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Plant Sterols and Sterolins: Potential Immune System Modulators

Posted Mar 09 2011 9:47pm
Plant Sterols and Sterolins: Potential Immune System Modulators
Robert L. Pastore, Ph.D. – Nutritionist for the Hoffman Center

Sterols are plant fats found in all plant-based foods. Sterols, including cholesterol, are in the same large classification family of steroids but they do not have the negative effects that are often associated with steroids. Sterolins are glucosides, which are molecular structures joined to the sterol. Sterolin is easily destroyed, and without it, the sterol does not have the same immune-enhancing benefits. In nature, plants never contain sterols only. The sterols are always associated with their glucoside sterolin. The original research on sterols and sterolins was based on an extract of the African Hypoxis plant or “African Potato”. Its nomenclature derived due to the potato-like appearance of the Hypoxis plant. Due to the presence of other potentially harmful substances contained within the Hypoxis plant, other plants were investigated as sources for the sterols and sterolins used in supplementation.

Wheat, for instance, contains about 4,200 milligrams of plant sterols per 100 grams, while wheat flour contains only about 52 milligrams of total plant sterols per 100 grams! The removed bran contains about 4,500 milligrams of total plant sterols per 100 grams and the unrefined oil about 2,600 milligrams per 100 grams. Crude plant oils are a relatively rich source of phytosterols and their glucosides, but most of these are removed during refining. While soybeans contain about 160 milligrams of total plant sterols per 100 grams, the crude oil contains approximately 350 milligrams. This is reduced to 220 milligrams when the oil is refined and is further reduced during hydrogenation. This applies to all plant oils.

In order to consume 100 milligrams of plant sterols, however, one would have to eat 500 to 700 grams of fresh vegetables and fruit or about 200 grams of flour products (without additives). This amount has to be doubled for a normal dietary supply due to the fact that sterols and sterolins are tightly bound to plant fiber and therefore are not completely absorbed. When processed food is eaten or when one is under stress, the attenuated rate of sterolin/sterol absorption is more acute. Slimming diets, ill health and old age also seriously reduce the intake of sterols and sterolins.

Sterols and sterolins seem to illicit immune regulating effects. Before we discuss this let s take a closer look at the immune system.

The immune response has two ways of dealing with foreign pathogens. The B-lymphocytes synthesize specific antibodies called immunoglobulins. This is known as humoral immunity. The other system involves T-lymphocytes, which regulate the synthesis of antibodies as well as direct killer cell activity and the inflammatory response of delayed type hypersensitivity. This system is known as cell-mediated immunity. The T-cells are further divided into helper lymphocytes (Th) and cytotoxic cells (Tc), also known as suppressor cells. When the T-cells encounter a foreign pathogen (antigen) they further secrete a number of communication molecules called lymphokines, cytokines, interleukins or interferons. These factors further elaborate and direct the immune response to a specific antigen. The whole process is a symphony of many co-factors, which are orchestrated into a sophisticated immune response. The T-helper cells are directly involved in assisting B-cells as well as coordinating their own cell-specific defense. The T-helper cells are further divided into two distinct lines of defense. The Th1 cells promote the cell-mediated line of defense and inhibit the other line known as Th2 cells, which regulate the humoral defense. The Th2 cell lines control the B-cells and inhibit the cell-mediated response of the Th1 lymphocytes. A careful balance between these two functions is thus achieved. When one line predominates, there is the opportunity for immune dysregulation to occur, resulting in either a hyper-immune response causing an autoimmune disease or a hypo-immune response resulting in an uncontrollable infection such as AIDS or tuberculosis.

The Th1 helper cells secrete lymphokines such as interleukin-2 and gamma interferon. Th2 helper cells secrete pro-inflammatory lymphokines such as interleukin-6, interleukin-4 and interleukin-10. Interleukin-1 appears to be released in response to a specific injury and acts as an inflammatory mediator. Interleukin may be over-expressed in diseases such as rheumatoid arthritis and osteoarthritis. Interleukin-1 deficiency is associated with metastatic tumors, nutritional deficiencies and certain autoimmune diseases. Interleukin-6 is associated with pro-inflammatory responses as well as mediating the proliferation and maturation of T-cells. High levels of interleukin-6 have been associated with a variety of autoimmune conditions such as rheumatoid arthritis, Sjogren’s syndrome, multiple myelomas, and some cancers such as cervical and bladder cancer. Interleukin-2 is a growth factor for T-cell maturation as well as an inducer of T-cell cytotoxicity and natural killer cell activity. An interleukin-2 deficiency would cripple the cell-mediated immune response and its stimulation would enhance the overall efficacy of the immune system. Immune dysregulation occurs when the two sides of the immune response become imbalanced.

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