While you may eat oysters for their calcium content, oyster shell is the real calcium powerhouse. Oyster shell becomes calcium carbonate when ground down. If you take calcium supplements, oyster shell may be the source of the calcium you're ingesting. While calcium supplements made of coral aren't safe for those with a shellfish allergy, you may be able to take calcium carbonate from oyster shells. Speak with your doctor about this and any other supplement you are taking.
Oysters
A raw oyster doesn't contain much calcium, just 7 mg in a 3-oz. serving. It does, however, contain significant zinc -- 14.93 mg in a 3-oz. serving. In addition, oysters are low in fat and calories, and relatively light in cholesterol. A 3-oz. serving of a raw Pacific oyster contains 1.95 g of fat, 69 calories and 42 mg of cholesterol. A raw oyster does contain significant iron, with 4.34 mg per 3-oz. serving, making it a healthy choice for iron in your diet.
Calcium Carbonate
Calcium carbonate made of ground oyster shells is an easily digested form of calcium supplement. The USDA recommends you have 1,000 mg of calcium a day as part of a healthy diet. If you're not achieving that daily amount with what you eat, calcium carbonate supplements may help. However, your body can only absorb 500 mg at a time, so if you're supplementing the full amount, take the supplements at different times.
Caution
If calcium carbonate made of ground oyster shell is your preferred calcium supplement, check if it contains lead. The calcium supplements made of oyster shell test positive for lead in some cases, which may be toxic. An April 2000 test of calcium carbonate conducted by the scientists at the University of California, Santa Cruz, found that lead levels were acceptable in most brands of antacid, another form of calcium carbonate, and infant formula. However, two thirds of commercial calcium supplements created from oyster shell, bone meal or dolomite failed California's lead standards established in 1999.
Considerations
For best absorption, take your calcium carbonate at meal time. This way, you get the most benefit from the ground oyster shells and help maintain bone and skeletal strength. In addition, experiment with different supplements. Calcium citrate is also a good option for calcium supplementation. Either supplement may cause digestive issues, so start with 500 mg and add more as your body can tolerate.
References
- MayoClinic.com; Shellfish Allergy: Prevention; June 2009
- USDA National Nutrient Database for Standard Reference: Mollusks, Oyster, Pacific, Raw
- Columbia University's Health Q&A Internet Service; What's Up With Calcium Supplements; September 2003
- "Environmental Health Perspectives"; Lead in Calcium Supplements; Genine M. Scelfo, A. Russell Flegal; April 2000
- Office of Dietary Supplements: Calcium
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