage may be related to women suffering from severe morning sickness. Morning sickness itself is a sign of successful implantation, but pregnant women may reduce their coffee intake because of nausea.

In previous studies, smoking has often been associated with coffee intake, but this adjustment does not necessarily occur, so some of this risk may be due to smoking. The American College of Obstetricians and Gynecologists recommends that pregnant women consume less than 200 milligrams of coffee a day. This equates to 1-2 cups of coffee per day. (One cup of instant coffee contains 50-100 mg caffeine; freshly brewed coffee contains 100-150 mg caffeine per cup)

Coffee and Blood Pressure

One last thing to note has to do with your heart. High caffeine intake raises blood pressure in a short time and raises plasma homocysteine levels, another risk factor for heart disease. Coffee is not associated with long-term risk of heart disease.

People with high blood pressure or heart disease, the elderly, teenagers, children and those who do not drink coffee regularly are more sensitive to caffeine in "energy" drinks, colas and coffee. Choosing decaffeinated coffee can help these people.

It should be noted that most coffee studies are based on population-based observational studies designed to find associations, not causes. That's partly because it's very difficult to randomize a trial of drinking more coffee and measure health outcomes over a period of years. But maybe it's a good idea--who wants to volunteer for this kind of research?