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Health Effects Of Drinking Distilled Water

In the following discussion I cover a questions that comes up fairly commonly:  The question takes several forms, but the essence boils down to  whether very pure water (treated with Reverse osmosis, Distillation, or Deionization- RDD treatment)  is either bad or good for the body because of the complete lack of ions.

If you are reading this page, you have probably read or heard the statement: "Water that has been distilled is good for your health (or bad for your health - take your pick) because it is almost completely lacking in dissolved minerals.

I have done considerable study on this topic, but actual experimental evidence (in scientific journals) about the health effects of drinking RDD treated water seems to be almost non-existent On the other hand, the discussions, opinions, and arguments about whether or not RDD water is good or bad to drink abound!

Obviously, the discussion below will focus only on the presence or absence of the "good/beneficial" ions (like calcium, magnesium, and potassium) that are removed by RDD processes.  It is a given that it is good to remove all harmful ions like lead, mercury, etc. (as well as other harmful contaminants) by RDD or by any other process.

The thing that strikes me most about these RDD purification discussions is that those promoting the idea that "water without ions is bad" are typically the groups selling filters that do not remove calcium, magnesium, phosphorus, etc. (the "beneficial mineral ions") from the water. Those stating that "RDD water is beneficial" ("and actually preferable to drinking water containing minerals") are - no surprise - the ones selling RDD systems. Many "health-related sites" are somewhere in between - if one of their diets or cleanses requires some sort of body "purification" they will often suggest drinking RDD processed water to help leach harmful contaminants out of the body (see argument 2 below).  

There are two threads to the "RDD water is harmful to health" argument:  
   1) Essential minerals are removed from the water - and that's bad, and 
   2) Demineralized water 'leaches' minerals from your body - and that's  also bad.

1) Argument 1: All the calcium and magnesium are removed from the water by RDD processes, and, because calcium and magnesium are essential nutrients and necessary for life, the removal of those mineral ions from the water is harmful to health.  

Response 1: It is true that RDD removes the "good" minerals along with the harmful contaminants, but it is by no means true that drinking water is the only source (or even the primary source) of these minerals.  The recommended daily requirements for calcium and magnesium are about 1,000-1,200 mg and 300-400 mg respectively (with specific requirements varying by age, gender, etc.).

According to one table the hardness scale provides information about the amount of calcium in various degrees of hard water.

Classification grains/gal

mg/l or ppm 
CaCO3 equivalent

mg/l or ppm 

Soft 0 - 1 0 - 17.1 0 - 7
Slightly hard 1 - 3.5 17.1 - 60 7 - 24
Moderately hard 3.5 - 7.0 60 - 120 24 - 48
Hard 7.0 - 10.5 120 - 180 48 - 72
Very Hard 10.5 & over 180 & over 72 and over

NOTE: Other organizations may use slightly different classifications.

According to the table above, water that is slightly to moderately hard will contain around 24 mg/l of calcium.   Reports I have seen indicate that magnesium levels are about 12 - 15% of the calcium levels (or about 3.6 mg/l).  One liter (about 1 quart or four 8-oz drinks) of hard to very hard water will contain around 72 mg/l of calcium and perhaps 11 mg/l of magnesium.  Extremely hard water, though, can contain over 1,000 mg/l calcium carbonate (CaCO3), or over 400 mg of calcium 

So, drinking eight {8} glasses (about 2 liters) of slightly to very hard water a day will provide your body with about 14 - 144 mg of calcium. That translates to a maximum of about 1.2% to 12% of the daily 1,000 to 1,200 mg of calcium your body requires. In that same 8 glasses of water you will be supplying your body with about the same percentage of your daily requirement of magnesium.  One glass of milk, by comparison, contains about 300-350 mg of calcium - over twice as much as 8 glasses of very hard water.

Drinking water that contains calcium and magnesium then, can realistically be a source of up to about 12 % of your daily requirements for these minerals. On the other hand, your body does not care where the minerals come from, drinking water, diet, or supplement - so, as long as you get enough calcium and magnesium (and other essential minerals) from somewhere, there should be no health problems for most people from drinking RDD processed water simply because the water is lacking essential minerals.  As noted above, though, over 800 mg of calcium could be supplied to the body by drinking 2 liters of extremely hard water.

**There is a qualification to the statement above.  While the body does not care where the minerals ultimately come from - that is, calcium from milk or from supplements is used by the body the same as calcium obtained from water, the bioavailability of calcium (or other minerals) is affected by the form in which the calcium is delivered to the body.  Calcium citrate, for example has been shown to be 2.5 times more bioavailable (easier for your body to use) than calcium carbonate.  Some articles attribute that difference in absorption to the fact that organic forms of calcium (citrate, lactate, etc.) dissolve more easily in the stomach - releasing the calcium ions - than calcium carbonate (which is where much of the calcium in water comes from and which you might find in an inexpensive supplement).  Other studies I have read indicate there is little difference.  It must be noted, however,  that the calcium in water is already dissolved.  I have not read the result of studies where the absorption of dissolved types of calcium supplements are compared, but I suspect that the bioavailability of any calcium that arrives in the stomach already dissolved may be similar.

Another point I have read recently is that cooking in water that is low in minerals (RDD water) will extract more minerals from food than cooking with normal water thus lowering the amount of minerals in the diet.  This sounds like a reasonable critique or RDD water, however I have not read results of actual experiments that measured and compared the calcium and other mineral levels in food prepared with normal and RDD water.

A warning: Do NOT believe the hype you may read about coral calcium providing any advantages over other sources of calcium, either in the diet or in supplements.  Coral calcium is simply calcium carbonate.  It is, however, unregulated and unpurified and (like calcium supplements from oyster shell, dolomite, and bone meal) may contain harmful levels of heavy metals like lead and mercury.  This type of scam is similar to the altered water scams discussed elsewhere on my site in that they are very expensive, and all evidence about the benefits of these products is self-generated and not supported by any legitimate scientific studies.  They differ in that the altered water scams are typically harmful only to your pocket book, while these unregulated supplements can be harmful to your health as well as your pocket book.

**That said, there is a body of evidence that is hard to ignore that points to reported health benefits from drinking hard water instead of soft water. As several of the articles below point out, however, there is no consensus about the actual cause of the findings (may be something in the soft water that is harmful rather than the calcium and magnesium ions in the hard water that are beneficial, for example) or even how real the effect is.

RDD water will also have all fluoride removed (natural and/or added).  Depending on your stance on the benefits or harm from fluoride in your drinking water (a whole different discussion that is even more contentious than the RDD/non-RDD issue), that may be an issue. In some locations, drinking water is a major source of fluoride. So, if you are a believer in the benefits of fluoride in drinking water, you may wish to make certain you and your family obtain enough of that chemical from other sources.

The National Academy of Sciences and the National Osteoporosis Foundation
Hard Water Hardness Calcium Magnesium Water Corrosion Mineral Scale
Linus Pauling Institute - Micronutrient Information Center - Calcium

Drinking Water and Health, Volume 1
Watering Your Heart: How a Little Magnesium May Help

Calcium Citrate vs. Calcium Carbonate

Coral Calcium The answer to how do you spell HYPE?

Backgrounder on Calcium Forms

Calcium Info - Supplements

Calcium - Encyclopedia of Alternative Medicine

The "Mother" of all magnesium and health sites:
  A couple of representative articles
  Magnesium and calcium in drinking water and cardiovascular mortality
  Calcium and magnesium in drinking water and risk of death from cerebrovascular disease.
  Minimum Magnesium Standard for Drinking and Bottled Water Would Save 150,000 Lives Annually

2) Argument 2: RDD water, since it is devoid of all substances (including ions), is "aggressive" and will deplete the minerals from your body causing serious harm over time.

Response 2: If you are talking pipes and storage containers, RDD water could be considered more "aggressive" than water containing dissolved substances.  Water without anything in it will tend to dissolve anything it comes in contact with (the copper or iron in a pipe, the lead from a solder joint or brass fixture, etc.) more 'aggressively' than water that already contains some dissolved substances. Also, one of the "things" easily dissolved by RDD water is carbon dioxide. This forms a weak acidic solution (carbonic acid) which can cause further dissolving and corrosion of materials that it comes in contact with - that's how caves get formed - soft, acidic rain water dissolves limestone (calcium carbonate) becoming hard water in the process of forming the cave structure.

The above is a good argument for only storing RDD water in clean glass containers which are chemically inert.

Now, does this "aggressiveness" of RDD processed water translate to actually leaching minerals out of the human body? I have looked regularly in the scientific literature for good evidence of this alleged phenomenon without success. I have not been able to find anything in the literature specifically about long-term effects of drinking RDD water on health - the only articles I can find are about he health effects of soft water and lead back to the hard vs. soft water health benefits discussed above.  I use the word 'contaminated' below to describe anything besides pure water.

** From my understanding of how digestion, food/water absorption, and the process of drinking RDD water must work, however, I am very skeptical about the possibility that drinking RDD water has any major negative impact on the human body (or positive impact either). Consider:
Ideally RDD water contains nothing except perhaps some CO2 picked up from the air.
Adding anything to that pure water will 'contaminate' it.
The alleged leaching of minerals from the body is said to take place in the small intestines because of the
     "pure, aggressive" water that comes in contact with the intestine lining - as opposed to hard water with a
     few milligrams of calcium or other ions which will not cause this leaching of minerals.
Consider the contents of your stomach, particularly after a meal - a huge mix of every conceivable type of
     organic and inorganic compound plus a healthy dose of hydrochloric acid.
It does not matter where pure water becomes 'contaminated' (in the ground, in the distribution system, on
     the counter, in your body) - adding anything (from any source) to water will 'contaminate' it.
Imagine two glasses of water on the counter - one containing clean, filtered tap water with a few milligrams
     of calcium and magnesium, and the other glass containing only pure, RDD processed water with no ions.
Imagine now the difference a few milligrams of ions will make when either glass of water hits the contents
     of your stomach! Since any alleged harmful effect of drinking RDD water does not happen until several
     hours later when molecules from the glass of water eventually reache your intestines, it is very difficult to
     believe that the presence or absence of a few ions in the original water will make any difference at all.

Another way to look at it: Since it does not matter to the body where water becomes 'contaminated' (externally or in your stomach), consider this "thought experiment":
Take a blender, throw in a cheeseburger meal with all the trimmings (chips, pickle, and a coke)** , turn the
     blender on and mix the together thoroughly.
Fill two glasses of water 1/2 full, one with pure RDD water, with no ions,  and one 'contaminated' with
     calcium and magnesium ions.  
Pour 1/2 of the burger mixture into each glass of water and mix.  
Now, which is the more 'contaminated' glass of water - is it really going to matter to your body which glass
     of water you drink - the glass of water that started with perhaps 2-18 mg of calcium ions or the glass of
     "pure" water that started with 0 mg.
Drink the mixtures - Yuck! 

** Using the nutrition guide at Colorado State University Cooperative Extension and adding together the calcium, sodium, and potassium levels of a hamburger patty, 1/2 oz cheese, bread, tomato slice, 20 chips, and a pickle, I found the total ion content of those three cations to be roughly 3,192 mg (nearly 3.2 grams).  That is several hundred times more than might be in the non-RDD water.  Calcium levels would be around 178 mg, Sodium  around  1,740 mg, and Potassium about 1,274 mg.  And, that's the concentration of just 3 ions.  All of the other 'contaminants' (other ions, carbohydrates, fats, and proteins) would make the initial difference between the RDD water and the filtered water even more insignificant.  

Since water from reverse osmosis and distillation systems are about two and four times more expensive respectively than good filtered water, the only negative impact I can see to these methods of treatment for most people is to the pocket book. 

**Several visitors have commented that drinking too much RDD water can lead to ion imbalances in the body which can cause serious health problems.  This is true, but so can drinking too much regular water.  The condition is known as water intoxication.  The discussion above assumes that people are eating regularly, getting enough minerals in the diet and supplements, and not drinking an excess of any type of water.

If, however, your water contains contaminants, like nitrates, that are not removed by filtration, then reverse osmosis and distillation treatment methods are a good options (often the most economical option) for producing clean, safe water for drinking and cooking.

References about digestion and absorption:

Digestion and Absorption (Water absorption is explained about 1/3 of the way down - rj)
Mechanism of water absorption. Osmotic water absorption is driven by the absorption of sugars and amino acids and other nutrients. In addition the absorption of ions powers water absorption via the standing osmotic gradient mechanism. Na, K-ATPase concentrated near heads of intercellular channels pumps Na + into intercellular space. Cl - enters intercellular space via tight junctions or basolateral plasma membrane [driven by its electrochemical gradient]. Slightly hypertonic NaCl near heads of intercellular spaces. Draws water osmotically. Hydrostatic flow of water and ions down intercellular channel, across basement membrane, to be carried away by capillaries.

An important function of both small intestine and colon is the absorption of water and electrolytes. Approximately 2000 ml of food and drink is ingested daily, and the volume of gastrointestinal secretions (salivary, gastric, biliary, pancreatic and intestinal) is about 8,000 ml daily; therefore, approximately 10 liters of fluid enters the intestine each day. Of the 8 liters secreted, about 1-1.5 liters enter as saliva, 2-3 liters are secreted by the stomach, about 2 liters enter as bile and pancreatic secretion (about 1 liter each), and about 2 liters are secreted by the small intestine.  (Please note that these figures are approximate, not absolute. Volumes may vary, depending on experimental method and conditions.) Of the 10 liters which enters the gut each day, only about 1 liter passes into the colon, about 90% having been absorbed across the small intestinal epithelium. Only about 150 ml is lost in the feces daily, with the remainder being absorbed by the colon. It should be obvious that any derangement in intestinal fluid absorption would profoundly influence the balance of fluid and electrolytes in the body, and that the normal functioning of the intestines plays a significant role in regulating water and electrolyte balance. The net absorption or net secretion of water in the intestine is the result of bidirectional movements of water from mucosa to serosa (m-->s flux or absorption) and from serosa to mucosa (s-->m flux or secretion). In the human intestine, these unidirectional fluxes exceed net movement 2-3 fold.  The rate and direction of net fluid movement depend on tonicity of the meal, and move toward the achievement of isotonicity {equal concentration of water on both sides of a membrane - RJ}
The intestinal mucosal surface consists of a bimolecular lipid membrane, which (presumably) contains small pores or channels. Water and water-soluble substances can hypothetically enter the cell through these pores only, while lipid-soluble substrates can directly cross the lipid cell membrane. Specialized protein pores, referred to as aquaporins (AQP) have been identified in many tissues, including colon epithelium; water channel isoforms in small intestinal epithelium remain to be discovered. Intestinal absorption of water is a passive process and requires movement of solutes. Water accompanies solute and moves across the intestinal mucosa in response to osmotic gradients. The rate of water uptake in any region of the intestine is a function of solute absorption in this region. All areas of the intestines (including small bowel and colon) absorb water, the relative amounts absorbed depending on the presence of solutes {things dissolved in water, sodium, calcium, sugar, etc. - RJ}, and the types of solutes present. In the jejunum, the active transport of sugars and amino acids causes passive movement of salt and water, which accounts for most of the water uptake in this area. In the ileum, most water movement is accounted for by active sodium transport. As described in Johnson (Gastrointestinal Physiology), coupled water and sodium transport involves a specialized mechanism that pumps sodium into the lateral spaces, resulting in relatively high osmotic pressure in that region. Water then enters the lateral space from the cell (transcellular flux) and--perhaps--the lumen (paracellular flux), reducing the osmotic pressure but increasing the hydrostatic pressure. Fluid is then forced out of the lateral space into the interstitial space. The net effect is that isotonic fluid is transported from the lumen into the extracellular fluid. This hypothesis of fluid absorption is illustrated in Figure 12-5, on page 137 of the Johnson resource.

Lecture 52. Gastrointestinal Secretion/Absorption (good diagrams)

Water Permeability of the Alimentary Canal

Stomach - A large J-shaped chamber lying between the esophagus and the small intestine.... HCl - secreted by the parietal cells of the oxyntic mucosa only into the lumen of the stomach, where the pH falls below 2. Activates Pepsin from Pepsinogen. Breaks down connective tissue and muscle. Kills microorganisms.

Small Intestine - site in the digestive tract where most digestion and absorption takes place.... Absorption - The products of Carbohydrate, Fat and Protein digestion are all absorbed in the small intestine, as well as water, electrolytes and vitamins. Most absorption occurs in the duodenum and jejunum.

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Copyright 2005 Randy Johnson. All rights reserved.