Is There a Market for Selenium-Enriched Pork?

Selenium is an essential trace mineral that is required in very minute amounts by all animals, including pigs. Certain soils in the U.S. and Canada are low in selenium, including the north central and eastern regions of Canada and the northeastern, Pacific, southwestern, and extreme southeastern regions of the U.S (see figure). As a result, crops grown in these areas are also low in this trace mineral and, without supplemental levels, diets mixed exclusively from ingredients grown in these regions will be deficient in selenium.

Figure 1. Map of Selenium Status in Canada and the U.S.

Legend:

Cross-hatched Areas:
Low - Approximately 80% of all forage and grain contain <0.10 ppm selenium

Dotted Areas:
Variable - Approximately 50% contain >0.10 ppm selenium, includes Alaska

Unmarked Areas:
Adequate - 80% of all forages and grain contain >0.10 ppm selenium, includes Hawaii

In the 1960s, selenium deficiencies in swine were reported in some areas of the Midwestern U.S., mainly in Indiana, Ohio, and Michigan. Typical symptoms of selenium deficiency in pigs resemble symptoms of vitamin E deficiency, including muscular dystrophy, pale muscles, small hemorrhages in heart muscle ("mulberry heart"), and necrosis of the liver. In 1974, the U.S. Food and Drug Administration (FDA) approved the addition of 0.1 ppm selenium to all swine diets. In 1982, the allowable level was increased to 0.3 ppm for young pigs because 0.1 ppm was not always effective at preventing deficiency symptoms. By 1987, the allowable level was increased to 0.3 ppm for all weights and classes of swine.

The dietary requirement for selenium suggested by the National Research Council in Nutrient Requirements of Swine (Tenth Revised Edition, 1998) ranges from 0.3 ppm for weanling pigs to 0.15 ppm for growing-finishing pigs, gestating-lactating sows, and breeding boars. Selenium, usually in the inorganic form of sodium selenite, is generally included in premixes, supplements and complete feeds that are sold to producers.

There is increasing interest in the benefits of supplemental selenium in human diets. Since selenium was determined to be essential, researchers have uncovered numerous health benefits related to dietary selenium. Selenium's primary role within the bodies of animals and humans is as a component of the antioxidant enzyme system. Glutathione peroxidase, an enzyme found in every cell in the body, neutralizes toxic peroxides that are formed during the conversion of body fat to energy. If these peroxides remain unchecked, they can damage cell components and cause a whole range of health problems, including cancer. Selenium is a component of at least 20 other functional proteins in the body, most of which have some type of protective function.

Despite the overwhelming evidence that trumpets the benefits of selenium on human health, there is a growing body of research that indicates humans are becoming selenium deficient. Soils in the regions where the majority of livestock feed grains and soybeans are grown are low in selenium. These soils in turn produce crops with low selenium concentrations, which leads to deficiencies further down the food chain in animal products, and, eventually, humans. Dr. Margaret Rayman, a professor at the University of Surrey in the United Kingdom, evaluated the selenium status of more than 42,000 people in Europe and the United States. Rayman has concluded, based on preliminary data, that the average selenium intake by Europeans and Americans is far below the 75 micrograms per person per day that is recommended by the United Kingdom's Reference Nutrient Intake and the U.S. National Academy of Science.

Organic selenium, produced through the fermentation of yeast, is another form of selenium that can be used as an alternative to sodium selenite for supplementing livestock feed. This organic selenium may play a role in reversing the trend towards lower selenium intakes, and the related health problems, in humans. Ultimately the use of organic selenium to improve the selenium status of humans may involve the consumption of selenium-enriched pork.

Dr. Don Mahan, a swine nutrition researcher at Ohio State University, conducted some of the early research on the effects of organic selenium in pork. His results indicate that loins from hogs fed organic selenium (yeast-derived seleno-cysteine) did have higher concentrations of selenium than loins from hogs fed inorganic selenium (sodium selenite). Mahan also reported that drip loss values were higher in pork from hogs fed inorganic selenium than hogs fed either organic selenium or a ration without any supplemental selenium. Organic selenium may also have implications for improved shelf life.

Four cooperatives in Korea are currently marketing "Selen Pork", a specific brand of selenium-enriched pork. In 2000, these cooperatives collectively raised about 100,000 "Selen Pork" hogs by feeding a special premix containing organic selenium. Analysis of ham and loin samples has shown that "Selen Pork" boasts approximately 10 times the selenium content of traditional pork, is leaner and juicier, and has a noticeably redder color - a characteristic favourable in marketing to Asian consumers. Although feed costs are slightly higher to raise "Selen Pork", it is priced at approximately 30% higher in the Korean market than traditional pork.

The FDA has recently approved organic selenium for use in swine and turkey feed, following up on their approval for broiler feed in 2000. In Canada, only two organic selenium products are currently approved for use in swine feed; both are selenium-enriched yeasts.

The consumption of selenium-enriched meat could have direct health implications for humans. In research conducted at the University of Arizona, a large group of men were given a pill containing either organic selenium or a placebo for an extended period of time. For the group that was given a daily supplement of organic selenium, there was a 63% decrease in prostate cancer, a 58% decrease in colon and rectal cancers, and a 45% decrease in lung cancer. In addition, the overall cancer death rate in this group was reduced by 50%. Other researchers have reported benefits of adequate selenium nutrition on Acquired Immune Deficiency Syndrome, immunity, fertility, and heart disease.

Time will tell whether or not selenium-enriched pork will catch on as a "health food". The meat industry has been touting meat's virtues as a superior source of nutrients, compared to food of plant origin, for many years. It looks like, with regards to selenium, the meat industry may have the upper hand.

Sources

Castaldo, D.J. 2002. Meat as a Bodyguard. Meat Processing. September 2002.
Cromwell, G.L. 2000. Selenium - A Unique Trace Element. University of Kentucky. April 2000.

http://www.saanendoah.com/map1.html - Kubota, J., W.R. Allaway, D.L. Carter, E.E. Cary and V.A. Lazar. 1967. Selenium in crops in the United States in relation to selenium-responsive diseases of livestock. J. Agric. Food Chem. 15:448

http://www.uky.edu/Ag/AnimalSciences/swine/documents
/seleniumauniquetraceelement.pdf
Nutrient Requirements of Swine. 1998. Chapter 4 - Minerals. National Research Council.