Is TDS linked to health and disease? Should we use RO water and if yes at what TDS levels

Presence of chemicals in groundwater has contributed to the prevalence of Chronic Kidney Disease of Unknown Origin (CKDu) in parts of Sri Lanka, although the exact combination of factors remains a mystery. Removing all the natural minerals from water could mitigate the spread of CKDu. Many studies link high TDS levels to CKDU and suggest that the levels should be < 100 in kidney patients.

Total dissolved solids or TDS is the term used to describe the inorganic salts and small amounts of organic matter present in solution in water. The principal constituents are usually calcium, magnesium, sodium, and potassium cations and carbonate, hydrogencarbonate, chloride, sulfate, and nitrate anions.  The presence of dissolved solids in water may affect its taste.

According to the Bureau of Indian Standards (BIS), the upper level of TDS levels in water is 500 mg/litre (500 parts per million); however, TDS level in the range of 300 ppm is considered excellent per WHO Guidelines. 

What should be the ideal TDS levels of water in kidney patients?

1. No recent data on health effects associated with the ingestion of TDS in drinking-water appear to exist; however, associations between various health effects and hardness, rather than TDS content, have been investigated in many studies [https://www.who.int/water_sanitation_health/dwq/chemicals/tds.pdf]
2. In early studies, inverse relationships were reported between TDS concentrations in drinking water and the incidence of cancer (1), coronary heart disease (2), arteriosclerotic heart 2 disease (3), and cardiovascular disease (4,5). Total mortality rates were reported to be inversely correlated with TDS levels in drinking-water (5,6).
3. A study in Australia reported that mortality from all categories of ischaemic heart disease and acute myocardial infarction was increased in a community with high levels of soluble solids, calcium, magnesium, sulfate, chloride, fluoride, alkalinity, total hardness, and pH when compared with one in which levels were lower (7).
4. An epidemiological study in the former Soviet Union indicated that the average number of "cases" of inflammation of the gallbladder and gallstones over a 5-year period increased with the mean level of dry residue in the groundwater (8).

Some important facts

1. TDS are minerals, salts and water-soluble metals.
2. According to the BIS, the ideal TDS for drinking water is below 300mg/Land the max permissible limit is 600mg/L. It is recommended that people with kidney problem should drink pure water having TDS level below 100 mg/L for better recovery.
3. Hardness and TDS are not same: Water hardness is the traditional measure of the capacity of water to react with soap, hard water requiring considerably more soap to produce a lather.

Hard water often produces a noticeable deposit of precipitate (e.g. insoluble metals, soaps or salts) in containers, including “bathtub ring”.

Hardness is most commonly expressed as milligrams of calcium carbonate equivalent per litre. Water containing calcium carbonate at concentrations below 60 mg/l is generally considered as soft; 60–120 mg/l, moderately hard; 120–180 mg/l, hard; and more than 180 mg/l, very hard (McGowan, 2000).

4. Dr Sanjay K Agarwal HOD AIIMS Nephrology has said that, according to IS 10500, the TDS of the water used for drinking purposes should be in the range of 300-600 mg/liters. The TDS of water obtained from RO water purifier is the range of 50-200 mg/liters which if near 200 mg/liters is considered good for drinking but as the value of TDS tends towards 50 mg/liters it could have the opposite effect and be harmful to our bodies. However, there is no such TDS level reported to be safe for kidney. Whatever is reported for drinking water, that should be safe for kidney also, if kidneys are normal functioning.
5. Natural and treated waters have a wide range of mineral content, from very low levels in rainwaters and naturally soft and softened water to moderate and very high levels in naturally hard waters and waters with high total dissolved solids content. Bottled and packaged waters can be naturally mineralized or naturally soft or demineralized. Thus, the mineral consumption from drinking-water and cooking water will vary widely, depending upon location, treatment and water source.
6. Reliable data on possible health effects associated with the ingestion of TDS in drinking water are not available. The results of early epidemiological studies suggest that even low concentrations of TDS in drinking-water may have beneficial effects, although adverse effects have been reported in two limited investigations.
7. Water containing TDS concentrations below 1000 mg/litre is usually acceptable to consumers, although acceptability may vary according to circumstances. However, the presence of high levels of TDS in water may be objectionable to consumers owing to the resulting taste and to excessive scaling in water pipes, heaters, boilers, and household appliances (see also the section on Hardness). Water with extremely low concentrations of TDS may also be unacceptable to consumers because of its flat, insipid taste; it is also often corrosive to water-supply systems. In areas where the TDS content of the water supply is very high, the individual constituents should be identified and the local public health authorities consulted. No health-based guideline value is proposed for TDS. However, drinking-water guidelines are available for some of its constituents, including boron, fluoride, and nitrate.

References

1. Burton AC, Cornhill JF. Correlation of cancer death rates with altitude and with the quality of water supply of the 100 largest cities in the United States. Journal of toxicology and environmental health, 1977, 3(3):465-478.
2. Schroeder HA. Relation between mortality from cardiovascular disease and treated water supplies. Variation in states and 163 largest municipalities. Journal of the American Medical Association, 1960, 172:1902.
3. Schroeder HA. Municipal drinking water and cardiovascular death rates. Journal of the American Medical Association, 1966, 195:81-85.
4. Sauer HI. Relationship between trace element content of drinking water and chronic disease. In: Trace metals in water supplies: occurrence, significance and control. University of Illinois bulletin, 1974, 71(108):39.
5. Craun GF, McGabe LJ. Problems associated with metals in drinking water. Journal of the American Water Works Association, 1975, 67:593.
6. Crawford M, Gardner MJ, Morris JN. Mortality and hardness of water. Lancet, 1968, 1:1092.
7. Meyers D. Mortality and water hardness. Lancet, 1975, 1:398-399.
8. Popov VV. [On the question of a possible relationship between morbidity of the population with cholelithiasis and cholecystitis and the salt content and hardness of drinkingwater.] Gigiena i sanitarija, 1968, 33(6):104-105 (in Russian).

Dr KK Aggarwal

Padma Shri Awardee

President Confederation of Medical Associations in Asia and Oceania (CMAAO)

Group Editor-in-Chief IJCP Publications

President Heart Care Foundation of India

Past National President IMA