Does coffee leach calcium out of the body? Understanding the connection

October 10, 2025 •

4 min read

According to a 2021 study, consuming high doses of caffeine (800 mg over six hours) nearly doubled the amount of calcium excreted in urine. While this finding might seem alarming, the question of whether coffee leaches calcium out of the body has a much more complex answer rooted in moderation and individual diet.

Quick Summary

Moderate coffee intake has a negligible effect on overall calcium balance in individuals with adequate dietary intake. While caffeine can slightly increase urinary calcium excretion, the body compensates. High consumption, however, may pose a risk, especially for those with low calcium levels or pre-existing bone density issues.

Key Points

Moderate Consumption is Safe: For most healthy adults, enjoying 2-3 cups of coffee daily does not negatively impact bone health, provided dietary calcium is sufficient.
Excess Caffeine Increases Excretion: High doses of caffeine, typically over 400 mg daily, have been shown to increase urinary calcium loss.
The Body Compensates: The human body is equipped to compensate for the minor, temporary calcium losses associated with moderate caffeine intake.
Dietary Calcium is Key: The potential negative effect of caffeine is far more pronounced when overall dietary calcium intake is already low.
At-Risk Individuals Need Caution: Postmenopausal women and those with pre-existing low calcium levels are more susceptible to the potential bone-density impacts of high caffeine.
Add Milk to Offset Loss: Simply adding a small amount of milk (1-2 tablespoons) to your coffee can effectively counteract the minimal amount of calcium lost.
Conflicting Research Exists: Due to confounding variables, studies on coffee and bone health have yielded mixed results, emphasizing the importance of considering overall lifestyle rather than focusing solely on coffee intake.

The Caffeine-Calcium Connection: Fact vs. Fiction

For years, a persistent health myth has suggested that coffee is detrimental to bone health because it actively 'leaches' calcium from the body. The truth is far more nuanced. Caffeine, the primary active ingredient in coffee, is a mild diuretic that can cause a small, short-term increase in urinary calcium excretion. Additionally, some studies suggest it may slightly inhibit intestinal calcium absorption. However, the net effect of moderate coffee intake on overall calcium balance in healthy individuals with a sufficient diet is minimal.

How Caffeine Affects Calcium Metabolism

Caffeine interacts with calcium metabolism in a few key ways. The diuretic effect is the most understood, causing the kidneys to flush out slightly more calcium in the hours immediately following consumption. For context, one cup of coffee is estimated to cause a loss of only 2 to 4 mg of calcium—a negligible amount compared to the 300 mg in a single cup of milk.

Furthermore, research indicates that caffeine may affect the body's use of vitamin D. Since vitamin D is crucial for absorbing calcium from the gut, this interference could theoretically impact calcium levels. However, as with other effects, the significance of this interaction is minimal with moderate caffeine consumption and adequate vitamin D intake.

The Role of Dietary Calcium

Perhaps the most important factor in the coffee-calcium relationship is a person's overall dietary calcium intake. The transient increase in calcium excretion from a few cups of coffee is easily compensated for by the body, especially when dietary calcium is abundant. A problem only arises when high caffeine consumption is paired with a consistently low calcium diet over many years, as the body's compensatory mechanisms may not be enough to prevent long-term bone density loss. This is particularly relevant for individuals who skip dairy or other calcium-rich foods.

Research Findings: A Mixed Bag

Scientific studies on coffee and bone health have presented a range of conclusions, which has contributed to the ongoing confusion. Some large observational studies, and even recent meta-analyses, show a surprising inverse relationship or no negative association at all.

Studies on Bone Density

A 2024 meta-analysis found that coffee consumption was associated with a reduced risk of osteoporosis. Another study published in 2024 suggested that moderate habitual coffee intake (≤ 2 cups per day) had a protective effect against osteopenia and osteoporosis in older adults. However, it's worth noting that many studies on this topic are observational and depend heavily on self-reported dietary habits, making it challenging to isolate the effect of coffee from other lifestyle factors.

Epidemiological vs. Controlled Studies

There is a notable difference between short-term controlled studies and long-term epidemiological ones. Controlled studies, like the University of South Australia research, can precisely measure the acute effects of caffeine, confirming the increase in urinary calcium. In contrast, large epidemiological studies track populations over time and consider a wider array of lifestyle variables. Their findings often suggest that the moderate consumption of coffee is either neutral or even beneficial to bone health. These conflicting results highlight the complexity of isolating a single factor in a person's diet and lifestyle.

Impact on Different Demographics

The effect of coffee on calcium and bone health is not universal and can be significantly influenced by individual factors such as age, genetics, and menopausal status.

Postmenopausal Women

Postmenopausal women are one of the groups most at risk for osteoporosis due to declining estrogen levels, and some studies have shown they may be more susceptible to the negative effects of caffeine. A study on elderly postmenopausal women found that those with a high caffeine intake (>300 mg/day) and a specific vitamin D receptor (VDR) genotype experienced higher rates of bone loss at the spine. However, for women with adequate calcium intake, the effect was found to be minimal or non-existent.

Other At-Risk Groups

Teenagers: Adolescence is a crucial period for bone development and calcium deposition. Binge-consuming energy drinks or other high-caffeine beverages during this time could pose a risk if paired with a poor diet.
The Elderly: Older individuals, particularly those with low calcium intakes, may not compensate as effectively for caffeine-induced calcium losses.
Individuals with Low Dietary Calcium: Those who regularly consume less than the recommended daily allowance of calcium are at higher risk of their bone health being negatively impacted by high caffeine intake.

Comparison of Coffee Intake and its Effects


Factor	Moderate Coffee Consumption	High Coffee Consumption
Daily Intake (Approx.)	2–3 cups (up to ~300 mg caffeine)	>4 cups (over ~400 mg caffeine)
Effect on Urinary Calcium	Small, temporary increase in excretion.	Larger, more significant increase in excretion.
Impact on Absorption	Minimal impact on intestinal absorption.	Slight reduction in intestinal absorption efficiency.
Net Calcium Balance	Balanced and typically unaffected in healthy adults with adequate calcium intake.	Potential for negative calcium balance, especially with low dietary intake.
Risk to Bone Density	Low to none, especially when calcium intake is sufficient.	Possible long-term risk of accelerated bone loss, particularly in susceptible populations.

Conclusion: So, does coffee leach calcium out of the body?

In conclusion, the claim that coffee leaches calcium out of the body is largely a myth in the context of moderate consumption and adequate dietary calcium. While the caffeine in coffee does cause a small, transient increase in urinary calcium excretion, this is typically offset by the body's natural compensatory mechanisms. The potential for negative effects on bone density is primarily a concern for individuals with very high caffeine intake (over 400 mg/day) or those with consistently low calcium consumption, particularly postmenopausal women and other at-risk groups. To protect bone health while enjoying coffee, focus on maintaining a diet rich in calcium and vitamin D, and consider adding milk to your brew. For more detailed information on a specific study related to this topic, you can refer to this University of South Australia study.

Frequently Asked Questions

Since the effect of coffee on calcium is primarily linked to its caffeine content, decaffeinated coffee is considered to have a negligible, if any, impact on calcium absorption and excretion.

For a standard cup of coffee, the amount of calcium lost is very small, estimated to be only about 2 to 4 milligrams. This is a negligible amount for most people, especially when compared to dietary sources of calcium.

High coffee consumption is considered a potential risk factor, but it is not a direct cause of osteoporosis. The risk is mainly associated with high intake combined with insufficient dietary calcium, particularly in susceptible individuals like postmenopausal women.

No, the effect can vary. Factors like genetics (e.g., VDR genotype), age, gender, and pre-existing bone density status can influence how much a person is affected by caffeine's impact on calcium metabolism.

Moderate coffee consumption is generally defined as around 2 to 3 cups per day, which is approximately 300 mg of caffeine. For most healthy adults, this amount does not pose a significant risk to bone health when calcium intake is adequate.

The most effective way is to ensure you meet your daily calcium requirements, typically by consuming 1,000 to 1,200 mg per day through diet. Adding milk or a calcium-fortified alternative to your coffee is a simple way to help offset any minor losses.

Yes, the caffeine in other beverages like tea, sodas, and energy drinks can also have a similar, albeit potentially smaller, diuretic effect that leads to minor calcium loss.