Because Rosemary is a natural antioxidant it slows the oxidation of oils.
Here is some more data on Rosemary from http://www.thehealthierlife.co.uk/natural-remedies/herbs/rosemary-health-benefits-00145.html
Rosemary is a popular herb adding spice to soups, stews, meat and fish dishes.
Rosemary has long been used as a medicinal remedy to soothe stomache upsets, digestive disorders and headaches.
An imbalance of oestrogen hormones in women is a contributory factor in breast cancer. Dr Zhu and colleagues from the Department of Chemical Biology, State University of New Jersey in the US, found that a 2 per cent concentration of rosemary extract was able to significantly inactivate excess oestrogen in just 3 weeks. Researchers believe that it works by stimulating liver enzymes, which inactivate oestrogen hormones like oestrone and oestradiol
The antioxidants contained in rosemary help to protect your body’s cells from damage by free radicals. The antioxidants include monoterpenes, phenolic diterpenes and flavonoids, which are renowned for their ability to slow down the production of free radicals.
Rosemary is also a rich source of vitamin E (alpha tocopherol), another potent antioxidant, which further contributes to its free radical fighting powers.
DNA is your genetic blueprint It is particularly prone to injury from free radicals. Left unchecked, this damage can eventually lead to cells proliferating out of control, which greatly increases the risk of cancer. Scientists from the department of Mutagenesis and Carcinogenesis, Cancer Research Institute of Slovak Academy of Sciences, in the Slovak Republic, have found that rosemary extract can significantly help to protect DNA against free radical damage.
Anti-Aging For Skin
According to researchers at the Faculty of Medicine, University of Catania, Italy, rosemary extract helps protect the individual components of skin cells, which may prevent age-related skin damage such as wrinkles. In a follow-up study the Italian researchers found that rosemary extract is able to exert even greater benefits. In particular, it was shown to safeguard a protective protein called HSP70. The role of this protein is to reduce damage caused by stress, free radicals and other toxins on the skin.
Rosemary extract has been shown to inactivate toxins and then eliminate them from your liver, before they can inflict any serious damage. Scientists from the French National Institute of Agronomic Research in Dijon, found rosemary extract encouraged detoxifying enzymes - including cytochrome P450, glutathione transferase and quinone reductase - to flush harmful toxins from the liver. In effect, rosemary stimulates your liver to work more efficiently, which helps you feel more healthy and energetic.
Japanese and US researchers found that the carnosic acid in Rosemary protects the brain from free radical damage, helps protect against strokes and neurodegenerative diseases such as Alzheimer's.
Researchers in the UK found the scent of Rosemary boosted long-term memory.From: http://www.newsmaxhealth.com/headline_health/Natural_Brain_Boosters/2011/01/25/372701_4.html