Drinking deep seawater (DSW) with high levels of magnesium (Mg) decreased serum lipids in animal studies. Therefore the effects of drinking DSW on blood lipids and its antioxidant capacity in hypercholesterolemic subjects were investigated. DSW was first prepared by a process of filtration and reverse osmosis, and then the concentrated DSW with high levels of Mg was diluted as drinking DSW. Forty-two hypercholesterolemic volunteers were randomly divided into three groups: reverse osmotic (RO) water, DSW (Mg: 395 mg/L, hardness 1410 ppm), and magnesium-chloride fortified (MCF) water (Mg: 386 mg/L, hardness 1430 ppm). The subjects drank 1050 mL of water daily for 6 weeks, and blood samples were collected and analyzed on weeks 0, 3, and 6. Drinking DSW caused a decrease in blood total cholesterol levels and this effect was progressively enhanced with time. Serum low-density lipoprotein–cholesterol (LDL-C) was also decreased by DSW. Further, total cholesterol levels of subjects in the DSW group were significantly lower than those in the MCF water or RO water groups. Compared with week 0, the DSW group had higher blood Mg level on weeks 3 and 6, but the Mg levels were within the normal range in all three groups. DSW consumption also lowered thiobarbituric acid-reactive substances (TBARS) values in serum. In conclusion, DSW was apparently effective in reducing blood total cholesterol and LDL-C, and also in decreasing lipid peroxidation in hypercholesterolemic subjects.
Deep seawater (DSW) is clean, sanitary, and characterized by low temperature, nonpathogenic, abundant nutrients, and high content of minerals such as, magnesium (Mg), calcium (Ca), potassium (K), etc.1–3 In recent years, DSW has been widely used in various industries, such as food processing, agriculture, and the pharmaceutical and cosmetic industries. Cardiovascular disease and cerebrovascular diseases are major causes of mortality in developing countries, and the second and third highest causes of mortality in Taiwan, respectively. There are a number of factors involved in the etiology of cardio-cerebrovascular diseases, but undeniably, the primary factor is atherosclerosis. As hypercholesterolemia is the major cause of atherosclerosis, a treatment for hyperlipidemia would be of obvious benefit for the prevention of atherosclerosis.
Animals studies show that administration of DSW to rabbits fed a high-cholesterol diet resulted in decreases in blood total cholesterol and low-density lipoprotein–cholesterol (LDL-C) levels, and accelerated the reduction of blood lipid concentrations in hyperlipidemic rabbits.4 Moreover, Kimura et al.3 pointed out that higher Mg (600 and 1000 ppm) water made from DSW decreased cholesterol by 18% and 15%, respectively, and may be a useful natural drink to improve lipid metabolism and to prevent atherosclerosis in rats. Recent study showed that mice given DSW experienced lower blood total cholesterol and triacylglycerol concentration when compared with those given pure water.5 Drinking of DSW, therefore, appeared to alleviate the myocardial injuries caused by a high lipid/cholesterol diet. On the other hand, DSW was suggested to have a potential role as an anti-obesity agent and might play beneficial roles in glucose metabolism.6–7
Epidemiological studies show that Mg depletion in drinking water is associated with the risk of cardiovascular diseases8–9 and this effect was attributed to the protective effect of high content of Ca and Mg, indicating that Mg was protective against acute myocardial infarction. Recently, Kishimoto et al.10 showed that Mg supplementation could improve postprandial hyperlipidemia in healthy subjects. Moreover, Mg intake is inversely associated with prevalence of the metabolic syndrome and oxidative stress.11 These results indicate that the hardness of drinking water, especially its Mg content, is associated with retarding the development of cardiovascular diseases.
To date, to the best of our knowledge, there is no report describing the effect of DSW on lipid metabolism in a human study. In the present study, we investigated the effect of the intake of DSW rich in Mg, at a degree of hardness of 1400 ppm prepared from concentrated DSW, for 6 weeks on lipid metabolism and its antioxidant capacity in hypercholesterolemic subjects.
Subjects and Methods
DSW was obtained from the Pacific Ocean at a depth of 662 m, at a distance of 5 km off the coast of Hualien County, Taiwan. The obtained water was subjected to a process of filtration, reverse osmosis, and concentration. The concentrated DSW had a hardness of 300,000 mg/L and Mg content was 75,000 mg/L.
Water for this experiment included: (1) reverse osmotic (RO) water, produced by reverse osmosis of DSW; (2) DSW, obtained by diluting the concentrated DSW with RO water to achieve a Mg concentration of 350 mg/L and hardness of 1400 mg/L; and (3) Magnesium-chloride fortified (MCF) water, obtained by dissolving magnesium chloride hexahydrate (MgCl2·6H2O, purity 98%) in RO water to get a similar Mg content to that of DSW. All water used in the experiment was pasteurized and bottled and provided by Taiwan Yes Deep Ocean Water Co., Ltd.
Between April 2009 and November 2009, 42 hypercholesterolemic individuals (23 men and 19 women) were selected from a population in Northern Taiwan for this 6-week study at Cardinal Tien Hospital in Yung Ho (New Taipei City, Taiwan). Inclusion criteria for the study were serum total cholesterol>200 mg/dL and LDL-C>130 mg/dL, 30–65 years old and BMI between 22 and 28 kg/m2. No subjects in this study had a history of cardiovascular diseases, diabetes, chronic inflammation, liver/kidney disease, or hypothyroidism. None of the subjects used herbal medicines, or took supplements such as Monascus, phytosterols, or fish oil, which are known to affect blood lipid levels.
The subjects accepted into the study were requested to maintain their regular diet and exercise regimen. They were instructed to avoid social drinks and to limit alcohol consumption to less than 2 servings/day. The volunteers were informed about the content and detailed procedures of the study, and signed consent was obtained from all subjects prior to participation in the study. The study was conducted according to the guidelines laid down in the Declaration of Helsinki and the protocol was approved by Fu Jen Catholic University’s Institutional Review Board.
The experiment was conducted using double-blind, randomized controlled DSW supplementation. The subjects were randomly divided into three groups as follows: (1) RO group (7 men and 7 women), (2) DSW group (10 men and 4 women), and (3) MCF water group (6 men and 8 women). All subjects in this study drank three bottles of water (350 mL/bottle) daily, for a total volume consumed daily by each subject of 1050 mL. The amount of Mg in the water was equivalent to the Recommended Daily Allowance (RDA). Subjects were advised to consume one bottle of water every morning, afternoon, and evening, and to try to finish drinking each bottle of water by drinking from the bottle 3–4 times. Mg concentrations in RO water, DSW and MCF water were 1.3, 395 and 386 mg/L, respectively. The hardness concentrations of the water were: 8 ppm for RO, 1410 ppm for DSW, and 1430 ppm for MCF (Table 1).
|Mineral/salt||RO water (mg/L)||DSW (mg/L)||MCF water (mg/L)|
Analyzed by SGS Taiwan Ltd. The levels (ppb) of trace elements in DSW were, lithium 48.8, selenium 8.69, silicon 4.02, molybdenum 2.81, zinc 1.61, and strontium 1.93.
RO water, reverse osmotic water; DSW, deep seawater; MCF water, magnesium-chloride fortified water; ND, not detectable.
Blood sampling and serum lipid and mineral analysis
Blood samples were collected into vacuum tubes without anticoagulants on weeks 0, 3, and 6, between 9:00 and 10:00 after 10- to 12-hour fasting. Samples were centrifuged at 1400 g for 15 min and serum was collected. Serum samples were kept at −80°C for further analysis as previously reported.12
Commercial enzymatic kits (Randox Lab., Ltd.) were used to analyze serum total cholesterol, LDL-C, and high-density lipoprotein–cholesterol (HDL-C)13 and triacylglycerols.14 Serum thiobarbituric acid-reactive substances (TBARS) were measured by the method of Oteiza et al.,15 using tetraethoxypropane as the standard. Total antioxidant status of serum was analyzed according to the method of Miller et al.16 and expressed as trolox equivalent antioxidant capacity. Alanine aminotransferase (ALT), aspartate aminotransferase (AST) and blood urea nitrogen (BUN) were measured using commercial kits (Randox). The mineral levels of serum Mg and Ca were measured using commercial kits (Randox). Sodium (Na) and K concentration of serum were analyzed by atomic absorption spectroscopy.
Basic characteristics and food intake
Anthropometric data were collected from all subjects in the study. At the beginning (week 0) and at the end (week 6) of this study, food intake was recorded for three consecutive days (one was required to be a holiday or Saturday/Sunday). Before the study, subjects were educated using food charts and a food exchange list. The nutrition composition of the 3-day dietary records was calculated using Nutritionist Professional software (E Kitchen Business Corporation), and the nutrient database was based on the Taiwan food composition table (Department of Health, 2009, www.doh.gov.tw/FoodAnalysis/ingredients.htm).
SAS 9.1.3 software was used to conduct the statistical analysis. Data were expressed using mean and standard deviation. Data were analyzed by one-way analysis of variance followed by inspection of all differences between pairs of means by Duncan’s multiple-range test in basal data, different water treatment at same period and drinking water at various times. Food intakes between after and before experiments were analyzed by paired t-test. Correlations between serum Mg level and serum total cholesterol were tested by Pearson’s correlation analysis. P<.05 was considered to be statistically significant.
Baseline characteristics of the subjects and 3-days food intake
Age, height, body weight, waist circumference, hip circumference, blood pressure, and liver functions were recorded before the experiment and no statistical differences were noted (Table 2). Although differences in renal function were shown among three groups, their BUN values were in the normal range (7–21 mg/dL), suggesting normal kidney function. The concentrations of cholesterol, HDL-C, LDL-C, and triacylglycerols in subjects showed no significant differences among the groups at beginning of experiment.
|Parameter||RO water||DSW||MCF water|
|Body weight (kg)||68.6±16.6||68.8±11.6||69.0±11.7|
|Waist circumference (cm)||86.9±8.3||86.2±7.7||86.3±8.0|
|Hip circumference (cm)||98.6±8.0||98.0±5.2||98.5±4.6|
|Systolic blood pressure (mm Hg)||125±11||123±13||121±17|
|Diastolic blood pressure (mm Hg)||79±9||82±9||80±10|
|Total cholesterol (mg/dL)||241.2±23.3||243.9±15.5||242.0±27.9|
|Aspartate aminotransferase (U/L)||29.7±12.1||24.9±7.9||27.6±7.4|
|Alanine aminotransferase (U/L)||29.9±11.8||26.6±8.3||27.7±6.4|
|Blood urea nitrogen (mg/dL)||11.8±2.7b||14.9±3.5a||12.4±3.1ab|
Values are mean±SD, n=14.
SD, standard deviation; HDL-C, high-density lipoprotein–cholesterol; LDL-C, low-density lipoprotein–cholesterol.
Table 3 shows the food intake 3 days before and 3 days after the experiment. No statistical differences were found in energy intake, carbohydrate, fat, protein, dietary fiber, vitamin E, or vitamins B1, B2, B6, B12, or C. Intake of minerals, such as K, Ca, Mg, iron, and zinc showed no differences before or after the experiment. Na intake was lower (P=.033) before the study in the DSW group, but no difference was found between RO and MCF groups.
|Before||After||P value||Before||After||P value||Before||After||P value|
|Vitamin A (μg RE/day)||957±538||1104±1054||0.653||1456±1252||717±553*||0.012||1248±1225||1108±842||0.635|
|Vitamin E (mg α-TE/day)||7.3±3.0||11.4±10.0||0.190||9.5±5.8||8.8±3.1||0.630||7.8±3.0||9.4±4.6||0.253|
|Vitamin B1 (mg/day)||1.2±0.8||1.0±0.2||0.333||0.9±0.3||0.9±0.2||0.994||1.0±0.6||0.9±0.3||0.419|
|Vitamin B2 (mg/day)||1.2±0.8||1.2±0.7||0.916||1.0±0.5||1.0±0.4||0.396||1.0±0.3||0.9±0.3||0.215|
|Vitamin B6 (mg/day)||1.4±0.6||1.3±0.3||0.395||1.2±0.5||1.2±0.4||0.761||1.2±0.4||1.2±0.5||0.779|
|Vitamin B12 (μg/day)||4.8±4.1||5.1±5.3||0.826||4.9±4.2||6.2±4.5||0.395||5.3±4.2||3.6±2.2||0.244|
|Vitamin C (mg/day)||102±43||108±60||0.770||136±99||103±49||0.329||102±61||119±100||0.466|
Values are mean±SD, n=14.
Effects of DSW on serum and lipoprotein lipids
Compared with the level at week 0, serum total cholesterol of the DSW group showed a 7% and 13.7% decrease at weeks 3 and 6, respectively (Table 4), and this effect was progressively enhanced with time. In addition, there was a significant decrease in serum LDL-C level of 11.7% and 15.4% at weeks 3 and 6, respectively, compared with that of week 0. Further, total cholesterol levels of subjects in the DSW group were significantly lower than those of the MCF or RO groups, and the changes in LDL-C and HDL-C showed a similar pattern of change to that of total cholesterol. Compared with the ratio of LDL-C/HDL-C at week 0, a lower tendency was observed at weeks 3 and 6 in the DSW group. Drinking DSW had no significant effect on triacylglycerol levels. On the other hand, there showed no gender-dependent difference in serum or lipoprotein lipids.
|Parameters/groups||Week 0 (mg/dL)||Week 3 (mg/dL)||Week 6 (mg/dL)|
Values are mean±SD, n=14.
Effects of DSW on serum minerals, liver and kidney functions, and blood pressure
No statistical differences were found in serum Mg, Na, K, and Ca levels in the DSW group during the experimental period (Table 5). There was no difference in serum Mg between the DSW and MCF groups. There was no evidence of deficiency or over-dosage of Mg; Mg concentration was within a normal range throughout the entire study. However, Mg levels at weeks 3 and 6 were higher than that of week 0 in DSW and MCF groups. Figure 1 shows the relationship between serum Mg and total cholesterol at weeks 0, 3, and 6. Although there was no significant correlation between Mg and cholesterol at those time points, Figure 1 shows an inverse tendency between the two factors at weeks 0 (r=−0.26119, P=0.0948) and 6 (r=−0.26396, P=0.0912).
|Parameter/groups||Week 0||Week 3||Week 6|
Values are mean±SD, n=14.
Water types had no effect on the activities of AST and ALT. In addition, no statistical differences were observed in BUN and blood pressure during the experiment (data not shown).
Effects of DSW on serum antioxidant capacity and fat peroxidation
In the present study, we determined the state of oxygen stress by measuring serum TBARS values and total antioxidant capacity (TAC). The results indicated no significant differences among these three groups in serum TAC (Table 6). However, TBARS values were lower at weeks 3 and 6 than at week 0 in the DSW group.
|Parameter/groups||Week 0||Week 3||Week 6|
|Serum TEAC (mM)|
|Serum TBARS (nmol/mL)|
Values are mean±SD, n=14.
TEAC, trolox equivalent antioxidant capacity.
At the beginning of the study, the average values of serum total cholesterol among the three groups were in the range of 241–244 mg/dL, and LDL-C was in the range of 143–156 mg/dL. According to the ATP III of NCEP (U.S. National Cholesterol Education Program, 2001), subjects in this study had marginally high or high values of serum cholesterol and LDL-C, which therefore disposed them to a high risk of developing cardiovascular diseases. We found that the total blood cholesterol and LDL-C levels were reduced in hyperlipidemic subjects, and this reduction was proportional to the length of drinking time. These data were consistent with the results obtained from previous animal studies.4,17 Further, Miyamura et al.18 also found a decline of total cholesterol and LDL-C in rabbits fed a high cholesterol diet with DSW drinking for 12 weeks, and DSW was more effective than surface seawater in preventing atherosclerosis.
Although the mechanism of the cholesterol-lowering action of Mg is unknown, the hypocholesterolemic effects of DSW are thought to be the influence of minerals.2,4,11 Rabbits fed a high cholesterol diet supplemented with Mg (36 mg/100 g) for 6 months were found to have a significant decrease in serum cholesterol with reduced cholesterol accumulation on artery walls, and increased lipid excretion in feces.19 Vaskonen20 proposed Ca and Mg might bind with fatty acids and bile acids in the small intestine, which then inhibits the absorption of saturated fatty acid, a mechanism which has also been demonstrated inhibit fat absorption.10
DSW is rich in minerals, and in our study the Mg concentration was 395 mg/L. Studies have indicated that Mg supplementation could potentially reduce total blood cholesterol3 and prevent some kinds of cardiovascular disease, including atherosclerosis.21,22 Intake of desalted DSW with high Mg improved lipid metabolism and was apparently capable of preventing atherosclerosis. Recently, Schoppen et al.23 pointed out that drinking sodium bicarbonate–rich mineral waters could reduce postprandial lipemia in healthy postmenopausal women when compared to drinking low mineral content water. Moreover, these mineral rich waters improve lipid profile in moderately hypercholesterolemic young subjects and could be applied in dietary interventions to reduce cardiovascular risk.24
It is known that hardness of drinking water is related to cardiovascular diseases.25 Yang et al.26 indicated that there was a significant increase in mortality in ischemic cardiovascular disease if hardness of drinking water was below 150 ppm. The hardness of drinking water in the current study was 1410 ppm, and we assumed this would reduce the risk of cardiovascular diseases in our subjects. Mg was the major mineral in DSW used in this study, and Mg levels were 50 times higher than Ca levels. Based on the results of previous studies, it is reasonable to postulate that Mg levels have an inverse correlation with cardiovascular diseases.
However, there are many minerals and trace elements in DSW, such as sulfate, lithium, selenium, molybdenum, silicon, and zinc, etc. In the present study, a reduction of serum cholesterol concentration and TBARS level was observed only in subjects drinking DSW but not those drinking MCF water. However, serum Mg level was increased only at the 3rd week by drinking DSW. Thus, the Mg content in these types of water could not be a sole factor behind this effect. We therefore postulate that Mg was not the sole factor in reducing lipids, as other trace elements may also be involved. Further studies are warranted to further clarify the mechanism.
Our results showed that DSW was capable of significantly decreasing TBARS values. Similar results regarding antioxidative capacity of DSW was reported in male hamsters’ serum and liver.5 In another study, administration of DSW to rabbits fed a high cholesterol diet for 12 weeks resulted in lowering TBARS values.18 The lower content of Mg in RO water might cause an oxidative stress, and the similar results were showed between TAC and Mg intake in healthy young adults.27
The food intake that was recorded for a 3-day period at the beginning and at the end of the study revealed no differences in intake of antioxidants (such as vitamin E, vitamin C, iron, zinc, etc.) between pre- and poststudy data. Therefore, any possible mechanism by which food intake could have reduced values of TBARS is unclear, which suggests that the lower values were caused by water consumption and not by factors related to food intake. Rayssiguier et al.28 reported that Mg deficiency could enhance fat peroxidation in animal tissues and decrease antioxidants. Apparently, free radicals were involved in the process. Mg deficiency in rats increased blood TBARS values and free radicals generation.29,30
On the other hand, DSW utilized in the present study had higher sulfur salt content (167 mg/L) than that of the RO or MCF. Sulfur is a nonmetallic element, and comprises 0.25% of human body weight.31 Sulfur is contained in methionine, cysteine, and taurine, and takes part in many enzyme reactions and is involved in protein synthesis. Recent research indicates that sulfur-containing molecules may play an important role in antioxidation, and are involved in oxidative stress caused by aging and age-related disorders.32,33
In conclusion, we have confirmed the null hypothesis that DSW was effective in significantly reducing serum total cholesterol and LDL-C in hypercholesterolemic subjects, and these hypocholesterolemic effects progressively increased with duration of DSW administration. DSW also lowered serum TBARS values in hyperlipidemic subjects. There was a tendency of reverse correlation between serum Mg and cholesterol concentration. The other trace elements in DSW may be involved in the overall lipid-lowering effects, and further studies are warranted to elucidate the underlying mechanisms.
This research was supported by a grant from the Industrial Development Bureau (Grant No. 9831101073-6), Ministry of Economic Affairs. We are also grateful to Taiwan Yes Deep Ocean Water Co., Ltd. (Taipei, Taiwan) for offering samples of water.
Author Disclosure Statement
No competing financial interests exist.
Articles from Journal of Medicinal Food are provided here courtesy of Mary Ann Liebert, Inc.