This is one of the most common questions a doctor gets, with nothing short of terror in some patients’ voices.

Coffee is a fascinating substance, and there are varying genetic types in terms of how your body processes coffee.  Most people can generally be safe drinking 2 cups a day without any problem (though certain genetic types see a rise in cardiovascular events at more than 2 cups per day). But in terms of bone health there are a couple of considerations before giving coffee the seal of approval.

Generally speaking, any foods that you eat or drink that are acidic have the theoretical potential to cause bone loss. In order to understand this we will need a quick chemistry lesson:

An acid is a substance that donates hydrogen ions. Because of this, when an acidic substance like coffee enters the body, the balance between hydrogen ions and hydroxide ions is shifted. Now there are more hydrogen ions than hydroxide ions in the solution. This solution is acidic.

The opposite is a base substance, one that “soaks up” hydrogen ions. This kind of solution is alkaline.

Acid and base are measured in pH, in comparison to pure water. Pure water is neutral pH, in the middle, at 7. Black coffee is 100 times more acidic than pure water, and baking soda is 100 times more alkaline than pure water.

Our blood pH is very tightly regulated between 7.35 and 7.45. Blood pH regulation is one of the most tightly controlled numbers in our bodies. Calcium is also very tightly regulated. The strict regulation of both blood pH and calcium indicate how vital the right balances are to a well-functioning system.

Our bodies control the acid/base balance through the kidneys, lungs, and a buffer system. The kidneys excrete excess acids or bases as required for proper pH balance. The lungs release carbon dioxide, which is acidic. The pH of the blood increases – becomes more base – as breathing becomes faster and deeper. By adjusting the speed and depth of breathing, the brain and lungs are able to regulate the blood pH minute by minute.

The buffer system consists of acids and bases (carbonates and bicarbonates) on hand to balance out the blood as the body’s environment shifts from metabolic processes producing acidic waste.

There is a lot of debate about the acid/base situation and how it affects the body and the bones. It is not true that the blood will shift outside of its tightly regulated parameters. But it is true that the blood must regulate itself exactly because the system around it, our body, is influenced by the foods we eat and the environment we live in – affecting acidity or alkalinity.

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Western diets are generally high in acidic foods such as meat and grains – and coffee.

A diet of acidic foods can impose a high acidic load that can lead to a low level of metabolic acidosis.   At this point we will breathe out carbon dioxide, but the body might also draw calcium, which is alkaline, from the bones into the blood to help the buffer system counteract the acidic load.

When we look at one high quality study of 489 women published in the American Society of Clinical Nutrition, we find that caffeine does in fact increase the rate of bone loss – “Women with high caffeine intakes had significantly higher rates of bone loss at the spine than did those with low intakes.”

It was also noted in this study that women with a specific genetic variant in the Vitamin D receptor (the tt variant) were at greater risk for this deleterious effect.

It is only a correlation, and there may be other life style factors that go in hand with high coffee consumption that contribute to the bone loss.   But if we look at another high acidic load food that we eat a lot of, protein, we do not see bone loss necessarily but we do see increased calcium excretion. This paradox is  explained by the idea that although excess acid (protein in this case) load causes the body to pull calcium, the extra protein enhances bone growth.

So. It looks as if high coffee consumption may in fact impact bone mass. What’s a coffee lover to do?

First of all, you can ensure that you are helping your body stay in good health by eating a good variety of alkaline foods – vegetables, fruits and legumes. This will, among other things, balance the acidic foods.

It is also important to make sure you have sufficient minerals including calcium in your diet on a daily basis – then your body is less likely to draw calcium from your bones.

And directly, you can add chicory to your coffee. Chicory is alkaline, and also adds a delicious depth to the coffee, providing a natural balance to the acidity.