A SCIENTIFIC RESEARCH HAS BEEN CONDUCTED SEVERAL TIMES ON CUBILOSE (EDIBLE BIRD NEST)

Review of Scientific Research on Edible Bird's Nest

淺談燕窩的科學研究

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.

摘要：燕窩在華人社會是其中一種非常普及的健康食品。一直以來，人們都相信燕窩有多種不同之效用，因此燕窩 市場不斷在擴展。由於燕窩的價值絕不便宜，故此假燕窩和一些帶有誤導性的推銷描述不斷在市場上出現。本文將簡略 回顧一些有關燕窩辨別真偽的技術與藥理效用之科學研究，希望藉此能加深社會對燕窩的認識。

Background

Swiftlets (collocaliini) are tiny insectivorous birds that are distributed from the Indian Ocean , through Southeast Asia and North Australia to the Pacific[1]. Amongst various species of swiftlets in the genus of Collocalia, only the nests of four species habituating in the Southeast Asian region have commercial value because of human consumption. They are Collocalia fuciphaga, Collocalia germanis, Collocalia maxima and Collocalia unicolor[2]. Collocalia species, average 6.5g in weight, have glossy plumage[1]. Their nests are constructed with salivary glue, a cementing substance, and may incorporate other materials such as vegetation or feathers. It takes about 20 days to finish the nest. The edible bird's nest ( 燕窩 in Chinese) making up with purely salivary glue are much more expensive than those incorporating with other materials (see Figure 1 in p.40).

In Hong Kong and in Chinese societies throughout the world, traditional Chinese medicine (TCM) is commonly used to treat diseases and enhance health. It is believed that TCM herbs have wide-ranging effects for enhancing health, lowering risk of diseases and promoting life span [3,4,5]. Being one of the TCMs, edible bird's nest is believed to have health enhancing effects such as anti-ageing, growth promoting and immunoenhancing properties. In fact, the medicinal use of edible bird's nest can be traced back to 17th century[6]. However, edible bird's nest is different from most of the TCMs. It is not only a medicine to make people healthy but also a pleasant food. Traditionally, it is double boiled with rocky sugar to make a delicacy known as "bird's nest soup".

Although the size of Collocalia is small, the market generated by it is tremendous. The estimated market of edible bird's nest in 2004 is worth about HK$ 3 billions in Hong Kong . The local market is the world's largest consumer of edible bird's nest[2,7]. The annual percentage increase of the local market is in doubledigit[7]. It may be due to the fact that Hong Kong people are more and more concerned about their health and the status of TCM has risen after a series of government policies on TCM. Moreover, a dual nature of edible bird's nest, that could be treated as medicine or/and food, may play a role. In the past, people could only buy dried edible bird's nests. For the advancement in food technology, large variety of edible bird's nest related products emerge to the market. They are readily to serve products. No cooking process is required. Amongst those new products, most of them are still in the traditional form as bird's nest soup, such as instant bird's nest in different concentrations. Some instant bird's nest may also supplement with other TCMs. Apart from the traditional form, there is a trend of using edible bird's nest extract as one of the chief ingredients of the products. These products focus mainly on the medicinal use of edible bird's nest. However, some of them may exaggerate the therapeutic use of edible bird's nest. 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. The imitation substitute commonly used is the edible plant-exude, gum karaya or sterculia[8]. Recently, there are reports of fake edible bird's nest made from fishes' skin, mushroom or algae in China [9]. 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, pig's skin 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.

Further Studies

Edible bird's nest has been used for several hundred years. Its usage is based mainly on historical, anecdotal and observational reports of its benefit. Scientific evidence for its efficacy is still limited. The putative health benefits such as resisting ageing and improving immunity of edible bird's nest may be linked, at least in part, to EGF-like activity and mitogenic factor. However, there may be other mechanisms involved. In addition, there may be additive, synergistic or antagonistic effects between different components of edible bird's nest. Work is needed to establish health-related effects of edible bird's nest, for example, through assessing biomarker response, isolating and identifying the active components and investigating their possible interaction. In Hong Kong, many people take edible bird's nest regularly. It is worth establishing epidemiological study to measure relationship of consistent use of edible bird's nest and its putative beneficial effects in human beings. For the large market of edible bird's nest, developing a systematic method to identify the sources of edible bird's nest and check the authenticity of its sample is, undoubtedly, indispensable.

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.

References

[1] Lee, P.L., Clayton, D.H., Griffiths, R. & Page, R.D. (1996) Does behavior reflect phylogeny in swiftlets (Aves: Apodidae)? A test using cytochrome b mitochondrial DNA sequences. Proc Natl Acad Sci U S A. 93:7091(7096.

[2] Lau, A.S.M. & Melville, D.S. (1994) International Trade in Swiftlet Nests with Special Reference to Hong Kong (Traffic Inter-national, Cambridge, U.K.).

[3] O'Hara, M.A., Kiefer, D., Farrel, K. & Kemper, K. (1998) A review of 12 commonly used herbs. Arch Fam Med. 7:523(536.

[4] Craig, W.J. (1997) Health-promoting properties of common herbs. Am J Clin Nutr. 70:491S(499S. [5] Yuan, R. & Yuan, L. (2000) Traditional Chinese medicine: an approach to scientific proof and clinical validation. Pharm Therapeut. 86:191(198.

[6] Kong, Y.C., Keung, W.M., Yip, T.T., Ko, K.M., Tsao, S.W. & Ng, M.H. (1987) Evidence that epidermal growth factor is present in swiftlet's (Collocalia) nest. Comp Biochem Physiol B. 87:221(226.

[7] Leung, C.Y. (2004) Three billions market competition for edible bird's nest shops. Economic Digest. 1197:68(69.

[8] Sam, C.T., Tan, P.H. & Lim, C.H. (1991) Establishing the authenticity of edible bird's Nest. ISFM Medicine Scientific Review. 3:1(4.

[9] Li, X., Xi, X. & Che, W. (2003) Analysis and assessment of quality in import-export bird nest. Guangzhou Food Science and Technology. 19:72 & 89.

[10] Huang, H, Xi, X., Chen, W. & Chen, J. (2003) Determination of content of bird nest by spectrophotometer. Guangzhou Food Science and Technology. 19:68.

[11] Kathan, R.I.I. & Weeks, D.I. (1969) Structure studies of collocalia mucoid. I. Carbohydrate and amino acid composition. Arch Biochem Biophys. 134:572(576.

[12] Colombo, J.P., Garcia-Rodenas, C., Guesry, P.R. & Rey, J. (2003) Potential effects of supplementation with amino acids, choline or sialic acid on cognitive development in young infants. Acta Paediatr Suppl. 92:42(46.

[13] Ng, M.H., Chan, K.H. & Kong, Y.C. (1986) Potentiation of mitogenic response by extracts of the swiftlet's (Collocalia) nest. Biochem Int. 13:521(531.

[14] Yano, S., Kondo, K., Yamaguchi, M., Richmond, G., Hutchison, M., Wakeling, A., Averbuch, S. & Wadsworth, P. (2003) Distribution and function of EGFR in human tissue and the effect of EGFR tyrosine kinase inhibition. Anticancer Res. 23: 3639(3650.

[15] Herbst, R.S. & Langer, C.J. (2002) Epidermal growth factor receptors as a target for cancer treatment: The emerging role of IMC-C225 in the treatment of lung and head and neck cancer. Semin Oncol. 29:27(36.

[16] Zhang, M., Wang, D. & Wang, J. (1994) The effect of the ZHENZHU-YANWO extracts on animal function. Pharmaceutical Biotechnology. 1:49(51.

 

 

用燕窩製成的佳餚：鮮百合冰糖燕窩

Bird Nest Nitrite, is it safe?

On 15th August some province in China were repoted that edible bird nest contains high nitrite. Again, there are many rumors speculating regarding this matter and cause many traders, operators and even consumers confused and concerned.
Then the question is, what is nitrite and is it harmful? how to avoid this substance if consumers concern about this substance and want to consume this delicacy food. Many informations actually descrbies what nitrite is. Here is just short summary of what nitrite is.

Nitrites are a normal part of human diet, found in most vegetables.[1][2][3] Spinach and lettuce can have as high as 2500 mg/Kg nitrate, curly kale (302.0 mg/kg) and green cauliflower (61.0 mg/kg), to a low of 13 mg/Kg for asparagus. Nitrite levels in 34 vegetable samples, including different varieties of cabbage, lettuce, spinach, parsley and turnips ranged between 1.1 and 57 mg/Kg, e.g. white cauliflower (3.49 mg/kg) and green cauliflower (1.47 mg/kg).[4][5] Boiling vegetables lowers nitrate but not nitrite.[5] Fresh meat contains 0.4-0.5 mg/Kg nitrite and 4–7 mg/Kg of nitrate (10–30 mg/Kg nitrate in cured meats).[3] The presence of nitrite in animal tissue is a consequence of metabolism of nitric oxide, an important neurotransmitter.[6] Nitric oxide can be created de novo from nitric oxide synthase utilizing arginine or from ingested nitrate or nitrite.[7] Most all research on negative effects of Nitrites on humans predates discovery of nitric oxide's importance to human metabolism and human endogenous metabolism of nitrite.
Recently, sodium nitrite has been found to be an effective means to increase blood flow by dilating blood vessels, acting as a vasodilator. Research is ongoing to investigate its applicability towards treatments for sickle cell anemia, cyanide poisoning, heart attacks, brain aneurysms, and pulmonary hypertension in infants.[9][10]
An intravenous mixture including sodium nitrite solution has been used as an emergency treatment for cyanide poisoning (see Cyanide#Antidote).
There are raised concern that sodium nitrite is the formation of carcinogenic nitrosamines if it is exposed under high temperature. But, two scientific reports from the National Academy of Sciences (issued in 1981 and 1982). The 1981 report stated that nitrite does not cause cancer, although some population studies have found an association between high exposure to nitrite levels and certain cancers. Also, nitrite does not act directly as a cancer-causing agent in animals. The NAS recommended that both these issues be researched further.

Based on facets presented, Nitrite can occur in our daily meals and it is not so harmful as long as it keeps it under certain amount. Although sometimes we can find  even higher than the regulations standard in our normal meals such as lectuce. But these all can be avoided  as long as our meals are well prepared. Nitrites are very soluable in water. People would normally wash their food before they cook as  a result it keeps the nitrates down to consumable level nonetheless.

In recent issues, many consumers of bird nest concern this matter. Well, it is actually unnecessary. on 20th July 2011 One of stores in Hangzhou province in China has answered to that concern and has conducted a test by the Zhejiang Institute of science and technology. The report shows that the nitrate contents on BLOOD NEST only 2.5mg/kg and WHITE NEST 1.2mg/kg after being preparely served and stewed. (soak bird nest for 5-6 hours and change the water every hour). This report and the fact shows that there is significant reduce on nitrites level to a consumable level (max 30mg/kg WHO rules and regulations). This certainly will NOT bring harm.

Apart from negative impact on nitrites, consumers must not forget that there are many advantages and many substances in edible bird nest that improves human health. The glycoprotein in edible bird nest considerably to be very effective in boosting human immune. There are still some further study ongoing in bird nest related to its chemical compound and substance. Some study says they found an enzym that helps cell regeneration.

In conclusion, there are many substances in one food product. Good or bad depends on the perspective of the people. As long as it follows under a certain level according to the food rules and regulations. It can be consumable.
A KNOWLEDGE on how to prepare a meal is absolutely necessary in this matter. The stores also hold responsible to give their consumer information on how to prepare their products before being consumed. Regardless negative issues on edible bird nest there are many advantages that can be obtained by having this delicacy that have been in chinese people for hundred years.

Blood nest is VERY SAFE to be consumed

On June 3rd 2011, there was a report from Guangdong Inspection and Quarantine Bureau that some of blood nest in the market were detected with nitrite. This report however were not entirely correct, though it has caused a great impact in the bird nest industry.

The test done by Guangdong inspection were not yet clear whether was tested in raw or after proper preparation. Because all kinds of bird nest are never meant to be served in raw. There are several proper methods to prepare this delightful dishes that has been for hundred years among the chinese people such as "soaking in water for quite some time". In my opinion, if the test was done in a proper preparation, it would be very safe to be consumed.

I must admit there are maybe some small portion of dishonest traders create the red colors from the chemical, and it is harmful to the industry; nevertheless we shouldn't generalize that all blood nest are produced by chemical reaction, in fact most of the product in market are NOT.
The actual blood nest in the beginning happens naturally in caves of Thailand, Indonesia and Malaysia. If we look again into the bird nest market in Hongkong and China these days,  we can find a lot of original blood bird nest from the Thailand caves. These days this natural process also occurs naturally in bird nest houses.

According to article that i found (http://vetonews.com/index.php?option=com_content&view=article&id=6970%3Ablood-nest-is-safe-to-consume-according-to-scientific-research&Itemid=34) , the blood nest is actually formed by the fermentation process of the white nest, which also come from the same species Collocalia fuchipaga.

This fermentation occurs in both houses and caves because of the suitable “microclimate” and
substance exist in the room/cave. We have to be know that the natural fermentation process inevitably would also allow the formation of by-product Nitrite (NO2¯) in the blood nest.
But notice here that it is not purposely added to the white nest to change the color become red. If anyone tries about to put nitrite into white nest, it will certainly not change into red.

Therefore, we need to get the fact straight first in order to protect our customers yet not mislead them. Nitrite is a common substance which is highly soluble in its nature. Nitrite in blood nest can be
easily washed because it not in the fibers;
For example we can soak the nest into 1 liter of water for 2 hours and the nitrite content
already fall so drastically below the consumable level. This preparation practice is done anyway by the consumer regardless there is nitrite or no nitrite in the nest.

In conclusion, based on the facts and some research done and tested by specialised scientists, as long as it is served with proper preparation the blood nest is very SAFE to be consumed.