True water, a simple molecule of H2O, doesn't technically expire in the way that organic products like milk or juice do. The 'expiration date' or 'best-by' date seen on a bottle is for the packaging, not the liquid itself. For alkaline water, however, the situation is more complex. The beneficial properties—specifically the elevated pH and antioxidant potential—are not permanent and will degrade over time. Understanding this process is key to getting the most out of your alkaline water purchase.
The Science Behind Alkaline Water's Potency Loss
Alkalinity in water is not a fixed state. It is created either naturally, by water absorbing minerals as it passes over rocks like limestone, or artificially, through a process called electrolysis. The stability of the alkalinity depends heavily on its source and how it is stored.
- Ionized Alkaline Water: Water processed through an ionizer to raise its pH is highly perishable. The antioxidant properties, delivered by hydroxyl ions, begin to dissipate rapidly, sometimes within 24 hours of ionization. The high pH level also begins to drop off, returning closer to neutral over one to two weeks, as the water is exposed to carbon dioxide (CO2) from the air. CO2 is slightly acidic and, when absorbed into the water, begins to neutralize the alkalinity.
- Natural Alkaline Water: Sourced from springs with natural minerals, this type of water tends to be more stable due to the inherent mineral buffering capacity. However, even naturally sourced water will see a gradual decrease in its alkaline properties when stored, especially in plastic containers, as CO2 can still permeate the packaging over long periods.
Factors Affecting Alkaline Water's Shelf Life
Several external factors can accelerate the degradation of alkaline water's properties and, over extended periods, compromise its taste and safety.
Storage Conditions
- Temperature: Storing alkaline water in high temperatures, such as a hot car or a sun-drenched garage, is detrimental. Heat can cause the plastic of the bottle to break down more quickly, leaching chemicals like antimony and phthalate esters into the water, which affects taste and potentially poses a health risk. Cool storage is essential.
- Light: Direct sunlight and UV exposure can also speed up the breakdown of plastic packaging and promote microbial growth in water that is no longer freshly sealed. Storing water in a dark place is always recommended.
- Air Exposure: Once opened, alkaline water's lifespan is significantly reduced. Constant exposure to air and ambient CO2 will cause the pH to drop and the antioxidant potential to vanish rapidly.
Container Material
- Plastic: Most bottled alkaline water comes in polyethylene terephthalate (PET) plastic. While generally safe, this material is slightly permeable to air and can leach chemicals over time, especially when exposed to heat.
- Glass: A superior option for storing alkaline water. Glass is non-reactive and less permeable than plastic, helping to preserve the water's properties and taste for longer.
- Aluminum: Water in aluminum cans can have a longer shelf life compared to plastic, as the material is less permeable and reactive.
What Happens When You Drink 'Expired' Alkaline Water
If the water has been properly stored in a sealed container, drinking it past its 'best-by' date is not likely to be unsafe. The main consequence will be a loss of the very properties you bought it for. The pH will have lowered, and any antioxidant benefits will be long gone. The taste may be noticeably 'off,' tasting stale, metallic, or chemically, especially if it was stored improperly. For an opened bottle, the risk of bacterial contamination from repeated sips and environmental exposure increases significantly over time.
Comparison: Fresh vs. Stored Alkaline Water
| Feature | Fresh Alkaline Water | Properly Stored (Sealed) | Improperly Stored (Heat/Light) |
|---|---|---|---|
| pH Level | High (e.g., 8-9.5) | Gradually lowers over weeks/months | Rapidly drops to neutral or acidic |
| Antioxidant Potential | High (for ionized) | Diminishes within 24-48 hours | Non-existent |
| Taste | Crisp, clean, or smooth | May develop a stale or off-flavor | Noticeably altered by plastic leaching |
| Safety | High | Safe, but quality may be affected | Potential for chemical leaching and contamination |
| Best for | Immediate consumption to reap all benefits | Prepping for short-term consumption, emergency supply | Avoid consuming if taste/smell is compromised |
How to Properly Store Alkaline Water for Maximum Freshness
To ensure your alkaline water retains its peak quality and properties, follow these storage guidelines:
- Use the Right Container: For homemade or dispenser water, use an airtight, non-reactive glass container. If using a plastic bottle, choose one that is BPA-free.
- Keep it Cool and Dark: Store bottles in a pantry, cupboard, or the refrigerator, away from direct sunlight, heat sources, and chemical fumes.
- Minimize Air Exposure: Fill your storage containers to the top to reduce the amount of trapped air. This limits exposure to CO2.
- Consume Quickly: For ionized water, drink it within 24-48 hours for optimal benefits. Even properly stored bottled alkaline water should be consumed before its 'best-by' date for the freshest taste.
- Avoid Contamination: Keep opened bottles sealed tightly and do not leave them exposed to air. Avoid storing water near strong-smelling items, as the water can absorb odors.
Conclusion
So, does alkaline water ever expire? Not in a way that makes it unsafe for consumption if properly stored and sealed. However, its signature benefits, particularly the elevated pH and antioxidant properties, are temporary and will diminish over time. The 'best-by' date on bottled alkaline water is a reliable indicator for optimal quality, not a hard-and-fast safety deadline. To fully enjoy the potential advantages of alkaline water, it is best to drink it fresh, soon after it's produced or opened, and always store it in a cool, dark place away from contaminants. For more information on bottled water safety and quality standards, the International Bottled Water Association offers useful guidance.
