Cholesterol is found in all cells of the body, primarily as a structural component of cell membranes, but it has other vital important functions. Stored in the adrenals, testes, and ovaries, it is converted to hormones such as the sex hormones (androgens and estrogen's) and the adrenal corticoids(including cortisol, corticosterone, aldosterone). In the liver, cholesterol is the precursor of the bile acids which when secreted into the intestine to aid in the digestion of food, especially fats.

It has been implicated as a major factor in the development of many cardiovascular disease, but especially arterio-sclerosis. This disease involves a process of fatty deposit buildup on the lining of large and medium-sized arteries. The presence of fatty deposits, called plaques, leads to a loss of elasticity and a narrowing of vessels and this constriction to blood-flow ultimately deprives organs of their blood supply. Clots may lodge in arteries supplying the heart and cause a heart attack, or the brain and so cause a stroke.

Diets rich in saturated fats, cholesterol, and calories appear to be chiefly responsible for high blood cholesterol, and such diets are therefore believed to promote atherosclerosis. However, the plaque forming tendency of cholesterol is influenced by the type of lipoproteins that transport it in the blood. The low-density lipoproteins are clearly atherogenic, but the high-density lipoproteins appear to prevent accumulation of cholesterol in the tissues. The blood levels of these lipoproteins is partially governed by dietary factors, especially the type of vegetable lipids (phytosterols) eaten.

This highlights the value of plants, both as medicine and nutrition for such health problems. The processes involved are complex and not understood. Plants provide a way to balance cholesterol absorption in a way that has evolved a sour bodies evolved, effecting fat metabolism and blood chemistry in an inherently integrated manner. As medical research has focused on this issue, a number of common dietary components are revealing themselves to be active in lowering cholesterol levels in the blood. It is not always known how they achieve it though.

Cayenne pepper and other plants that contain the phenolic compound capsaicin have a well demonstrated effect in lowering blood cholesterol levels, as does the widely used spice Fenugreek. Caraway is another aromatic spice with demonstrable cholesterol lowering properties. A whole range of Asian herbal remedies new to western medicine are proving to be valuable in this field, Emblica officinalis; and Ligustrum lucidum are examples.

Garlic and Onion have an international reputation as remedies for lowering blood pressure and generally improving the health of the cardiovascular system. A recent study was conducted on two groups, one consisting of 20 healthy volunteers who were fed Garlic for 6 months and the other of 62 patients with coronary heart disease and raised serum cholesterol. Beneficially changes were found in all involved and reached a peak at the end of 8 months. The improvement in cholesterol levels persisted throughout the 2 months of clinical follow-up. The clinicians concluded that the essential oil of Garlic possessed a distinct hypolipidemic, or fat reducing, action in both healthy people and patients with coronary heart disease.

An abhorrent technique used in studying cholesterol and arterio-sclerosis is to feed a high fat-high cholesterol diet to rats or other laboratory animals. This leads to increased levels of fats in the liver, and cholesterol and triglycerides in blood serum, liver and kidneys. A common finding is that when Garlic oil is fed to animals maintained on the high fat-high cholesterol diets, there is a significant reduction of cholesterol levels, often nearing those seen in untreated control animals. This strongly points to the Garlic oil enhancing the breakdown of dietary cholesterol and fatty acids. Paper after paper have been published repeating these findings, findings well known amongst medical herbalist's.