On the one hand is contains polyphenols that act like antioxidants, but on the other hand even two coffees a day raises markers of inflammation, including homocysteine which is an established indicator of dementia risk.
A major study involving almost 400,000 people in the UK’S Biobank shows that those having 6+ coffees a day, or three double expressos, have more than double the risk of dementia compared to 1 to 2 coffees a day. They also had increased brain shrinkage in the hippocampal region associated with Alzheimer’s. Why? Two studies in the Netherlands found that two coffees a day raise homocysteine, a toxic amino acid, by about 10%, while caffeine tablets without coffee increased it by 5%. It appears that it is mainly the caffeine content that is increasing risk. However, those having none, or only decaf, had very slightly higher, but not significant risk compared to those having 1 or 2 coffees. Much like alcohol especially red wine, a little may offer protection, a lot of increases risk.
Another study, again using UK Bio Bank data, found significant dose-dependent association beyond three cups/d coffee with dementia risk if those with degenerative nervous system disorders not related to dementia were removed from the analysis, while moderate-to-high tea intake was negatively associated with incident dementia therefore reducing risk.
Coffee does, however, have some plus sides. Four meta-analyses examining liver cancer, report a risk reduction of 38% in those who drank 2-3 cups of coffee per day and 41% in those who drank more than 4 cups. Drinking six cups of coffee a day, while bad for the brain, was shown to halve the risk of fatal prostate cancer, according to a study published in the Journal of the National Cancer Institute with each cup of coffee reducing overall prostate cancer risk by about 5%.
What’s the protective factor in coffee?
Exactly why coffee has these protective effects is a subject of much debate. While there is evidence that caffeine itself has benefits tea, which also contain caffeine, doesn’t show the same protective benefit for cancer. Paraxanthine, the main primary metabolite of caffeine, has been shown to slow down pre-cancerous liver cell growth, and in turn the progression of liver fibrosis, alcoholic cirrhosis and liver cancer. Chlorogenic acid, may reduce oxidative stress in the liver, in turn reducing the risk of fibrosis and development of cancers. There are about 1,000 different compounds in coffee.
Both caffeine and chlorogenic acid, however, raise homocysteine, which is a concern especially regarding Alzheimer’s risk.
Coffee may help protect against diabetes and weight gain.
Two studies have shown that coffee doesn’t cause the release of insulin, and may even reduce insulin resistance. 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, 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, the hormone that controls blood sugar levels, was almost halved.
Caffeine, hence coffee, is an addictive stimulant. If, for example, you can’t wake up without it, then you have a level of dependence probably due to ‘down-regulation’ of adrenalin receptors. In other words you’ve become adrenalin resistant in much the same way that we can become insulin resistant. Coffee can, in this sense, be an energy depleter, although the immediate effect is energy increase. I liken this to a wave hitting the shore. The latent energy we have is in the wave. As it crashes into the shore there’s an energy surge or release occurs, as it also does with caffeine, but the after-effect is energy depletion.
How coffee is decaffeinated makes a difference to both the taste and what’s left behind. Almost all decaf uses a chemical solvent. The exception are those that use the “swiss water” process which is used almost exclusively used for decaffeination of organic coffee. This is probably the best to choose if you like the taste of coffee but not the buzz.
If you want to know more about how you can support your brain, make sure you complete our free Cognitive Function Test here to give you your plan of action on how you can upgrade your own brain in the next 6 months.
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Food for the Brain is a non-for-profit educational and research charity that offers a free Cognitive Function Test and assesses your Dementia Risk Index to be able to advise you on how to dementia-proof your diet and lifestyle.
By completing the Cognitive Function Test you are joining our grassroots research initiative to find out what really works for preventing cognitive decline. We share our ongoing research results with you to help you make brain-friendly choices.
Please support our research by becoming a Friend of Food for the Brain.
1 Zhang Y, Yang H, Li S, Li WD, Wang Y. Consumption of coffee and tea and risk of developing stroke, dementia, and poststroke dementia: A cohort study in the UK Biobank. PLoS Med. 2021 Nov 16;18(11):e1003830. doi: 10.1371/journal.pmed.1003830. PMID: 34784347; PMCID: PMC8594796.
2 Schaefer SM, Kaiser A, Behrendt I, Eichner G, Fasshauer M. Association of Alcohol Types, Coffee, and Tea Intake with Risk of Dementia: Prospective Cohort Study of UK Biobank Participants. Brain Sciences. 2022; 12(3):360. https://doi.org/10.3390/brainsci12030360
3 Grubben MJ, Boers GH, Blom HJ, Broekhuizen R, de Jong R, van Rijt L, de Ruijter E, Swinkels DW, Nagengast FM, Katan MB. Unfiltered coffee increases plasma homocysteine concentrations in healthy volunteers: a randomized trial. Am J Clin Nutr. 2000 Feb;71(2):480-4. doi: 10.1093/ajcn/71.2.480. PMID: 10648261; 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; J. Geleijnse, ‘Habitual coffee consumption and blood pressure: An epidemiological perspective’, Vascular Health Risk Management, 2008 Oct; 4(5): 963–970;
4 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.
5 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; see also 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]
University of Guelph
6 Moisey LL, Kacker S, Bickerton AC, Robinson LE, Graham TE. Caffeinated coffee consumption impairs blood glucose homeostasis in response to high and low glycemic index meals in healthy men. Am J Clin Nutr. 2008 May;87(5):1254-61. doi: 10.1093/ajcn/87.5.1254. PMID: 18469247.
