The main constituents of coffee are caffeine, polyphenols, diterpenoids and trace minerals. (1) Coffee is one of the most commonly consumed beverages worldwide. (2)
Is coffee beneficial to health? (General)
· 2 large cohort studies found that coffee consumption was associated with favourable profiles of several biomarkers in key metabolic and inflammatory pathways, including some that are specifically linked to cardiovascular disease (CVD). (1)
· An umbrella review of 201 meta-analyses found that coffee consumption was more often associated with BENEFIT than harm for a range of health outcomes and a range of exposures (including high versus low consumption, any versus none, and one extra cup a day). (3)
· 3 – 4 cups a day (versus no cups a day) was found to be associated with the largest relative risk reduction for all-cause mortality, cardiovascular mortality, and cardiovascular disease. (3)
POSITIVE HEALTH EFFECTS
Coffee, Type 2 Diabetes, and Metabolic Effects
Coffee consumption (up to as much as 7-9 cups a day) has been shown to decrease risk of developing Type 2 Diabetes. (2)
Mechanisms of action:
· Coffee enhances physiological functioning of the pancreatic beta cells.
· Coffee improves glucose tolerance. (2)
· Possible reduction in soft drink consumption as coffee consumption increases (hypothesis). (4)
· The caffeine and CGA (chlorogenic acid) in coffee effects insulin and glucose homeostasis via modulation of the adenosine receptor, signaling, inhibition of intestinal glucose absorption, reduction of hepatic glucose output, and improvement of pancreatic islet insulin secretion or peripheral insulin sensitivity and glucose uptake. (4)
· Coffee consumption may exert protective effects on T2D through stimulation of anti-inflammatory cytokines. (4)
· Recent data suggests that the effects of coffee on metabolic functioning, such as improved insulin signaling, glucose disposal, and reduced adiposity, might be linked to a reduction of oxidative stress and modulation of immune cell functions. There is also the possibility that these effects occur due to modulation of the microbiome. (4)
These findings are supported by a systematic review and meta-analysis (2018), which concluded that higher coffee consumption is associated with lower risk of developing type 2 diabetes. (4)
An RCT in overweight men with moderate-mild elevation of fasting plasma glucose demonstrated that 16 weeks of consumption of caffeinated coffee (5 cups/day) modestly improved waist circumference and decreased waist circumference. This effect only occurred with caffeinated coffee. (4)
Accumulating evidence suggests that habitual coffee consumption may contribute to better metabolic control by reducing oxidative damage, body fat mass, and caloric intake. (4)
Anti-Inflammatory Pathways and Coffee
Many of the health-related effects of coffee might be due to its effect of anti-inflammatory pathways. (1) Several studies show that high habitual intake of coffee prevents oxidative stress and blocks the activation and release of several pro-inflammatory cytokines. (4) Coffee contains several antioxidants and components that may help to reduce enzymatic and mitochondrial production of ROS (reactive oxygen species). (4)
Coffee and Cancer
High vs. low consumption was associated with 18% lower risk of the incidence of cancer. (3) The cafestol and kahweol (lipid components) of coffee beans have been shown to reduce colorectal cancer specifically, as they decrease genotoxicity and inhibit the cytochrome. (2)
Coffee and Parkinson’s Disease
Coffee consumption, even just one cup a day, has been shown to decrease the risk of developing Parkinson’s Disease. (2) There is evidence that coffee improves neuronal stability.
Does it have to be caffeinated to get these positive health benefits?
It depends which health effect you’re looking at … Many of the associations observed are similar for caffeinated and decaffeinated coffee, which suggests that other constituents of coffee are responsible for health effects. (1) This is not the case with reducing the risk of Type 2 Diabetes, where caffeinated coffee shows a much stronger protective effect. (4)
NEGATIVE HEALTH EFFECTS
Calcium and Caffeine
Caffeine is a naturally occurring purine alkaloid compound in the coffee bean. (2) Caffeine consumption is negatively associated with calcium levels. Just one cup a day has been shown to decrease levels of calcium in the body by 4-7mg, increasing risk of bone fractures. (2) This association between coffee drinking and increased risk of fracture is only seen in women, not men. (3)
Several proven risks shown for pregnant women or those trying to conceive.
· Higher intake of coffee (around 500-1000mg caffeine) has been associated with delayed conception for women. (2)
· In pregnant women, high consumption of coffee versus low/no consumption, was associated with low birth weight, preterm birth in the 1st and 2nd trimester, and mental retardation in offspring. (2, 3)
· Excessive intake has also been shown to increase the risk of spontaneous abortion. (2)
Coffee and Cholesterol Levels
Some studies have shown that excessive amounts of coffee consumption is strongly associated with the development of heart disease. (2) This is most likely due to its lipid component, called cafestol, which is found in the coffee oil. Cafestol is highest in Turkish and French coffees, and lowest in filtered coffee. (2) Cafestol increases the LDL, and overall cholesterol levels in the body, kicking off the process of coronary heart disease, stroke, cardiac arrhythmia, and hypertension. (2)
· Greater than 10 cups a day aggravated the process of heart attacks.
· 6-7 cups enhanced the severity of cardiac arrhythmia. (2)
Excessive Coffee Intake and Mineral Deficiencies
Excessive coffee intake has been associated with mineral deficiencies, particularly iron and zinc. This is caused by the phytates and polyphenols in the coffee beans, which inhibit the absorption and bioavailability of iron by 25-70% and zinc by 20-32%. (2)
Coffee and Sleep
An RCT of young adults showed a significant effect of caffeinated coffee consumption on sleep (not surprisingly!). The caffeinated group showed consistent decreases in the quality (40% decrease) and quantity (10% decrease) of their sleep. (5)
The average half-life of caffeine in a healthy individual’s plasma is 5 hours, although this can change dramatically between individuals. (6)
Coffee, Mood and Health-related Quality of Life
Caffeine has been shown (in RCTs) to directly and negatively impact participant’s mood and health-related quality of life (HRQL). This was especially strong for caffeine’s effect on anxiety and stress, with 3 out of 4 measures of anxiety showing significant increase during caffeine ‘treatment’ phase. (5)
This particular RCT also found a negative impact for caffeine on depression, but previous studies have found a positive or neutral effect. The discrepancy may be due to differences in caffeine dosage or the health of the sample population. (5)
Written by Clare Carrick as part of her 2020 internship with Wholefood Healing
1. El-Sohemy A. Coffee and health: what we still don't know.
2. Ahsan F, Bashir S. Coffee consumption: health perspectives and drawbacks. J Nutr Obes. 2019;2(1):1-4.
3. Poole R, Kennedy OJ, Roderick P, Fallowfield JA, Hayes PC, Parkes J. Coffee consumption and health: umbrella review of meta-analyses of multiple health outcomes. bmj. 2017 Nov 22;359.
4. Carlström M, Larsson SC. Coffee consumption and reduced risk of developing type 2 diabetes: a systematic review with meta-analysis. Nutrition reviews. 2018 Jun 1;76(6):395-417.
5. Distelberg BJ, Staack A, Elsen KD, Sabaté J. The effect of coffee and caffeine on mood, sleep, and health-related quality of life. Journal of Caffeine Research. 2017 Jun 1;7(2):59-70.
6. Vanderveen JE, Armstrong LE, Butterfield GE, Chenoweth WL, Dwyer JT, Fernstrom JD, Kanarek RB, Levander OA, Sternberg EM. Caffeine for the sustainment of mental task performance: formulations for military operations. National Academy, Washington, DC. 2001.