Stacy Sims, PhD: The Science of Hydration, The Case for Sugar and Sodium in Fluids, and Individualizing Your Plan

September 8, 2015

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Stacy Sims, PhD, is an Environmental Exercise Physiologist and Nutrition Scientist specializing in thermoregulation, hydration, performance nutrition, and sex differences in athletes, implementing strategies to improve performance outcomes and overall health. She’s the co-founder of Osmo Nutrition, natural sports nutrition products for hydration.

On this show we provide another perspective on the topic of hydration as a follow-up to a recent episode featuring Dr. Tim Noakes and Dr. Phil Maffetone. The discussion with Stacy includes:

Stacy’s mission in the world of exercise phys, nutrition and sport and her extensive background as an endurance athlete

Her hyponatremia story while racing the Ironman World Champs in Kona during a “high hormone” phase, and how electrolytes “saved” her

Hormonal influences of the menstrual cycle affect fluid dynamics

Taper time is to stock up on electrolytes

WHAT YOU ARE DRINKING: Does it matter?

Why hydration is not a black or white issue and why it’s very individual

As such, why Stacy thinks “just water” is not enough

Do both sodium and glucose allow for best results for fluid absorption?

The physiological reasoning for why we need sodium with fluids during exercise

The physiological reasoning for adding carbs/sugar with a drink – “for ideal fluid absorption, you need a bit of sugar”

Instead of sugar in the drink can you do water with real foods that have some carb, sodium and electrolytes?

The synergy between fluids and whole food solid fuels

The argument against salt tabs and electrolyte pills

How to add the ideal amount of salt to your drinks and hydration needs

How do drinks with some sugar affect fat-adaptation and fat-burning?

Is some sugar in sports drinks “healthy” assuming that it’s being used for exercise and optimal fluid absorption in athletes, and not for sedentary people? Or should athletes consider scaling back on sugar during exercise?

Discussing how there is a time and place for using specific sports nutrition products, but that they’re not needed for every session

Is sugar and calories during exercise and racing ok for overfat athletes looking to lose weight?

History and science of osmolality in sports drinks – why did Gatorade become a 6-8% carb solution? (Palatability vs. physiology/science)

Making your own sports drink vs. buying a sports drink like Osmo

Do we really need to buy sports drinks or can we just as easily (and more cheaply) make our own?

Need to stop and reload on fuel and fluids while training? Stacy’s #1 tip to get properly hydrated and fueled from convenience store items (hint: don’t buy the sports drink!!!)

Types of solutions:
hypotonic – fastest fluid absorption
isotonic – less absorption
hypertonic – least absorption of all

Types of sugars: discussing fructose, glucose, maltodextrin and different transporters to take in these sugars

Risks of fructose, especially for women – less efficient; sits in the gut for longer

risks of maltodextrin – hyperosmolar environment and an increased osmotic pressure = GI discomfort

what combo do you recommend, i.e. is fructose + glucose better than just fruc?

Discussing “all-natural sugars” – maple syrup vs. honey, which is natural and just simply glucose and some fructose

Why dates may be a superior “all-natural” fuel over other dried fruits (hint: it’s the type of sugar)

When to drink to thirst

When to drink on a schedule

How to make use of pee sticks to measure hydration

The effect of heat and environment on hydration needs

Research vs. real world: thoughts on what we find in lab settings vs autonomous outdoor exercise

DEHYDRATION – Is dehydration necessarily all evil? Or does it depend? How will training status decide that?

The competing interests of blood: to muscle for work, and to skin for cooling (sweating/evaporation of sweat)

They said dehydration not a problem and even beneficial with weight loss. thoughts?

The benefits of heat acclimation to prevent severe dehydration

Is there a way to tell if you are a) properly hydrated and b) if you are becoming dehydrated c) experiencing hypnoatremia?
-hyponatremia -headaches, bloating, dizziness
-proper hydration: 500-800ml an hour during
-impossible to match what you lose during exercise so rehydrate after (foods and drinks)

Bottom line: practice and prepare!

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