By Jennifer Copley (Last Updated 16 October 2012)
Coffee drinking increases the risk for a number of medical problems in susceptible individuals, and may sabotage efforts to maintain a healthy body weight.
Drinking coffee is associated with a number of health benefits, including reduced risk for Parkinson’s disease, diabetes, colon cancer, and even suicide. However, on the negative side, coffee can cause a number of problems for susceptible individuals, particularly in large doses.
Coffee and Hypoglycemia
Caffeine causes a release of glycogen by the liver, which can generate wild swings in blood sugar, causing attacks of hypoglycemia, also known as low blood sugar (Kaslow, 2012; Kerr et al., 1993). Hypoglycemia has a variety of unpleasant symptoms, including weakness, nervousness, sweating, and heart palpitations.
Coffee and Cholesterol
In some individuals, coffee can raise cholesterol, which increases the risk of developing cardiovascular disease (Baylor College of Medicine, 2007).
Coffee and Fertility
Women who are pregnant or attempting to get pregnant should avoid excess caffeine consumption, which may increase the risk for a variety of fertility problems. Research into caffeine’s effects on fertility has yielded mixed results, though a recent study reported by CTV News found that the risk of miscarriage doubled with the consumption of 2 or more cups of coffee per day, and others have linked high caffeine consumption with reduced fertility. Numerous studies have also found caffeine consumption by pregnant women to be associated with low birth weight. The American College of Obstetricians and Gynecologists recommends that pregnant women consume no more than 1 to 2 cups of coffee per day.
Coffee and Anxiety Symptoms
Caffeine can overstimulate the central nervous system. This not only causes anxiety in susceptible individuals, but can also exhaust the adrenal glands over time, decreasing resistance to stress and thus increasing vulnerability to disease pathogens and other health hazards (Kaslow, 2012). See the Caffeine page for a comparison of caffeine levels in popular foods and beverages.
Coffee and Osteoporosis
Because excess coffee consumption may prevent the full absorption of necessary minerals, it increases the risk of developing osteoporosis. A study of nearly 1,000 postmenopausal women conducted by Barret-Connor et al. (1994) found that long-term consumption of 2 or more cups of caffeinated coffee per day was associated with decreased bone density, regardless of age, alcohol and tobacco consumption, hormone use, and other factors. However, there are indications that these negative effects can be mitigated by adding milk.
Many people who quit coffee often experience withdrawal symptoms such as fatigue, headache, decreased energy and alertness, difficulty concentrating, and even irritability and depression. These symptoms usually begin within 12-24 hours of quitting caffeine and hit a peak within 20-51 hours. Overall, symptoms tend to last anywhere from 2-9 days.
Coffee and Weight Gain
Caffeine in coffee may aid short-term weight loss for some people, but it may also increase the risk of long-term weight gain by triggering the release of stress hormones and creating a greater risk for hypoglycemia, which stimulates the appetite. As for whether or not this translates into actual weight gain, studies have yielded mixed results. For example, Kovacs et al. (2007) found that higher caffeine intake increased the likelihood of gaining weight, whereas Lopez-Garcia et al. (2006) found a slightly reduced risk of weight gain among those who increased their caffeine intake (these are just two examples – a search of peer-reviewed journal articles yields many more studies that could be used to support each side of the caffeine and body weight debate). The Decaf Diet: Is Caffeine Making You Fat by Eugene Wells also makes a strong and well-researched case for the negative long-term effects of caffeine on body weight.
Caffeine may increase the risk for weight gain by interfering with sleep. Patel et al. (2006) found that women who slept for fewer hours each night were at greater risk for weight gain. The fact that excess caffeine intake or drinking caffeinated beverages in the evening can interfere with sleep supports the theory that there is a link between coffee consumption and weight gain for some people.
Overall, research suggests that green tea is better for maintaining a healthy weight than coffee. Green tea provides caffeine but in lower amounts, so it is less likely to trigger hypoglycemia (and the resulting food cravings) or sleep problems. Also, most people drink green tea on its own, whereas coffee is often loaded up with with cream and sugar, which add a large number of calories.
The varying research results suggest that there are many factors that determine whether caffeine will increase the risk of weight gain or aid weight loss for a particular individual. Overall lifestyle and personal physiology will likely influence the effects of caffeine on each person, which means that coffee may be harmful for some people but beneficial for others (in moderation).
Coffee and Iron Absorption
Coffee consumed with meals can decrease absorption of iron by 50%, and iron deficiency can lead to anemia (Anderson & Fitzgerald, 2010). Research conducted by Morck et al. (1983) indicates that coffee inhibits iron absorption when consumed with food or one hour after eating, though drinking coffee one hour before eating did not negatively impact iron absorption.
Should You Drink Coffee?
People with any of the following conditions should avoid coffee or at least check with a doctor before consuming it:
- Bladder or kidney problems
- Bowel problems such as colitis and diverticulitis
- Chronic fatigue syndrome
- Fibrocystic breast disease
- Generalized anxiety and/or panic attacks
- Heart problems
- Hiatal hernia
- High blood pressure
- High cholesterol
- Liver disease
- Osteoporosis or family history of osteoporosis
- Prostate problems
- Severe PMS
- Urinary tract irritation
Overall, the decision to consume coffee should be based on your personal health profile. If you suffer or are at risk for the conditions that coffee can aggravate, it is better to avoid it. If you are not at risk for these conditions, coffee consumption is unlikely to cause problems, and you may even enjoy a number of the health benefits associated with coffee.
This article is provided for informational purposes only and is not intended to represent medical advice. If you have any concerns regarding your health or whether or not coffee could aggravate a preexisting medical condition, you should consult your doctor.
- Anderson, J., & Fitzgerald, C. (2010). “Iron: An Essential Nutrient.” Colorado State University Extension, ext.colostate.edu.
- Barrett-Connor, E., & Chang, J.C., & Edelstein, S.L. (1994). “Coffee-Associated Osteoporosis Offset by Daily Milk Consumption.” Journal of the American Medical Association, 271(4): 280-283.
- Baylor College of Medicine (2007, June 15). “How Coffee Raises Cholesterol.” ScienceDaily.com.
- CARE Study Group. (2008). “Maternal Caffeine Intake During Pregnancy and Risk of Fetal Growth Restriction: A Large Prospective Observational Study.” BMJ, 337: a2332.
- CTV News. (22 January 2008). “Caffeine Doubles Miscarriage Risk, Study Finds.” CTV.ca.
- Ensminger, A.H. (1994). Foods and Nutrition Encyclopedia. CRC Press.
- Grodstein, Goldman, M.B., Ryan, L., & Cramer, D.W. (1993). “Relation of Female Infertility to Consumption of Caffeinated Beverages.” American Journal of Epidemiology, 137(12): 1353-1360.
- Kaslow, J., MD. (2012). “Health Issues Associated with Coffee and Caffeine.” Drkaslow.com.
- Kerr et al. (1993). “Effect of Caffeine on the Recognition of and Responses to Hypoglycemia in Humans.” Annals of Internal Medicine, 119(8): 799-804.
- Kirchheimer, S. (Reviewed by Michael W. Smith, MD, 2004). “Coffee, the New Health Food?” WebMD.
- Kovacs, B., MS, RD. (Reviewed by Melissa Conrad Stöppler, MD, 2007). “Caffeine.” MedicineNet.
- Kovacs, E.M.R., Lejeune, M.P.G.M., Nijs, I., & Westerterp-Plantenga, M.S. (2004). “Effects of Green Tea on Weight Maintenance After Body-Weight Loss.” British Journal of Nutrition, 91(3): 431-437.
- Lopez-Garcia, E., van Dam, R.M., Rajpathak, S., Willett, W.C., Manson, J.E., & Hu, F.B. (2006). “Changes in Caffeine Intake and Long-Term Weight Change in Men and Women.” American Journal of Clinical Nutrition, 83(3): 674-680.
- Mathur, R., MD. (Reviewed by William C. Shiel, Jr., MD, FACP, FACR, 2005). “Hypoglycemia.” MedicineNet.
- Morck, T.A.; Lynch, S.R.; & Cook, J.D. (1983). “Inhibition of Food Iron Absorption by Coffee.” American Journal of Clinical Nutrition, 37(3), 416-420.
- Patel, S.R., Malhotra, A., White, D.P., Gottlieb, D.J., & Hu, F.B. (2006). “Association Between Reduced Sleep and Weight Gain in Women.” American Journal of Epidemiology, 164(10): 947-954.
- Wells, E. (2010). The Decaf Diet: Is Caffeine Making You Fat? Amazon Digital Services.