Shark cartilage toxicity warning

A common dietary supplement has been found to contain substances that harm the nervous system.
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01.Contaminants found in shark cartilage products

Joint formula pills in the shape of a shark

A study of 16 shark cartilage products on sale in the US found all samples were contaminated with mercury, and 15 were contaminated with a neurotoxin linked to motor neuron disease called beta-Methylamino-L-alanine (BMAA). While the amounts were small, mercury and BMAA together have a synergistic effect – that is, they enhance the effects of each other.

This raises concerns about shark cartilage products sold in Australia. Available in health food stores, pharmacies and online, they're promoted for treatment of cancer (for which there is no evidence) and osteoarthritis – chondroitin can be derived from shark cartilage (but also comes from birds and mammals) and is combined with glucosamine in some osteoarthritis supplements, although the jury is still out on whether they’re helpful.

The Australian regulatory framework allows supplements from animal cartilage, which are considered low-risk ingredients, to be listed on the Australian Register of Therapeutic Goods (they carry AUST L on the label) with a lesser degree of checking than higher-risk products. The listing process relies on claims by sponsors, with random checks by the regulators.

Australian medical researcher, Dr Rachael Dunlop, points out: “In most cases, the worst side effect you can expect from this self-regulated process is a lightening of your wallet. But when it comes to neurotoxic contaminants that have been linked to triggering terminal disease, the consequences are clearly much more serious.

“The fact that [AUST] L products are not tested for safety and efficacy by the TGA before they appear on the shelves is something most consumers do not know. I hope this latest research leads to consumers being cautious when choosing what they put in their mouths, especially when the risks outweigh the benefits. Just because it’s natural, that doesn’t make it safe.”

About mercury, BMAA and neurotoxicity

Mercury is often found in fish and other seafood in the form of methylmercury, and can affect the human nervous system, impairing vision and movement, and causing sensations such as pins and needles.

BMAA is produced by cyanobacteria (blue-green algae) and finds its way into the food chain when consumed by land and water animals, or it can be directly consumed through the water supply. Its effects on the nervous system have been documented both in animals that eat it in the wild and in people who eat animals that have eaten it. There is ongoing lab research as to its role in neurodegenerative diseases such as motor neuron disease, Parkinson’s disease and Alzheimer’s disease.



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