Magnesium is a vital mineral that plays a role in over 300 biochemical reactions in the body, from nerve function to blood pressure regulation. While diet is the primary source, the magnesium found in drinking water, a key component of water hardness, offers a bioavailable and accessible way to boost intake. The amount considered 'good' in water depends on various factors, including water source, individual dietary needs, and potential health conditions.
Optimal Magnesium Levels in Water: What the Experts Say
For many years, the World Health Organization (WHO) has recognized the potential health benefits of magnesium and calcium in drinking water, especially concerning cardiovascular health. However, the WHO has not set an official guideline value for magnesium concentrations in drinking water, noting that sufficient evidence is still being collected to prove causality. Despite this, several regional and national standards offer guidance:
- Bottled and Dispensed Water: National sanitary standards in some countries consider optimal magnesium levels for bottled and dispensed water to be between 30 and 50 mg/L. A limit of 80 mg/L is often set.
- U.S. EPA Guidance: The U.S. Environmental Protection Agency (EPA) has recommended an ambient water quality standard of 35 mg/L, suggesting this level would provide a dose corresponding to approximately 20% of the estimated acceptable daily intake (ADI) for adults.
- Research Findings: Some researchers suggest that water with moderately high levels of magnesium (e.g., 10–100 mg/L) could potentially help prevent cardiovascular disease deaths, especially for those with low dietary intake.
Health Benefits of Magnesium in Water
The magnesium present in drinking water, particularly in harder water areas, has been associated with several positive health outcomes:
- Improved Cardiovascular Health: Studies have linked low levels of magnesium in water to higher rates of cardiovascular disease mortality. Magnesium helps regulate blood pressure and supports heart function. A 2022 study found that drinking water with higher magnesium concentrations was associated with a lower risk of stroke in postmenopausal women.
- Enhanced Bone Formation: Magnesium plays a critical role in the structural development of bone and influences hormones that regulate bone health, like parathyroid hormone and vitamin D.
- Migraine Prevention: Some studies suggest an association between magnesium deficiency and migraines. Supplementing with magnesium, potentially through water, may reduce the frequency and severity of attacks in some individuals.
- Type 2 Diabetes Management: Magnesium is involved in glucose metabolism. A diet rich in magnesium is associated with a lower likelihood of developing diabetes, and magnesium deficiency can impair insulin action.
- Better Sleep and Stress Reduction: Some evidence suggests that magnesium-enriched water can help improve sleep quality and reduce stress.
The Difference Between Hard and Soft Water
The magnesium and calcium content primarily determines whether water is considered hard or soft. As water flows over rock formations, it picks up these minerals. Below is a comparison of water types based on their mineral content.
| Water Type | Magnesium & Calcium Content (Approx.) | Typical Effects |
|---|---|---|
| Soft | < 60 mg/L | Low mineral content. Easy lathering with soap. May not contribute significantly to mineral intake. |
| Moderately Hard | 60–120 mg/L | Moderate mineral content. Balances mineral intake with minimal scaling. |
| Hard | 120–200 mg/L | Higher mineral content. Creates soap scum and limescale buildup. A good source of dietary minerals. |
| Very Hard | > 200 mg/L | Very high mineral content. Leads to significant limescale, potential bitter taste. |
Risks of Excessive Magnesium in Water
For healthy individuals with normal kidney function, the risk of magnesium toxicity from drinking water is low because the kidneys efficiently excrete any excess. However, there are a few points to consider:
- Laxative Effect: Magnesium salts, especially magnesium sulfate, are known for their laxative properties. Water with high concentrations of these salts can cause diarrhea, nausea, and abdominal cramping.
- Taste: Some sensitive individuals can detect the bitter taste of magnesium in water at concentrations as low as 80 mg/L or even lower.
- Health Conditions: Individuals with impaired kidney function should be cautious about high magnesium intake from any source, including water.
How to Check and Adjust Your Water's Magnesium Levels
If you are interested in the mineral content of your water, there are several ways to find out and adjust it:
- Test Your Water: Many local water utilities can provide information on your area's water hardness. At-home test kits are also available, or you can send a sample to a certified laboratory for detailed analysis.
- Use Water Filters: Standard water filters often remove contaminants but leave beneficial minerals like magnesium intact. However, some advanced systems, like reverse osmosis (RO), strip the water of almost all minerals.
- Remineralize Treated Water: For those using RO or distillation systems, special filters or mineral drops can be used to add magnesium back into the water.
Conclusion
While drinking water is not the primary source of dietary magnesium, it can provide a significant, bioavailable supplement to your overall mineral intake. Water with a moderate mineral content, typically considered hard, offers a great way to boost your magnesium without overdoing it. An optimal level of around 30–50 mg/L appears to provide health benefits without the risks associated with very high concentrations, such as a laxative effect. By understanding your water's hardness and using filters or remineralization techniques if necessary, you can ensure your daily hydration contributes positively to your nutritional needs.
For more detailed information on dietary magnesium, consider visiting the National Institutes of Health Fact Sheet on Magnesium.
