Will extra magnesium help prevent colon cancer?
Possibly. Animal studies suggest that dietary magnesium may play a role in the prevention of colorectal cancer, but there is very little human data. I?m aware of no studies that have used supplemental magnesium and then assessed benefits. However, a recent Swedish retrospective analysis did suggest a positive relationship. In this study, researchers looked at the diets of more than 60,000 women. They found that women who consumed the most magnesium, 255 mg/daily or greater, were less likely to develop colorectal cancer compared with those who had the lowest intake, 209 mg/daily or below.1 That is certainly suggestive, but not conclusive.
Additionally, these findings are a bit at odds with an earlier study looking at levels of calcium and magnesium in drinking water. That study showed a significant association with calcium and a decreased risk for colon cancer, but did not show an association with magnesium.2 Speaking of calcium, there is strong research that taking at least 900 mg of calcium/day modestly decreases risk for colorectal cancer.3,4 As for magnesium, even though its correlation with colorectal cancer is not as clear, I think individuals at increased risk would be prudent to make sure they get adequate levels.
Do fish oils relieve psoriasis?
Several studies suggest that oral fish oil supplements have a beneficial effect on psoriasis. Older observations suggest some individuals improve with high levels (3 g to 6 g for three to 12 months) of oral eicosapentaenoic acid. But in these studies not everyone improved, and the effects were variable and modest.5 In addition, some controlled studies report no positive effect, which is somewhat puzzling.6
It certainly makes sense that EPA should work. This fatty acid has demonstrated anti-inflammatory effects and, therefore, an inflammatory condition like psoriasis would seem likely to respond. However, it may be that very large amounts are needed. Two studies have shown that intravenous omega-3s resulted in a marked reduction of psoriasis. The rapidity of the response to intravenous use clearly exceeded the spotty effects with oral supplementation.7,8 So taking EPA does seem to decrease the inflammatory process that underlies psoriasis, but getting clinical effects from oral supplementation may not always be possible. Therefore, just taking fish oils may not be enough. One may want think about using other natural therapies to get reasonable responses and include EPA in the mix.
I was told that having osteoarthritis increases my risk for cardiovascular disease and death. Is this true?
I think someone gave you this information a little out of context. There is, in fact, a Finnish study showing an association with mortality and osteoarthritis. However, it was OA in the fingers, not OA generally, that showed this association. And even here, the report found only a modest association. In particular the last joint of the fingers, called the distal interphalangeal joint, seemed associated with increased mortality. After adjusting for other risk factors, women with OA in the same fingers of both hands, as measured by X-ray, showed a slightly increased risk of death over those who did not. In men, OA in any finger joint predicted an increased risk for cardiovascular deaths only.9
This is interesting but has a few caveats. The study was relatively small and focused on a specific population that we should be cautious about extrapolating. Given that, what may be the cause of the correlation? It could be a connection with inflammation. It has been shown that OA is associated with a mild increase in an inflammatory marker called high sensitivity C-reactive protein.10 Hs-CRP has been in the news frequently during the past few years because it has been associated in numerous studies with an increased risk for cardiovascular disease and death.11 So OA, because it may cause an increase in inflammation, may have more than just local effects. It is an interesting hypothesis, and adopting a lifestyle that promotes foods and nutrients that have anti-inflammatory effects may be important for a lot of reasons. However, I wouldn?t just focus on OA of the fingers as an increased cause for mortality.
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1. Larsson SC, et al. Magnesium intake in relation to risk of colorectal cancer in women. JAMA 2005;293(1):86-9.
2. Yang CY, Chiu HF. Calcium and magnesium in drinking water and risk of death from rectal cancer. Int J Cancer 1998;77(4):528-32.
3. McCullough ML, et al. Calcium, vitamin D, dairy products, and risk of colorectal cancer in the Cancer Prevention Study II Nutrition Cohort (United States). Cancer Causes Control 2003;14(1):1-12.
4. Terry P, et al. Dietary calcium and vitamin D intake and risk of colorectal cancer: a prospective cohort study in women. Nutr Cancer 2002;43(1):39-46.
5. Kojima T, et al. Long-term administration of highly purified eicosapentaenoic acid provides improvement of psoriasis. Dermatologica 1991;182(4):225-30.
6. Soyland E, et al. Effect of dietary supplementation with very-long-chain n-3 fatty acids in patients with psoriasis. N Engl J Med 1993;328(25):1812-6.
7. Mayser P, Grimm H, Grimminger F. N-3 fatty acids in psoriasis. Br J Nutr 2002;87 Suppl 1:S77-82.
8. Grimminger F, et al. A double-blind, randomized, placebo-controlled trial of n-3 fatty acid based lipid infusion in acute, extended guttate psoriasis. Rapid improvement of clinical manifestations and changes in neutrophil leukotriene profile. Clin Investig 1993;71(8):634-43.
9. Haara MM, et al. Osteoarthritis of finger joints in Finns aged 30 or over: prevalence, determinants, and association with mortality. Ann Rheum Dis 2003;62(2):151-8.
10. Spector TD, et al. Low-level increases in serum C-reactive protein are present in early osteoarthritis of the knee and predict progressive disease. Arthritis Rheum 1997;40(4):723-7.
11. Ridker PM. Clinical application of C-reactive protein for cardiovascular disease detection and prevention. Circulation 2003; 107(3):363-9.