Reports have suggested that some people should not use a cartilage supplement. This concern is based only on theory, not clinical evidence. This would include those people with cardiovascular disease, women who are planning to be or are pregnant, nursing mothers, anyone having or having had surgery within 30 days, and athletes training intensely. None of these concerns have been proven in clinical trials, however. Because shark cartilage contains calcium, people who ingest large amounts of shark cartilage (60 to 100 grams per day) may be consuming excessive amounts of this mineral. However, no cases of calcium toxicity resulting from the ingestion of shark cartilage have been reported.
While use of gelatin, collagen hydrolysate, or type II collagen has not resulted in any reports of serious side effects, people with known sensitivities to chicken or beef should consult a doctor before using them.