The Wulzen anti-stiffness factor is a compound that was originally discovered in molasses and unpasteurised cream. Its discoverer Rosalind Wulzen, showed that the compound could reverse the calcification of joints in osteoarthritis. More recently the Wulzen factor has been identified in a larger range of foods including legumes, nuts, seeds, vegetables and unpasteurised dairy produce. Chemically the Wulzen factor is actually a phytosterol called stigmasterol. Stigmasterol along with its chemically related campesterol and sitosterol are produced in plants and are structurally related to cholesterol. A number of 5-alpha saturated derivatives of the sterols called stanols (campostanon, sitostanol and stigmastanol) are also known to be present in plants and have been isolated in the diets of humans. The intake of sterols and stanols in the diet is naturally low in humans and absorption is very poor. However, supplements and fortified foods containing sterols and stanols are now available and this can increase intake considerably.
Recently interest in phytosterols has increased because of research suggesting that they can inhibit the absorption of dietary cholesterol. This may result from the ability of phytosterols to compete with the absorption of cholesterol in the gut, thereby lowering plasma levels. However, as endogenous synthesis of cholesterol accounts for most of the circulating cholesterol, and due to the fact that synthesis increases as dietary intake falls, it is unclear as to how plant sterols such as stigmasterol actually cause changes in plasma lipoprotein cholesterol. Some evidence from human cell culture experiments suggest that some of the dietary sterols actually inhibit human cholesterol biosynthesis, which is a more reasonable explanation for the observed effects of their ingestion. Whatever the mode of action, human studies clearly show a plasma cholesterol lowering effect for dietary sterols. However their long term health benefits for this purpose have not been investigated and are therefore unknown.
Another important health role for sterols and stanols may be as anti-cancer agents. Rats fed carcinogens develop fewer tumours if concomitantly fed plant sterols. Originally it was thought that sterols may alter rates of colorectal cancer by the modification to bile acid production. However, animal studies showing protective effects do not always show changes to bile acid synthesis rates and so other mechanisms of action may be apparent. Other studies have suggested that the addition of sterols to the diets of animals may inhibit carcinogenesis due to a reduction in cell proliferation in the mucosa of the gut. However, plant sterols may also have antioxidant effects, and as the aetiology of cancer may involve the generation of free radicals, the antioxidant capacity of plant sterols may explain some of their therapeutic effects against cancer and other diseases. The ability of stigmasterol to block the breakdown of cartilage explains its original capacity to lessen the symptoms associated with osteoarthritis as discovered by Wulzen.