Clams can be a beneficial food to include in your diet, as they are moderately low in calories and rich in protein. However, eating too many clams can have detrimental effects, as some of the nutrients clams provide can be harmful in large doses. If you feel you are experiencing harm from eating clams or any other food, seek professional medical attention immediately.
Clam Nutritional Profile
Clams, like other types of seafood, are relatively low in calories, with 126 per 3-oz. serving. Each 3-oz. serving of cooked clams provides 21.7 g of protein, with 1.7 g of fat and 4.4 g of carbohydrates. Clams are rich in a variety of nutrients, including potassium, iron, selenium and vitamin B-12. Note that cooking clams in oil or butter will alter the nutritional values.
One of the risks of eating too many clams is taking in too much selenium. Your body needs selenium for the proper function of your immune system and thyroid, but the daily suggested intake of this nutrient is 55 mg, less than 1 mg more than 3 oz. of clams provides. If you eat multiple servings of clams, you could ingest too much selenium, which may cause upset stomach, fatigue, nerve damage and irritability. The Institute of Medicine recommends never exceeding 400 mg of selenium in a day.
Vitamin B-12 Overdose
Vitamin B-12 is an essential vitamin that supports the manufacture of amino acids and an enzyme involved in producing hemoglobin, which carries oxygenated blood throughout your body. Unfortunately, too much vitamin B-12 may result in rashes and itching, diarrhea or a blood vessel disease known as peripheral vascular thrombosis. Each 3-oz. serving of clams contains 84 mcg, which is more than 32 times the daily suggested intake of 2.6 mcg.
Iron is a vital nutrient your body uses to make cellular energy and to transport oxygen. However, regularly consuming too much iron may cause liver damage, diabetes, diarrhea and upset stomach. The University of Maryland Medical Center also suggests that too much iron may increase your risk of Alzheimer's disease, certain cancers and heart disease, but notes that "the evidence isn't clear." The recommended daily intake of iron is 8 mg for men and 18 g for women, and a 3-oz. serving of clams contains 24 mg.