Black vs decaf: Does coffee affect blood sugar and insulin?

Research has shown that there are several beneficial effects of caffeine, such as improved attention, alertness and physical performance. A typical cup of coffee (240 ml) provides approximately 100 mg caffeine, although this amount can vary a lot. The European Food Safety Authority (EFSA) concluded that “habitual intakes of caffeine up to 400 mg per day do not give rise to safety concerns for non-pregnant adults.” So this means that up to four cups of coffee a day are safe for most people.

Caffeine keeps you awake by binding to adenosine receptors in the brain. It may alter the activity of neurotransmitters like dopamine and norepinephrine. In some individuals, however, there can be adverse effects, such as disturbed sleep patterns, tremors, increase in blood pressure, and heart rate/rhythm disturbances. These stimulatory effects tend to attenuate over time if we have coffee regularly and are more evident in occasional drinkers. However, those with pre-existing cardiac rhythm problems have to be particularly careful. Some may get “acidity” or heartburn with coffee. Women who are pregnant, trying to become pregnant or are breastfeeding also need to be cautious about caffeine.

Decaffeinated coffee is a good option if one is sensitive to caffeine. The decaffeination process removes 97 per cent or more of the caffeine. A typical cup of decaffeinated coffee has about 2 mg of caffeine (as opposed to 100 in a regular one).

Can coffee help people with diabetes?

A 2009 study with 40,000 participants showed that drinking three cups of coffee reduced the risk of developing Type 2 diabetes by 40 per cent. Another study showed that drinking three to four cups of coffee per day was associated with an approximately 25 per cent lower risk of developing Type 2 diabetes.

However, caffeinated coffee can impair insulin sensitivity in people with diabetes and raise blood sugar levels. One study showed that post-meal blood sugar was eight per cent higher when participants had 250 mg caffeine (equal to two cups of coffee) along with the meal. However, long-term consumption can lead to improvements in glucose metabolism.

Coffee Power Punch

Therefore, a good option for people with diabetes is to drink decaffeinated coffee — you get the benefits of antioxidants (polyphenols) and minerals (magnesium, chromium) without affecting insulin sensitivity.

Avoid adding sugar, cream or milk, else you will be increasing calories and fat and might offset any health benefits attributable to basic black coffee. Cappuccinos and lattes are not the best choices for people with diabetes.

If you have diabetes, it may be prudent to consider using decaffeinated coffee, although it is likely that two cups a day of regular black coffee will do you no harm.

Does coffee offer long-term health benefits?

Studies have shown a possible association between coffee and decreased mortality. A recent study published in BMC Public Health suggested that individuals who drink coffee and sit for over six hours daily have lower mortality rates than non-coffee drinkers who sit for similar periods. The study had a 13 year follow-up period.

Coffee has been shown to help with weight management due to its metabolism-boosting and appetite-suppressing qualities. Moderate coffee intake, between two and four cups a day, may offer some protection against Alzheimer’s disease, Parkinson’s disease, Type 2 diabetes, liver disease (including liver cancer), heart attack and stroke.

(Dr Mithal is chairman of endocrinology and diabetes at Max Healthcare)