More than 5,000 papers tell you: Why is it not recommended to drink purified water for a long time?

Since the outbreak of the epidemic, food health and safety have attracted more and more attention. Water is a high-frequency necessity in daily life, and people are paying more and more attention to the quality of drinking water and its relationship with health. More and more experts and scholars are investing in research on how to drink water scientifically? What impact will different types of drinking water have on health?

A paper titled "Qualitative Evidence-Based Research on the Effects of Purified Water on Health" from the Department of Nutrition and Food Hygiene, School of Public Health, Peking University, comprehensively analyzed the effects of drinking purified water on human health through more than 5,200 domestic and foreign literature, and proposed that the choice of purified water or mineral water should be based on one's own situation. For people who lack minerals in their diet, it is not recommended to drink purified water on a daily basis. For patients with urinary stones, purified water may have a certain protective effect.

Why does drinking water affect bone health?

More than 20 years ago, domestic experts conducted experiments to understand the relationship between drinking water hardness and bone density. According to hygiene standards, water with a total hardness of less than 75 mg/L is called soft water, and water with a total dissolved solids (TDS) content of less than 100 mg/L is called low-mineral water. The results showed that among people who drank tap water (low hardness), 10.1% had good bone density, and among people who drank deep groundwater, 65.1% had good bone density [1]. In other words, drinking water hardness is directly related to bone density.

Bone density is one of the important indicators for diagnosing osteoporosis. Osteoporosis can be divided into primary and secondary types. Primary osteoporosis can be divided into three types: postmenopausal osteoporosis (type I), senile osteoporosis (type II) and idiopathic osteoporosis (including adolescent type). Type I mainly occurs in women within 5 to 10 years after menopause, and type II mostly occurs in people over 70 years old.

There have also been studies abroad on the relationship between drinking water hardness and osteoporosis. In 2005, a study on drinking water for menopausal women with insufficient daily calcium intake showed that after 6 months, the serum bone remodeling indicators parathyroid hormone (PTH) and serum type 1 collagen cross-linked C-terminal peptide (S-CTX) of the group drinking high-calcium water decreased, which means that senile bone loss was significantly inhibited [2].

Recently, the team led by Professor Shu Weiqun of the Third Military Medical University of the Chinese People's Liberation Army published a paper titled "Drinking Natural Mineral Water Helps Maintain Bone Health in Young Mice with Metabolic Acidosis" in the authoritative nutrition journal "Nutrition Frontiers". The study randomly divided 60 3-week-old female young mice into 3 groups. Under the premise of providing a regular diet, they drank purified water and two weakly alkaline natural mineral waters (bicarbonate type and sulfate type natural mineral water). In each group, the blood, urine and femur data of young mice with metabolic acidosis after drinking different waters were compared and analyzed to evaluate the effects of different drinking water on the bone health of young mice with metabolic acidosis.

(Compared with acidic purified water, weakly alkaline natural mineral water can better neutralize the acid in the blood, buffer the acid-base balance in young mice, and reduce the calcium loss in young mice under metabolic acidosis. Weakly alkaline natural mineral water significantly reduces the titrated acid value (D), ammonium ion value (E) and net acid excretion value (F) in the urine of young mice)

Studies have shown that compared to acidic purified water, drinking natural mineral water rich in bicarbonate can not only replenish mineral elements such as potassium, calcium, sodium, and magnesium, but also regulate the acid-base balance and reduce calcium loss in bones, thus benefiting the body's bone health [3].

Drinking the right water can also protect cardiovascular health?

The discussion on the relationship between water hardness and cardiovascular disease has a long history. Since the 1950s, scholars from Japan, the United States and Europe have conducted a number of epidemiological studies on the relationship between the two.

The Essentials of Medical Geology published in 2005 summarized and concluded these viewpoints. Generally speaking, water hardness has a certain preventive effect on cardiovascular disease, especially when the water quality is between soft water and medium hardness, the preventive effect is more significant; every 6 mg/L increase in water magnesium concentration can reduce the incidence of congenital heart disease by 10%, and drinking water with a magnesium concentration of >98 mg/L can reduce the mortality rate of acute myocardial infarction in men and women by 19% and 25%, respectively [4].

Professor Shu Weiqun's team conducted drinking water intervention observations on a variety of subjects including rats and New Zealand rabbits, using tap water (TDS: 229 mg/L), natural water (TDS: 87.2 mg/L), artificial mineral water (TDS: 10.9 mg/L), and purified water (TDS: 12 mg/L) with significantly different mineral contents.

The results showed that after 6 months of intervention, purified water increased the TC TG atherosclerosis index of rats; after 12 months of intervention, purified water increased the levels of cardiovascular disease markers homocysteine ​​(Hcy), hypersensitive C-reactive protein (hs-CRP) and arginase in New Zealand rabbits, and artificial mineral water and purified water caused more obvious pathological changes in the heart and aortic arch.

In 2019, a cross-sectional study conducted in Slovakia on people aged around 40 came to a similar conclusion. The study found that the difference between the arterial age and the actual age of the group aged 46.3 ± 7.66 drinking soft water with low calcium and magnesium content was 4.32 years higher than that of the hard water group [5]. In other words, low water hardness has a certain negative impact on human cardiovascular health, which is manifested as a high degree of arteriosclerosis and a high arterial age.

Is purified water completely inedible? No, patients with urinary stones can drink it

Does purified water have no benefits to human health? Of course not. Many studies have shown that purified water has a protective effect on patients with urinary stones.

A study conducted in China in 2017 on 528 cases found that untreated spring water and well water were relatively hard; tap water was standardized and had a lower hardness than spring water and well water; boiled water had the lowest hardness. The proportion of patients with urolithiasis who drank raw water, well water, and spring water was significantly higher than that of the normal population, while the proportion who drank tap water and boiled water was significantly lower than that of the normal population. The study believes that low water hardness is a protective factor for urolithiasis[6].

In 1999, a crossover randomized controlled trial in Italy also reached a similar conclusion. The experiment was conducted on 18 volunteers aged around 46 years old. The results showed that drinking hard water was associated with higher urine pH and higher bicarbonate content (HCO-3 in hard water = 1 031 mg/L, HCO-3 in soft water = 73 mg/L). Compared with tap water and soft water, urinary calcium levels during hard water intake were significantly increased, indicating that the additional intake of calcium and water between meals would increase calcium excretion [7].

It can be seen that in the prevention and treatment of calcium kidney stones, drinking soft water (containing no or less soluble calcium and magnesium compounds) is better than hard water, because soft water is associated with a lower risk of calcium stone recurrence. For most people, it is recommended to choose drinking water rich in natural minerals for daily drinking, especially for the middle-aged and elderly people who are prone to osteoporosis, and adolescent students in the critical period of bone development.

【References】:

[1]: Shao Xunsheng, Wang Jianshe. Study on the relationship between bone density and soft water hardness in a training base [J]. Modern Scientific Instruments, 1999(4):50.

[2]: Meunier PJ, Jenvrin C, Munoz F, et alConsumption of a high calcium mineral water lowers biochemical indices of bone remodeling in postmenopausal women with low calcium intake[J].Osteoporosis Int200516(10):1203-1209

[3]: Latest research: Drinking weakly alkaline mineral water is good for bone health (lifetimes.cn) https://www.lifetimes.cn/article/47IRDTgn8s2

[4]: Selinus O, Alloway B, Centeno JA et al. Essentials of Medical Geology: Impacts of the Natural Environment of Public Health [M.Environ Health Perspect, 2005.113(11):A780

[5]: Rapant S, Cveckova V, Fajcikova K, et al. Hard water, more elastic arteries: a case study from Krupina district, Slovakia [J]. International Journal of Environmental Research and Public Health, 2019,16(9):1521

[6]: Chen Shaolin, Yao Jun, Xiao Manxian, et al. Study on the influence of drinking water habits on urolithiasis in Huaihua residents[J]. Nursing Research, 2017, 31(13): 1639-1640.

[7]:Bellizzi V,Denicola L,Minutolo R,et al. Effects of water hardness on urinary risk factors for kidney stones in patients with idiopathic nephrolithiasis [J]. Nephron,1999,81 (Suppl. 1): 66-70.