While there are few people in the UK who might be considered malnourished, there are many who don’t have sufficient intakes of certain key vitamins and minerals.

The health benefits of these and other micronutrients are receiving growing attention and, for many years, the pharmaceutical industry has been making the most of some people’s fascination with their “wellbeing”.

There are opportunities for egg producers to tap into the market, too, while producing a product that can benefit their hens, as well as consumers.

Indeed, it is believed that the body uses nutrients more efficiently when they are eaten as a food rather than swallowed in a pill.

Some foods are already fortified by manufacturers’ to make sure the population is not deficient in certain key micronutrients. For example calcium, iron, vitamin B1 (thiamin) and nicotinic acid may be added to flour or breakfast cereals.

But eggs can also provide the perfect vehicle for nutrient delivery. They are a nutrient-dense food supplying high quality protein, along with vitamins and minerals. And the ability to manipulate their content by changing the hen’s diet leads to the possibility of creating enriched eggs.

The body uses nutrients more efficiently when eaten as a food rather than swallowed as a pill
Zoe Kay

If the levels of certain nutrients fed to hens are increased sufficiently, then higher levels will be found in their eggs. And studies have shown that consumption of enriched eggs has the desired effect of increasing nutrient levels in people.

The three main nutrients that have been used so far are omega-3 fatty acids, selenium and lutein (see panel, right).

Long chain omega-3 fatty acids would not normally feature in a layer diet, unless it contained fish. But it can be supplemented from other sources. Selenium, however, is already added to poultry diets for its essential role in health and productivity. And marigold extract is used as a natural source of yellow pigments, for yolk colour, but comes with the added benefit of lutein.

Healthy eggs

With nutritional enrichment of laying hen diets it is not only consumers who benefit. There are significant advantages for producers in terms of bird health, performance and even egg quality.

Just as in humans, antioxidants prevent free radical damage in birds and can improve health.

Hens naturally put longer chain docosahexaenoic acid (DHA) – a component of omega 3 – into the eggs they lay, to provide chicks with an essential nutrient for their development. In a natural situation they would obtain omega-3 from insects, some of which have a similar content to that of fish. In commercial production, omega-3 may be obtained from algal sources and this may have the added benefit of providing natural carotenoids, improving yolk pigmentation.

The addition of selenium can also be a plus. Selenium has been shown to have positive effects on egg production, feed conversion and immunity. Egg quality is also improved, including thicker shells, increased breaking strength, less shell abnormalities and improved internal quality.

It has been observed that selenium levels in wild bird’s eggs are substantially higher than in commercial hatching eggs.

Scientific evidence

A large number of scientific trials into the feeding of enriched diets to laying hens have been carried out, demonstrating the levels of feed supplementation required to give a significant increase in the eggs.

In two trials looking into the effects of omega-3, corn-soya diets for laying hens were supplemented with oil from the microalgae strain Schizochytrium (SP-1 from Alltech), at different inclusion rates. DHA levels in the hens’ eggs were then analysed (see Table 1). In both studies, DHA content of eggs increased linearly with dietary SP-1 inclusion level.

It is understood that this fatty acid is absorbed intact and transferred to the egg yolk.

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Another experiment looked at the effect of organic selenium (Sel-Plex from Alltech), using Hyline Brown hens fed a corn-soya diet with two levels of supplementation.

The higher inclusion level led to a greater level of selenium in both the albumen and yolk (see Table 2). Researchers also noted that eggs containing a higher amount of organic selenium remained fresh for longer.

Selenium methionine (Se-met) from selenium yeast is effectively transferred to egg yolks and albumin. Chickens can’t synthesise Se-met, therefore feeding sodium selenite has much less effect on selenium levels in eggs.

Commercial possibilities

Omega-3 eggs are popular across the globe and are even named on health websites as a good way to get DHA into the diet. Brands sold in the UK include Intelligent Eating Tasty Omega-3 eggs from Stonegate, and Golden Irish Omega 3.

The only selenium enriched eggs currently sold in the UK are Boost the Roost from St Ewe Eggs, though across Europe and the rest of the world the concept has been marketed for some time.

The Lakes Free Range Egg Company’s Laid with Love brand are enriched with lutein.

Noble Foods was an early adopter of the enriched egg concept, producing the international brand Columbus Eggs and latterly Goldenlay Omega3. Rob Newell, head of brands at Noble Foods said: “I am a believer in the concept of enriched eggs as a nutritionally sound way of improving people’s diet.

“However, a balance needs to be struck between the challenges of producing the eggs themselves and an effective level of omega-3. For instance, effects on egg size and palatability need to be considered,” he explains. “Trends come and go. But coupling the overall health benefits of eggs with increased levels of several micronutrients is still interesting.”

Clarity on nutrient health claims, along with health advice that no longer limits egg consumption, have also helped the enriched egg market.

Conclusion

Evidence and experience shows that it is possible to create functional, enriched eggs to help correct dietary deficiencies.

For example, one selenium-enriched egg can deliver approximately 50% of the recommended daily allowance (RDA), and omega-3 eggs can deliver DHA and EPA in place of oily fish.

Enriched eggs offer a way to increase the levels of health-promoting micronutrients, without significantly changing eating habits. Consumers buy, cook and eat eggs in the same way, just simply having to choose an enriched brand.

Eggs can be marketed well as a functional food as they are increasingly seen to be part of a healthy diet. Consumer awareness of the health benefits of DHA and selenium, in particular, means that they are ideal candidates for enriching eggs.

Working with several micronutrients may increase their marketability, as well as providing effective tools for brand promotion.


Table 1. Effect of feeding microalgae to laying hens

Treatment

DHA/egg (mg)

Study 1

Study 2

Control

49

44

0.5% SP-1

74

n/a

1.0% SP-1

89

90

2.0% SP-1

115

126

3.0% SP-1

n/a

137

Based on averages of 12 replicates of three eggs per replicate

Table 2. Effect of organic selenium supplementation of layer diets

Dietary addition

Selenium levels (ng/g)

Albumen

Yolk

0.2ppm selenium

231.5

584.8

0.4ppm selenium

345.0

779.5

Dietary supplements for laying hens

Omega-3

This is a type of essential polyunsaturated fatty acid and can’t be made in the body. Alpha-linolenic acid (ALA) is the precursor for all omega 3’s. However, health benefits are associated with the longer chain docosahexaenoic (DHA) and eicosapentaenoic acid (EPA). DHA is known to play important roles in brain development and function, being particularly important for pregnant women and children. There is lots of evidence that DHA and EPA may protect against health challenges such as strokes and heart attacks.

The main dietary source of DHA and EPA is oily fish and seafood. But for poultry feed, omega-3 fatty acids are often supplied by flaxseed oil, as the use of fish oils can taint eggs. Regulations, price and availability can also be an issue for fish oils. But while flaxseed supplies ALA, it doesn’t contain a high concentration of DHA itself. The alternative is a micro-algal source, which has a greater efficiency at enriching eggs with DHA.

Selenium

The UK reference nutrient intakes (RNIs) for selenium are 60mcg for women and 75mcg for men. But it is estimated that actual intakes only amount to 39mcg per day – a significant shortfall. European soils are low in selenium, which affects levels in cereals and, in turn, animal proteins. Selenium is found in a number of enzymes important to human health, including glutathione peroxidase, which protects cell membranes from damage by free radicals. Evidence shows that selenium is key to immunity and thyroid metabolism, as well as being essential for reproduction.

Lutein

This is a potent antioxidant and important for eye health. As well as being found in marigolds, it is also a component of green leafy vegetables and coloured fruits, along with zeaxanthin. It may help protect against eye diseases in later life, such as age-related macular degeneration and cataracts.