The Truth about Coffee

Every day Britons drink 70 million cups of coffee – roughly two each per adult. Is it good or bad for you? Do coffee drinkers die young or live longer?

Many people get caught in the sugar, nicotine, caffeine trap, thinking this combination is good for energy. But in fact this combination feeds increasing fatigue, anxiety and weight gain. In my own research we surveyed over 55,000 people and found the two foods that most predict fatigue and stress are caffeinated drinks and sugary foods, both addictive substances. Many people become hooked on caffeine and sugar to keep going, gaining weight and losing health as a result.

But what are the long-term consequences? Do coffee drinkers live longer or die young? A study following the fate of almost 400,000 people found that, overall, coffee drinkers are more likely to die younger.(1) But is that a result of the coffee or associated habits? When the researchers adjusted for smoking, the risk of death actually reversed. Coffee drinkers tended to have a slightly lower risk of death, although the decreased risk didn’t consistently become greater the more coffee was drunk. Slightly less risk was observed for deaths due to heart disease, respiratory disease, stroke, diabetes, and infections, but not for deaths due to cancer.

Coffee, diabetes and weight

However, as far as diabetes is concerned you may be pleased to know that there is now enough evidence to show that coffee actually decreases risk. In fact there have been eighteen studies involving almost half a million people that show overall that coffee, decaffeinated coffee and tea do slightly reduce risk of diabetes.(2) There are various theories as to why this might be since having a lot of caffeine itself isn’t good for your health. Both tea and coffee are high in antioxidants, which is a potential benefit.

Two recent studies have shown that coffee doesn’t cause the release of insulin, and may even reduce insulin resistance.(3),(4) Interestingly, this effect is true for both coffee and decaf coffee, suggesting that it is isn’t the caffeine that reduces insulin resistance. In fact, decaf may even help keep insulin producing cells healthy.

Before you hit the coffee though, there’s something you need to know. Rather than reducing insulin resistance, if you combine coffee with a carb snack such as a croissant or a muffin, it has the opposite effect. To explore the consequence of this much loved combination researchers at Canada’s University of Guelph gave volunteers a carbohydrate snack, such as a croissant, muffin or toast, together with either a decaf or coffee. Those having the coffee/carb combo had triple the increase in blood sugar levels and insulin sensitivity was almost halved(5). This combination of high blood glucose levels and poor insulin function are a recipe for weight gain and increased diabetes risk because the excess blood glucose is dumped into storage as fat. This study shows that coffee with a carbohydrate snack is a dangerous combination. However, the decaf didn’t make a difference to the glycemic load of the snack.

One possible explanation for coffee’s protective effect is that it might help weight loss. There is some evidence for this but it’s not conclusive.(6) However, there is no question that having a coffee does tend to take the edge off hunger. This is because coffee promotes the release of the hormone glucagon, which helps raise glucose by breaking down glycogen. Coffee stimulates adrenal hormones and these, in turn, give you a burst of energy getting you ready to hunt. But, the trick is not to go hunting for sugar.

Coffee – good or bad for cancer?

While some studies have shown an increased incidence of pancreatic cancer with coffee consumption,(7) further studies have not shown such an association. Over the last decade considerable research has been done on the cancer-coffee link. Most of these studies have come to the conclusion that coffee is unlikely to increase the risk of any cancer, except possibly for bladder cancer.

Coffee may also reduce risk of fatal prostate cancer. Drinking six cups of coffee a day can half the risk of fatal prostate cancer, according to a study published in the Journal of the National Cancer Institute.(8) Dr Wilson from the Harvard School of Public Health surveyed 48,000 health professionals every four years for two decades, and found that in addition to the dramatic risk reduction for lethal forms of the disease, each cup of coffee reduced overall prostate cancer risk by about 5%. Decaf coffee produced a similar reduction, so the protection is likely to be related to non-caffeine compounds of coffee.

However, caffeine may increase symptoms of fibrocystic breast disease, a common but benign breast condition – a significant association was found in those drinking four or more cups a day.(9)

Coffee raises inflammation

Caffeine also raises levels of the stress hormones adrenalin and cortisol and also substances that reliably indicate inflammation, such as interleukin-6, TNF, C-reactive protein and homocysteine(10). A Greek study from 2004 that involved over 3,000 participants found that those consuming 200ml of coffee – two cups – had between 28 and 50 per cent higher levels of three kinds of inflammatory markers compared to non-coffee consumers.(11) It also raises blood pressure, although decaf does not.(12)

Coffee and Alzheimer’s

There’s no doubt that coffee raises homocysteine levels, which are strongly associated with increased risk of Alzheimer’s disease.

A group of doctors from the University Hospital Nijmegen tested the effects of coffee by assigning volunteers to drink a litre of unfiltered coffee a day – that’s about four cups – for two weeks. At the start of the two weeks their average H score was 12.8 µM, slightly above the national average of 10 to 11. At the end of the two weeks their H score was 14.(13)

A study by Dr Verhoef and co. at the Wageningen Centre for Food Sciences in the Netherlands showed that two cups of regular coffee increased homocysteine by 11% after only four hours, while caffeine tablets without coffee increased it by 5%. (14)

However, whether coffee drinking actually increases Alzheimer’s risk is not yet clear. There are studies pointing both ways.

In summary, the research does suggest that, if you are going to drink coffee it is best to do it on its own, without either a sweetener or carb snack, then wait at least 30 minutes before eating. Also, it is best to not overdo it, having perhaps one or two coffees a day at most. More than this is likely to make you more stressed and agitated.

Almost all the benefits of coffee are also reported for decaf, which eliminates a fair amount of the downsides. So, a decaf a day may actually help rather than hinder your health as far as diabetes and blood sugar control is concerned.


1. Neal D. Freedman et al., ‘Association of Coffee Drinking with Total and Cause-Specific Mortality’N Engl J Med 2012; 366:1891-1904May 17, 2012
2. R. Huxley et al., ‘Coffee, decaffeinated coffee, and tea consumption in relation to incident type 2 diabetes mellitus: a systematic review with meta-analysis’, Archives of Internal Medicine, 2009 Dec 14;169(22):2053-63
3. T. Wu et al., ‘Caffeinated coffee, decaffeinated coffee, and caffeine in relation to plasma C-peptide levels, a marker of insulin secretion, in U.S. women’, Diabetes Care, 2005 Jun; 28(6):1390-6
4. R. C. Loopstra-Masters et al., ‘Associations between the intake of caffeinated and decaffeinated coffee and measures of insulin sensitivity and beta cell function’, Diabetologia, 2010 Nov, [Epub ahead of print]
5. University of Guelph
6. J. A. Greenberg et al., ‘Coffee, diabetes, and weight control’ American Journal of Clinical Nutrition, 2006 Oct; 84(4):682-93.
7. ‘Food, Nutrition and the Prevention of Cancer’, World Cancer Research Fund, American Institute for Cancer Research (1997)
8. Wilson KM et al., ‘Coffee consumption and prostate cancer risk and progression in the Health Professionals Follow-up Study.’J Natl Cancer Inst. 2011 Jun 8;103(11):876-84.
9. K. Ishitani et al., ‘Caffeine consumption and the risk of breast cancer in a large prospective cohort of women’, Archives of Internal Medicine, 2008 Oct. 13;168(18):2022-31
10. D Panagiotakos et al,. ‘The Association Between Coffee Consumption and Plasma Total Homocysteine Levels: The ATTICA Study’, Heart Vessels, vol. 19(6), 2004, pp. 280-6
11. A. Zampelas et al., ‘Associations Between Coffee Consumption and Inflammatory Markers in Healthy Persons: The ATTICA Study’, American Journal of Clinical Nutrition, vol. 80(4), 2004, pp. 862-7
12. J. A. Greenberg et al., ‘Coffee, diabetes, and weight control’ American Journal of Clinical Nutrition, 2006 Oct; 84(4):682-93
13. J. Geleijnse, ‘Habitual coffee consumption and blood pressure: An epidemiological perspective’, Vascular Health Risk Management, 2008 Oct; 4(5): 963–970
14. P. Verhoef et al., ‘Contribution of caffeine to the homocysteine-raising effect of coffee: a randomized controlled trial in humans’, American Journal of Clinical Nutrition, 2002 Dec; 76(6): 1244-1248