Not everything in your water is there to harm you. Hard water — water with high dissolved mineral content, primarily calcium and magnesium — has been associated in multiple large population studies with reduced rates of cardiovascular disease, lower blood pressure, and reduced risk of certain cancers. The minerals in water are bioavailable, meaning the body can absorb and use them. For populations with marginal dietary mineral intake, water can be a meaningful nutritional source.
This creates a genuine tension in water filtration: the same processes that remove harmful contaminants also remove beneficial minerals. Reverse osmosis — the most effective broad-spectrum filtration method — produces essentially mineral-free water. Distilled water is completely demineralized. If you are filtering your water comprehensively (which this series recommends for contaminant removal), you need to think about what you are removing along with the contaminants, and how to address it.
WHAT HARD WATER IS
Water hardness is determined by dissolved calcium and magnesium content, measured in milligrams per liter (mg/L) or grains per gallon (GPG). The USGS classifies water as soft (0-60 mg/L as calcium carbonate), moderately hard (61-120 mg/L), hard (121-180 mg/L), and very hard (above 180 mg/L). Most of central Illinois has hard to very hard water — the limestone geology that underlies the region dissolves readily into groundwater, contributing high calcium and magnesium.
Hard water is immediately noticeable: it leaves scale deposits on fixtures and appliances, reduces soap lathering, leaves spots on dishes and glassware, and can reduce the lifespan of water heaters and plumbing. These are the practical inconveniences that drive most people to install water softeners. The health dimension of water hardness is less commonly discussed.
THE HEALTH CASE FOR MINERALS IN WATER
Cardiovascular protection — The relationship between water hardness and cardiovascular health has been documented across dozens of epidemiological studies spanning multiple countries and decades. Populations drinking harder water consistently show lower rates of cardiovascular disease and cardiac mortality than populations drinking soft water, with the effect being strongest for magnesium. The mechanism is not fully elucidated but likely involves magnesium’s role in cardiac muscle function, blood pressure regulation, and anti-inflammatory pathways.
Magnesium — The mineral with the strongest health evidence in water. Magnesium is involved in over 300 enzymatic reactions in the body. It is essential for energy production, protein synthesis, DNA repair, muscle and nerve function, blood glucose regulation, and blood pressure. Magnesium deficiency is extremely common in the modern Western diet — estimated at 50-80% of the population depending on the measure used — and low magnesium is associated with cardiovascular disease, type 2 diabetes, metabolic syndrome, depression, migraine, and muscle cramping. Water is a meaningful source of bioavailable magnesium, particularly in hard water regions. Removing it through softening or RO without replacing it is not a neutral action.
Calcium — Bone health, muscle function, nerve transmission, and blood clotting all depend on calcium. Water calcium contributes to daily intake, and the bioavailability of calcium from water compares favorably to dairy sources. Concerns about calcium in water promoting kidney stones or arterial calcification are not well-supported for most people at typical water calcium levels — the relationship between dietary calcium and kidney stones is complex and is more strongly influenced by oxalate intake, hydration status, and vitamin K2 status than by water calcium specifically.
Trace minerals — Depending on the geology of your source water, water may also provide meaningful amounts of zinc, selenium, silica, and other trace minerals. This varies widely by location and is worth knowing about if you are evaluating your water’s nutritional contribution.
WATER SOFTENERS — WHAT THEY DO AND THE TRADE-OFF
Standard ion exchange water softeners remove calcium and magnesium from water and replace them with sodium (or potassium, in salt-free alternatives). This eliminates scale, improves soap lathering, and extends appliance life. It also removes the cardiovascular-protective minerals and adds sodium to drinking water — a concern for people with hypertension, kidney disease, or sodium-restricted diets.
The sodium added by a water softener varies with incoming water hardness. Very hard water, fully softened, can add 200-400 mg of sodium per liter — a significant contribution for someone managing blood pressure. Most water softener installations include a bypass for a cold drinking water tap — an unsoftened line for drinking and cooking that preserves mineral content and avoids sodium addition. If you have a softener without this bypass, it is worth adding.
Potassium chloride can be used instead of sodium chloride in water softeners, substituting potassium for calcium and magnesium instead of sodium. This avoids the sodium concern and adds potassium (which most Americans are also deficient in) but costs more and may not be available everywhere. Worth asking about if you use a softener.
REMINERALIZATION AFTER RO OR DISTILLATION
If you filter with RO or drink distilled water, remineralization is worth addressing. Options range from simple to comprehensive.
Remineralization filter stage — Many RO systems offer a remineralization cartridge as a final stage that adds calcium and magnesium back to filtered water. This is the most convenient solution and is worth including in an RO system purchase or adding to an existing system.
Mineral drops — Concentrated mineral drops (magnesium, trace minerals) added to filtered water are widely available and effective. Look for products that specify the mineral content per dose so you can control what you’re adding.
A pinch of mineral-rich salt — Adding a small amount of high-quality sea salt or Himalayan pink salt (which contains trace minerals) to filtered water provides electrolytes and trace minerals. This is a simple, low-cost approach. Not as precise as mineral drops but better than purely demineralized water.
Nettle leaf tea — Strongly brewed nettle leaf tea is rich in calcium, magnesium, iron, and other minerals. Drinking a cup or two daily as part of your water intake is a food-based way to address mineral intake while supporting kidney function. The plants are free if you harvest from your land — see the Flora Archive for identification and harvest guidance.
Dietary mineral sources — The most reliable approach to mineral adequacy is diet. Dark leafy greens (magnesium, calcium, iron), nuts and seeds (magnesium, zinc), legumes (magnesium, potassium), dairy or fortified alternatives (calcium), and sea vegetables (comprehensive trace minerals). Water mineralremoval is manageable if dietary mineral intake is solid. It becomes more significant if both dietary and water mineral intake are low.
WHAT VERY HARD WATER DOES
While moderate water hardness is associated with health benefits, extremely hard water (above 300-400 mg/L) may contribute to kidney stone formation in susceptible individuals — particularly those who form calcium oxalate stones and who have low fluid intake. This is not a concern for most people but worth noting if you have a history of kidney stones. Your nephrologist or urologist can advise based on your stone type and your water’s mineral profile.
Very hard water also creates significant scale accumulation in appliances, reduces water heater efficiency, and may damage plumbing over time. The practical case for softening very hard water is reasonable — the key is preserving an unsoftened drinking water line or remineralizing filtered water.
THE PRACTICAL FRAMEWORK
Know your water hardness — it is in your Consumer Confidence Report for municipal water or can be tested inexpensively for well water. If you are filtering with RO, add a remineralization stage or use mineral drops. If you have a softener, ensure you have an unsoftened drinking water line. If you are drinking demineralized water without supplementing minerals, evaluate your dietary mineral intake and address any gaps through food first, supplementation second. The goal is contaminant removal without inadvertent mineral depletion.
Cross-reference: Know Your Water — Building Your Water Protocol | Know Your Water — PFAS | Know Your Body | Flora Archive — Nettle | Root Cellar — Water Protocols
FROM THE WASTELAND
Leaf Juice — Wasteland Survival Series, Book 1
Nettle leaf tea — the most practical mineral-rich water addition in this post — has full preparation protocols in Leaf Juice alongside other mineral-supportive herbs.
Paperback | Kindle