Coffee and Diabetes -- Is the Miracle Cure Found?

Can coffee and diabetes go hand in hand?

The health benefits of coffee have been subject of controversy for so long that we almost stopped paying attention. We just drink it. People who love coffee can’t live without it event though coffee has been blamed for all kinds of trouble. However, recently discovered properties might win over even the biggest coffee opponents.

Coffee and Diabetes Facts:

In the last 9 years numerous studies have shown that the more coffee you drink, the lesser the risk for type 2 diabetes. The reason for this beneficial effect was not really understood (until very recently).

In 2002 Dutch researchers (1) who studied 17,000 men and women in the Netherlands concluded that people who drank 7 cups a day (or more) were 50% less likely to develop type 2 diabetes. Drinking less coffee had less of an impact on diabetes onset. Because the mechanism of the connection between coffee and diabetes was not clear, the researchers cautioned people that 7 cups of coffee per day might cause other health problems.

In 2004, another study (14) included 126,000 people. The results from this study showed that men who had 6 cups of coffee a day reduced their chances of developing type-2 diabetes by 50%, and women who drank the same amount cut their risk by 30 %.

Throughout 2006 several studies were conducted in Europe, Japan and the United States. Van Dam et al. (3,4,5) reviewed the results of studies of coffee and diabetes conducted around the world. They excluded studies on type 1 diabetes, animal studies and studies of short-term exposure to coffee or caffeine, leaving 15 epidemiological studies (cohort or cross-sectional). They identified 9 cohort studies including 193,473 participants and calculated the relative risks using a random-effects model.

One interesting detail that came out of this extensive analysis was that the risk was lower for participants who consumed filtered coffee than for those who consumed pot-boiled, Turkish/Greek coffee. Because the consumption of boiled and instant coffee was relatively limited in the studies, the current findings mostly reflect consumption of drip-filtered coffee.

Serving sizes for coffee and strength of coffee brew can differ substantially within and between countries. The size of standard coffee cups is larger in the US (250 ml) (11), compared with Europe (125 ml) (12). Generally the coffee brew is much weaker in the US compared with Europe(13).

This meta-analysis of cohort studies supports the significant inverse association between coffee consumption and risk for type 2 diabetes. In the range of 4-6 cups per day there is 28% lower risk and in the range of 6-7 cups per day the risk is 35% lower to develop type 2 diabetes. The research team also concluded that longer-term intervention studies of coffee consumption and glucose metabolism (6) were warranted to examine the mechanisms underlying the relationship between coffee consumption and type 2 diabetes.

What do we know now about coffee and diabetes that we didn’t before?

Coffee and Diabetes: The breakthrough

In 2010 Atsushi Goto, and Dr. Simin Liu (15), researchers at UCLA discovered a possible mechanism on molecular level that could explain the protective effect of coffee.

The study found that women who drank 4 cups of caffeinated coffee each day had significantly higher levels of a protein called sex hormone–binding globulin (SHBG) than non-drinkers. They were 56% less likely to develop diabetes than were the women who did not drink coffee.

This significant protective effect of coffee drinking disappeared when the findings were adjusted for levels of sex hormone–binding globulin (SHBG) which means that the direct link between coffee and type 2 diabetes is mediated through this hormone.

This study was based on earlier work by Liu and his colleagues that had identified two mutations in the gene coding for SHBG, one could increase the risk for diabetes, while the other could decrease it, depending on the levels of SHBG in the blood. The higher the SHBG levels, the lower the risk for diabetes. Coffee plays an important role in turning on the gene that determines a higher production of SHBG and hence a lower risk for diabetes.

The genetic nature of the effects of coffee is very important because it indicated that SHBG may indeed play a causal role in affecting risk for type 2 diabetes. The study also found that drinking decaffeinated coffee was not significantly associated with SHBG levels, and didn’t play the same protective role as the caffeinated coffee.

Why is this finding about coffee and diabetes so important?

It was thought that coffee may improve the body's tolerance to glucose by increasing glucose metabolism or improving its tolerance to insulin, but for the first time there is a scientific proof that hormones like SHBG in the blood can be influenced by dietary factors such as coffee intake.

What are the implications of these results?

The results about the connection between coffee and diabetes are significant for 2 major reasons:

1. Type 2 Diabetes Prevention

According to the American Diabetes Association nearly 8% of the population in the U.S. has diabetes. Type 2 diabetes is the most common form of the disease and accounts for about 90 to 95% of these cases, or about 22 million people. As Dr. Liu, a co-author of the study puts it, "we now know that this protein, SHBG, is critical as an early target for assessing the risk and prevention of the onset of diabetes."

2. Improving Sex Drive and Treatment of Erectile Disfunction

SHBG is known to regulate the activity of the sex hormones, testosterone and estrogen. The decline of this hormone is linked to low sex drive in men. This could influence the treatment of andropause and prevent the side effects of low testosterone levels. It can also help to better understand the high rate of erectile dysfunction among men suffering from type 2 diabetes.

Coffee and diabetes connection summary:

According to the latest studies on the effect of coffee and diabetes prevention, coffee drinking can significantly reduce the risk for developing the disease by regulating the level of SHBG (hormone in the blood that is related to the activity of sex hormones). Having at least 4 cups per day might be beneficial, but before you decide to go crazy about coffee you should first consult your health provider to avoid any side effects or complications of any other conditions you may have.

1. Van Dam, R.M. and Feskens, E.J.M. Lancet, 360, 1477-1478, 2002.

2. Saremi, A. et al. Diabetes Care, 26, 2211-2212, 2003. 3. Van Dam, R; Frank B. Hu, MD, PhD JAMA. 2005;294(1):97-104. doi: 10.1001/jama.294.1.97

4. Van Dam, R. et al. Diabetes Care, 29, 398-403, 2006

5. Van Dam, R. et al. Nutrition, Metabolism and Cardiovascular Disease, 16, 69-77, 2006.

6. Smith, B. et al, Diabetes Care, Volume 29, 2006

7. Salazar-Martinez E, Willett WC, Ascherio A, et al. Coffee consumption and risk for type 2 diabetes mellitus. Ann Intern Med. 2004;140:1-8.pmid:14706966

8. Rosengren A, Dotevall A, Wilhelmsen L, Thelle D, Johansson S. Coffee and incidence of diabetes in Swedish women: a prospective 18-year follow-up study. J Intern Med. 2004;255:89-95.pmid:14687243

9. Tuomilehto J, Hu G, Bidel S, Lindstrom J, Jousilahti P. Coffee consumption and risk of type 2 diabetes mellitus among middle-aged Finnish men and women. JAMA. 2004;291:1213-1219.pmid:15010442

10. Yamaji T, Mizoue T, Tabata S, et al. Coffee consumption and glucose tolerance status in middle-aged Japanese men. Diabetologia. 2004;47:2145-2151.pmid:15662555

11. Bracken MB, Triche E, Grosso L, Hellenbrand K, Belanger K, Leaderer BP. Heterogeneity in assessing self-reports of caffeine exposure: implications for studies of health effects. Epidemiology. 2002;13:165-171.pmid:11880757

12. Ärnlöv J, Vessby B, Riserus U. Coffee consumption and insulin sensitivity. JAMA. 2004;291:1199-1201.pmid:15010440

13. Schaafsma G. The content of coffee in the Netherlands: caffeine, minerals, trace elements and vitamins [in Dutch]. Voeding. 1989;50:223.

14. Tuomilehto J, Hu G, Bidel S, Lindstrom J, Jousilahti P. Coffee consumption and risk of type 2 diabetes mellitus among middle-aged Finnish men and women. JAMA. 2004;291:1213-1219.pmid:15010442

15. Goto A. et al.: Coffee and caffeine consumption in relation to sex hormone-binding globulin and risk of type 2 diabetes in postmenopausal women. Diabetes. 2011 Jan;60(1):269-75. Epub 2010 Oct 28.

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