Coffee and diabetes revisited

[Guest guest]

Hi All,

The pdf-available below again comes thumbs-up for coffee

It seems to be the caffeine that does it.

That insulin sensitivity/glucose is possibly involve is nice.

JAMA, March 10, 2004—Vol 291, No. 10 1199

Johan Arnlov, Bengt Vessby

Coffee Consumption and Insulin Sensitivity

To the Editor: Coffee consumption has been associated with

a substantially lower risk of developing type 2 diabetes.1 How-ever,

despite the widespread use of coffee, there are few data

on the specific effects of coffee on the 2 main causes of diabe-tes,

ie, insulin resistance and defective insulin secretion. We

investigated the association between coffee consumption and

both insulin sensitivity and insulin secretion in a sample of el-derly

Swedish men without diabetes.

Methods.

We reanalyzed cross-sectional data collected be-tween

1990 and 1994 from the Uppsala Longitudinal Study of

Adult Men (ULSAM). A dietitian instructed all participants to re-cord

their dietary intake using a 7-day precoded food diary. Cof-fee

and tea consumption were recorded 6 times daily (breakfast,

lunch, supper, between meals, and in the evening). Amounts of

sugar, cream, and milk used in coffee, as well as of cookies, cakes,

and biscuits consumed with coffee, were also recorded at these

occasions. ...

Results.

Data on insulin sensitivity, insulin secretion, and

coffee consumption were available for 1088 of the original 1221

participants (89%). Participants with type 2 diabetes were ex-cluded,

leaving 936 participants for analysis. Baseline charac-teristics

of the sample at the time of data collection are pre-sented

in TABLE 1.

Coffee consumption was not significantly associated with in-sulin

sensitivity in univariate analysis (TABLE 2). Because intake

of sugar, milk, pastries, and alcohol was not normally distrib-uted

after logarithmic transformation, we decided to dichoto-mize

these variables according to dietary guidelines of the Swed-ish

National Food Administration (Table 1). After adjustment for

tea consumption, amounts of sugar and cream used in coffee,

amounts of cookies, cakes, and biscuits consumed with coffee,

alcohol consumption, body mass index, physical activity level,

and smoking status, we found that a 1-cup increase of coffee per

day was associated with 0.16-units higher insulin sensitivity (Table

2). Further adjustment for age, daily intake of dairy products, fat,

protein, carbohydrates, total energy intake, and waist girth, as well

as inclusion of participants with diabetes, did not substantially

change the results (data not shown). Notably, both consump-tion

of tea and use of sugar were found to be independently as-sociated

with insulin sensitivity (Table 2).

No associations were found between coffee consumption and

early insulin response (EIR) (ie, 30-minute increment of in-sulin

per 30-minute increment of glucose) during an oral glu-cose

tolerance test, even after the above multivariate adjustment,

indicating

there was no effect of coffee consumption on insulin secretion

(univariate regression coefficient, 0.25; P=.33).

We also found significant univariate correlations between

coffee consumption and several factors associated with an un-healthy

lifestyle: daily total energy intake (P.001), amounts

of sugar and pastries consumed with coffee (P.001), and body

mass index (P=.02). Furthermore, smokers had a higher cof-fee

consumption compared with nonsmokers (3.8 [sD, 1.6] vs

3.3 [sD, 1.7] cups/d, respectively; P.001). We found no sig-

nificant relationship between coffee consumption and level of

physical activity.

Comment. As in previous studies,1 we found that excessive

coffee drinking was associated with other variables that sug-gest

an unhealthy lifestyle. After controlling for these vari-ables,

however, we found that both coffee and tea consump-tion

were related to improved insulin sensitivity. Given that

caffeine has been reported to impair insulin action,3 our data

suggest that other substances in these drinks are responsible

for our findings. For instance, both coffee and tea contain phe-nolic

compounds with antioxidant activity,4,5 which is rel-evant

because oxidative stress might promote insulin resis-tance.

2 It is possible that antioxidants in coffee could improve

insulin sensitivity, given that insulin sensitivity has been re-ported

to be associated with activity of antioxidants.6 Long-term

consumption of coffee might also result in acquired tol-erance

to caffeine, which could explain a different metabolic

effect compared with short-term use of caffeine.3

As use of sugar was independently associated with de-creased

insulin sensitivity, sugar may negate the benefits of cof-fee.

However, it is also possible that such moderate amounts

of sugar merely reflects other unmeasured aspects of an unfa-vorable

lifestyle, rather than an effect of sugar itself.

Our study has several limitations. First, the cross-sectional

design does not enable us to draw conclusions regarding

cause and effect. Furthermore, as we only examined white

men of a similar age, this study may have limited generaliz-ability

to women, and to other age and ethnic groups. How-ever,

the ULSAM cohort appears particularly suitable to inves-tigate

the present aim, as it is the largest sample in which

insulin sensitivity had been examined directly, together with

a reliable method used for determining coffee consumption

and additives.

The proposed antidiabetogenic effect of coffee 1 seems to in-volve

improved insulin sensitivity rather than improved beta-cell

function. Thus, it could be relevant to perform controlled

trials in insulin resistant individuals to investigate a potential

insulin-sensitizing effect of coffee.

1. van Dam RM, Feskens EJ. Coffee consumption and risk of type 2

diabetes melli-tus.

Lancet. 2002;360:1477-1478.

2. Riserus U, Basu S, Jovinge S, Fredrikson GN, Arnlov J, Vessby B.

Supplemen-tation

with conjugated linoleic acid causes isomer-dependent oxidative

stress and

elevated C-reactive protein: a potential link to fatty acid-induced

insulin resis-tance.

Circulation. 2002;106:1925-1929.

3. Greer F, Hudson R, Ross R, Graham T. Caffeine ingestion decreases

glucose

disposal during a hyperinsulinemic-euglycemic clamp in sedentary

humans. Dia-betes.

2001;50:2349-2354.

4. Natella F, Nardini M, Giannetti I, Dattilo C, Scaccini C. Coffee

drinking influ-ences

plasma antioxidant capacity in humans. J Agric Food Chem.

2002;50:6211-

6216.

5. Rietveld A, Wiseman S. Antioxidant effects of tea: evidence from

human clini-cal

trials. J Nutr. 2003;133:3285S-3292S.

6. Bruce CR, Carey AL, Hawley JA, Febbraio MA. Intramuscular heat

shock pro-tein

72 and heme oxygenase-1 mRNA are reduced in patients with type 2

diabe-tes:

evidence that insulin resistance is associated with a disturbed

antioxidant de-fense

mechanism. Diabetes. 2003;52:2338-2345.

Cheers, Al Pater.