Hydration for optimal health and performance | Stacy Sims, PhD

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Most of us probably don’t give much thought to the nuances of hydration, but in Episode #259, I’m joined by Dr Stacy Sims to dive into the science behind this essential aspect of our daily lives. With the prevailing notion that drinking 2 litres of plain water a day is sufficient for our hydration needs, we challenge this widely held belief in our conversation.

“The more you learn about hydration and the more you learn about the small intestine and how everything is absorbed, the more you realise how much stronger marketing is over science in the whole hydration world.”

Stacy T. Sims, MSC, PhD, is a forward-thinking international exercise physiologist and nutrition scientist who aims to revolutionise exercise nutrition and performance for women. She has directed research programs at Stanford, AUT University, and the University of Waikato, focusing on female athlete health and performance and pushing the dogma to improve research on all women. Dr Sims has published over 70 peer-reviewed papers, several books, and regularly features as a speaker at professional and academic conferences. She has undertaken significant research in the field of hydration and performance and is extremely well situated to speak on today’s topic.

“Oftentimes when people are drinking all the time they’re always thirsty, and their body weight is going up and down so much… it’s an indication that there’s a misstep in that fluid balance, even though their urine is light/straw coloured.”

In this episode, we cover a range of topics related to hydration and its impact on physical performance. You’ll learn about the basic biology of hydration, how to determine if you’re properly hydrated, and whether water alone is sufficient or if we need to add electrolytes and glucose. We discuss how hydration needs change throughout the menstrual cycle, and how to calculate fluid requirements at an individual level.

“You don’t have to drink eight to ten glasses a day. You don’t have to walk around with a water bottle all day, and you will still get benefits if you just make small little changes and make that water and fluid work for you.”

Dr. Sims shares her research findings and insights from working with athletes, debunking myths about hydration, including the effectiveness of coconut water and the role of caffeine. Additionally, we explore the differences in hydration requirements between men and women, as well as how to optimise hydration strategies for various activities, such as high-intensity interval training, resistance training, and endurance events. By the end of the episode, you’ll have a deeper understanding of the science of hydration and practical tips to improve your own hydration strategies for better performance and overall well-being.

Specifically, we discuss:

  • Intro (00:00)
  • Dr. Stacy Sims on hydration (1:25)
  • Nuances of hydration (3:35)
  • Electrolytes (7:02)
  • The problem with plain water (12:02)
  • How much sodium do you need in a hot or cold environment? (15:00)
  • Sodium and fluid intake during exercise (16:31)
  • Dehydration and its effects on performance (20:07)
  • Importance of slow and steady hydration (22:22)
  • Distilled water and hydration (23:38)
  • Is adding salt healthy? (24:59)
  • How to tell if you’re dehydrated (25:52)
  • How much water should you drink a day? (27:47)
  • Coconut water for hydration? (28:22)
  • Why do electrolyte supplements have potassium, magnesium, and sodium? (30:25)
  • Carbohydrates and hydration (31:49)
  • Carbohydrate intake during endurance performance (36:52)
  • Hydration on low carb diets (38:36)
  • Fluid balance requirement for men and women (40:44)
  • The urine specific gravity test (44:53)
  • Sauna for men and women (46:51)
  • Are coffee and tea dehydrating? (48:00)
  • More hydration myths (50:03)
  • Hydration before an endurance event (51:00)
  • Creatine (52:08)
  • Frequent urination at night (54:30)
  • Dehydration among athletes (56:40)
  • Outro (58:45)

This insightful conversation with Dr Stacy Sims is a great reminder of the importance of continually re-evaluating our everyday health behaviours and digging deeper to ensure we’re making the best choices for our bodies. Dr. Sims is an expert in the field of hydration, and this conversation opens an essential dialogue for anyone looking to improve their performance and well-being. This episode not only provides valuable insights into the science behind hydration but also offers practical guidance on how to optimise your own hydration strategies for better performance.

To connect with Dr Stacy Sims, you can find her on InstagramFacebook, and TikTok. Visit her website, https://www.drstacysims.com, to learn more about Dr Sims and find resources to improve your performance.

The best way to support the show is to use the products and services offered by our sponsors. To check them out, and enjoy great savings, visit theproof.com/friends.

Enjoy, friends.


More about Stacy Sims, MSC, PhD

STACY T. SIMS, MSC, PHD, is a forward-thinking international exercise physiologist and nutrition scientist who aims to revolutionize exercise nutrition and performance for women.

She has directed research programs at Stanford, AUT University, and the University of Waikato, focusing on female athlete health and performance and pushing the dogma to improve research on all women.

With the unique opportunities, Silicon Valley has to offer, during her tenure at Stanford, she had the opportunity to translate earlier research into consumer products and a science-based layperson’s book (ROAR) written to explain sex differences in training and nutrition across the lifespan. Both the consumer products and the book challenged the existing dogma for women in exercise, nutrition, and health. This paradigm shift is the focus of her famous “Women Are Not Small Men” TEDx talk.

Her contributions to the international research environment and the sports nutrition industry has established a new niche in sports nutrition; and established her reputation as the expert in sex differences in training, nutrition, and health. As a direct result, she has been named:

  • One of the top 50 visionaries of the running industry (2015) by DMSE Sports.
  • One of the top 40 women changing the paradigm of her field (2017) by Outside Magazine.
  • One of the top four visionaries in the outdoor sports industry (2017) by Outside Magazine – Genius Issue (no electronic version but here is the proof).
  • One of the top four individuals changing the landscape in triathlon nutrition (2017) by Triathlete Magazine

Dr. Sims has published over 70 peer-reviewed papers, several books and is a regularly featured speaker at professional and academic conferences, including those by USOC and USA Cycling.

Stacy currently holds a Senior Research Associate position with SPRINZ- AUT University, supervises PhD students, writes academic papers, and is on the advisory board of some cutting edge companies including Tonal Strength Institute, WILD.AI, and EXOS.  She also has her own business (www.drstacysims.com) where she creates and delivers online learning material focused on women training with their physiology across the lifespan.

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