Coffee Drinking Revisited: Recent research shows therapeutic benefits to consuming coffee

By Mark J. Smith, Ph.D. and Loren Cordain, Ph.D. Professor Emeritus, Colorado State University

Note: Read our latest thoughts on drinking coffee, Is Coffee Paleo?

Previous blogs at The Paleo Diet about coffee have not exactly given a glowing report for the common beverage.

However, the research on coffee is expanding rapidly with over seven percent of all studies on its health effects being published in the last year. A great deal of new research is pointing in the direction that previously unknown benefits may help outweigh the negatives, resulting in a potential zero-sum game for those having a hard time eliminating coffee from their daily regime. That being said, new research also continues to show negative effects.

From a Paleo perspective, a prudent action may be to continue placing coffee consumption in your 15%, non-Paleo category, and consider its elimination altogether if you have health issues that the research suggests could be caused by its consumption. This latter approach is effective whenever addressing the consumption of non-Paleo foods as it can help individuals stay compliant with the Paleo dietary template while eliminating problematic foods as needed. It’s also important to consider the source of your coffee. Obtaining your coffee from brewers that follow organic practices (and note that some can’t afford the certification but still do) helps eliminate some of the negatives while maintaining the positives.

Coffee drinking is one of the most ubiquitous dietary habits in the modern world. Enjoying a good cup of Java to start the morning is an accepted morning ritual in Western culture. Coffee provides a warming drink while giving you a good jolt of caffeine unless you drink decaf.

Over the years, coffee drinking and caffeine consumption have been critically examined by the medical and health community – is coffee good for our health? Bad for our health? Or does it have no effect? A search of the US National Library of Medicine using “coffee” reveals 12,320 research papers on the topic. Narrowing the search to the more appropriate term “coffee consumption” reduces the number of papers to 3,810. Over seven percent of these papers were published just in the last year.

One of the most powerful analytical tools scientists and epidemiologists have employed to answer complex nutritional questions over the past 20 years is meta-analyses. Meta-analyses are in essence an analysis of analyses. Statisticians have developed special procedures that allow them to analyze multiple studies even when the studies do not necessarily agree. Meta-analyses, therefore, unify the results of multiple studies and provide a powerful insight into the collective study results.

Because coffee drinking is such a widespread habit in the western world, thousands of research studies have examined its effects on our health and well-being and meta-analyses of these studies have recently appeared. Generally, they indicate coffee drinking has little or no adverse effects on our health, and may actually prevent disease^1-28. In fact, meta-analyses of all-cause mortality demonstrate that coffee consumption reduces the risk of death from all causes combined^1-4. Similarly, a meta-analysis of prospective, observational studies indicated that coffee drinking reduced the risk of oral, pharynx, liver, colon, prostate, endometrial, and melanoma cancers¹⁹ – a result that is consistent with other meta-analyses of specific cancers^11-23. Further, meta-analyses have shown potentially lowered health risks with coffee consumption for a variety of conditions including cardiovascular disease (CVD) risk^5-10, kidney disease²⁵, gout²⁴, urinary incontinence²⁷, and non-alcoholic liver disease²⁸. It may even increase longevity²⁶.

However, the picture becomes cloudier when another meta-analysis of seven randomized controlled trials showed that acute coffee ingestion reduces insulin sensitivity in healthy subjects²⁹ and a meta-analysis of prospective observational studies demonstrated that coffee consumption increases the risk for lung cancer³⁰. It is also important to recognize that meta-analyses derived from observational studies hold considerably less clout than those derived from randomized controlled trials or even single randomized controlled trials themselves. Consequently, a systematic review of epidemiological studies and randomized controlled trials of coffee consumption and sleep showing a deleterious effect has to be recognized as significant³¹. Further, acute coffee consumption impairs or worsens the glycemic response³², so along with the finding that acute coffee ingestion reduces insulin sensitivity²⁹, these studies are suggestive that coffee may alter normal glucose metabolism.

One of the issues with earlier research on coffee consumption was that it focused on caffeine. More recent research has expanded its focus to other prominent biologically active compounds, particularly the main polyphenols of coffee: chlorogenic acids (CGAs)³³. Perhaps the conflicting findings from the meta-analyses of coffee drinking can be attributed to the fact that dietary polyphenols are substrates for the microbiota in the colon³⁴. Key to maintaining gastrointestinal health is the interaction of these polyphenols and their metabolites with epithelial cells, as well as modulating gut microbial composition. In their review of polyphenols and the gut microbiota, Hervert-Hernández et. al. point out that “polyphenols may act as promoting factors of growth, proliferation, or survival for beneficial gut bacteria—mainly Lactobacillus strains—and thus, exerting prebiotic actions and inhibiting the proliferation of some pathogenic bacteria such as Salmonella and Helicobacter pylori species.”

The gut microbiome in human physiology is now one of the most important areas of research in human health and disease. Its complexity and individual variability is well established and so it should not be surprising that individuals could have a very different response to coffee consumption, containing a high polyphenol content, given an extremely varied microbiome from person to person. So perhaps coffee is only beneficial, and hence should only be consumed by, those with a healthy microbiome? Since a Paleo diet helps promote a healthy microbiome, those following the diet may well be the ones to benefit the most from a cup of Java.

Phenolic acids are the main polyphenols made by plants and recent research has also shown that these polyphenols help to lower lysophosphatidylcholines which are known to be a pathological component of oxidized-LDL as well as having pro-inflammatory properties³⁵. This demonstrates another potential health benefit of consuming coffee.

CGAs, independent of caffeine content, have also been shown to improve vascular function, in particular by increasing flow-mediated dilatation³⁶. The improvements appear to be directly related to the CGA content of the coffee, making the coffee bean roasting process all the more important.

Taking into consideration all of the research on coffee consumption, both positive and negative, it appears that based on individual responses, coffee can potentially be a healthy addition to one’s dietary template. That being said, for certain individuals, coffee may not represent a healthy option and one should assess the physiological response to its consumption on an individual basis. However, if one ultimately chooses to include coffee in their dietary plan, it makes sense to obtain coffee from roasters that utilize practices that maximize the quality of the coffee and the associated beneficial biologically active compounds.

References

All Cause Mortality

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[2] Grosso G, Micek A, Godos J, Sciacca S, Pajak A, Martínez-González MA, Giovannucci EL, Galvano F. Coffee consumption and risk of all-cause, cardiovascular, and cancer mortality in smokers and non-smokers: a dose-response meta-analysis. Eur J Epidemiol. 2016 Oct 3. [Epub ahead of print]

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Cardiovascular Disease

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Cancer

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Gout

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Kidney Disease

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Longevity

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Urinary Incontinence

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Non-Alcoholic Liver Disease

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No category

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