Coffee is probably the most popular daily beverage in the world and at the current rate of consumption might even supersede tea in a few years time. The health benefits of coffee seems to be a growing portfolio of research. We know that coffee consumption has been associated with a lower risk of multiple health outcomes. Checking the various research papers for the benefits of various foods, it is often possible to see a new study regarding coffee on nearly every check.
Coffee is a brewed drink. It is prepared from roasted coffee beans which are taken from berries of two species of plant. The two main species are Coffea arabica and C. robusta. They are grown generally throughout the sub-tropical regions of the world.
It may also be the most researched foodstuff in the world because of the wide range of health benefits. Indeed, it was not that long ago that coffee was considered a health hazard because of the association with increased levels of arthritis and even cancer. Now, the World Health Organization (WHO) will be removing it from the list of possible carcinogens.
The Key Component- Caffeine
The main and perhaps most important compound in coffee is caffeine. It is a mild CNS (central nervous system) stimulant and is part of the group of compounds known as the methylxanthines. Caffeine is also found in tea and many of the health benefits associated through this compound are common to both coffee and tea. The caffeine content in both beverages depends mainly on its content in plants and how the ingredients for the beverage are prepared.
The potential health benefits associated with coffee drinking are mainly on these particular topics:-
- Mental alertness
- Energy and metabolism
- Cardiovascular disease (heart attacks, heart failure, strokes)
- Type 2 diabetes
- Liver disease
- Liver cancer
- Uterine and bowel diseases
- Parkinson’s disease
- Lowering adiposity
Large-scale studies indicate that coffee consumption is associated in a general way with reduction in mortality on a number of fronts. One study set out to established whether caffeinated or decaffeinated coffee was influential on death levels in both sexes (Ding et al., 2015). The study was based on total and cause-specific mortality among 74 890 women in the Nurses’ Health Study (NHS), 93 054 women in the Nurses’ Health Study II, and 40 557 men in the Health Professionals Follow-up Study. The results bore scrutiny based on the large number of participants and the prospect of high levels of statistical significance. The conclusion: drinking coffee albeit caffeinated or not was associated with a lower risk of death. Not all studies are so positive because one found that heavy coffee drinking was associated with an increased risk of death (Liu et al., 2013).
Effect on Metabolism
Coffee drinking has long been associated with raising metabolism which in turn has helped many to reduce their body fat. It appears that raising metabolism helps to burn fat off quicker which implies that weight loss is faster assuming all other aspects of diet and exercise are kept constant (Koot & Deurenberg, 1995). The effect is linked to caffeine which stimulates the nervous system. In that process, fat cells are broken down. However, not all effects are necessarily due to coffee.
One study (Muhammad et al., 2019) suggests that in a population in Indonesia, there was a relationship between coffee drinking and a reduction in body fat characterised as adiposity. However, this was independent of total caffeine intake. There was also an association with a certain gene for the production of uncoupling protein 2 (UCP2).
Effect on Adiposity And Fat Distribution
A recent study in the Journal of Nutrition (Cao et al., 2020) has revealed that higher coffee consumption is associated with a lowering in levels of body fat. The distribution of this body fat is also influenced by how much coffee is drunk. The one caveat is there appears to be a gender-related aspect to this.
Women seem to benefit more if they drink two or three cups of coffee. They were found to have lower levels of total body and abdominal fat than those women who did not drink so much.
The study looked at data from the famous NHANES (National Health and Nutrition Examination Survey) study. The participants filled in Food Frequency Questionnaires which included coffee consumption. As well as categorising the levels of coffee drunk, respondents also assessed caffeinated and decaffeinated coffee. Trunk fat and total fat percentage and the level of distribution were measured via whole-body DXA scans.
The dose-response relationship is more evident in women than men when it comes to fat distribution. In women, there was a strong association between the amount of coffee consumed and a reduction in body fat.
Generally, there was nearly a 3 per cent reduction in total body fat amongst women when they drank between two and three cups of coffee daily. It did not matter whether it was caffeinated or decaffeinated, whether they smoked or not or suffered chronic disease or were in great health.
Only in men aged between 20 and 44 years of age who drank a similar number of cups of coffee daily, was there any reduction in their general body fat. They showed a reduction of 1.3 per cent in total fat and 1.8 per cent less trunk fat.
It suggests that amongst other benefits, drinking coffee could be a valuable nutritional tool in dieting. The authors speculate that:
“It could be that coffee, or its effective ingredients, could be integrated into a healthy diet strategy to reduce the burden of chronic conditions related to the obesity epidemic.”
Effects On Metabolic Syndrome
Metabolic Syndrome (MetS) is an umbrella term for many conditions including diabetes, obesity and high blood pressure which all impact on general well-being. Most especially, there is an increase in the risk of heart disease.
Research in 2019 by scientists at the universities of Navarre in Spain and Catania in Italy have found a strong association between drinking coffee and metabolic syndrome. This research was conducted independently of each other but commissioned by the Institute for Scientific Information on Coffee. The body is supported by all the major European coffee producers such as Jacobs Douwe Egberts, illycaffe, Nestle, Lavazza, Paulig and Tchibo.
It appears that drinking between one and four cups of coffee can reduce the risk of conditions developing such as diabetes type-2, hypertension (high blood pressure) and thus reduce heart disease. Just drinking between three and four cups daily could lower the risk of these conditions by the order of 25 per cent.
Perhaps what is most interesting is that decaffeinated coffee has some of these health benefits too. That suggests that something else other than caffeine is responsible. As we have often discussed elsewhere, it is most likely to be the polyphenols in coffee which are responsible. It is full of polyphenolic acids and flavonoids.
Effects on Diabetes
As we have already mentioned in reference to coffee drinking and metabolic syndrome, there are some specific pieces of research that look at diabetes generally.
A number of studies now show a strong association with protection against type 2 diabetes. One large study published in Diabetes Care in 2015 showed there was a strong association with coffee consumption and a reduction in type-2 diabetes. The association was dose responsive indicating that the more that was drunk, the lower the risk of developing diabetes (Ding et al., 2014).
One of the more interesting aspects is research that has examined the role of filtered coffee. Scientists at Umeå University found that consuming filtered coffee may be better at reducing the risk of type 2 diabetes when compared to drinking boiled coffee (Shi et al., 2019). The research team looked at various levels of metabolites produced depending on the type of coffee they produced.
A filter coffee is one where hot water is poured over ground beans sitting on a filter. A boiled coffee is one where boiling water is added to ground beans in a cup. Boiled coffee appears to have some similarity with that made in a cafetière, espresso machine or percolator.
The hypothesis was that filtering the coffee would positively affect the level and type of metabolite produced or entering people drinking it. Professor Rikard Landberg, Professor in Food Science at Chalmers, and Affiliated Professor at the Department of Public Health and Clinical Medicine at Umeå University, said:
“We have identified specific molecules – ‘biomarkers’ – in the blood of those taking part in the study, which indicate the intake of different sorts of coffee.
“These biomarkers are then used for analysis when calculating type 2 diabetes risk. Our results now clearly show that filtered coffee has a positive effect in terms of reducing the risk of developing type 2 diabetes. But boiled coffee does not have this effect.”
Based on the results of these biomarkers, those people drinking between 2 and 3 cups of filtered coffee per day had a 60% lower chance of being diagnosed with type 2 diabyteses compared to those drinking just one cup.
Boiled coffee appears to have little if no impact on reducing the risk of diabetes. However the researchers have the caveat that an absence of association is affected by the low numbers of consumers of boiled coffee followed in this study.
Particular types of molecules that may be influential are the diterpenes which have been associated with cardiovascular disease. Professor Landberg also stated:
“It has been shown that when you filter coffee, the diterpenes are captured in the filter. As a result, you get the health benefits of the many other molecules present, such as different phenolic substances. In moderate amounts, caffeine also has positive health effects.”
The team will now examine the role of diterpenes on glucose metabolism and how they influence diabetes risk.
Effect on Parkinson’s Disease
A US study examined the associated between coffee drinking and the development of Parkinson’s disease (Ross et al., 2000). The disease affects at least 3% of the US population over 65 years of age. Treating Parkinson’s is becoming ever more important because this percentage might double in 30 years time. That study indicated that drinking coffee was associated with a significantly lower incidence of the disease. The association was suggested to be through the action of caffeine.
Effect on Liver Disease
Coffee drinking may well lower the risk of developing cirrhosis of the liver, especially in alcohol drinkers, by 22%. This was a study by the Kaiser Permanente Medical Care Program, California, USA. The main conclusion was that a specific compound in coffee was responsible for protecting the liver from the debilitating effects of alcohol induced cirrhosis. It was not clear if other forms of cirrhosis were also positively affected but none the less it has spawned a number of research studies.
Effect on Liver Cancer
Hepatocellular carcinoma (HCC) which is one of the main forms cancer in the liver claims many lives. In one study, the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC Study), nearly 111,000 people were assessed in terms of their coffee intake and the development of HCC (Kurozawa et al., 2005). All participants were between ages 40 and 79. A number of other factors such as gender, age, presence of other diseases and conditions like diabetes, alcohol consumption and smoking habits were taken into account. The overriding finding was an inverse association between coffee consumption and death from HCC.
Effect on Endometrial Cancer
Following a number of studies which indicated that there was an association of sorts between coffee drinking and the development of endometrial cancer, one large meta-analysis appears to provide firmer evidence for a positive benefit of coffee in this regard (Je and Giovannucci, 2012).
Effect on Lethal Prostate Cancer
A study of nearly 48,000 men in the Health Professionals Follow-up Study showed that there was strong inverse association with coffee consumption and the development of lethal prostate cancer (Wilson et al., 2011). Interestingly, the association was linked not to caffeine but the presence of non-caffeine compounds.
There is also an association with a reduction in basal cell carcinoma (Song et al., 2012) and melanoma (Loftfield et al., 2015).
Underlying Mechanisms For Benefits
At the molecular level, there has been little evidence until relatively recently as to the mechanisms underlying the reason for coffee’s efficacy. One area of interest is the effect of coffee consumption and the regulation of hormonal levels particularly in relation to reducing the risk of diabetes.
Research at the UCLA showed that coffee consumption can increase the plasma levels of an important sex hormone called SHBG (sex hormone-binding globulin) (Ferrini and Barrett–Connor, 1996; Goto et al., 2010). This protein regulates the biochemistry of the two main sex hormones used by humans which are testosterone and oestrogen. These two hormones in concert with other metabolic hormones are involved in the development of Type-2 diabetes. Drinking coffee is directly associated with a reduction in levels of estrogen (oestrogen) because of the effect on increased circulating levels of SHBG. It has also been shown to reduce the levels of C-peptide which is a marker of insulin secretion and plasma adiponectin which is an insulin sensitizer.
Issues With Coffee Drinking
Drinking can affect sleep and create what some call a jittery sensation and even anxiety. It is also a diuretic which means that frequent urination is an issue. Some people who drink significant amounts suffer palpitations.
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3rd February 2020. Revised to include recent research from Sweden on the association of filtered versus boiled coffee on reducing the risk of diabetes.