What it does in the body
- Blood glucose maintenance between meals (hepatic glycogen)
- Rapid energy source for muscle contraction (muscle glycogen)
- Buffer against hypoglycemia during fasting
- Exercise performance fuel (depleted in ~60-90 minutes of intense exercise)
- Emergency energy reserve during stress response
How much you need (Daily Value)
| Group | Recommended | Source |
|---|---|---|
| Adult male | No dietary RDA; stored from carbohydrate intake. Typical stores: liver 100-120g, muscle 350-500g | Physiology textbooks |
| Adult female | Slightly lower stores due to lower muscle mass; liver 80-100g, muscle 250-350g | Physiology textbooks |
| Pregnancy | Hepatic glycogen stores critical; adequate carbohydrate intake prevents fasting ketosis | ACOG |
| Children | Smaller stores proportional to body size; more susceptible to fasting hypoglycemia | AAP |
| Older adults | Reduced glycogen stores capacity due to sarcopenia; maintain adequate carbohydrate intake | ESPEN |
Richest food sources
| Food | Amount | Where |
|---|---|---|
| Liver (beef, cooked) | 2-5g per 100g (glycogen content varies with freshness) | global |
| Shellfish (oysters, mussels) | 2-5g per 100g (glycogen-rich) | global |
| Fresh meat (immediately post-slaughter) | 0.5-1g per 100g (rapidly converts to lactic acid) | global |
| Sweet corn (very fresh) | Trace amounts | global |
| Note: Most dietary glycogen comes from endogenous synthesis from carbohydrates, not from food | N/A | global |
If you don't get enough
Mild: Fatigue during exercise, bonking/hitting the wall in endurance sports
Moderate: Fasting hypoglycemia, poor exercise tolerance, inability to maintain blood sugar between meals
Severe: Glycogen storage diseases: hepatomegaly, severe hypoglycemia, lactic acidosis, cardiomyopathy (depending on type)
Time to onset: Hepatic glycogen depleted in 12-24 hours of fasting; muscle glycogen depleted in 60-120 minutes of intense exercise
Too much
Upper limit: Storage capacity is self-limiting (~500-600g total). Excess glucose beyond glycogen capacity is converted to fat via de novo lipogenesis
Glycogen storage beyond capacity is not possible (converted to fat). GSD pathological accumulation causes organ damage in glycogen storage diseases
How well you absorb it
Dietary glycogen (from meat and liver) is digested like starch — amylase and glucosidases break it down to glucose for absorption
Helped by: Insulin (promotes glycogen synthesis), Post-exercise window (enhanced glycogen synthase activity), Carbohydrate co-ingestion with protein
Hindered by: Glucagon (promotes glycogenolysis, not storage), Cortisol and epinephrine (promote breakdown), Glycogen storage diseases (enzyme deficiencies)
Cooking & storage
Glycogen in fresh meat rapidly degrades to lactic acid post-mortem (rigor mortis process). Fresh shellfish (oysters, scallops) retain more glycogen, contributing to their sweet taste. Cooking does not preserve dietary glycogen.
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