[Este artículo está disponible en español. La traducción al español apareció por primera vez en la revista Pensar.]
What are green-lipped mussels? My imagination conjures up a SpongeBob SquarePants episode featuring a clam-like creature with green lips, and I can’t help wondering what would happen if they applied red lipstick? Imagination can be fun; but to get back to reality, green-lipped mussels are a shellfish naturally found in New Zealand and now cultivated and sold as a dietary supplement in the form of a freeze-dried powder or lipid extract. They are also known as Perna canaliculus, New Zealand mussel, greenshell mussel, kuku (Is that a mis-spelling of cuckoo? I would agree that it’s probably cuckoo to use them for medicine!), and kutai. They should not be confused with Perna viridis, the Asian green mussel, which can harbor deadly toxins.
Interest in green-lipped mussels first arose when it was observed that Maoris living on the coast had a lower prevalence of arthritis than those living inland or than Europeans. Coastal Maoris had access to green-lipped mussels and ate them regularly, often raw. OK, but there’s no reason to assume that the rate of arthritis had anything to do with this one component of their diet. There could be many other explanations for the observations. There was no attempt to pin down the real reason, just a leap of logic and a rush to marketing. Science provided a rationale when it discovered that the mussels contained chemicals that might help decrease swelling and might have anti-inflammatory properties.
I see a couple of problems with this line of thinking. In the first place, if coastal Maoris had less arthritis, wouldn’t that mean that green-lipped mussels prevented arthritis? So shouldn’t they be selling it to prevent arthritis? Why would they assume it would be effective as a treatment? There are two common types of arthritis: osteoarthritis and rheumatoid arthritis. Osteoarthritis is classified as a non-inflammatory arthritis, so why would anti-inflammatories be expected to work for it? Rheumatoid arthritis is a form of inflammatory arthritis; but if you just treat the pain and inflammation, that means you’re not getting the disease-modifying anti-rheumatic drugs (DMARDs) that have been proven effective in helping protect the joints from permanent damage and deformity. Another problem: the latest statistics from New Zealand show that Maoris are more likely to have arthritis than non-Maoris.
People take these supplements for arthritis, asthma, ADHD, and many other conditions. But as WebMD says, “There is no good scientific evidence to support any of these uses.”
It’s natural, so it must be safe. Right? Wrong!
According to WebMD, “New Zealand green-lipped mussel is POSSIBLY SAFE for most people. It can cause some side effects such as itching, gout, abdominal pain, heart burn, diarrhea, nausea, and intestinal gas. In rare cases, it might cause liver problems.” It is rated “possibly unsafe” for pregnant women, and there is insufficient evidence to evaluate safety during breastfeeding.
What Does the Science Say?
As I started to look for scientific evidence, the first study I found was pretty puny. It was a small pilot study that was open-label with no control group. Subjects were likely to be biased, because they knew when they were taking the drug. I found a lot of studies in dogs, horses, and rats. I kept looking, and I soon found a randomized double-blind placebo-controlled study of eighty humans with osteoarthritis of the hip and knee. It found Lyprinol (a patented extract from Perna Canaliculus) “very effective.” The evidence was confusing; it was all over the place, with some studies saying it worked and some saying it didn’t.
When different studies disagree, the next step is a systematic review. Fortunately, Edzard Ernst and Christopher Cobb had already done the heavy lifting for me. In their excellent systematic review, they found mixed outcome measures that were not conclusive, “with only two of five randomized controlled trials attesting benefits for rheumatoid and osteoarthritis patients.” Their conclusion?
“There is little consistent and compelling evidence, to date, in the therapeutic use of freeze-dried green-lipped mussel powder products for rheumatoid or osteoarthritis treatment, particularly in comparison to other cheaper alternative nutriceutical supplements of proven efficacy. However, further investigations are necessary to determine whether green-lipped mussel supplements, such as Seatone, are therapeutic options in the management of arthritis.”
Nuff said. I’m not buying.
This article was originally published as a SkepDoc’s Corner column on the CSI website.