US research aims to further enrich eggs and poultry meat

Research over many years has shown that the consumption of long-chain omega-3 polyunsaturated fatty acids provides a large range of health benefits, including lowering the risk of heart disease and death.

American consumption of omega-3 is low

Too few Americans are consuming enough of this vital nutrient to reap the benefits, which has prompted scientists at Penn State’s College of Agricultural Science to fortify foods people frequently eat, such as eggs and chicken, with the omega-3 fatty acids. Kevin Harvatine, associate professor of nutritional physiology at Penn State, said action was needed to reduce the incidence of obesity, heart disease and insulin resistance, which was reaching epidemic proportions in the United States. “Production of nutritionally enriched eggs and poultry meat will help consumers meet health goals and help egg and poultry producers to increase the value of their products,” he added.

Benefits of essential fatty acids

Professor Harvatine and Robert Elkin, professor of avian nutritional biochemistry, have found that alpha-linolenic acid can help. It is an 18-carbon omega-3 fatty acid, which is found in flaxseed, walnuts, soybeans, nut oils and leafy vegetables and is one of two essential fatty acids that the human body cannot produce on its own. It is vital for cardiovascular, cognitive and immune system health and is also touted for its anti-inflammatory properties. The other essential fatty acid, linoleic acid, is an 18-carbon omega-6 fatty acid commonly found in corn, many vegetable oils and a wide variety of snacks and fast foods. While it can be beneficial, consuming too much – which many people do – is not good because it promotes inflammation. In addition, linoleic and linolenic acids compete for the same set of enzymes in the liver that convert them into longer-chain derivatives, which have opposing functions in the inflammatory process. As a result, when the ratio of omega-6 to omega-3 fatty acids favours the former, fewer heart-healthy long-chain omega-3 fatty acids are produced by the liver and transported to tissues such as the brain and retina, where they have other physiological functions.

Adults: Omega-3 daily intake of 250mg

Prof Harvatine said omega-3 needs vary, but in general, healthy adults should set a target of about 250 milligrams per day each of the 2 most important types:

1. Eicosapentaenoic acid and (known as EPA) and
2. Docosahexaenoic acid (known as DHA).

These contain a greater number of carbon atoms and unsaturated double bonds, and are heart-healthy. Foods rich in long-chain omega-3s including fatty fish such as salmon, tuna, mackerel and herring but few Americans eat the 1-2 servings per week recommended by the American Heart Association.

While supplements are available, the researchers believe it is better to reach omega-3 nutritional targets through food, such as enriched poultry meat and eggs, because, says Professor Elkin, “it’s perhaps a more effective ways to reach a greater number of people who are concerned about health risks associated with the consumption of certain fish species, the sustainability and environmental effects of aquaculture, or simply prefer to not eat fish for a variety of reasons.” US citizens eat about 267 eggs a year and consume 91 lbs of chicken, according to 2017 figures from the National Chicken Council. The goal of the scientists is to create poultry products that are richer in long-chain omega-3 fatty acids but lower in omega-6 fatty acids. Although the chicken is able to convert the 18-carbon omega-3 fatty acid found in plants to the heart-healthy long-chain omega-3s, it is very inefficient.

Researchers found that supplemental dietary flaxseed oil resulted in an enrichment of egg yolks with EPA and DHA. Photo: Dreamstime

Benefits of reducing linoleic acid in diet

In a recent study, published in Lipids, the scientists hypothesised that reducing the dietary level of linoleic acid would promote greater conversion in the liver of linoleic acid to EPA and DHA, while supplementing the hens’ diets with a high-oleic acid soybean oil would simultaneously further enrich eggs with oleic acid without influencing egg EPA and DHA contents. The researchers found that, as compared to controls, supplemental dietary flaxseed oil resulted in an enrichment of egg yolks with EPA and DHA, but simultaneously supplementing the hens’ diet with both flaxseed oil and high-oleic soybean oil maximally reduced the yolk deposition of linolenic acid, long-chain omega-3 fatty acids and total omega-3 fatty acids by 37, 15 and 32% respectively.

The results suggested that dietary oleic acid was not neutral with regard to the overall process by which dietary linolenic acid was absorbed, metabolised and deposited into egg yolk, either intact or in the form of longer chain/more unsaturated omega-3 fatty acid derivatives.

They believed that oleic acid may simply have out-competed linolenic acid for absorption in the intestine, which ultimately would result in less omega-3 fatty acid enrichment of egg yolks.

The ‘oleic acid effect’

“It is possible that oils rich in oleic acid might hinder the body’s ability to reap the full nutritional benefits of EPA and DHA if consumed along with fatty fish or omega-3 fatty acid supplements, such as fish oil capsules.

“This also could be occurring in people consuming a Mediterranean diet, in which oleic acid-rich olive oil is the principal source of fat and moderate to low amount of fish are eaten,” added Prof Elkin. Studies are underway to confirm the finding in laying hens with other oils that are rich in oleic acid, in order to demonstrate that it is an “oleic acid effect” and not an effect that is only specific for high-oleic soybean oil. “The importance of this research to the egg industry is that we have learned of a potentially new hindrance to enriching eggs with omega-3 fatty acids, and that information can be used when trying to develop the next generation of designer eggs,” he added.