Phytochemicals such as polyphenols are subject to the same principles of pharmacology and biochemistry as other xenobiotics and pharmaceuticals. Their conversion to forms capable of being absorbed from the small or large intestine is often an important first metabolic step. However, metabolism does not stop there — glucuronidation of polyphenols immediately occurs in the intestinal cells, resulting in very little of the polyphenol entering the blood stream and being distributed to the rest of the body. The low blood concentrations (in the low nM range) of the unconjugated polyphenols are often taken as a sign that they are not biologically active. However, many studies have shown that oral intake leads to well-defined anti-inflammatory responses and antioxidant events, suggesting that either the low polyphenol concentrations are adequate to induce biochemical changes, or that localized tissue metabolism to more active compounds occurs.