Vitamin P is not actually a vitamin; instead the term refers to several substances more accurately called flavonoids or bioflavonoids that occur naturally in many types of plants. One scientifically proven benefit of taking bioflavonoids is that they make it easier for the body to absorb vitamin C. There are also many other claims made about the benefits of vitamin P, including that it can protect against inflammation and infection, alleviate pain, strengthen blood vessels, prevent cataracts, boost the immune system, and be used to treat and prevent allergies and cancer. Some of these claims are supported by preliminary scientific studies, but scientists do not yet know how vitamin P works or how effective it is, and there is no recommendation of a daily dosage. Good sources of bioflavonoids in the diet include dark chocolate, green tea, red wine, apples, citrus fruits, and many other fruits and vegetables.
Quercetin is one bioflavonoid commonly included under the label of vitamin P. Studies show it has some antioxidant properties, meaning it prevents the oxidation, or breakdown, of certain other molecules, such as vitamin C. It also has some anti-inflammatory properties, which could make it useful in the treatment of conditions like arthritis, which involves inflammation of the joints. There have been some claims that quercetin can be used to treat and prevent cancer, but these health benefits have not been proven.
Rutin is another flavonoid component of vitamin P that is being studied by medical researchers. Studies done in vitro, meaning in test tubes rather than on people or animals, have shown that, like quercetin, rutin has potential anti-inflammatory properties. It has also been shown to thin the blood and improve circulation. Other studies show that this bioflavonoid can strengthen the walls of the blood vessels in the body, which can have beneficial effects on the circulatory system. Some health practitioners recommend rutin as a treatment for various conditions such as hay fever, varicose veins and glaucoma, but most such treatments are still experimental.
It is often recommended to take vitamin P together with vitamin C supplements, because bioflavonoids inhibit the breakdown of vitamin C, making it easier for the body to absorb this vitamin. There is no recommended daily intake of vitamin P, though 500 mg is sometimes mentioned as an appropriate dosage. Eating a diet rich in fruit and vegetables will provide enough vitamin P for the body to function properly.