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Understanding those minerals in your bottled water

Minerals are inorganic compounds, that is, compounds without carbon. The body cannot produce most minerals on its own but needs them for many bodily functions. It is therefore essential to ingest these substances via food or drinks.

Any water bottled from a natural source, for example, a spring or aquifer, will contain some minerals. Prepared water, that is, water that has been prepared through reverse osmosis or distillation, typically has the minerals it originally contained removed. It may or may not be remineralised after purification.

The level of the mineral content in the water, and its composition, will depend on the amount of minerals dissolved from the rock it passed through. Depending on this composition, natural waters may contribute to the recommended daily intake of minerals while providing a natural source of healthy hydration.

“Like the planet we inhabit, our bodies comprise mostly water – the brain is 85% water, our blood is 90% water, and the liver, one of our most vital organs, is 96% water. Water — in all its forms — is therefore a vital component of our diet, as well as the healthiest beverage option for societies plagued by diseases such as obesity and diabetes,” said South African National Bottled Water Association (SANBWA) Executive Director, Charlotte Metcalf.

“Depending on the composition of the water, natural mineral waters can play a role in ensuring you or I receive our recommended daily intake of minerals. Each natural mineral water is different, with its own distinct taste, a unique set of properties and a specific mineral content derived from the geological conditions of the areas where the water is sourced. Consumers can choose their natural mineral water by taste, preference for still or sparkling.”

The important macro minerals found in natural waters are Calcium, Magnesium, Sodium, Chloride, Potassium, Sulphur, Iron and Zinc.

  • ​​​​Calcium is necessary to build strong bones and teeth, helps the heart to beat, and keeps muscles healthy and helps them contract. It must be consumed daily as the body cannot produce it. The RDA for anyone 14 years and older is 1000+mg and the upper limit 3000mg. According to the SANBWA Standard, there is no maximum permitted level of calcium in all categories of packaged waters.
  • Magnesium can’t be produced by the body, so it also needs to be consumed daily via a wholesome and balanced diet as it aids in bone growth and the function of nerves and muscles. The RDA for adults is between 300-400 mg. According to the SANBWA Standard, there is a maximum permitted level of magnesium in prepared waters of 70 mg/l but none for natural waters.
  • Another mineral that the body can’t produce on its own, sodium, is an electrolyte that helps control fluid balance in cells as well as aiding in muscle flexing and the flow of nerve impulses. The RDA for adults is 1500 mg. According to the SANBWA Standard, there is no maximum permitted level of sodium in any of the packaged water categories.
  • Chloride is an electrolyte that helps control fluid balance in cells, it helps maintain pH balance, and forms part of the acid found in the stomach which is necessary for digestion. The RDA for adults is 2300 mg. The SANBWA Standard suggests that a maximum level of sodium 250 mg/l in all of the packaged water categories be observed.
  • Potassium is an electrolyte aiding in the control of blood pressure and water balance in cells, and therefore helps maintain pH balance. It is vital for muscle contraction and nerve impulses, helps with proper function of heart and kidneys, and is necessary for carbohydrate and protein metabolism. The RDA for adults is 4 g (Source *). Again, there is no maximum dictated by the SANBWA Standard.
  • The human body does not produce any sulphate and the RDA for adults is 45 μg*. It forms part of proteins (it has a stabilising function) as well as part of the vitamins biotin and thiamin, and the hormone insulin, and is involved in body’s detoxification processes. According to the SANBWA Standard, the maximum permitted level of sulphate in prepared water is 250 mg/l and less than 1000 mg/l when measured as SO4 for natural waters. For all categories, the maximum permitted level of sulphite is 0.1 mg/l when measured as H2S.
  • Iron is vital for healthy blood as it helps red blood cells carry oxygen. It also plays a role in maintaining a healthy immune system, helps with brain development and function, and forms part of the enzyme reactions that carry messages from one nerve cell to another. Females (RDA 18 mg) need more iron than males RDA 8 mg), especially pregnant females (27 mg). According to the SANBWA Standard, the maximum permitted level of iron is 0.2 mg/l.
  • Zinc is involved in the synthesis or degradation of major metabolites such as carbohydrates, lipids and proteins, as well as in enzyme activity. It helps maintain a healthy immune function, in the stabilisation of the protein and genetic structure in cells, and in communication and division of cells. The RDA is 11 mg for males and 8 mg for females. According to the SANBWA Standard, the maximum permitted level of zinc in all categories of prepared waters is 5 mg/l.

Sources:

  • South African National Bottled Water Association (SANBWA) Bottled Water Standard 2018
  • Stellenbosch University:

https://www.sun.ac.za/english/faculty/healthsciences/nicus/how-to-eat-correctly/nutrients/dri

  • United States Department of Agriculture:

https://www.nal.usda.gov/fnic/dietary-reference-intakes

http://www.nationalacademies.org/hmd/~/media/Files/Activity%20Files/Nutrition/DRI-Tables/2_%20RDA%20and%20AI%20Values_Vitamin%20and%20Elements.pdf?la=en

*         NCBI:

https://www.ncbi.nlm.nih.gov/books/NBK222301/