Q. I've heard that mussel extracts may help with arthritis. What is the science behind this?
A. You are probably referring to an extract of green-lipped mussels (Perna canaliculus), which is now found in many anti-arthritic natural products. Initial animal research, started more than 25 years ago, showed the extract might serve as an anti-inflammatory agent. The extract also reduced gastric irritation common from use of nonsteroidal anti-inflammatory drugs when co-administered with them.1 Later animal research also demonstrated promise as an anti-inflammatory—likely related to the extract's omega-3 fatty acid and/or glycosaminoglycans content. (Glycosaminoglycans form the building blocks for connective tissues such as cartilage.)
All these animal studies demonstrated improvement in some types of arthritis symptoms when compared with placebo.2,3However, early human studies failed to show improvement when the extract was administered to patients with rheumatoid arthritis.4 A more current human, nonplacebo-controlled study has supported its use in osteoarthritis of the hip and knee.5 Even so, a recent review that looked at all published controlled trials studying the clinical effectiveness of green-lipped mussel extract found that only two of five randomized controlled trials showed benefit for rheumatoid or osteoarthritis patients.6 They suggest this may be due to a lack of stabilization in the omega-3 polyunsaturated fatty acids. Thus, the evidence to date is far from consistent or persuasive. So I'd hold off until more is known.
Q. Should I take vitamin D if I live where the sun don't shine?
A. If the sun really doesn't shine, I'd first suggest you move back to planet Earth. If the problem is that you live in a northern region or get more cloudy days than sunny ones, you should probably consider taking a vitamin D supplement. This is especially true if you don't eat foods naturally containing vitamin D (fatty fish) or those that have a lot of vitamin D added (dairy products).
Probably the easiest way to assess vitamin D status is to do a blood test that measures the amount of 25-hydroxy vitamin D, also called 25 (OH)D. A low serum level of 25 (OH)D is the main marker for a vitamin D deficiency. This test should be done from November to March, when sunlight is lowest. If results are below 30 ng/ml, supplementation should be undertaken.7,9 If you can't get that test done, and if you live in the northern sections of the country, supplementing with 500 to 1,000 IU of vitamin D, at least for half the year, is probably a useful strategy. At those levels, vitamin D is extremely safe. The recommended daily intake of vitamin D for children and adults is 200 to 600 IU per day, depending on age. The National Academy of Sciences' Institute of Medicine uses 2,000 IU per day as the safe upper limit.10
1. Rainsford KD and Whitehouse MW. Gastroprotective and anti-inflammatory properties of green lipped mussel (Perna canaliculus) preparation. Arzneimittelforschung 1980;30(12): 2128-32.
2. Bui LM and Bierer TL. Influence of green lipped mussels (Perna canaliculus) in alleviating signs of arthritis in dogs. Vet Ther 2003;4(4):397-407.
3. Halpern GM. Anti-inflammatory effects of a stabilized lipid extract of Perna canaliculus (Lyprinol). Allerg Immunol 2000;32(7):272-8.
4. Larkin JG, Capell HA and Sturrock RD. Seatone in rheumatoid arthritis: a six-month placebo-controlled study. Ann Rheum Dis 1985;44(3):199-201.
5. Cho SH, et al. Clinical efficacy and safety of Lyprinol, a patented extract from New Zealand green-lipped mussel (Perna Canaliculus) in patients with osteoarthritis of the hip and knee: a multicenter 2-month clinical trial. Allerg Immunol 2003;35(6):212-6.
6. Cobb CS and Ernst E. Systematic review of a marine nutraceutical supplement in clinical trials for arthritis: the effectiveness of the New Zealand green-lipped mussel Perna canaliculus. Clin Rheumatol 2005;Oct 12:1-10. [Published online ahead of print]
7. Garland CF, et al. The Role of Vitamin D in Cancer Prevention. Am J Public Health 2005; Dec 27. [Published online ahead of print.]
8. Webb AR, Kline L and Holick MF. Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J Clin Endocrinol Metab 1988;67(2):373-8.
9. Gorham ED, et al. Vitamin D and prevention of colorectal cancer. J Steroid Biochem Mol Biol 2005;97(1-2):179-9
10. Dietary reference intakes. Nutr Rev 1997;55(9):319-26.
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