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Coffee: Black or leave room for milk?



Coffee has developed into an integral part of our day that it has even developed into a culture. But we need to ask ourselves about the health benefits and potential negative effects of caffeine, and other nutritional properties that come along with coffee. We're going to tackle a number of topics surrounding coffee, so stay tuned for multiple parts as we celebrate coffee this entire week!


The first question we ask is, do you take coffee black or take it with milk. Milk can have wonderful properties, but if we're interested in weight loss, we have to factor this as part of a caloric source.



Milk Misconceptions


So what do we have to say about milk, the major dairy product that many are avoiding? First off, milk is a complex food. This means that it has multiple nutritional properties that can be beneficial, and detrimental to one's health. Depending on the type of milk or dairy you are choosing, it may be high in saturated fats. Typically for milk-based espresso drinks, the default is to use a higher fat milk; so you can opt for a lower fat milk (2%, 1%, skim) for those of us who are more weight-conscious, or are minding saturated fat intake for cardiovascular health reasons. That being said, the fat in the milk is important in the process of vitamin D and calcium absorption; so the best compromise is to choose 1%.




Another concern for many are the hormones that are reported in milk and dairy products made from milk. There is no regulation against the use of rBST (recombinant bovine somatotropin) in the United States, which is where a lot of the controversy stems from. But, in Canada, growth hormones are actually banned for use in cows and bovine. So rest assured, the dairy produced in Canada are hormone-free.


Milk is also a source of protein. Though calorically, it might not be the most prominent macronutrient, milk is actually a well-balanced food. Think about it- if this is meant to keep young babies well-nourished, it must be very nutritious. If we keep milk and dairy products to a moderation, it is actually a very powerful food.


Black Coffee


Now, what about caffeine itself? Caffeine is a chemical structure that is extracted from coffee beans and dried tea leaves. One thing to note is that the longer the source of caffeine (coffee grind or tea leaves) come in contact with water, the more caffeine is extracted. There have been links to a few health factors revolving around caffeine. The most prominent negative links are related to hypertension and blood pressure, osteoporosis, and diuretic effects of coffee.



Caffeine and Blood Pressure

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.





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. The origin has to do with the basic mechanisms of our kidneys. Basically, if consumption of caffeine and phosphorus sources are increased, calcium may not be optimally reabsorbed back into the blood stream. This can compromise bone health. However, the results of studies revolving around caffeine and bone health is 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.




Diuretic effects of Caffeine

Actually, there is not an increase in diuresis (production of urine) with the consumption of 1-2 cups of coffee (~230mg caffeine). So with anything, keep coffee intake to a moderate amount. At doses higher than 240mg, there is some diuresis noted, but not to the point of dehydration. That being said, it is still a good idea to follow up a cup of coffee with a cup of water!


TL;DR

So what's the consensus for Coffee?

  • Caffeine does not increase average blood pressure long-term, or have negative effects on cardiovascular health. But if you are a "slow metabolizer" of caffeine, consider having less amount of caffeine in your daily routine.

  • Caffeine does not directly cause a decrease in bone mineral density, but is a much more complex process.

  • Caffeine does not have a significant diuretic effect.


Hope you enjoy a cuppa on National Coffee day!



References

  1. Cows and Hormones. Dairy Nutrition. Publish date unknown. [cited 2019 Sep 28]. https://www.dairynutrition.ca/facts-fallacies/product-quality/cows-and-hormones .

  2. W, Judelson DA, Watson G, Dias JC, et al. Fluid, electrolyte, and renal indices of hydration during 11 days of controlled caffeine consumption. Int J Sport Nutr Exerc Metab. 2005 Jun [cited 2019 Sep 28];15(3):252-65. Abstract available from: