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Tuesday, April 1, 2008

Coffee: Concerns, Benefits and the Bottom Line

Recent research has shown coffee in a whole new light. The world’s most popular beverage may not be as harmful to health as we once thought. A concentrated source of antioxidants, coffee may even have a protective effect against certain diseases. Do the newfound perks outweigh the known side effects? A review of the most recent findings puts benefits and concerns in perspective.

Diabetes Mellitus

Earlier this year, two studies in Finland investigated the relationship between coffee consumption and type two diabetes mellitus (DM2).

One followed more than 20,000 men and women for more than 13 years, on average. Researchers concluded that those who drank three or more cups of coffee each day were less likely to develop DM2 - regardless of body mass index, alcohol consumption, or physical activity.

The other study examined metabolic markers in the blood associated with an increased risk of DM2 including elevated glucose and insulin levels. Drinking coffee was found to have a positive impact on these markers and regular coffee drinkers were less likely to have problems with blood sugar regulation.

Heart Disease

Harvard researchers studied more than 128,000 men and women free of cardiovascular disease. They found no relationship between coffee consumption and the development of heart disease, even when results were adjusted for age, smoking status, alcohol use, and body mass index. Researchers in Norway concur. After following more than 41,000 postmenopausal women for 15 years, they concluded that coffee drinkers had lower rates of inflammatory diseases, including cardiovascular disease, probably because antioxidants in coffee inhibit inflammation in the body.

Other studies have investigated the relationship between drinking coffee and risk factors for developing heart disease, such as hypertension and increased levels of homocysteine in the blood. Although caffeine can temporarily increase blood pressure, data from the Nurses’ Health Studies I and II - which included more than 155,000 women - found no association between habitual coffee consumption and hypertension in women.

A small study in the Netherlands found that chlorogenic acid, a polyphenol in coffee, raised homocysteine levels by 12 percent. Homocysteine may irritate blood vessels and cause blood to clot more easily, increasing the risk of heart disease, stroke and atherosclerosis. A study in Greece also demonstrated that coffee raises homocysteine levels, but the effect was only significant when people consumed at least 500 ml (about 16 ounces or 2 cups) of coffee each day.

Liver Disease

Researchers in Maryland investigated the association between hospitalization or death due to chronic liver disease and consumption of coffee or tea. They concluded that people who were at high risk for liver problems - such as alcoholics, diabetics and overweight individuals - and drank two or more cups of coffee or tea each day had half the risk of chronic liver disease as those who drank less than one cup per day.

Other studies have focused on specific liver diseases, such as cirrhosis and a form of cancer called hepatocellular carcinoma (HCC). Researchers in California followed more than 125,000 people without known liver problems for 16 to 23 years. They concluded that those who drank coffee were less likely to develop liver cirrhosis, especially alcoholic cirrhosis, than those who abstained. A study in Italy found that people who drank two or more cups of coffee each day reduced their risk of developing HCC, and Japanese studies concluded that the chance of dying from HHC was lower in individuals who drank at least one cup of coffee each day.

Parkinson’s Disease

Researchers in Hawaii examined the relationship between coffee and Parkinson’s disease. More than 8,000 Japanese-American men were followed for 30 years, and those who consumed more coffee and caffeine had a lower incidence of Parkinson’s disease. A study in Singapore found a dose-dependent relationship: for every three cups of coffee consumed each day, there was a 22 to 28 percent risk reduction.

Other studies estimate that, regardless of genetic susceptibility, coffee drinkers have a 30 percent reduced risk of developing Parkinson’s disease. Experts think the caffeine in coffee has a protective effect on the brain, blocking adenosine receptors and stimulating the release of dopamine. Some drugs, called dopamine agonists, used to treat Parkinson’s disease have a similar mechanism.

Side Effects

Most of the recent scientific studies scrutinizing coffee have been positive, but coffee isn’t necessarily a health food. Side effects can include restlessness, nervousness, psychomotor agitation, gastrointestinal problems, insomnia, rapid or irregular heart rate, increased production of gastric acid and increased excretion of minerals including calcium, magnesium, zinc and potassium. There are also concerns about drinking coffee during pregnancy. A recent study of more than 88,0000 women in Denmark found that the risk of fetal death was higher in pregnant women who drank coffee, especially after 20 weeks of gestation.

The Bottom Line

Everything considered, coffee can be part of a healthy lifestyle. Regular drinkers may experience lower rates of type two diabetes mellitus, heart disease, liver disease and Parkinson’s disease. However, moderation is important and coffee should never be used as a regular replacement for the good sleep that is essential to good health. Limiting intake to a cup per day is ideal. However, pregnant women, individuals who experience negative side effects and those with elevated levels of homocysteine in their blood should seek an alternative.

REFERENCES

Anderson LF et al. Consumption of coffee is associated with reduced risk of death attributed to inflammatory and cardiovascular diseases in the Iowa Women’s Health Study. American journal of clinical nutrition, 83(5):1039-46, May 2006.

Bech BH et al. Coffee and fetal death: a cohort study with prospective data. American journal of epidemiology, 162(10):983-90, Nov 2005.

Bidel S et al. Effects of coffee consumption on glucose tolerance, serum glucose and insulin levels – a cross-sectional analysis. Hormone and metabolic research, 38(1):38-43, Jan 2006.

Gale C and Martin C. Tobacco, coffee and Parkinson’s disease. British Medical Journal, 326(7390):614, Mar 2003.

Gelatti U et al. Coffee consumption reduces the risk of hepatocellular carcinoma independently of its aetiology: a case-control study. Journal of hepatology, 42(4):444-6, Apr 2005.

Hu G et al. Joint association of coffee consumption and other factors to the risk of type two diabetes: a prospective study in Finland. International journal of obesity, 25 Apr 2006.

Klatsky AL et al. Coffee, cirrhosis and transaminase enzymes. Archives of internal medicine, 166(11):1190-5, Jun 2006.

Kurozawa Y et al. Coffee and risk of death from hepatocellular carcinoma in a large cohort study in Japan. British journal of cancer, 93(5):607-10, Sep 2005.

Lopez-Garcia E et al. Coffee consumption and coronary heart disease in men and women: a prospective cohort study. Circulation, 113(17):2045-53, Apr 2006.

Olthof MR et al. Consumption of high doses of chlorogenic acid, present in coffee, or black tea increase plasma total homocysteine concentrations in humans. American journal of clinical nutrition, 73(3):532-8, Mar 2001.

Panagiotakos DB et al. The association between coffee consumption and plasma total homocysteine levels: the “ATTICA” study. Heart vessels, 19(6):280-6, Nov 2004.

Ragonese P et al. A case-control study on cigarette, alcohol, and coffee consumption preceding Parkinson’s disease. Neuroepidemiology, 22(5):297-304, Sep-Oct 2003.

Ruhl CE and Everhart JE. Coffee and tea consumption are associated with a lower incidence of chronic liver disease in the United States. Gastroenterology, 128:24-32, Dec 2005.

Tan EK et al. Dose-dependent protective effect of coffee, tea and smoking in Parkinson’s disease: I study in ethnic Chinese. Journal of the neurological sciences, 216(1):163-7, Dec 2003.

Winkelmayer WC et al. Habitual caffeine intake and the risk of hypertension in women. Journal of the American medical association, 294(18):2330-5, Nov 2005.

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