Understanding Calcium and Drinking Water
Calcium is a vital mineral required for bone strength, nerve function, and muscle regulation. While dairy products and fortified foods are well-known sources, drinking water can also provide a calorie-free source of this essential mineral. The degree to which drinking water can increase your calcium intake depends heavily on the water's mineral content, which varies based on its source and how it's treated. Hard water, for instance, is naturally rich in calcium and magnesium, while purified water contains negligible amounts.
The Role of Hard Water
Water's hardness is primarily determined by its calcium and magnesium concentration. As rainwater travels through mineral-rich rock formations like limestone, it dissolves these minerals, carrying them into aquifers that serve as drinking water sources. Consequently, residents in areas with hard water consume a constant, albeit variable, supply of naturally occurring calcium. Some studies suggest that the calcium from hard water can contribute a meaningful portion of the recommended daily intake, particularly for those with low dietary calcium.
Comparing Tap, Mineral, and Purified Water
- Tap Water (Municipal): Calcium levels in tap water are highly dependent on the local source and treatment process. For example, surveys in the U.S. and Canada have found tap water calcium levels ranging from negligible amounts up to over 130 mg/L. For most people, tap water provides a modest, but not negligible, daily calcium intake.
- Mineral Water (Bottled): As the name suggests, mineral waters often have a much higher and more consistent mineral content than tap water. Some brands, particularly those labeled 'calcium-rich' (over 150 mg/L), can deliver a significant boost to your daily calcium intake. Studies show that the calcium in mineral water is highly bioavailable, meaning the body absorbs it efficiently.
- Purified Water (Bottled): Processes like reverse osmosis, used to create purified water, remove almost all minerals, including calcium. For individuals relying on purified water, this source contributes virtually no calcium to their diet.
How Bioavailable is Water Calcium?
Research has shown that the calcium dissolved in water is readily absorbed by the body, often with a bioavailability comparable to, or even better than, dairy products. The efficiency of absorption is influenced by the low concentration and the ionic form of calcium in water, which contrasts with the solid-state calcium in many foods and supplements. Spreading calcium intake throughout the day via drinking water can also optimize absorption.
The Broader Picture: Hydration and Bone Health
While the calcium content of your water is relevant, proper hydration is even more critical for overall bone health. Healthy bones are approximately one-third water, and proper hydration supports bone remodeling and nutrient transport. Dehydration can trigger an increase in parathyroid hormone (PTH), which leads to calcium being leached from the bones into the bloodstream to maintain balance. Conversely, adequate water intake is necessary for calcium absorption and for flushing toxins from the body that could otherwise accumulate in bones and joints.
Water Type vs. Calcium Intake: A Comparison
| Feature | Hard Tap Water | Mineral Water | Purified Water | Whole Milk (for comparison) |
|---|---|---|---|---|
| Typical Calcium (mg/L) | 50-150 mg/L | >150 mg/L (some brands) | Negligible (<10 mg/L) | ~300 mg/240 mL (cup) |
| Consistency | Varies regionally and seasonally | Consistent by brand and source | Consistently low | Consistent by product |
| Contribution to RDA | Minor to moderate | Can be significant | None | Significant |
| Bioavailability | Good | Good, often comparable to milk | N/A | Good |
| Considerations | Can cause limescale buildup in appliances | Costs more and comes in plastic bottles | Can have low pH and strip pipes | Contains calories and potential allergens |
Conclusion
To answer the question, yes, drinking water can increase your calcium intake, but the extent of this increase depends entirely on the type of water you consume. Hard tap water and, more significantly, calcium-rich mineral water can contribute to your daily needs. However, purified water offers no calcium benefits. For most people, dietary sources like dairy and leafy greens remain the primary way to meet daily calcium recommendations. Nevertheless, staying properly hydrated with mineralized water is an excellent, calorie-free strategy to supplement your diet and support overall bone health. For those with low dietary calcium or conditions like lactose intolerance, choosing a high-calcium mineral water can be a valuable part of their nutritional plan. The key takeaway is that both hydration and mineral intake are essential for strong bones, and your choice of water plays a supportive role.
For more information on bone health, consult the National Institutes of Health on osteoporosis and other related topics.
