by Craig Weatherby
Diabetes affects an estimated 24 million (one in 12) Americans, at a total annual cost of some $174 billion, with $116 billion for prescription drugs alone.
You've probably heard that epidemiological (diet-health) studies have statistically linked coffee drinking to a reduced risk of diabetes… with similar but lesser benefits associated with tea drinking.
For example, a Japanese research team recently calculated that people who reported quaffing a cup or more of coffee per day are 31 percent less likely to develop diabetes, compared with people who drink less.
As they wrote, “The results imply that coffee consumption decreased the risk of developing diabetes. The protective effect may exist aside from the influence of caffeine intake” (Oba S et al. 2010).
The last part of their conclusion—that caffeine is one of the diabetes-deterring agents in tea and coffee—enjoys significant scientific support, including a recently published study in mice.
The Japanese team's findings fit with the results of 18 separate studies involving nearly 500,000 people, which were analyzed last year by scientists from the University of Sydney, Australia (Huxley R et al. 2009).
The Aussie's analysis of data from prospective-type epidemiological studies showed that drinking three to four cups of coffee or tea daily may cut the risk of developing diabetes by one-quarter.
They also found that drinking tea or decaf coffee also provided some protection, suggesting that caffeine is not the only beneficial factor in tea and coffee.
Indeed, some research indicates that the potential anti-diabetes effects of tea and coffee stems from their polyphenol antioxidants.
The polyphenol antioxidants in tea and coffee appear to counter oxidative stress, which is known to hamper insulin-secreting cells in the pancreas and raise levels of insulin resistance.
Coffee also contains lots of chlorogenic acid—a polyphenol antioxidant virtually absent from tea—which forms compounds that reduce absorption of sugar from foods.
And the magnesium natural to coffee may also play a role in deterring diabetes.
What the new mouse study showed
Scientists from Nagoya University report that coffee prevented the development of high blood-sugar levels in lab mice, as well as improving their sensitivity to insulin, thereby reducing the risk of diabetes.
“Our results indicated that caffeine is one of the most effective anti-diabetic compounds in coffee… the present results suggest that coffee consumption may help to prevent type-2 diabetes and metabolic syndrome” (Yamauchi R et al. 2010).
A strain of lab mice that develops diabetes easily were divided into two groups, with one getting plain drinking water while the other received diluted coffee.
After five weeks of feeding, the researchers noted that the coffee-drinking animals did not develop high blood sugar levels (hyperglycemia).
In addition, the coffee-quaffing animals' showed lower levels of pro-inflammatory proteins called cytokines (e.g., MCP-1 and IL-6), compared to the water-drinking controls.
(However, one human study found that drinking coffee raises levels of inflammation, while tea did not… see “Coffee Found Inflaming; Tea Seen as Smarter Caffeine Source.”)
Importantly, similar positive effects were seen when, instead of coffee, the animals were given plain water with added caffeine.
As the Japanese team concluded, “These results suggest that coffee exerts a suppressive effect on hyperglycemia by improving insulin sensitivity, partly due to reducing inflammatory cytokine expression... caffeine may be one of the effective anti-diabetic compounds in coffee” (Yamauchi R et al. 2010).
The caffeine in tea and coffee—and in the Latin American favorites guaraná and yerba mate—may also boost brain efficiency and help protect it from age-related decline: see “Caffeine May Boost Brain Power and Deflect Dementia.”
Huxley R, Lee CM, Barzi F, Timmermeister L, Czernichow S, Perkovic V, Grobbee DE, Batty D, Woodward M. Coffee, decaffeinated coffee, and tea consumption in relation to incident type 2 diabetes mellitus: a systematic review with meta-analysis. Arch Intern Med. 2009 Dec 14;169(22):2053-63. Review.
Oba S, Nagata C, Nakamura K, Fujii K, Kawachi T, Takatsuka N, Shimizu H. Consumption of coffee, green tea, oolong tea, black tea, chocolate snacks and the caffeine content in relation to risk of diabetes in Japanese men and women. Br J Nutr. 2010 Feb;103(3):453-9. Epub 2009 Oct 12.
Yamauchi R, Kobayashi M, Matsuda Y, Ojika M, Shigeoka S, Yamamoto Y, Tou Y, Inoue T, Katagiri T, Murai A, Horio F. Coffee and caffeine ameliorate hyperglycemia, fatty liver, and inflammatory adipocytokine expression in spontaneously diabetic KK-Ay mice. J Agric Food Chem. 2010 May 12;58(9):5597-603.