Understanding Nitrates: The Good, the Bad, and the Source
Nitrates ($NO_3$) and nitrites ($NO_2$) are chemical compounds composed of nitrogen and oxygen that are naturally found in our environment and our food. Nitrates are present in soil, water, and plants, with certain vegetables containing naturally high levels. Nitrates are converted to nitrites by bacteria, both in the environment and in the human body, particularly by bacteria in the mouth.
For a long time, nitrates and nitrites were considered potentially harmful, mainly due to the formation of N-nitroso compounds (NOCs) in the body, which have been linked to cancer risk. However, recent research has revealed a more nuanced picture. Nitrates from plant sources are accompanied by protective compounds like vitamin C, which can inhibit the formation of NOCs. In fact, dietary nitrates from vegetables and beets have been shown to have cardiovascular benefits by converting to nitric oxide (NO), a molecule important for blood vessel health.
Conversely, nitrates and nitrites added to processed meats like bacon and hot dogs, used as preservatives, have been associated with a higher risk of certain cancers. The key difference lies in the source and the accompanying nutrients. A balanced diet with lots of vegetables is beneficial, but exposure from other sources, especially high concentrations in drinking water, requires careful management.
How to Reduce High Nitrates in Food
For those seeking to limit their nitrate intake, particularly from added sources, several kitchen techniques can be effective. It's important to remember that this primarily applies to added nitrates in processed foods and to a lesser extent, naturally occurring ones in vegetables, which are typically accompanied by protective antioxidants.
- Choose wisely: Opt for uncured or nitrate-free processed meats, as some manufacturers offer these alternatives. The source of your vegetables also matters. Winter-grown produce from greenhouses can have higher nitrate concentrations than sun-ripened summer vegetables.
- Wash thoroughly: For leafy greens and root vegetables, washing them can help remove surface-level nitrates. Soaking vegetables with a high surface area, like lettuce or broccoli, for a few minutes in clean water can be effective.
- Peel vegetables: As nitrates are often more concentrated near the skin of certain vegetables like potatoes, peeling them can significantly reduce the nitrate content.
- Blanch or boil: Cooking high-nitrate vegetables like spinach, beets, and potatoes by blanching or boiling can significantly reduce nitrate levels, by 40-80% according to some studies, especially if you discard the cooking water. However, remember that deep-frying can increase nitrate levels.
- Eat fresh: Eating freshly prepared food and avoiding prolonged storage of cooked vegetables, especially leafy ones, is crucial. Nitrite-forming bacteria can increase nitrite concentration in cooked and stored vegetables.
- Add antioxidants: Pairing nitrate-rich foods with vitamin C-rich foods, such as an orange with processed meat, can help inhibit the conversion of nitrates to potentially harmful nitrosamines. Vegetables high in antioxidants like vitamin C and polyphenols also serve this purpose.
How to Remove High Nitrates from Water
High nitrate levels in drinking water are a serious health concern, particularly for infants under six months of age, as it can cause 'blue baby syndrome' (methemoglobinemia). Unlike food, boiling water does not remove nitrates; in fact, it concentrates them as the water evaporates. Effective nitrate removal from water requires specific filtration methods.
Common methods for water nitrate removal:
- Reverse Osmosis (RO): A system that forces water through a semi-permeable membrane, which filters out up to 98% of nitrates along with other contaminants. RO systems can be installed at a single tap (point-of-use) or for the entire house.
- Ion Exchange: Similar to a water softener, this system uses a special resin that exchanges nitrate ions for chloride ions. This can be a point-of-use or point-of-entry system.
- Distillation: This process boils water and then condenses the steam back into a liquid, leaving behind contaminants like nitrates. It is a very effective method, but can be slow and energy-intensive.
Comparison Table: Water Filtration Methods for Nitrate Removal
| Feature | Reverse Osmosis (RO) | Ion Exchange | Distillation |
|---|---|---|---|
| Effectiveness | Highly effective (up to 98% reduction) | Very effective, exchanges nitrate for chloride | Highly effective, removes nearly all contaminants |
| Cost | High initial cost, moderate ongoing filter replacement | Equipment cost varies, requires periodic resin regeneration | High energy cost, slow production rate |
| Installation | Point-of-use (e.g., kitchen sink) or point-of-entry (whole house) | Point-of-use or point-of-entry | Typically point-of-use |
| Process | Pressurized water forced through a membrane | Water flows through a resin bed | Water is boiled and condensed |
| Maintenance | Regular filter changes are necessary | Requires periodic regeneration with salt | Requires periodic cleaning of boiling chamber |
When to Take Action: Testing and Awareness
If you use a private well for drinking water, it is highly recommended to test it for nitrates annually, or if you are pregnant or have infants in the home. Testing is the only way to be certain of your water's nitrate concentration, as you cannot detect it by taste, smell, or sight. For public water supplies, you can check your local water utility's report for nitrate levels.
Beyond water, being aware of food sources is important. While the nitrates in vegetables are not a major concern due to their nutritional profile, consuming large quantities of processed meats frequently increases exposure to added nitrates and nitrites. Adopting a varied, balanced diet rich in whole foods is a solid nutritional strategy for managing nitrates effectively.
Conclusion
Managing high nitrate exposure from both diet and water involves a multi-pronged approach based on the source. In drinking water, the solution is clear: certified filtration systems like reverse osmosis, ion exchange, or distillation are necessary, and boiling is to be avoided. When it comes to food, mindful choices and proper preparation techniques are key. Opt for unprocessed meats when possible and use simple cooking methods like boiling or blanching for some high-nitrate vegetables. Ultimately, prioritizing a diverse, whole-food diet provides a balanced approach to mitigating potential nitrate risks while still reaping the benefits of nitrate-rich vegetables. Consult with local health authorities or a nutrition professional for personalized advice, especially concerning infants and pregnant women.
For more information on water quality standards, you can visit the U.S. Environmental Protection Agency (EPA) website.
