Introduction

Sodium is a mineral and electrolyte which is required in the body for maintaining fluid balance, nerve function, and muscle contractions. Sodium is naturally found in many whole foods, as well as often being added in larger amounts to others as a preservative. Sodium is understood to regulate blood pressure and plasma volume. Additionally, adequate sodium intake is known to help maintain proper hydration by aiding water retention, ensuring that cells receive the essential nutrients they need. In terms of performance, sodium plays an important role in maintaining strength and endurance, and may also help in preventing muscle cramps, especially for those engaging in intense physical activities or training in hot climates.

Traditionally, sodium intake has been associated with poor health and diseases such as cardiovascular disease and stroke. However, more recently this notion has been challenged by research, with suggestions that sodium alone is unlikely to be the driver of worldwide hypertension epidemic and may have little impact on blood pressure in otherwise healthy individuals (Gao et al., 2024). Further research found that both low and high sodium intake has its potential risks, whilst middle ground intake. The meta analysis study suggested that increased sodium intake may play a role in the risk of stroke morbidity and mortality. However, the increased sodium intake does not seem to have a significant effect on cardiac death and total mortality, which is contrary to what was previously believed.  (Zhu et al., 2018). Graudal & Jurgens (2018) support this suggestion, in that both low and high sodium intakes are likely to cause issues. O’Donnell et al., (2020) suggest that lower sodium recommendations as per general guidelines of less than 2.3g per day may be unproven in reducing cardiovascular issues. They go on to state that the evidence outlines that most of the world’s population consuming a moderate range of dietary sodium (2.3-4.6g per day) is not associated with increased cardiovascular risk, which is more likely to occur when sodium intake exceeds 5g per day.

Interestingly, it has been reported that a high sodium to potassium ratio is associated with an increased risk of hypertension, cardiovascular diseases, and overall mortality. Specifically, individuals with a higher ratio are more likely to experience adverse health effects compared to those maintaining a balanced ratio (Mosallanezhad et al., 2023). So, general recommendations to increase dietary potassium intake should be adhered to. You can find a comprehensive list of potassium rich foods on our blog article about potassium.

Dietary Recommendations of Sodium

Research indicates that the global average sodium intake is approximately 3,950 milligrams per day, which is nearly double the World Health Organization's (WHO) recommended limit of 2,000 milligrams (Thout et al., 2019). The World Health Organization (WHO) recommends a daily sodium intake of less than 2,000 mg, which is roughly equivalent to 5 grams of salt per day. The American Heart Association (AHA) recommends a daily sodium intake of no more than 2,300 milligrams (mg) for most adults, with an ideal limit of 1,500 mg per day for those who are at higher risk of heart disease. In the UK The National Health Service (NHS) advises adults to consume no more than 2,400 mg of sodium per day, equivalent to about 6 grams of salt.

Dietary Sources of Sodium

A significant proportion of sodium intake comes from processed and packaged foods rather than from salt added during cooking or at the table. Specifically, over 75% of sodium in the average modern diet is stated to be from hidden sources in processed foods such as bread, cheese, and processed cereals (Magripis et al., 2011). Cold cuts and cured meats account for approximately 5.1% of daily sodium intake, and pizza at 4.9%. Other significant sources include poultry, burgers, pasta mixed dishes, and snack foods (Ahmed et al., 2023).

This hidden sodium level is generally understood to be what contributes to the excessive daily intake observed globally, often leading to a higher risk of hypertension and cardiovascular diseases in those at risk populations. However, this also suggests that simple dietary changes which promote an increased consumption of wholefoods and reduction in processed food is likely to significantly reduce daily sodium intake (Hendriksen et al., 2015).  Further research supports this notion, with evidence suggesting that dietary counselling, education programs, and the use of food labels may significantly reduce sodium consumption by an average of 15 - 20% (Khalesi et al., 2022). 

That said, the existing research appears to support the idea that both high and low sodium intakes are associated with negative health outcomes. It would also appear that at risk groups are those with high blood pressure, overweight or obesity, poor lifestyles and less active. Furthermore, evidence supports the idea that those with a primarily wholefood diet will naturally consume less sodium than those who regularly consume processed foods. 

How Sodium Intake Affects Athletic Performance & Hydration

Whilst the modern consensus from studies is relatively clear on how much sodium the general population should have, there are many bodies of research which have looked at athletes; specifically, how sodium intake should differ for athletes, how it affects hydration, the impact it has on muscle cramps, and how all these factors affect athletic performance. We’ll now explore this research, discussing how athletes should utilise sodium to maximise their hydration and physical performance. 

Sodium Considerations for Athletes

Research has indicated that athletes, especially endurance, can lose significant amounts of sodium through sweat, with losses varying widely depending on factors like intensity of the exercise, exercise duration, and environmental conditions such as heat. It’s discussed in the research that athletes can lose between 0.5 to 3 grams of sodium per hour of intense exercise. This substantial sodium loss may lead to hyponatremia, characterised by low sodium levels in the blood, which can significantly impair performance and may potentially pose health risks (Veniamakis et al., 2022; Ranchordas et al., 2017).

Valentine (2007) specifically discusses that whilst the RDA of sodium may be sufficient for the average person, the case changes for athletes. He further states the idea that athletes are at high risk of issues associated with excessive sodium losses, which is an often unrecognised factor considered for athletes’ dehydration. He also presents the idea that sodium recommendations are best individualised in the knowledge that sweat sodium losses are highly variable.

How Sodium Affects Hydration 

Research demonstrates that sodium intake significantly improves cellular hydration and helps maintain plasma volume during exercise (Evans et al., 2017; Veniamakis et al., 2022; Titze, 2008). More research looked at athletes who had had body mass depleted by 2% through exercise. These athletes were then split into groups who ingested fluids with variable amounts of sodium (0mmol/L, 50mmol/L, and 100mmol/L). The study showed that sodium levels above 50 mmol/L helped maintain positive fluid balance throughout the recovery. It also showed that those supplemented with 0mmol/L fluid had an increase of 6.8% of plasma volume 1.5 hours post drink, whilst those supplemented with 50mmol/L and 100mmol/L had increases of 12% and 12.8% respectively, supporting that sodium intake improved hydration post exercise vs drinking plain water (Shirreffs & Maughan, 1998).

Stachenfeld (2008) specifically looks at how sodium affects hydration by the mechanism of stimulating thirst. In Stachenfeld’s study, when subjects only drank water during the early stages of rehydration, their plasma volume was quickly replenished, but this caused a lowering in the plasma sodium concentration thus reducing subjects’ sense of thirst before their body fluids were fully restored, resulting in only partial rehydration. In contrast, when subjects took sodium tablets with their water, they drank more, which helped maintain higher plasma sodium levels, and more effectively restored both their total and extracellular fluids. The research illustrates how the mechanism of sodium stimulating thirst aids more complete fluid recovery post exercise.

Another study which was published in 2021 explored the hydrating potential and properties of various drinks, to assess the Beverage Hydration Index (BHI). The research indicates that drinks containing sodium, such as oral rehydration solutions, have a substantially higher BHI compared to plain water. Specifically, sodium-containing beverages improved hydration significantly more than water, as they both helped to retain fluid and reduce urine output (Millard-Stafford et al., 2021). In terms of the amount of sodium in fluids, Veniamakis et al. (2022) suggest 300-600mg of sodium per hour of exercise for athletes. 

Sodium’s Effects on Hyponatremia and Muscle Cramps

Sodium replacement during exercise, particularly endurance exercise in hot environment is incredibly important for maintaining fluid and electrolyte balance and muscle contractility. Hyponatremia is a state which occurs when blood sodium concentrations fall to abnormally low levels, likely as a result of consuming water only during exercise and failing to replace sodium. Studies suggest that in cases of potential hyponatremia, sodium’s intake can mitigate the drop in blood concentrations, but cannot eliminate it. The researcher states that attention should first be paid to the individual amount of fluids consumed and then to the amount of sodium consumed. (Veniamakis et al., 2022).

Miller (2018) explored the causes and solutions for exercise-associated muscle cramps. His research indicated that muscle cramps during exercise are primarily caused by neuromuscular fatigue and electrolyte imbalances, particularly the loss of sodium. Dehydration and insufficient sodium levels can disrupt nerve function and muscle contraction, leading to cramps. The study suggests that proper hydration and adequate electrolyte intake including sodium should be high on the list of preventative measures. Additionally, regular conditioning and stretching exercises can enhance neuromuscular efficiency, further preventing the onset of muscle cramps during exercise.

Sodium’s Impact on Athletic Performance

Research does suggest that sodium alone is unlikely to impact endurance performance to a significant degree (McCubbin & Costa, 2018). This ultimately implies that maintaining hydration and electrolyte balance with sodium in combination with sufficiency fluid is key to improving performance. Munson et al., (2020) however, looked at tennis players who were supplemented with just sodium and fluid. They found that players who consumed 50 mmol/L of sodium before and during a 1 hour tennis training session reduced urine osmolality and improved groundstroke performance in nationally ranked tennis players. There was also evidence of dose response effects, showing that taking in greater sodium concentrations resulted in greater improvements in groundstroke performance. This improvement was attributed to sodium's role in sustaining plasma volume and preventing dehydration, which is instrumental for maintaining endurance, strength, and agility during prolonged matches.

The Effects of General Hydration on Health and Performance

There are significant links between hydration and cardiovascular health, as well as cognitive function and liver function. Similarly, hydration has been shown to significantly affect athletic performance. This section of the article will go on to explain both of these phenomena.

Hydration’s Effects on Health

Proper hydration is key for maintaining cardiovascular health, cognitive function, and kidney function. Approximately 60% of the human body is composed of fluid. This fluid is essential for many physiological functions, including maintaining cellular integrity, affording biochemical reactions, and facilitating nutrient and waste transport. 

Chronic dehydration has potential to lead to kidney stones, urinary tract infections, and even kidney failure in severe cases. Overhydration, or hyponatremia, can cause swelling of cells, which is particularly dangerous in the brain, potentially leading to seizures or coma. Furthermore, fluid imbalance can impair cognitive functions such as attention, memory, and executive function. Dehydration can also lead to difficulties in concentration, increased perception of effort, and overall mental fatigue. Studies have shown that even mild dehydration can negatively impact mood, increase anxiety, and reduce cognitive performance.

Dehydration’s Impact on Performance

One study which was published in the Journal of Applied Physiology examined the impact of dehydration on both physical and mental performance. It found significant negative effects on physical and cognitive abilities. The research indicates that even mild dehydration, defined as a 2% loss of body weight due to fluid loss, can impair physical performance by up to 20% (Goulet, 2013). Dehydration has been shown to also reduce endurance, strength, and power, whilst also increasing the perception of effort, leading to earlier onset of fatigue. Additionally, cognitive functions such as attention, coordination, and reaction times are adversely affected, which can further hinder athletic performance and everyday activities (Ganio et al., 2011). 

Conclusion

In conclusion, this article has provided a comprehensive analysis of sodium's role in both general health and athletic performance, illustrating the balance needed between avoiding excessive and insufficient sodium intake. It has discussed the importance of moderate sodium consumption for maintaining optimal health and highlights that athletes in particular, might need higher sodium intake to compensate for losses through sweat, especially during extended or intense physical activities, or exercise in hot weather. The research encourages a balanced dietary approach, integrating more whole foods and reducing processed food intake, which could significantly lower health risks associated with improper sodium levels, while also catering to the specific needs of athletes for enhanced performance and hydration. If you’re an athlete looking to increase your sodium intake, then be sure to check out our hydration drinks.

Frequently Asked Questions (FAQs)

What is the role of sodium in the body?

Sodium is essential for maintaining fluid balance, nerve function, and muscle contractions in the body. It helps regulate blood pressure and plasma volume and is required for aiding hydration by promoting water retention.

How does sodium intake affect blood pressure and cardiovascular health?

Recent research indicates that sodium's impact on blood pressure in healthy individuals may be minimal. However, both excessively low and high sodium intakes have been shown to potentially lead to health issues. It is generally recommended to consume a moderate amount of sodium, particularly for cardiovascular health.

What are the recommended daily limits for sodium intake?

The World Health Organization recommends less than 2,000 mg of sodium per day, while the American Heart Association suggests a limit of no more than 2,300 mg for most adults, and ideally less than 1,500 mg for those at higher risk of heart disease. The NHS advises no more than 2,400 mg per day.

What are the primary sources of sodium in the modern diet?

The majority of sodium in modern diets comes from processed and packaged foods, accounting for over 75% of average intake. Key sources include bread, cheese, processed cereals, cold cuts, cured meats, and snack foods. Those on whole food diets generally get less dietary sodium.

How does sodium intake affect athletic performance and hydration?

Higher sodium intake is required for athletes, as it helps maintain proper hydration and plasma volume, which can prevent hyponatremia and muscle cramps. Adequate sodium has been shown to improve hydration more effectively than water alone, especially during intense physical activities or in hot climates.

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