Linseed oil is a natural oil derived from the flax plant that has industrial uses as well as nutritional value. The uses of linseed oil include as a woodworking varnish and gloss enhancer to paint, in the manufacture of linoleum tile flooring, and as an antioxidant food supplement. Since linseed oil is composed of healthy omega-3 fatty acid compounds, it is recommended for many ailments related to heart disease and diabetes.
Among the common health uses of linseed oil are treatments for such widely diverse conditions as cancer, arthritis, and skin conditions like eczema. The benefits of treating all of these conditions are based on linseed's concentration of omega-3 fatty acids. It is also seen as a natural laxative source that helps to relieve indigestion symptoms, as well as the effects of ulcers. Its uses also extend to hormonal treatments for both men and women, such as menopause in women and inflammation of the prostate gland in men, as it contains phytoestrogen compounds similar to human hormones that tend to decline in concentration with age.
As both a sealant and lubricant in paints and polishes, linseed oil's uses are widespread. Raw linseed oil has been an ingredient in these products since before the invention of synthetic substitutes, as it acts as a slowly drying wood preservative as well as being able to provide a protective coating to masonry and concrete. Boiled linseed oil dries much faster than the raw variety, and is often recommended for commercial applications where there will be foot traffic or handling of the object, such as a tool handle, relatively quickly after coating.
While the uses of linseed oil are diverse, many commercial synthetic replacements have superior performance characteristics. The advantages that using linseed oil still has as of 2011 include that it costs about half as much as synthetic preservatives for wood treatments, and it has restorative properties for putties and coatings that have dried out over time. The ability for raw linseed oil to dry slowly over the course of weeks also makes it better suited as a caulking ingredient in putties used around windows to maintain a tight seal. In this instance, synthetic compounds can dry too quickly and separate from the joint between the wood and glass in the process.
The advantages to the uses of linseed oil can also be seen as disadvantages depending on the circumstances. At times, it may not dry completely, especially if it is too heavily concentrated or applied in a cold climate. It doesn't offer any protection from ultraviolet light due to its low molecular weight as well, which over time can damage the material it has been coated to protect. A build-up of multiple coatings of linseed oil on a surface can also be difficult to remove if flooring is being prepped so that it can be repainted or varnished with other materials.