Researchers from Harvard School of Public Health in Boston, MA, as well as from the German Institute of Human Nutrition in Nuthetal, Germany, conducted a study on diabetes prevention.
Funding for the study did not influence any aspects of the research, including study design, data collection, analysis, publication decisions, or manuscript preparation.
The study received financial support from the National Institutes of Health through grants DK58845 and CA50385.
The study was received on December 13, 2011, accepted on March 22, 2012, and published in June 2012.
It is important for individuals to be aware of the symptoms of prediabetes, which include increased thirst, frequent urination, fatigue, blurred vision, and slow-healing wounds. By recognizing these symptoms early on, individuals can take steps to reduce their risk of developing type 2 diabetes.
In addition to the findings mentioned in the abstract, the study also revealed that women who replaced one serving of SSBs or fruit juices with other beverages such as coffee, tea, or artificially sweetened beverages did not experience the same decrease in T2D risk. This suggests that water specifically may have unique benefits in reducing the risk of developing type 2 diabetes in women.
Furthermore, the research found that the association between water consumption and T2D risk was more pronounced in women who were overweight or obese, as well as those with a family history of diabetes. This underscores the importance of considering individual risk factors when making dietary choices to prevent the onset of T2D.
Overall, these findings highlight the potential impact of beverage choices on diabetes prevention and suggest that substituting sugary drinks with water may be a simple yet effective strategy for reducing T2D risk in American women. Further research is needed to explore the underlying mechanisms behind these associations and to determine whether similar effects are seen in other populations.
INTRODUCTION
Extensive research has explored the association between beverage consumption and T2D risk, noting that coffee intake may reduce T2D risk, while SSBs and fruit juices could increase it. Experts suggest swapping these sugary drinks with no-calorie or low-calorie options like water to lower T2D risk.
We examined how plain-water intake and the substitution of water for SSBs or fruit juices impact T2D risk in a cohort of women. Additionally, we investigated the relationship between total beverage intake and the risk of developing T2D in this group.
SUBJECTS AND METHODS
Study population
The Nurses’ Health Study II began in 1989 with 116,671 female nurses, of which 82,902 were included in our analysis after exclusions. Institutional review boards of Brigham and Women’s Hospital and Harvard School of Public Health approved the NHS II.
Assessment of water and other beverage intakes
Regular follow-up questionnaires provided updated data on lifestyle factors, weight, smoking, physical activity, and other risks for chronic diseases.
Assessment of covariates
Participants diagnosed with diabetes completed supplementary questionnaires to verify their status. Cases were confirmed based on specific criteria.
Assessment of diabetes
Person-years were calculated from the baseline questionnaire date to the diagnosis of T2D, death, or end of follow-up. Cox proportional hazards models were utilized to estimate T2D risk related to plain-water consumption, adjusting for various factors such as age, BMI, race, and dietary patterns.
| Traits | Drinking Plain Water 2 | ||||
| |||||
| Number of Participants | 17,524 | 11,820 | 25,707 | 15,422 | 12,429 |
| Age (y) | 36.1 ± 4.7 | 36.3 ± 4.6 | 36.1 ± 4.6 | 36.1 ± 4.7 | 36.1 ± 4.7 |
The average age of participants in the study was 36.1 years with a standard deviation of 4.7. Another group had an average age of 36.3 years with a standard deviation of 4.6. The remaining groups all had an average age of 36.1 years, with standard deviations ranging from 4.6 to 4.7.
| Body Mass Index (kg/m2) | 24.0 ± 5.1 | 23.9 ± 4.8 | 24.3 ± 5.1 | 24.8 ± 5.2 | 25.4 ± 5.5 |
| Weekly MET-hours of Physical Activity 3 | 17.3 ± 24.4 | 18.2 ± 25.2 | 20.2 ± 26.0 | 23.1 ± 28.4 | 28.0 ± 32.3 |
Statistics show Mean ± SD for all values or percentage.
An equivalent measure is 240 mL in a single cup.
MET-h refers to metabolic equivalent task hours.
Throughout a period of 1,115,427 person-years of monitoring, we observed 2718 new cases of T2D. The risks of T2D linked to plain-water consumption, as analyzed with a 4-year time lag, are presented in Table 2. When adjusting for age and BMI, there was no significant correlation between plain-water intake and the risk of developing T2D within different intake categories. The results remained consistent even after considering various lifestyle and risk factors such as diet quality, with Relative Risks (95% CIs) of 0.93 (0.82, 1.05), 0.93 (0.83, 1.05), 1.09 (0.96, 1.24), and 1.06 (0.91, 1.23) respectively (P-trend = 0.15).
TABLE 2.
Analysis of Type 2 diabetes based on plain-water intake within a 4-year lag period
| Plain-water intake | Cases/person-years | Age – and BMI-adjusted model 1 | Multivariable model 1 2 |
| 503/215,788 | 1.00 | 1.00 | |
| 1 cup/d | 551/245,514 | 0.91 (0.81, 1.03) | 0.93 (0.82, 1.05) |
| 2–3 cups/d | 868/374,218 | 0.88 (0.78, 0.98) | 0.93 (0.83, 1.05) |
| 4–5 cups/d | 485/173,941 | 1.00 (0.88, 1.14) | 1.09 (0.96, 1.24) |
| ≥6 cups/d | 311/105,967 | 0.95 (0.83, 1.10) | 1.06 (0.91, 1.23) |
| P-linear trend 3 | 0.92 | 0.15 |
All the values are RRs with 95% CIs in brackets.
The assessment treated plain-water intake as a continuous variable.
In an alternative analysis considering only baseline water intake, the results were comparable to the reference group (P-trend = 0.13; refer to Table 3 in the online issue under “Supplemental data”). A variation in the analysis which used current water intake also showed similar outcomes. Additionally, in a sensitivity analysis without a 4-year lag, a slight positive association was noticed in participants who consumed the highest amount of plain water (≥6 cups/d) compared to the reference group (P-trend = 0.01), while other categories did not show significant differences compared to the reference group (refer to Table 3 under “Supplemental data” in the online issue).
During predefined stratified analyses (Table 3), a tendency towards an increased risk of T2D was evident in more physically active women (>9 MET-h/wk; P-trend = 0.10 in this subgroup) and women with high cholesterol levels (P-trend = 0.07 in this subgroup). However, the interaction p-values were not significant for both scenarios (P-interaction > 0.10).
TABLE 3.
Analysis of Type 2 diabetes based on plain-water intake in the 4-year lagged analysis: results of the stratified analyses 1
| Plain-water consumption | ||||||
| 1 cup/d | 2–3 cups/d | 4–5 cups/d | ≥6 cups/d | P-linear trend | ||
| Stratified by BMI | ||||||
| 1.00 | 1.03 (0.82, 1.30) | 0.95 (0.76, 1.19) | 0.95 (0.72, 1.24) | 1.09 (0.80, 1.49) | 0.66 | |
| ≥30 kg/m 2 (2057 cases) | 1.00 | 0.92 (0.79, 1.06) | 0.93 (0.81, 1.06) | 1.12 (0.97, 1.30) | 1.01 (0.85, 1.19) | 0.21 |
| Stratified by physical activity level | ||||||
| 1.00 | 0.83 (0.71, 0.98) | 0.90 (0.78, 1.05) | 1.11 (0.93, 1.32) | 1.04 (0.84, 1.29) | 0.27 | |
| ≥9 MET-h/wk (1106 cases) | 1.00 | 1.11 (0.89, 1.38) | 1.11 (0.91, 1.35) | 1.21 (0.97, 1.50) | 1.23 (0.97, 1.55) | 0.10 |
| Stratified by hypertension | ||||||
| Yes (1080 cases) | 1.00 | 0.85 (0.70, 1.04) | 0.82 (0.69, 0.99) | 0.99 (0.81, 1.22) | 1.01 (0.80, 1.27) | 0.72 |
| No (1638 cases) | 1.00 | 0.99 (0.84, 1.16) | 0.98 (0.85, 1.13) | 1.14 (0.97, 1.35) | 1.03 (0.85, 1.25) | 0.33 |
| Stratified by high cholesterol | ||||||
| Yes (1247 cases) | 1.00 | 1.03 (0.86, 1.24) | 1.06 (0.89, 1.25) | 1.10 (0.90, 1.34) | 1.21 (0.97, 1.51) | 0.07 |
| No (1471 cases) | 1.00 | 0.86 (0.73, 1.01) | 0.84 (0.72, 0.98) | 1.08 (0.91, 1.29) | 0.96 (0.78, 1.17) | 0.78 |
Thirty-five women were not considered in the analysis due to missing physical activity level values. MET-h refers to metabolic equivalent task hours.
Overall beverage consumption did not show a significant association with T2D risk (refer to Table 4 under “Supplemental data” in the online issue). Among specific beverages, a daily intake of one cup of coffee was linked with a 10% reduced risk of T2D (RR: 0.90; 95% CI: 0.87, 0.92), while one serving of SSBs per day was associated with a 9% increased risk (RR: 1.09; 95% CI: 1.05, 1.14), and one serving of fruit juices daily had an 11% higher risk (RR: 1.11; 95% CI: 1.05, 1.17). The risks associated with ASBs, tea, and milk were minimal (refer to Table 4 under “Supplemental data” in the online issue). Substituting 1 cup of plain water per day for 1 serving of SSBs or fruit juices was correlated with 7% (95% CI: 3%, 11%) and 8% (95% CI: 2%, 13%) lower risks of developing T2D, respectively (Figure 1). Additionally, substituting coffee or milk for SSBs or fruit juices was significantly linked to a 12–17% risk reduction, and replacing ASBs or tea for SSBs or fruit juices was tied to a 5–7% lower risk.
FIGURE 1.
DISCUSSION
In this extensive study of US young and middle-aged women, no direct association was found between plain water consumption and the risk of T2D. Nevertheless, there was a moderate reduction in risk when plain water was used as a substitute for SSBs or fruit juices.
In the years 2005–2006, the average daily water intake for men in the United States was 3.5 liters, while for women it was 2.9 liters, according to data from NHANES. This information was gathered through 24-hour dietary recalls, taking into account plain water, beverages, and moisture from foods. Our study utilized a Food Frequency Questionnaire (FFQ) to collect data on water and beverage intake, excluding moisture from foods, focusing only on plain water and other beverages. For women aged 26–45, the median total fluid intake was 8.2 servings per day, in line with NHANES findings. Interestingly, although plain water intake was lower in our research compared to NHANES, women who consumed more plain water tended to have higher BMIs and were more physically active.
Interestingly, in our study, there was no significant link between plain water or total fluid intake and the risk of developing Type 2 Diabetes (T2D). However, a French study proposed that a low intake of plain water could potentially elevate the risk of new-onset hyperglycemia. Various factors influence the intake of total fluid and plain water, such as age, body size, physical activity, existing health conditions, and environmental temperature. In our cohort, water intake showed a strong correlation with BMI, possibly indicating that obese individuals consumed more water due to symptoms of prediabetes or other health issues. The increase in water consumption could also be a result of reverse causation related to symptoms of diabetes.
Replacing sugary drinks like sweetened beverages (SSBs) or fruit juices with plain water has been linked to a decreased risk of developing T2D. SSBs and fruit juices have both been associated with a higher risk of T2D. By substituting these drinks with plain water, there is a potential to significantly reduce the risk of T2D within the general population. Additionally, replacing SSBs or fruit juices with coffee or milk has shown a lower risk of T2D, consistent with previous research. However, artificially sweetened beverages (ASBs) and tea have shown a slight increase in the risk of T2D.
Despite some limitations such as a predominantly European ancestry population and possible errors in dietary assessments, our study, which included a large sample size and repeated evaluations of diet and lifestyle factors, offers valuable insights into making healthier beverage choices to lower the risk of diabetes.