Caffeine and Heart Health
There has been much talk regarding caffeine and its detrimental effects on cardiovascular health. With regards to blood pressure, the current evidence stands that 1–2 cups of coffee increases blood pressure (both systolic and diastolic) in the short term, for about 1–3 hours. However, evidence from the few long-term studies available shows no strong causal relationship between hypertension and caffeine consumption.
Taking genetics into consideration, the overall picture is much more complex than previously thought. A particular polymorphism (slight variations of a certain gene) may have drastically different effects in terms of how we process caffeine. Depending on the genetic variant we possess, we are categorized into “fast” or “slow” metabolizers of caffeine. Those who are “slow” metabolizers (AC or CC genotype of the CYP1A2 gene) are associated with more negative effects, including myocardial infarction, high blood pressure, and other cardiovascular-related issues. The extent of application to all ethnicities is yet to be determined, but the research seems promising for the time being.
Diuresis and Hydration Status
From the studies currently available, it appears that at low doses of caffeine, diuresis (i.e. increased urination) does not occur. At doses above 240 mg, there was some diuresis noted in some individuals. Unfortunately, no conclusion can be made regarding dehydration resulting from caffeine consumption.
To keep overall hydration status in check, a friend of mine shared an interesting habit when drinking coffee: she drinks a cup of water for every cup of coffee she has, in addition to her normal water intake. While there is no evidence regarding this practice, it does give a more mindful approach to how much caffeine and water intake one has daily.
Caffeine and Bone Health
Coffee has often been claimed as the culprit of osteoporosis and poor bone health. Like most other claims, quotes were taken out of context. Consider Renal Physiology 101: When one type of ion is found in higher levels in the blood, it possesses a competitive advantage over other ions. As a result, the latter gets inhibited from being reabsorbed back into the blood stream at the renal level. With this mechanism in mind, if consumption of caffeine and phosphorus sources are increased, calcium may not be optimally reabsorbed back into the blood stream, thereby compromising bone health. However, when comparing studies more closely, the data appears to be inconsistent.
Many other factors determine bone health and bone mineral density (BMD), and these need to be considered. For instance, the cause may not be caffeine intake alone, but more importantly the lack of calcium-rich beverages (such as milk or plant-based alternatives) from the overall diet. Changes in physical activity, as well as other factors leading to hormone imbalance can also affect BMD and risk for osteoporosis.
Finally, there is no adverse effects on bone health and calcium balance if intake of caffeine is below 400 mg/day, and as long as calcium intake is adequate.
Tolerance and Withdrawal Symptoms
Tolerance to drugs is built with chronic use of the drug, as a way for our body to more efficiently process the chemical. Similarly, tolerance to caffeine is built with regular intake of the substance, even in small amounts of 100 mg/day. This may result in withdrawal symptoms, such as headaches, upon removal of caffeine from the diet.
Current recommendations
From Dietitians of Canada
- For children:
- Age 12 and under: < 2.5 mg of caffeine per kg of body weight
- Age 4–6: < 45 mg of caffeine/day
- Age 7–9: < 62 mg of caffeine/day
- Age 10–12: < 85 mg of caffeine/day
- For women of childbearing age: < 300 mg of caffeine/day
- For healthy adults: < 400 mg of caffeine/day (equivalent to roughly 2 cups of filtered coffee, or 3 cups of brewed coffee)
Is the world running out of coffee?
Recently, I came across articles online discussing the current shortage of coffee (much to my horror). Climate changes affect coffee yield, and while the demand for and consumption of coffee have dramatically increased, drought is said to be a significant cause in Brazil’s decrease in coffee bean production.
End Note
Coffee is a true love of mine, and I hope you that you learned something new and interesting about it from this comprehensive series. If you have any questions or suggestions for great cafés in whatever part of the world you’re in, I’d love to hear about them: karen@athoughtfulmeal.com.
For myself, I like to limit espresso drinks to maximum 1–2/day. I also try to increase my water intake and not let coffee substitute for any beverage I normally incorporate in my day.
References
Dietitians of Canada. Caffeine. In: Practice-based Evidence in Nutrition [PEN]. 2015–08–19[cited 2016–02–20] Available from:http://www.pennutrition.com. Access only by subscription.
Da Costa LA. 2011. of Caffeine Consumption and Risk of Myocardial Infarction. Graduate Department of Nutritional Sciences, University of Toronto.
Dietitians of Canada. In: Does caffeine stimulate diuresis and negatively impact fluid balance among healthy adults? [PEN}. 2012–10–22 Available from:http://www.pennutrition.com. Access only by subscription.
Office of the Surgeon General (US). Bone Health and Osteoporosis: A Report of the Surgeon General. Rockville (MD): Office of the Surgeon General (US); 2004. 6, Determinants of Bone Health. Available from http://www.ncbi.nlm.nih.gov/books/NBK45513/
Dietitians of Canada. Bone Health: Is the consumption of coffee detrimental to bone health?. In: Practice-based Evidence in Nutrition [PEN]. 2011–02–13[cited 2016–03–12] Available from:http://www.pennutrition.com. Access only by subscription.
Dietitians of Canada. Caffeine Background. In: Practice-based Evidence in Nutrition [PEN]. 2013–03–06[cited 2016–02–22] Available from:http://www.pennutrition.com. Access only by subscription.
Dietitians of Canada. Caffeine and Health. [cited 2016–02–02] Available from http://www.dietitians.ca/Dietitians-Views/Food-Regulation-and-Labelling/Caffeine-and-Health.aspx
Gizmodo. A World Coffee Shortage Is Inevitable. 2015–12–21[cited 2016–02–23]. Available from http://gizmodo.com/a-world-coffee-shortage-is-inevitable-1749113494.
Bloomberg. Global Coffee Shortage Looms as Market Braces for Climate Change. 2015–10–01[cited 2016–02–23]. Available from http://www.bloomberg.com/news/articles/2015-10-01/global-coffee-shortage-looms-as-market-braces-for-climate-change