Hydration

Defining Hydration

Hydration is a term that is heavily thrown around in today's society. Many individuals correlate water intake with good health, fitness, and body fat percentage, all things that would be considered optimal. However, chugging water by the gallon is far from optimal. It only considers one major aspect of hydration, and completely neglects the other: electrolytes. Electrolytes is a very broad term, defined as particles that carry an electric charge, either positive or negative. However, in the context of physiology and hydration, electrolytes can be considered essential minerals that can be dissolved in water to form positive and negative ions, which can then be used for metabolic purposes. Optimal intake of both these electrolytes and water is what one needs to take account of in order to truly optimize their hydration.

What Minerals are Electrolytes, and How Much Do I Need?

Sodium, Potassium, Chloride, Phosphate, Magnesium, and Calcium are all considered electrolytes, however their relative importance and intake requirements vary greatly.

Sodium is the most widely known and widely consumed of the bunch, as you can find it in table salt (Sodium Chloride). Daily recommended intakes for sodium, and the rest of the electrolytes, differ widely based on climate and activity level. Regardless, a minimum intake of 500 milligrams and a maximum intake of 2,400 milligrams is optimal (remember that table salt is composed of Sodium and Chloride in a 1:2 ratio, so 1500 mg and 6000 mg of table salt would fit these recommendations).

Potassium is probably the second most well known electrolyte, despite citizens consistently being shown to be deficient. While the daily recommended intakes vary by gender and age, Men aged 18-50 require 3,400 mg and Females require 2,600.

When it comes to Chloride intake, there are very few studies that have investigated the optimal RDI. Despite this, the EFSA recommends consuming 3.1 grams of chloride daily for adults, regardless of gender.

Phosphate is the fourth electrolyte under consideration. It, similarly to Sodium, can have potentially negative effects when consumed at high doses. This, combined with the fact that it is abundant in most diets, means that an upper limit should be established for optimal intake. For adults over 19, an intake of 750 mg would be optimal. Additionally, an upper limit of 4000 mg per day would be required for optimal health.

Next is Magnesium. Recommendations for Magnesium include 400-420 mg for men, and 310-320 mg for women. Excessive amounts of magnesium are readily excreted by the kidneys, however supplemental forms can sometimes cause negative health impacts. Therefore, there is no upper limit for magnesium from whole sources, but an upper intake limit of 350 mg through supplementation is desired.

Last is Calcium, a mineral that is not often considered for its importance as an electrolyte but rather for bone integrity and health. Young adults and teenagers aged 11-24 should intake 1,500 mg, and both men and women aged 25-50 should shoot for 1,000 mg of calcium per day.


How Much Water Should I Drink?

Despite being far and away the most well-known and well-studied electrolyte, required daily intakes of water vary heavily based on numerous variables such as climate, activity levels, energy intake, size, surface area, age, sex, and many more. As such, it is incredibly difficult to establish general guidelines for its intake. Due to this, estimates on the safer/higher intake side will be given, as it is quite rare for hyper-hydration to occur in the average citizen. A recommendation of 2500-3700 ml/day for adult men and 2000-2700 ml/day for adult women is reflected by the current literature. However, one should stick to an intake closer to 3700/3700 ml/day for men and women, and maybe even exceed this value, as slight hyper hydration seems to be favorable to slight hypo hydration.

Replenishing Hydration Intra-Workout

Once again, the rate of fluid loss due to sweating varies wildly. However, a general guideline for water/fluid intake can be established: replenish fluids at a rate equal to the rate excreted - not more, not less. Now obviously the precision required for an exact match is unfeasible for the vast majority of people, but a relatively similar rate is desirable. Additionally, while carbohydrate intake is not extensively covered in this article, 30-60g of rapidly digested carbs should be ingested per hour of intense activity. Additionally, sodium can be included in intra-workout fluids during bouts of intense exercise lasting more than 2 hours.

In Summary

  • Sodium Intake: minimum intake of 500 milligrams and a maximum intake of 2,400 milligrams is optimal

  • Potassium Intake: men aged 18-50 require 3,400 mg and Females require 2,600.

  • Chloride Intake: 3.1 grams of chloride daily for adults

  • Phosphate Intake: for adults over 19, an intake of 750 mg would be optimal. Additionally, an upper limit of 4000 mg per day

  • Magnesium Intake: 400-420 mg for men, and 310-320 mg for women.

  • Calcium Intake: young adults and teenagers aged 11-24 should intake 1,500 mg, and both men and women aged 25-50 should shoot for 1,000 mg of calcium per day.

  • Water Intake: 2500-3700 ml/day for adult men and 2000-2700 ml/day for adult women

  • Replenishing Intra-workout: replenish fluids at a rate equal to the rate excreted - not more, not less

References