Mountaineering on Health TLDRLSS

Why Should You Keep Eating Candy at High Altitudes? Is Carbohydrate the 'Most Oxygen-Saving' Energy Source? How to Drink Water Without Cramping? Dehydration Actually Worsens Altitude Sickness! A Complete Guide to Precise Hydration!

Thu, 21 May 2026 21:30:00 +0800

When climbing, guides always tell you to suck on a candy or eat a chocolate bar. What is the science behind this?

At high altitudes, eating the right things is more important than eating well. Choosing the wrong food will make your body suffer more in a low-oxygen environment, while choosing the right food can help you last for several more hours.

Why Keep Eating Candy at High Altitudes? The Oxygen-Saving Science of Carbohydrates

You might think eating candy is just for “replenishing energy,” but in low-oxygen high-altitude environments, the significance of eating candy goes far beyond that.

For the human body to convert food into energy, it needs to consume oxygen. Comparing carbohydrates and fat, when consuming the same amount of oxygen, burning sugar generates 8% to 10% more energy than burning fat.

Energy Source	Characteristics	Oxygen Efficiency
Carbohydrates (Sugar)	Simple structure, high proportion of oxygen atoms	Oxygen Saver, quickly converted to energy with little oxygen
Fat	Complex structure, requires a lot of oxygen to decompose	High Oxygen Consumer, a slow remedy for an urgent need

At high altitudes, your body faces a “tight oxygen budget” every second.

Eating candy is like choosing the “oxygen-saving mode”.

Save precious oxygen for your brain and muscles, and you will naturally breathe easier.

This is why guides always tell you to suck on brown sugar, eat chocolate, or gummies.

Eating Candy Helps Red Blood Cells Release More Oxygen?

When the human body is in a high-altitude low-oxygen environment, red blood cells will absorb a large amount of glucose from the blood.

Red blood cells use this sugar to produce a molecule called 2,3-BPG. This molecule goes and binds with hemoglobin, forcing hemoglobin to “let go” and release the oxygen it holds to surrounding oxygen-deprived tissues and organs.

Replenishing enough sugar is like providing an endless supply of raw materials for red blood cells, speeding up oxygen release and utilization within the body.

Red blood cells release more oxygen the following steps:

Eat candy
Red blood cells absorb glucose
Produce 2,3-BPG
Increase oxygen release to surrounding oxygen-deprived tissues and organs

Eating Candy Can Make You Breathe Deeply Automatically?

Burning carbohydrates produces more carbon dioxide than burning fat.

After the concentration of carbon dioxide in the blood rises slightly, it triggers the respiratory center of the brain, which commands the lungs to spontaneously deepen and speed up breathing.

This deep breathing induced by eating candy actually allows you to unconsciously inhale more thin air from high altitudes, thereby increasing blood oxygen saturation.

What Foods to Eat at High Altitudes? Which Ones are Landmines?

Now that we know the benefits of carbohydrates, the next question is: how should we choose foods?

Trail Food: What to Eat While Hiking?

When climbing, the body is very short of oxygen, so you won’t have the energy to chew hard nuts or beef jerky.

Chewing itself consumes oxygen, and liquid or semi-liquid sugars are the best instant fuels.

Recommended Food	Reason
Energy Gel (Energy Drink)	Liquid, no chewing required, rapid absorption
Gummies, Brown Sugar Bars	High carb, easy to swallow
Raisins, Yogurt Bars	Small size, high calorie density

The core principle of trail food: high carb, easy to swallow, no long chewing required.

Meals: What to Eat at Camp?

Digestion at camp is slightly better than during movement, but gastrointestinal blood flow decreases at high altitudes, and digestion speed is still greatly reduced.

Recommended Food	Reason
Dehydrated Rice, Instant Noodles	Easy to digest, high calorie, dehydrated vegetables or egg drops can be added
Instant Mashed Potatoes	High carbohydrate content, virtually no chewing required

Why is Flatulence Easy at High Altitudes? Which Foods to Avoid at All Costs?

This is related to the physical law of Boyle's Law.

When atmospheric pressure drops, the volume of gas inside a closed container expands.

Your stomach and intestines originally contain gas; at high altitudes, these gases expand collectively.

In addition, when the body is hypoxic at high altitudes, it prioritizes sending blood to the brain and heart, reducing blood flow to the gastrointestinal tract and severely reducing digestive function.

Low air pressure + slow digestion = severe flatulence. Eating too full actually increases the cardiopulmonary burden.

High Altitude Diet Landmine List

Foods to Avoid	Reason
Beans (Red Beans, Soybeans)	Gas-producing food, worsens gastrointestinal flatulence
Carbonated Drinks (Cola, Beer)	A large amount of gas expands in low-pressure environments
Sweet Potatoes, Onions	Intestinal fermentation produces a large amount of gas
High-fat Foods	Digestion is highly oxygen-consuming, increasing the burden in hypoxic environments

How to Drink Water at High Altitudes? “Precise Hydration Method”

Many people “drink only when thirsty” when climbing, which is very dangerous on mountains.

High-altitude air is extremely dry, and combined with faster breathing, the body loses up to 1 to 2 liters of water per day just through breathing.

By the time you feel thirsty, your body is already dehydrated.

Hydration Formula: Small Amounts, Multiple Periods, Regularly

Timing	Water Intake	Principle
During Movement	Drink 50-100 ml (2-3 sips) every 15-20 minutes	Never chug 500 ml at once
Daily Total	`Weight(kg)` × `30ml` + `Climbing Hours` × `300ml`	60 kg climbing 6 hours = at least 3,600 ml

Water Temperature Matters: Refuse Ice Water

On dry and cold mountains, drinking ice water forces the body to consume precious calories to “heat” the water in the stomach to body temperature.

You must have a thermos in your backpack. Drinking warm water saves energy and prevents cold air from inducing airway spasms (high altitude cough).

Electrolyte Replenishment to Prevent Cramps

Drinking only pure water accelerates salt loss from the body; panting and sweating take away a lot of salt, and pure water will only make it worse.

Replenishment Method	Explanation
Add sports drink powder or effervescent tablets to the water bladder	Replenish lost sodium, potassium, magnesium
Suck on a salt candy regularly	Lowest cost, most effective for preventing thigh cramps

What is the Relationship Between Dehydration and Altitude Sickness?

This is the most easily overlooked yet most impactful link.

When the body is dehydrated, blood becomes thick. If blood is too thick, red blood cells flow slower, and the efficiency of carrying oxygen drops like an avalanche.

Dehydration not only makes you uncomfortable, it directly worsens altitude sickness, and can even cause your symptoms to be misdiagnosed as altitude sickness.

Chain Reaction of Dehydration	Result
Thick blood	Red blood cells flow slower
Reduced oxygen delivery efficiency	Increased tissue hypoxia
Headache, nausea, fatigue	Symptoms are almost identical to altitude sickness

Drinking plenty of water to keep blood thin allows red blood cells to flow smoothly like traffic on a highway, quickly delivering inhaled oxygen to the entire body.

Conscious and regular hydration is the simplest yet most easily overlooked step to prevent altitude sickness.

Reference

What is High-Altitude Illness? Does Physical Fitness Prevent Altitude Sickness? How to Acclimatize Before Climbing High Peaks? Treat Any Headache in the Mountains as Altitude Sickness First! 'Descend, Descend, and Descend' is the Only Cure!

Thu, 21 May 2026 15:30:00 +0800

Longing to stand on the peak of a high mountain, looking down at the magnificent sea of clouds and rolling ridges, but feeling inexplicably nervous at the mere mention of “altitude sickness”?

Many people believe that having good physical fitness and regular exercise habits prevents altitude sickness.

Altitude sickness has absolutely nothing to do with your physical fitness.

A marathon runner is not necessarily better at adapting to high altitudes than an average person, because the cause of altitude sickness is thin air and decreased oxygen partial pressure, unrelated to muscle endurance.

When we climb to altitudes above 2,500 meters, atmospheric pressure drops, causing oxygen molecules in the air to become sparse.

Taking 3,000 meters above sea level as an example, the oxygen content at the peak is only about 70% of that at sea level.

If the speed of ascent is too fast, the cardiopulmonary function and blood system fail to adapt to this sudden hypoxia, and the organs in the body will begin to protest.

This is High-Altitude Illness (or Altitude Sickness).

Three Classifications of Altitude Sickness

Based on severity and the affected organs, high-altitude illness is classified into three types:

Type	English	Core Symptoms	Danger Level
Acute Mountain Sickness (AMS)	Acute Mountain Sickness	Headache, accompanied by nausea, dizziness, insomnia, weakness	Most common, resolves on its own for most people
High-Altitude Cerebral Edema (HACE)	High-Altitude Cerebral Edema	Unsteady gait (ataxia), confusion, lethargy, coma	Extremely dangerous, can be fatal within 24 hours
High-Altitude Pulmonary Edema (HAPE)	High-Altitude Pulmonary Edema	Shortness of breath even at rest, dry cough, pink frothy sputum	Highest mortality rate, requires immediate treatment

Acute Mountain Sickness (AMS) is the most common type, usually appearing within 1 to 12 hours after arriving at high altitude, experienced by about 25% to 50% of travelers.

For most people, symptoms relieve within 2 to 3 days after the body adapts, but if it continues to worsen, it may progress to fatal cerebral edema (HACE) or pulmonary edema (HAPE).

Is a Headache Just a Cold? Never Think This Way in the Mountains

Early symptoms of altitude sickness are very similar to many common illnesses:

Common Misjudgment	Real Symptoms of Altitude Sickness
Thought to be a cold	Headache, general fatigue, nausea
Thought to be a hangover	Throbbing headache, insomnia, loss of appetite
Thought to be motion sickness	Dizziness, vomiting
Thought to be exhaustion	Weakness, decreased athletic performance

In the mountains, any headache must be treated as altitude sickness first, unless proven to be caused by other reasons.

Many mountaineering accidents are actually related to altitude sickness. Because high-altitude cerebral edema causes unsteady gait leading to falls off cliffs, and the weakness of acute mountain sickness makes people move slowly, failing to reach camp in time and causing hypothermia.

Never ignore symptoms just because you think it is “just a mild cold,” missing the best timing for descent.

Who is Prone to Altitude Sickness? Who are the High-Risk Groups?

The primary risk factors for altitude sickness are related to genetics and ascent speed:

Risk Factor	Explanation
Rapid ascent	The primary risk factor, ascending to altitudes above 2,800 meters within one day
History of altitude sickness	People who have experienced it before have a higher chance of recurrence
Individual genetic makeup	Natural adaptation speed to hypoxic environments varies from person to person
Unresolved cold/respiratory infection	Going uphill with airway inflammation can cause altitude sickness to worsen directly into pulmonary edema
Staying up late or extreme fatigue	Autonomic nervous system dysfunction reduces the body’s ability to regulate hypoxia

The following groups are not recommended to travel to areas above 2,500 meters:

Patients with unstable angina
Patients with pulmonary hypertension
Patients with severe chronic obstructive pulmonary disease (COPD)
Patients with sickle cell disease

Having no issues last time does not mean you will be fine this time.

Altitude adaptability is not always the same for every individual, and colds or staying up late can reduce your adaptability to zero.

How to Prevent Altitude Sickness? The "2500+300 Rule" and "Climb High, Sleep Low"

Prevention is key. Slowly ascend to allow the body to adapt.

Core Speed Guide

Rule	Explanation
First Night Altitude Control	On the first day of entering high altitude, keep the overnight altitude below 2,500 to 2,800 meters as much as possible
Daily Sleep Altitude Control	Above 3,000 meters, the net increase in sleeping altitude per night should not exceed 300 to 500 meters
Forced Rest Every 3 Days	After the sleeping altitude has risen continuously for 1,000 meters, stay one more night at the same altitude to adapt

Climb High, Sleep Low

During the day, you can climb higher to stimulate the body’s response mechanisms, but at night you should descend to a lower altitude to sleep, allowing the body to recover in an environment with higher oxygen content.

The golden rule of mountaineering: "Climb high, sleep low."

Pre-trip Preparation Checklist

Preparation Item	Explanation
Travel Medicine Clinic	Consult a physician before departure to evaluate the need for preventive medication (such as Acetazolamide)
Acclimatization in Advance	Stay in areas above 2,750 meters for 2 or more days within 30 days prior to departure
Layering Clothing System	Moisture-wicking base layer, warm middle layer, and windproof/waterproof outer layer
High-Carb Diet	Carbohydrates consume less oxygen than fats; replenish sugars anytime during the hike
No Alcohol and Smoking	Alcohol and sedatives suppress the respiratory center, worsening hypoxia

General Precautions at High Altitudes

At high altitudes, besides controlling the speed of ascent, daily behaviors also need adjustment:

Behavioral Control	Explanation
Reduce Strenuous Activities	Strenuous exercise accelerates blood oxygen consumption; slow down your pace and stabilize your breathing
Keep the Body Warm	Low temperatures increase pulmonary arterial pressure; use the layering system to dress up when cold and de-layer when warm
High-Carb Diet	Carbohydrates consume less oxygen than fats; replenish sugars anytime during the hike
Avoid Gas-Producing Foods	Foods like beans and carbonated drinks expand and bloat in the gastrointestinal tract under low air pressure, causing discomfort, which affects breathing and appetite
Actively Replenish Water	High-altitude air is dry, and rapid breathing causes significant water loss; replenish water in small amounts and multiple times
Monitor Yourself and Teammates	Physical conditions can change at any time in high altitudes; do not push yourself, and rest or descend immediately if you feel unwell

What to Do When Altitude Sickness Occurs? "Descend, Descend, and Descend"

Lowering altitude is the most effective and only way to treat altitude sickness.

Severity	Symptoms	Treatment
Mild	Headache, nausea	Stop ascending, rest and observe at the same altitude; take pain relievers to alleviate
Moderate	Vomiting, worsening headache	If no improvement after resting for 24 hours, descend immediately
Severe	Ataxia (unsteady gait), rest dyspnea	Descend immediately by at least 500 to 1,000 meters, while administering oxygen

Medications, oxygen cylinders, and Portable Altitude Chambers (PAC) are only "time-buying" tools to keep the patient stable until they can safely descend.

Never continue to push uphill just because symptoms are temporarily relieved after taking medication or inhaling oxygen.

When there is an issue with your body at high altitude, you must remember the "3D" formula:

Down, Down and Down (Descend, descend, and descend).

Never leave a person with altitude sickness alone; they must be accompanied by at least one teammate who is familiar with the route and possesses basic medical knowledge to descend.

The mountains will always be there.

Be fully prepared, do not rush, listen to your body, and everyone can safely enjoy the beauty of high altitudes.

Mountaineering on Health TLDRLSS

Why Should You Keep Eating Candy at High Altitudes? Is Carbohydrate the 'Most Oxygen-Saving' Energy Source? How to Drink Water Without Cramping? Dehydration Actually Worsens Altitude Sickness! A Complete Guide to Precise Hydration!

Why Keep Eating Candy at High Altitudes? The Oxygen-Saving Science of Carbohydrates

Eating Candy Helps Red Blood Cells Release More Oxygen?

Eating Candy Can Make You Breathe Deeply Automatically?

What Foods to Eat at High Altitudes? Which Ones are Landmines?

Trail Food: What to Eat While Hiking?

Meals: What to Eat at Camp?

Why is Flatulence Easy at High Altitudes? Which Foods to Avoid at All Costs?

High Altitude Diet Landmine List

How to Drink Water at High Altitudes? “Precise Hydration Method”

Hydration Formula: Small Amounts, Multiple Periods, Regularly

Water Temperature Matters: Refuse Ice Water

Electrolyte Replenishment to Prevent Cramps

What is the Relationship Between Dehydration and Altitude Sickness?

Reference

What is High-Altitude Illness? Does Physical Fitness Prevent Altitude Sickness? How to Acclimatize Before Climbing High Peaks? Treat Any Headache in the Mountains as Altitude Sickness First! 'Descend, Descend, and Descend' is the Only Cure!

What is High-Altitude Illness? Is it Related to Physical Fitness?

Three Classifications of Altitude Sickness

Is a Headache Just a Cold? Never Think This Way in the Mountains

Who is Prone to Altitude Sickness? Who are the High-Risk Groups?

How to Prevent Altitude Sickness? The "2500+300 Rule" and "Climb High, Sleep Low"

Core Speed Guide

Climb High, Sleep Low

Pre-trip Preparation Checklist

General Precautions at High Altitudes

What to Do When Altitude Sickness Occurs? "Descend, Descend, and Descend"

Reference