#200 – AMA #33: Hydration—electrolytes, supplements, sports drinks, performance effects, and more

In this “Ask Me Anything” (AMA) episode, Peter discusses all things related to hydration, starting with how water is distributed in the body and the important concept of tonicity. He explains the difference between dehydration and volume depletion and their respective health consequences and implications. He describes the different conditions which affect our daily water needs, as well as the signs of dehydration and how it can affect performance. Next, he discusses all the ways in which we can rehydrate and when it makes sense to add electrolytes, glucose—or a combination of both—to rehydration fluids. Additionally, Peter gives his take on the plethora of sports drinks on the market and which ones stand out from the rest. Finally, he concludes with some key takeaways related to hydration.

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Note from Peter: This podcast was recorded in early January 2022. At that time, I had no involvement with any company producing any of the hydration products that are discussed here. However, since recording this podcast, I’ve continued down the rabbit hole of getting deeper into this subject. I’ve become particularly enamored with one of the companies that I mention in this AMA and I am now a small investor in that company, which is LMNT. You can find a list of all my disclosures here.

We discuss:

• Peter’s incident leading to a renewed interest in hydration [3:15];
• Water in the human body: percentage, location, and implications [6:00];
• Defining tonicity—isotonic, hypotonic, and hypertonic [11:45];
• Defining dehydration and volume depletion [19:00];
• The health consequences of dehydration and volume depletion [21:45];
• How do we actually lose water? [25:30];
• How much water do we need every day? [28:00];
• Signs of dehydration during exercise and how it can affect performance [32:45];
• Is it possible to be overhydrated? [43:15];
• Electrolytes: benefits and when to include them in rehydration fluids [47:00];
• Glucose: benefits and when to include it in rehydration fluids 51:15];
• The ability of glucose to improve absorption of sodium [58:45];
• The type of carbohydrates in drinks than actually impact performance [1:02:00];
• Sodium during workouts: is there an optimal ratio of carbohydrate to sodium? [1:05:00];
• Pros and cons of sports drinks and which ones stand out [1:09:15];
• How much hydration comes from the food we eat? [1:14:30];
• Is there a downside to drinking electrolytes throughout the day even without exercise? [1:15:15];
• Key takeaways related to hydration [1:18:15]; and
• More.

Peter’s incident leading to a renewed interest in hydration [3:15]

Peter recently lost consciousness and fell and hit his head on a table 

• He attributes this incident to him being profoundly dehydrated
• He had recently given three units of blood a few days before the fall
• Two days later he took an overnight flight (which can cause dehydration)
• On Friday morning he completely lost consciousness and face-planted into a table

Figure 1. Damage from the face plant. [instagram.com/peterattiamd]

That got him thinking about:

• How can I mitigate this sort of thing from happening again?

• What does it say overall about my hydration status? 

• Is that partly what may contribute to why I sometimes feel lightheaded in the mornings?

Water in the human body: percentage, location, and implications [6:00]

What does it mean that ~60% of our body is water? Where is this water located?

• Water inside the cell is called Intracellular fluid (ICF): accounts for about two-thirds of water in the body [67%]
• Water outside the cell is called Extracellular fluid (ECF): about one third of the body’s water [33%]
  • About 25% of ECF is in blood/vasculature, which is therefore only about 8% of all water in the body — this is the plasma
    • Anytime you spin blood or see blood spun the tube, it’s red — after you spin it, it gets very dark at the bottom (predominantly, what you’re seeing is the platelets and the red blood cells which dominate everything else). And then you see a clearish yellow fraction, depending on how much lipids are in there (That’s the plasma, which is effectively the water).
  • About 60% of the ECF is Interstitial fluid  which is therefore only about 20% of all water in the body
    • This is the space that is between cells, but not in plasma, and it’s underappreciated for what it does
    • When you have a cold or you’re really, really sick, some people notice they actually might gain weight. 
    • And then they might notice that if they’re really paying attention in the days after they’re starting to get better, not only are they losing weight again, but they’re peeing like crazy — That’s because of the expansion of that interstitial space.
    • When we’re sick, our blood vessels become very leaky — That’s where we have all the white blood cells and immune in cells do something called extravasate from the vascular system so that they can go and reach the tissues. 
    • But that leaking is what leads to this swelling. 
    • Extreme example: Somebody in the ICU may look very puffed up
  • The remainder of ECF is transcellular fluid (includes digestive tract fluid, cerebrospinal fluid, and other fluid filling epithelium-lined spaces) [roughly 5% of all water in body]

*Summary of water content and location:

• About 67% of your total body water is inside cells.
• About 20% is in the interstitium (the area that exists between everything which can really expand when you’re sick)
• About 8% is in the vascular system.
• And about 5% is basically everything else, including CSF and things like that.

Does this change based on body composition?

• It will change based on body comp.
• Muscle is far higher in water content than fat. 
• Fat tissue is about 10% water by weight. 
• We refer to that as being “anhydrous,” without water. 
• Muscle is probably 75% water. 
• Take two individuals—One of them is 12% body fat. The other is 35% body fat. 
  • There’s absolutely going to be a difference in how much water that person is carrying. The more muscular person has a higher amount of their body weight made up in water.

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