Milk thistle (with active compound silibinin) could inhibit lung cancer growth and progression according to research from the University of Colorado published in the Journal of the National Cancer Institute (Vol. 98, pp. 846-85). Silibinin, a flavanone compound in milk thistle, stopped lung cancer growth and spread in mice.
Lung cancer is the most common form of cancer worldwide with over 1.2m new cases diagnosed annually. It also has a poor survival rate, with approximately 75% of people diagnosed with the condition dying within 12 months.
Milk thistle extract is a widely used dietary supplement. It generally contain 80 per cent silymarin, a flavonolignan mixture which contains approximately 40 per cent silibinin. The research used pure silibinin, not silimarin.
The researchers divided 90 mice into six groups and injected 75 mice with cancer-causing urethane (cancer development in two to three weeks) and 15 mice with a saline solution (control). After two weeks of eating a normal diet, the urethane-treated mice (all five groups) were each fed a diet supplemented with group specific doses of silibinin (zero, 0.033, 0.10, 0.33, 1.0 per cent).
After 18 weeks, the silibinin supplemented group had between 32 and 38 per cent less tumours than the urethane-only group, across all the dose range. After 29-weeks, the silibinin supplemented group had between 64 and 70 per cent less tumours than the urethane-only group, across all the dose range.
Mice that received the 1.0 per cent silibinin supplement, the highest dose used, had an amazing 93 per cent fewer large tumours than the urethane-only group. Significantly, silibinin prevented tumours from growing beyond a small size in a dose-related fashion.
The tumours in the silibinin supplemented mice had between 41 and 74 per cent fewer cells that tested positive for proliferation (spread) markers. The formation of blood vessels (angiogenesis), an indicator of growth and spread, was also found to be reduced in the silibinin groups, with reductions as high as 89 per cent.
The mechanism behind the effects is not clear, but the researchers suggest the flavanone may act on the expression of two enzymes (iNOS and COX-2), in addition to the vascular endothelial growth factor (VEGF), which promote tumour angiogenesis.
It is important to remember that the research involved an animal model of lung cancer. While mice do provide a useful and widely used human model, they clearly are not the same as humans. A comparable dose in a 70 kg human would be in the range of about 2 to 20 grams per day just for the three lower doses, and as high as 60 grams for the top dose.
However, research has indicated some high doses of silibinin are not toxic. For example, a recent study in human prostate cancer patients suggests that silibinin consumption up to about 6.7 g/day (equivalent to 20 g/day silibinin-phytosome in three equal doses) does not show any significant adverse health effect.
Milk thistle may be a natural substance of tremendous value in assisting people with lung cancer recovery. Unfortunately many people currently use radiation and chemotherapy which can dramatically reduce quality of life for little or no gain.