Shark Cartilage: What It Is, What It Might Do, and What to Watch For

Once marketed as a miracle cancer cure, shark cartilage is now mainly sold as a joint and cartilage supplement. The hype outpaced the science back then, so it's worth sorting fact from fiction before you buy or try it.

What it is and how it might work

Shark cartilage is the stiff tissue taken from shark skeletons. Supplements usually contain proteins and chondroitin-like substances that people think can help cushion joints. Some lab tests showed the material can affect blood vessel growth or inflammation, but lab results don’t always match what happens in people.

For joint pain, a few trials suggest modest symptom relief for some users — think small decreases in pain and slightly better mobility for a subset of people after weeks of use. For cancer, larger clinical trials did not confirm the early claims that shark cartilage slows tumor growth. Bottom line: joint support may be possible for some; anti-cancer claims are not supported by good human studies.

Safety, dosing, and smart buying tips

Common side effects are mild: stomach upset, constipation, or allergic reactions if you’re sensitive to fish. Avoid shark cartilage if you’re pregnant, breastfeeding, or have a serious seafood allergy. If you have planned surgery or are on medication, especially blood thinners, check with your doctor — supplements can complicate care.

Labels usually list doses from about 500 mg up to 3 g per day; many people try a product for 6–12 weeks to judge benefit. Start low and give it time, but if you see no improvement, stop and reassess with your clinician.

Sourcing matters. Sharks are long-lived and many species are overfished, so buying shark-derived products raises environmental and ethical issues. Look for brands that publish third-party testing results (NSF, USP, or ConsumerLab) to reduce the risk of contaminants. If sustainability or safety worries you, consider alternatives like glucosamine, chondroitin from other animal sources, omega-3s, or proven non-drug approaches such as strength training and physical therapy for joint health.

If you decide to try shark cartilage, pick a reputable brand, check for third-party testing, follow label directions, and talk to your healthcare provider when you have chronic conditions or take other drugs. Expect modest results at best for joint pain and no reliable evidence it treats cancer. Practical steps and realistic expectations will keep you safer and save money.