Fueling the Long Haul: A Functional Nutritionist’s Comprehensive Guide to Thru-Hiking Nutrition
I was introduced to the concept of thru-hiking when my husband (then my boyfriend) set his sights on hiking the…
The warmth of the sun on your legs, the fragrant smell of wildflowers, the exhilaration of being off the treadmill and back on the trail – summer trail running is the best! As you rack up trail miles this summer, staying hydrated is key to your performance, resilience, and recovery.
Summer heat and under-hydration can lead to negative health and performance consequences for trail runners, ranging from premature fatigue and a slowed pace to heat-induced illness. In this blog, we’ll discuss practical approaches to hydration for trail running so you can feel and perform your best and enjoy this season to the fullest!
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“Hydration” is defined as the process of providing a sufficient amount of liquid (namely water) to body tissues. Hydration keeps our mouth, nose, and eyes moist and healthy, helps regulate body temperature via sweat, lubricates joints, and helps transport vitamins, minerals, oxygen, and waste products in the blood and cells.
Hypohydration, a sustained decrease in body water, can impair endurance exercise performance (like trail running) through several mechanisms, including:
(Source)
A healthy hydration status, on the other hand, is associated with:
Optimizing hydration when trail running, especially during hot summer days, can significantly enhance your performance and recovery, giving you the edge you need to conquer challenging trails.
Signs of under-hydration (I will use the terms “hypohydration” and “under-hydration” interchangeably in this article) in active people like trail runners (but not severe dehydration – see the section on heat-induced illness for more on that topic) include:
Understanding your unique hydration needs is a powerful tool in your trail running arsenal. Taking a personalized approach to hydration can help you perform your best and recover quickly! Hydration needs are highly individual and are impacted by the following factors:
Let’s break down how these factors impact your hydration needs as a trail runner.
Age is a particularly relevant factor affecting hydration for Masters trail runners.
If you’re a seasoned trail runner aged 35 or above, known as a Masters athlete, it’s crucial to recognize the changes in thirst sensations and fluid balance that come with age, and adjust your hydration plan accordingly.
Masters athletes are more prone to dehydration for several reasons. For one, older adults have less total body water than younger athletes, meaning you are already starting at a disadvantage when maintaining a healthy fluid balance. (Source)
In addition, the glomerular filtration rate (GFR), the kidneys’ ability to filter waste and regulate fluid balance, decreases with age.
Finally, thirst sensations decrease with age, making detecting when you are truly thirsty harder. These three factors make it harder to stay hydrated as a Masters trail runner.
The solution? Developing a solid hydration plan for trail running in the summer (and throughout the year) and sticking to it! My DIY Sweat Test Worksheet is the perfect place to start because it will help determine your fluid loss during exercise. From there, I recommend working with a nutrition professional who can help you further dial in your fluid and electrolyte intake while considering the unique hydration needs of Masters athletes.
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Biological sex impacts hydration status. Specifically, female trail runners need to pay special attention to their hydration status, especially when running in the summer. For example, women’s bodies heat up faster, and they sweat less than men’s, meaning females may need to adjust their hydration strategy to cool their bodies effectively during exercise, such as trail running. (Source)
The longer and higher intensity your trail runs are, especially in the summer, the more fluid and electrolytes you’ll lose. Therefore, long or high-intensity trail runs will necessitate greater fluid intakes and a more intensive post-run rehydration strategy than shorter duration and lower intensity runs.
The climate you’re trail running in – hot and humid, hot and dry, high altitude and sunny, etc. – also affects your hydration needs. For example, hot and humid weather will limit evaporation and cause you to sweat more on your trail run, requiring you to drink more fluids to maintain a healthy hydration status.
You will still sweat in hot and dry conditions, but that sweat will evaporate quickly. This can make it feel like you’re not losing as much fluid as you would in hot and humid conditions, but don’t be fooled! You still need to hydrate thoughtfully to avoid dehydration in these conditions.
Trail runners who are more heat adapted/acclimated lose MORE sweat than runners who are not heat adapted. Think about this as an adaptive response (hence the term “heat adaptation”); if your body is used to the heat, it gets used to releasing more sweat (thus losing more fluid) to help your body regulate its temperature.
If you are hypohydrated, you will lose the benefits of heat acclimation because your body won’t be able to successfully dissipate heat.
If you trail run at altitude (like I do in Colorado), you’ll also need to consider the effects of altitude on your summer hydration plan.
Why do you need to pay special attention to your hydration status at altitude? There are a few reasons.
First, hypoxia (low oxygen levels in body tissues) and the low air humidity in high-altitude environments can increase fluid losses during training and at rest.
Secondly, when initially exposed to altitude (such as if you travel to altitude for a trail running race), you eliminate more water through respiration and diuresis (increased urine production).
Third, thirst can decrease at altitude. Together, these factors interact to increase fluid losses and the risk of dehydration at altitude. Fortunately, a solid hydration plan can help you hydrate optimally at altitude and reduce your risk of dehydration.
To prevent dehydration at altitude, you should monitor your urine color daily, aiming for light straw-colored urine. Dark, concentrated urine, on the other hand, can be an indicator of dehydration. In addition, make sure to hydrate appropriately pre-, during, and post-run. You’ll find guidance in the “How to Hydrate (and When)” section.
Some people are heavy sweaters and others are light sweaters. Your unique sweat rate and the relative amounts of the major electrolytes you lose in your sweat also affect your hydration needs. Check out my DIY Sweat Test Worksheet to determine your fluid loss during exercise.
There are also tests on the market that can assess your sweat sodium concentration. I’ve had several clients use the Levelen test. I don’t endorse any specific sweat sodium test at this time, but if you have a favorite one, please let me know in the comments!
In the meantime, some signs that you may be losing a lot of sodium in your sweat include experiencing frequent muscle cramping and noticing white, salty residue on your skin or clothes after sweating on a run.
So, what should you drink during your summer trail runs, and how should you optimize the timing of your hydration plan?
First, optimize your baseline hydration status. I recommend doing this by taking your body weight in lbs. and dividing by 2. This simple calculation will give you the amount of fluid in oz you should drink daily, and does not take into account fluid needs due to exercise.
Next, you can account for your trail running fluid needs by considering the length of your training sessions. If you are running for just 60-90 minutes, drinking only water should suffice for most trail runners. Runs longer than 90 minutes warrant consuming water plus a hydration mix with electrolytes and, for most runners, carbohydrates.
We want to drink water with electrolytes on longer runs (> 90 minutes) to replenish electrolytes lost via sweat. The main electrolytes we lose through sweat are sodium chloride, potassium, magnesium, and calcium. Sodium chloride and potassium are the dominant electrolytes in sweat, while calcium and magnesium are present in smaller amounts. The concentration of sodium chloride in sweat varies based on your diet (i.e., how much salt you eat), sweat rate, hydration, and how acclimated you are to heat. (Source)
It is crucial to balance your water intake with sodium intake to prevent hyponatremia, a low concentration of sodium in the blood that can be life-threatening.
When developing hydration plans for my trail runner clients, I often recommend an electrolyte blend without added sugars for daily use (hydration outside of your runs and other workouts), such as UCAN Hydrate, and an electrolyte mix with carbohydrates for long runs and workouts, such as Skratch Labs hydration mixes. The carb/electrolyte mix is essential during longer runs because certain carbohydrates facilitate the absorption of electrolytes in the intestine, optimizing electrolyte replenishment. (Source)
When selecting a carbohydrate/electrolyte mix, I recommend one without artificial flavors, colors, or other undesirable preservatives. Additives like these add to the burden of things your body needs to detoxify—your body is already working hard enough when running—we don’t need to add more burden to the mix with toxic additives.
When should you hydrate? Again, the ideal timing will vary from one trail runner to another, but generally, we want to hydrate adequately before, during, and after each run.
Hydrating well before a run sets you up for success during the run itself. Hydrating during your run will support your endurance and cognition while hydrating after your run will aid recovery.
Here’s a sample hydration template that works well for many of my trail runner clients during the base-building period of your training:
Here’s a sample hydration template that works well for many of my clients during the higher-intensity/higher-volume and race portions of their training season:
If there’s a big discrepancy between how much you currently drink during your trail runs and how much you should be drinking based on your sweat rate, I recommend working up to your goal fluid intake gradually to avoid gastrointestinal distress.
How much sodium (and other electrolytes) should you aim to replenish when trail running? Again, this is a highly individual matter. In my nutrition practice, I’ve found that aiming for 500-800 mg of sodium per 1 L (~34 oz) of water in hot conditions is a good place to start.
Sweat sodium testing can help you determine how much sodium you should consume based on your body’s unique pattern of sodium loss via sweat.
As a functional nutritionist, I’m enthusiastic about using whole foods as fuel for exercise and athletic events. Try my DIY Sports Drink recipe if you’d like to use whole-food ingredients for trail running hydration!
Directions:
Pertinent Nutrition Facts:
Provides 600 mg sodium/L and 60 g carbs/L.
You can adjust the amount of salt added to increase the drink’s sodium concentration if you are a salty sweater!
Foods with a high water content can also help you hydrate. Examples of foods and beverages other than water that can help you stay hydrated in the summer and throughout the year include:
Incorporating these foods and beverages into your daily diet can help you maintain a healthy baseline hydration status and a strong foundation for your summer trail running hydration plan.
As a functional nutritionist with an extensive research background, I would be remiss not to mention the importance of filtering your drinking water. Unfortunately, our tap and well water today in the United States is frequently contaminated with various toxins, from hormone-disrupting plastics to perfluorinated chemicals and pesticides. While staying hydrated is crucial for trail runners, it is equally important to ensure the water you’re drinking isn’t exposing your body to harmful chemicals. (Source, Source, Source)
In my nutrition practice, I encourage my clients to test their tap water for contaminants. Once they’ve discovered which contaminants predominate in their water, they can choose a water filtration option that will reduce levels of the contaminants, ensuring they have healthy, safe drinking water.
Here are a few more summer-specific hydration tips for trail runners:
It is crucial to be aware of the early signs of dehydration on the trail, including thirst, dizziness, and dark urine. Needless to say, if you start to feel dizzy and lightheaded or find that you stop sweating (all of which are signs of heat-induced illness), stop your run. Depending on the severity of your symptoms, contact emergency medical help as soon as possible.
There are two main types of heat-induced illness – heat exhaustion and heat stroke. Heat exhaustion occurs when the body cannot regulate its temperature properly in the heat, which is often due to fluid and salt depletion. Heat stroke, a true medical emergency, is a severe form of heat-induced illness involving an elevation in body temperature that can exceed 104 degrees Fahrenheit. (Source)
Symptoms of heat exhaustion include feeling faint or dizzy, excessive sweating, clammy skin, nausea or vomiting, and muscle cramps. Symptoms of heat stroke include confusion, lack of sweating, hot, dry skin, nausea or vomiting, and even loss of consciousness or seizures. While heat exhaustion can often be managed by resting in a cool place and taking measures to cool your body, heat stroke requires immediate medical attention.
Proper hydration can reduce the risk of heat exhaustion and heat stroke in athletes – all the more reason to dial in your trail running hydration strategy! (Source, Source)
As a functional nutritionist and avid trail runner, here are a few of my favorite hydration tools for summer trail running:
If your trail run is long and remote, I recommend bringing a water filtration tool such as a Life Straw or BeFree water filter bottle. This will allow you to filter the water you come across along the trail.
Optimizing your hydration is key to feeling and performing your best on summer trail runs. The key is to remember that your hydration needs as a trail runner are highly individual. It is crucial that you test and refine your hydration strategies during your training season and definitely before any trail races. Smart hydration is essential for strong performance, long-term health, and avoiding heat-induced illness.
What are your favorite hydration strategies or gear for summer trail running? Let me know in the comments!
The content provided on this nutrition blog is intended for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you have read on this blog.
The information and recommendations presented here are based on general nutrition principles and may not be suitable for everyone. Individual dietary needs and health concerns vary, and what works for one person may not be appropriate for another.
I make every effort to provide accurate and up-to-date information, but the field of nutrition is constantly evolving, and new research may impact dietary recommendations. Therefore, I cannot guarantee the accuracy or completeness of the information presented on this blog.
If you have specific dietary or health concerns, please consult a qualified nutritionist or another healthcare professional for personalized guidance.
I empower others through nutrition to conquer their mountain adventures, drawing from my own experiences.
With a background in Biomedical Science and an M.S. in Human Nutrition, I’m a Certified Nutrition Specialist and Licensed Dietitian Nutritionist. My journey in functional medicine has equipped me to work alongside athletes and tackle complex health cases. As a passionate trail runner, backcountry skier, and backpacker, I strive to support others on their paths to peak performance and well-being.
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