Celery is known as a low-calorie food, sometimes described as having “negative calories.” While the vegetable is mostly water and contains some vitamins, consuming it in excess can lead to unwanted health consequences. Though celery is safe and beneficial in moderation, high consumption poses specific risks, including digestive distress, chemical photosensitivity, and nutritional imbalances.
Gastrointestinal Distress from Excessive Fiber
Celery is an abundant source of insoluble fiber, which adds bulk to stool. A single medium stalk contains about 1.6 grams of fiber, and consuming a large quantity introduces an overwhelming load of this material into the digestive system. When the body suddenly processes an extremely high volume of fiber, it often reacts with noticeable discomfort.
This rapid increase in undigested material can cause abdominal cramping, excessive gas, and uncomfortable bloating. For those not accustomed to a high-fiber diet, the digestive system struggles to manage the sudden influx. Furthermore, celery’s high water content (over 95%) can combine with the fiber to loosen stools, potentially resulting in diarrhea.
Photosensitivity and Psoralens
Consuming large amounts of celery involves a unique risk from naturally occurring compounds called psoralens (furocoumarins). These chemicals are phototoxic, making the skin highly sensitive to ultraviolet (UV) light. When high concentrations of psoralens are ingested and the skin is exposed to sunlight, it can lead to a severe skin reaction.
This condition is known as phytophotodermatitis, which manifests as an exaggerated sunburn, sometimes involving blistering on sun-exposed areas. Psoralen concentration can be particularly high in celery that is damaged, stressed, or infected with fungus, and in celery seeds, increasing the risk of phototoxicity.
Celery Allergies and Oral Allergy Syndrome
Celery is a recognized food allergen, with reactions ranging from mild local symptoms to severe systemic responses. The most common reaction is Oral Allergy Syndrome (OAS), which occurs when the immune system mistakes celery proteins for similar proteins found in tree pollens, such as birch or mugwort.
OAS symptoms are usually confined to the mouth and throat, including itching, tingling, or slight swelling immediately after eating raw celery. A primary celery allergy is less common but can cause severe reactions, including hives, swelling, and anaphylaxis. Celery is a notable allergen in Europe, sometimes causing severe reactions even when cooked.
Calorie and Nutrient Deficiency Risk
While celery contains vitamins and minerals like vitamin K and folate, its nutritional profile is defined by extremely low caloric density. A cup of chopped celery contains only about 16 calories, requiring enormous volume to meet daily energy needs. Relying heavily on celery, often during extreme dieting, can displace other nutrient-dense foods.
This displacement can lead to insufficient intake of essential macronutrients, such as healthy fats, protein, and complex carbohydrates, necessary for proper metabolic function. By filling the diet predominantly with this low-calorie, high-water food, an individual risks a caloric deficit and potential deficiencies in broader vitamins and minerals, impacting long-term health.