Why does dehydration cause cravings for sweets and cold substances?

Why Dehydration Causes Cravings for Sweets and Cold Substances

Dehydration triggers sweet cravings primarily through the brain's hedonic reward pathways, where the body seeks rapid energy and fluid restoration through palatable, calorie-containing beverages, while cold substance cravings arise from the body's instinctive drive to consume hydrating fluids that feel refreshing and signal rehydration.

Neurobiological Mechanisms of Sweet Cravings During Dehydration

The Hedonic Pathway Activation

When dehydrated, the brain's ventral tegmental area and nucleus accumbens—the pleasure centers—become activated to motivate consumption of fluids that provide both hydration and energy 1. Sweet beverages trigger dopamine and opioid neurotransmission in the nucleus accumbens, establishing hard-wired craving pathways that the dehydrated body exploits to ensure fluid intake 1.

• Sucrose infusion directly into the nucleus accumbens alters dopamine and opioid neurotransmission, increasing intake of sweet substances 1
• The palatability of sweet drinks can override normal satiety signals, motivating fluid intake independent of actual energy need 1
• This represents an evolutionary adaptation where the body prioritizes rehydration through the most appealing available fluids 1

Metabolic Confusion Between Thirst and Hunger

Dehydration can create metabolic signals that the brain misinterprets as energy deficiency rather than pure fluid deficit 1. The body may seek carbohydrate-containing fluids (4-9% carbohydrate-electrolyte drinks) because these provide both hydration and rapid glucose availability 1.

• Water depletion causes raised plasma osmolality, which triggers thirst mechanisms that may be perceived as general discomfort or hunger 2
• The brain preferentially seeks energy-dense, sweet solutions when stressed by dehydration 1

Why Cold Substances Are Craved

Thermoregulatory and Sensory Signaling

Cold beverages provide immediate sensory feedback that signals successful rehydration to the brain, while also offering perceived cooling relief 1.

• Cold drinks are recognized as hydrating fluids across all beverage types—water, tea, coffee, milk drinks, fruit juices, and soft drinks 1
• The temperature sensation provides immediate palatability and reinforcement of drinking behavior 1
• In hot environments where dehydration risk increases, cold fluids offer dual benefits of hydration and thermoregulatory support 1

Preference-Based Hydration Response

The ESPEN guidelines emphasize that drinks should be chosen according to individual preferences to maximize intake, and cold beverages universally rank high in palatability during dehydration states 1.

• A range of cold drinks (sparkling water, flavored water, cold tea, coffee, milk drinks, fruit juices, soft drinks) all provide effective hydration 1
• The myth that only plain water hydrates should be dispelled—any palatable cold beverage promotes better fluid intake 1

Clinical Implications and Practical Guidance

Optimal Rehydration Strategy

For exertional dehydration without shock or altered mental status, 4-9% carbohydrate-electrolyte drinks are superior to plain water for addressing both the sweet cravings and hydration needs 1.

• These beverages satisfy the neurobiological drive for sweets while providing optimal fluid absorption 1
• Plain water or 0-3.9% carbohydrate drinks are less effective at satisfying the craving response 1
• Cold temperature enhances palatability and intake compliance 1

Important Caveats

Do not confuse sweet cravings from dehydration with actual hypoglycemia or other metabolic emergencies 1.

• Severe dehydration with confusion, inability to swallow, or altered mental status requires immediate medical evaluation, not just sweet beverages 1
• In older adults with dementia, loss of thirst perception may prevent normal craving responses, requiring proactive fluid offering 1
• Plasma osmolality >300 mOsm/kg indicates significant dehydration requiring more aggressive intervention than oral sweet beverages alone 3

Avoiding Common Pitfalls

The craving for sweets during dehydration should not be satisfied with excessive sugar intake that could worsen metabolic parameters 1.

• Limit sweet beverage intake to rehydration needs (50 mL/kg over 2-4 hours for mild dehydration) 1
• Once rehydrated, transition to maintenance hydration with varied beverages including non-sweet options 1
• Monitor for signs that dehydration is resolving (improved mental status, normalized urine output, resolution of postural symptoms) rather than continuing sweet beverage consumption 2, 4