Scientific Research 科学研究

Review of Scientific Research on Edible Bird's Nest  燕窝科学研究報告 

Department of Applied Biology and Chemical Technology,

The Hong Kong Polytechnic University

Shun Wan CHAN

Abstract:

Edible bird's nest is one of the widely used health foods in Chinese communities. The market generated by it is increasing because it exhibits a lot of beneficial effects to human beings. For its high market value, fake edible bird's nest and misleading promotional description emerged. This article briefly reviews the scientific research on authentication technologies and pharmacological effects of edible bird's nest. It is expected that people's knowledge on edible bird's nest could be enhanced.

For the limited supply and high price of edible bird's nest, it is not uncommon to hear reports of fake edible bird's nest in the market.  Therefore, it is a great concern on authenticating the genuineness of edible bird's nest. In this review, the author will briefly summarize some advanced technologies in authenticating edible bird's nest. The medicinal benefits of edible bird's nest with contemporary scientific evidence will also be given.

Authenticity of Edible Bird's Nest

The first comprehensive report on authentication of edible bird's nest can be traced back to the early 1990s. Sam et al., (1991) demonstrated the possibility to use scanning electron microscopy, energy dispersive X-ray microanalysis, flame atomic emission spectroscopy, inductively coupled plasma-atomic emission spectroscopy, ultraviolet-visible spectroscopy and other physico-chemical techniques to ascertain the authenticity of edible bird's nest[8]. Since they only made a comparison with some imitation bird's nest with substances from plant origins, it limited the generalizing ability of the techniques to other imitation materials. In addition, they relied on sophisticated equipment. It is hard for commercial testing laboratories to carry out. Recently, a research team in China has developed a simple but accurate and reliable spectrophotometry method to determine edible bird's nest content[10]. It could also be used to differentiate genuine edible bird's nest with saliva and Tremella fucifomis[10]. The method is based on the reaction between N-acetylneuramic acid and ninhydrin in acid solution. The method evaluates the internal content of N-acetylneuramic acid, a nine-carbon sugars, which is one of the major components in edible bird's nest.

Nutritional Content and Medicinal Use

Edible bird's nest contains mainly carbohydrates, amino acids and mineral salts. The major ingredients of edible bird's nest are glycoproteins[11]. Amongst the carbohydrates in edible bird's nest, sialic acid (9%) is the major one. It was found that exogenous source of sialic acid may contribute to neurological and intellectual advantages in infants[12]. However, the nutritional and biological mechanisms of sialic acid in human body are still under investigation. The other major carbohydrates include 7.2% galactosamine, 5.3% glucosamine, 16.9% galactose and 0.7% fucose[11].

Amino acids and mineral salts are also important components in edible bird's nest. Three non-essential amino acids (aspartic acid, glutamic acid, praline) and two essential amino acids (threonine and valine) can be found[11]. They could facilitate normal body functions such as repairing and immunity. Edible bird's nest is rich in mineral salts. It contains high content of sodium and calcium. It is because the source of edible bird's nest is derived from saliva Collocalia inhabiting mainly in limestone caves. In addition, low levels of magnesium, zinc, manganese and iron are also detected in edible bird's nest[8].

In spite of the long history of using edible bird's nest for medicinal purposes, there are not many scientific researches related to the therapeutic use of it in literature. The first scientific evidence was given by Ng et al. (1986) in Hong Kong. Edible bird's nest aqueous extract was found to potentiate mitogenic response of human peripheral blood monocytes to stimulation with proliferative agents, Concanavalin A and Phytohemagglutinin A[13]. It suggested that edible bird's nest might possess immunoenhancing effect by aiding cell division of immune cells.

One year later, other scientific evidence was published by Kong et al. They demonstrated an epidermal growth factor (EGF)-like activity in aqueous extract of edible bird's nest that stimulated the DNA synthesis in 3T3 fibroblast in a dose dependent manner in vitro[6]. EGF is a 6,000 Da polypeptide hormone produced by glands of the gastrointestinal tract, namely the salivary and Brunner's glands. It appears to play a crucial role in major normal cellular processes such as proliferation, differentiation and development[14]. It may offer a rationale for the medicinal use of edible bird's nest in ageing resistance. Since the receptor for EGF is highly expressed in a number of solid tumors, including breast, head-and-neck, non-small-cell lung, renal, ovarian and colon cancer[15], people are worried about a possibility to induce tumor progression and to resist chemotherapy/radiation treatment in tumor cells; in consequence, suggest that cancer patients should avoid edible bird's nest. In fact, there is no evidence supporting this suggestion. Currently we have evaluated the effects of aqueous extract of edible bird's nest on the viability on two human cancer cell lines, human breast cancer MCF-7 (ATCC HTB-22) and human liver cancer HepG2 (ATCC HB-8065). There was no observable effect on cell viability when comparing with the control group (unpublished data).

In 1994, a research team in China, evaluated the pharmacological effects of edible bird's nest and pearl powder containing formulation. The formulation was demonstrated to have immunoenhancing effects by elevating DNA synthesis of T-lymphacytes and circulating immunoglobulin M content in mice. In addition, the formulation also showed ageing retardation by increasing the level of superoxide dimutase[16]. However, the study did not explore whether the effects came from either edible bird's nest, pearl powder or both.

Acknowledgements

The author is grateful to Imperial Bird's Nest International Company Limited for providing intact bird's nests and their photos. Special thanks go to Ms. Siu-Hung Tsui for editorial assistance.

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