Are we being drowned by overhydration advice on the Internet?

Quality and accuracy of online nutrition-related information: a systematic review of content analysis studies

OBJECTIVE

This systematic review aimed to summarise the level of quality and accuracy of nutrition-related information on websites and social media and determine if quality and accuracy varied between websites and social media or publishers of information.

DESIGN

This systematic review was registered with PROSPERO (CRD42021224277). CINAHL, MEDLINE, Embase, Global Health and Academic Search Complete were systematically searched on 15 January 2021 to identify content analysis studies, published in English after 1989, that evaluated the quality and/or accuracy of nutrition-related information published on websites or social media. A coding framework was used to classify studies' findings about information quality and/or accuracy as poor, good, moderate or varied. The Academy of Nutrition and Dietetics Quality Criteria Checklist was used to assess the risk of bias.

SETTING

N/A.

PARTICIPANTS

N/A.

RESULTS

From 10 482 articles retrieved, sixty-four were included. Most studies evaluated information from websites (n 53, 82·8 %). Similar numbers of studies assessed quality (n 41, 64·1 %) and accuracy (n 47, 73·4 %). Almost half of the studies reported that quality (n 20, 48·8 %) or accuracy (n 23, 48·9 %) was low. Quality and accuracy of information were similar on social media and websites, however, varied between information publishers. High risk of bias in sample selection and quality or accuracy evaluations was a common limitation.

CONCLUSION

Online nutrition-related information is often inaccurate and of low quality. Consumers seeking information online are at risk of being misinformed. More action is needed to improve the public's eHealth and media literacy and the reliability of online nutrition-related information.

Exercise-Induced Hyponatremia: An Assessment of the International Hydration Recommendations Followed During the Gran Trail De Peñalara and Vitoria-Gasteiz Ironman Competitions

Introduction

Hyponatremia often occurs during the practice of endurance sports. We evaluated the impact on hyponatremia of the hydration recommendations of the Third International Exercise-Associated Hyponatremia Consensus Development Conference 2015 (3IE-AHCD) during the 2017 Gran Trail de Peñalara marathon (GTP) and the Vitoria Gasteiz Ironman triathlon (VGI).

Methods

Prospective study of GTP and VGI athletes participating in four information sessions in the months prior to the events, to explain that hydration should only be according to their level of thirst, per the recommendations of the 3IE-AHCD. Consenting event finishers were included in final analysis. Pre- and post-race anthropometric and biochemical parameters were compared.

Results

Thirty-six GTP (33 male) and 94 VGI (88 male) finishers were evaluated. GTP race median fluid intake was 800 ml/h, with 900 ml/h in the VGI race. 83.3% GTPfin and 77.6% VGIfin remained eunatremic (blood sodium 135–145 mmol/L). Only 1/36 GTP and 1/94 VGI participant finished in hyponatremia, both with a sodium level of 134 mmol/L. Fourteen percent of GTP, and 21.2% of VGI participants finished in hypernatremia, with no increase in race completion times. No participating athlete required medical attention, except for musculoskeletal complaints. Pro-BNP and Copeptin levels rose significantly. Changes in copeptin levels did not correlate with changes in plasma osmolality, nor total body water content in impedance analysis.

Conclusions

Recommending that athletes' fluid intake in endurance events be a function of their thirst almost entirely prevented development of hyponatremia, without induction of clinically significant hypernatremia, or a negative repercussion on race completion times.

Pathophysiological Mechanisms by which Heat Stress Potentially Induces Kidney Inflammation and Chronic Kidney Disease in Sugarcane Workers

BACKGROUND

Chronic kidney disease of non-traditional origin (CKDnt) is common among Mesoamerican sugarcane workers. Recurrent heat stress and dehydration is a leading hypothesis. Evidence indicate a key role of inflammation.

METHODS

Starting in sports and heat pathophysiology literature, we develop a theoretical framework of how strenuous work in heat could induce kidney inflammation. We describe the release of pro-inflammatory substances from a leaky gut and/or injured muscle, alone or in combination with tubular fructose and uric acid, aggravation by reduced renal blood flow and increased tubular metabolic demands. Then, we analyze longitudinal data from >800 sugarcane cutters followed across harvest and review the CKDnt literature to assess empirical support of the theoretical framework.

RESULTS

Inflammation (CRP elevation and fever) and hyperuricemia was tightly linked to kidney injury. Rehydrating with sugary liquids and NSAID intake increased the risk of kidney injury, whereas electrolyte solution consumption was protective. Hypokalemia and hypomagnesemia were associated with kidney injury.

DISCUSSION

Heat stress, muscle injury, reduced renal blood flow and fructose metabolism may induce kidney inflammation, the successful resolution of which may be impaired by daily repeating pro-inflammatory triggers. We outline further descriptive, experimental and intervention studies addressing the factors identified in this study.

Exercise-Associated Hyponatremia in Endurance and Ultra-Endurance Performance-Aspects of Sex, Race Location, Ambient Temperature, Sports Discipline, and Length of Performance: A Narrative Review

Exercise-associated hyponatremia (EAH) is defined as a plasma sodium concentration of <135 mmol/L during or after endurance and ultra-endurance performance and was first described by Timothy Noakes when observed in ultra-marathoners competing in the Comrades Marathon in South Africa in the mid-1980s. It is well-established that a decrease in plasma sodium concentration <135 mmol/L occurs with excessive fluid intake. Clinically, a mild hyponatremia will lead to no or very unspecific symptoms. A pronounced hyponatremia (<120 mmol/L) will lead to central nervous symptoms due to cerebral edema, and respiratory failure can lead to death when plasma sodium concentration reaches values of <110–115 mmol/L. The objective of this narrative review is to present new findings about the aspects of sex, race location, sports discipline, and length of performance. The prevalence of EAH depends on the duration of an endurance performance (i.e., low in marathon running, high to very high in ultra-marathon running), the sports discipline (i.e., rather rare in cycling, more frequent in running and triathlon, and very frequent in swimming), sex (i.e., increased in women with several reported deaths), the ambient temperature (i.e., very high in hot temperatures) and the country where competition takes place (i.e., very common in the USA, very little in Europe, practically never in Africa, Asia, and Oceania). A possible explanation for the increased prevalence of EAH in women could be the so-called Varon–Ayus syndrome with severe hyponatremia, lung and cerebral edema, which was first observed in marathon runners. Regarding the race location, races in Europe seemed to be held under rather moderate conditions whereas races held in the USA were often performed under thermally stressing conditions (i.e., greater heat or greater cold).

Sodium Intake Beliefs, Information Sources, and Intended Practices of Endurance Athletes Before and During Exercise

There is little information describing how endurance athletes perceive sodium intake in relation to training and competition. Using an online questionnaire, this study assessed the beliefs, information sources, and intended practices regarding sodium ingestion for training and competition. Endurance athletes (n = 344) from six English-speaking countries completed the questionnaire and were included for analysis. The most cited information sources were social supports (63%), self-experimentation (56%), and media (48%). Respondents generally believed (>50% on electronic visual analog scale) endurance athletes require additional sodium on a daily basis (median 67% [interquartile range: 40-81%]), benefit from increased sodium in the days preceding competition (60% [30-77%]), should replace sodium losses during training (69% [48-83%]) and competition (74% [54-87%]), and would benefit from sweat composition testing (82% [65-95%]). Respondents generally believed sodium ingestion during endurance exercise prevents exercise-associated muscle cramps (75% [60-88%]) and exercise-associated hyponatremia (74% [62-89%]). The majority (58%) planned to consciously increase sodium or total food intake (i.e., indirectly increasing sodium intake) in the days preceding competition. Most (79%) were conscious of sodium intake during competition, but only 29% could articulate a specific intake plan. A small minority (5%) reported using commercial sweat testing services, of which 75% believed it was beneficial. We conclude that endurance athletes commonly perceive sodium intake as important for their sporting activities. Many intend to consciously increase sodium intake in the days preceding and during competition, although these views appear informed mostly by nonscientific and/or non-evidence-based sources.

[Exercise-Associated Hyponatremia in Endurance Performance]

Exercise-Associated Hyponatremia in Endurance Performance Abstract. Exercise-associated hyponatremia is defined as a plasma sodium concentration of <135 mmol/l and was first described by Timothy Noakes at the Comrades Marathon in South Africa in the mid-1980s. A decrease in plasma sodium <135 mmol/l occurs with excessive fluid intake. Risk factors include long to very long endurance performance, extreme climatic conditions, female gender and competitions in the USA. Regarding its prevalence by sport, exercise-associated hyponatraemia tends to occur while swimming and running, but rarely when cycling. While mild exercise-associated hyponatremia does not lead to clinical symptoms, severe hyponatremia due to cerebral edema can lead to neurological deficits and even death. The best prevention of exercise-associated hyponatremia is the reduction of fluid intake during exercise.

Belief in the need for sodium supplementation during ultramarathons remains strong: findings from the Ultrarunners Longitudinal TRAcking (ULTRA) study

In the past, ultramarathon runners have commonly believed that consuming sodium supplements, as capsules or tablets, will prevent exercise-associated hyponatremia (EAH), dehydration, muscle cramping, and nausea, but accumulating evidence indicates that sodium supplementation during ultramarathons is not necessary and may be potentially dangerous. In this work, beliefs about whether sodium supplements should be made available at ultramarathons were assessed during 2018 among 1152 participants of the Ultrarunners Longitudinal TRAcking (ULTRA) study, of which 85.2% had completed an ultramarathon during 2014-2018. Two-thirds (66.4%) of study participants indicated that sodium supplements should be made available at ultramarathons, supported by beliefs that they prevent EAH (65.5%) and muscle cramping (59.1%). Of those indicating that sodium supplements should not be made available, 85.0% indicated it is because runners can provide their own, 27.9% indicated it is because they are not necessary, and 12.1% indicated they could increase thirst drive and cause overhydration. In general, there was a tendency for those who were older, less active in running ultramarathons in recent years, and with a longer history of ultramarathon running to be less likely to know that sodium supplements do not help prevent EAH, muscle cramping, and nausea. Novelty Ultramarathon runners continue to have misunderstandings about the need for sodium supplementation during ultramarathons. Few ultramarathon runners recognize that supplementing sodium intake beyond that in food and drink is generally not necessary during ultramarathons or that it could result in overhydration. Continued educational efforts are warranted to help ensure safe participation in the sport.

Proper Hydration During Ultra-endurance Activities

The health and performance of ultra-endurance athletes is dependent on avoidance of performance limiting hypohydration while also avoiding the potentially fatal consequences of exercise-associated hyponatremia due to overhydration. In this work, key factors related to maintaining proper hydration during ultra-endurance activities are discussed. In general, proper hydration need not be complicated and has been well demonstrated to be achieved by simply drinking to thirst and consuming a typical race diet during ultra-endurance events without need for supplemental sodium. As body mass is lost from oxidation of stored fuel, and water supporting the intravascular volume is generated from endogenous fuel oxidation and released with glycogen oxidation, the commonly promoted hydration guidelines of avoiding body mass losses of >2% can result in overhydration during ultra-endurance activities. Thus, some body mass loss should occur during prolonged exercise, and appropriate hydration can be maintained by drinking to the dictates of thirst.

Considerations in the Use of Body Mass Change to Estimate Change in Hydration Status During a 161-Kilometer Ultramarathon Running Competition

Hydration guidelines found in the scientific and popular literature typically advise that body mass losses beyond 2% should be avoided during exercise. In this work, we demonstrate that these guidelines are not applicable to prolonged exercise of several hours where body mass loss does not reflect an equivalent loss of body water due to the effects of body mass change from substrate use, release of water bound with muscle and liver glycogen, and production of water during substrate metabolism. These effects on the body mass loss required to maintain body water balance are shown for a 161-km mountain ultramarathon running competition participant utilizing published data for the total energy cost, exogenous energy consumption and percentage from each fuel source, average participant body mass, and the extent of soft tissue fluid accumulation during an ultramarathon. We assumed that total energy derived from protein ranges from 5 to 10%, all exogenous energy is used to support the energy cost of the race, glycogen utilization ranges from 300 to 500 g, water linked with glycogen ranges from 1 to 3 g per g of glycogen, and the mass of the bladder and gastrointestinal tract is unchanged from pre-race to post-race body mass measurements. These calculations show that the average participant of 68.8 kg must lose 1.9-5.0% body mass to maintain the water supporting body water balance while also avoiding overhydration. Future hydration guidelines should consider these findings so that the proper hydration message is conveyed to those who participate in prolonged exercise.

Ad libitum drinking adequately supports hydration during 2 h of running in different ambient temperatures

PURPOSE

To examine if ad libitum drinking will adequately support hydration during exertional heat stress.

METHODS

Ten endurance-trained runners ran for 2 h at 60% of maximum oxygen uptake under different conditions. Participants drank water ad libitum during separate trials at mean ambient temperatures of 22 °C, 30 °C and 35 °C. Participants also completed three trials at a mean ambient temperature of 35 °C while drinking water ad libitum in all trials, and with consumption of programmed glucose or whey protein hydrolysate solutions to maintain euhydration in two of these trials. Heart rate, oxygen uptake, rectal temperature, perceived effort, and thermal sensation were monitored, and nude body mass, hemoglobin, hematocrit, and plasma osmolality were measured before and after exercise. Water and mass balance equations were used to calculate hydration-related variables.

RESULTS

Participants adjusted their ad libitum water intake so that the same decrease in body mass (1.1-1.2 kg) and same decrease in body water (0.8-0.9 kg) were observed across the range of ambient temperatures which yielded significant differences (p < .001) in sweat loss. Overall, water intake and total water gain replaced 57% and 66% of the water loss, respectively. The loss in body mass and body water associated with ad libitum drinking resulted in no alteration in physiological and psychophysiological variables compared with the condition when hydration was nearly fully maintained (0.3 L body water deficit) relative to pre-exercise status from programmed drinking.

CONCLUSIONS

Ad libitum drinking is an appropriate strategy for supporting hydration during running for 2 h duration under hot conditions.

Considerations for ultra-endurance activities: part 2 - hydration

It is not unusual for those participating in ultra-endurance (> 4 hr) events to develop varying degrees of either hypohydration or hyperhydration. Yet, it is important for ultra-endurance athletes to avoid the performance limiting and potentially fatal consequences of these conditions. During short periods of exercise (< 1 hr), trivial effects on the relationship between body mass change and hydration status result from body mass loss due to oxidation of endogenous fuel stores, and water supporting the intravascular volume being generated from endogenous fuel oxidation and released with glycogen oxidation. However, these effects have meaningful implications during prolonged exercise. In fact, body mass loses well over 2% may be required during some ultra-endurance activities to avoid hyperhydration. Therefore, the typical hydration guidelines to avoid more than 2% body mass loss do not apply in ultra-endurance activities and can potentially result in hyperhydration. Fortunately, achieving the balance of proper hydration during ultra-endurance activities need not be complicated and has been well demonstrated to generally be achieved by simply drinking to thirst and avoiding excessive sodium supplementation with intention of replacing all sodium losses during the exercise.

Should Workers Avoid Consumption of Chilled Fluids in a Hot and Humid Climate?

Despite provision of drinking water as the most common method of occupational heat stress prevention, there remains confusion in hydration messaging to workers. During work site interactions in a hot and humid climate, workers commonly report being informed to consume tepid fluids to accelerate rehydration. When questioned on the evidence supporting such advice, workers typically cite that fluid absorption is delayed by ingestion of chilled beverages. Presumably, delayed absorption would be a product of fluid delivery from the gut to the intestines, otherwise known as gastric emptying. Regulation of gastric emptying is multifactorial, with gastric volume and beverage energy density the primary factors. If gastric emptying is temperature dependent, the impact of cooling is modest in both magnitude and duration (≤ 5 minutes) due to the warming of fluids upon ingestion, particularly where workers have elevated core temperature. Given that chilled beverages are most preferred by workers, and result in greater consumption than warm fluids during and following physical activity, the resultant increased consumption of chilled fluids would promote gastric emptying through superior gastric volume. Hence, advising workers to avoid cool/cold fluids during rehydration appears to be a misinterpretation of the research. More appropriate messaging to workers would include the thermal benefits of cool/cold fluid consumption in hot and humid conditions, thereby promoting autonomy to trial chilled beverages and determine personal preference. In doing so, temperature-based palatability would be maximized and increase the likelihood of workers maintaining or restoring hydration status during and after their work shift.

Exercise-Associated Hyponatremia: 2017 Update

Exercise-associated hyponatremia (EAH) was initially described in the 1980s in endurance athletes, and work done since then has conclusively identified that overdrinking beyond thirst and non-osmotic arginine vasopressin release are the most common etiologic factors. In recent years, EAH has been described in a broader variety of athletic events and also has been linked to the development of rhabdomyolysis. The potential role of volume and sodium depletion in a subset of athletes has also been described. This review focuses on the most recent literature in the field of EAH and summarizes key new findings in the epidemiology, pathophysiology, treatment, and prevention of this condition.