Review of Scientific Research on Edible Birds Spit Soup

Edible Birds Spit Soup 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 Birds Spit Soup and misleading promotional description emerged. This article briefly reviews the scientific research on authentication technologies and pharmacological effects of edible Birds Spit Soup. It is expected that people’s knowledge on edible Birds Spit Soup could be enhanced.

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 Birds Spit Soup ( 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 Birds Spit Soup is believed to have health enhancing effects such as anti-ageing, growth promoting and immunoenhancing properties. In fact, the medicinal use of edible Birds Spit Soup can be traced back to 17th century[6]. However, edible Birds Spit Soup 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 “Birds Spit Soup”.

Review of Scientific Research on Edible Birds Spit Soup

Although the size of Collocalia is small, the market generated by it is tremendous. The estimated market of edible Birds Spit Soup in 2004 is worth about HK$ 3 billions in Hong Kong . The local market is the world’s largest consumer of edible Birds Spit Soup[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 Birds Spit Soup, that could be treated as medicine or/and food, may play a role. In the past, people could only buy dried edible Birds Spit Soups. For the advancement in food technology, large variety of edible Birds Spit Soup 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 Birds Spit Soup, such as instant Birds Spit Soup in different concentrations. Some instant Birds Spit Soup may also supplement with other TCMs. Apart from the traditional form, there is a trend of using edible Birds Spit Soup extract as one of the chief ingredients of the products. These products focus mainly on the medicinal use of edible Birds Spit Soup. However, some of them may exaggerate the therapeutic use of edible Birds Spit Soup. For the limited supply and high price of edible Birds Spit Soup, it is not uncommon to hear reports of fake edible Birds Spit Soup 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 Birds Spit Soup made from fishes’ skin, mushroom or algae in China [9]. Therefore, it is a great concern on authenticating the genuineness of edible Birds Spit Soup. In this review, the author will briefly summarize some advanced technologies in authenticating edible Birds Spit Soup. The medicinal benefits of edible Birds Spit Soup with contemporary scientific evidence will also be given.

Authenticity of Edible Birds Spit Soup

The first comprehensive report on authentication of edible Birds Spit Soup 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 Birds Spit Soup[8]. Since they only made a comparison with some imitation Birds Spit Soup 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 Birds Spit Soup content[10]. It could also be used to differentiate genuine edible Birds Spit Soup 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 Birds Spit Soup.

Nutritional Content and Medicinal Use

Edible Birds Spit Soup contains mainly carbohydrates, amino acids and mineral salts. The major ingredients of edible Birds Spit Soup are glycoproteins[11]. Amongst the carbohydrates in edible Birds Spit Soup, 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 Birds Spit Soup. 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 Birds Spit Soup is rich in mineral salts. It contains high content of sodium and calcium. It is because the source of edible Birds Spit Soup 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 Birds Spit Soup[8].
In spite of the long history of using edible Birds Spit Soup 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 Birds Spit Soup 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 Birds Spit Soup 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 Birds Spit Soup 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 Birds Spit Soup 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 Birds Spit Soup. In fact, there is no evidence supporting this suggestion. Currently we have evaluated the effects of aqueous extract of edible Birds Spit Soup 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 Birds Spit Soup 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 Birds Spit Soup, pearl powder or both.

Further Studies

Edible Birds Spit Soup 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 Birds Spit Soup 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 Birds Spit Soup. Work is needed to establish health-related effects of edible Birds Spit Soup, for example, through assessing biomarker response, isolating and identifying the active components and investigating their possible interaction. In Hong Kong, many people take edible Birds Spit Soup regularly. It is worth establishing epidemiological study to measure relationship of consistent use of edible Birds Spit Soup and its putative beneficial effects in human beings. For the large market of edible Birds Spit Soup, developing a systematic method to identify the sources of edible Birds Spit Soup and check the authenticity of its sample is, undoubtedly, indispensable.

Acknowledgements

The author is grateful to Imperial Birds Spit Soup International Company Limited for providing intact Birds Spit Soups 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 Birds Spit Soup shops. Economic Digest. 1197:68(69.
[8] Sam, C.T., Tan, P.H. & Lim, C.H. (1991) Establishing the authenticity of edible Birds Spit Soup. ISFM Medicine Scientific Review. 3:1(4.
[9] Li, X., Xi, X. & Che, W. (2003) Analysis and assessment of quality in import-export Birds Spit Soup. Guangzhou Food Science and Technology. 19:72 & 89.
[10] Huang, H, Xi, X., Chen, W. & Chen, J. (2003) Determination of content of Birds Spit Soup 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.

The Science behind Birds Spit Soups (Epidermal Growth Factor (EGF) & Sialic Acid)

Recent research by academics has unveiled some key sciences that form the basis from which numerous health benefits can be derived from the regular consumption of this delicacy.

The nutritional value of 100g of dry nest includes 49.9g of water-soluble protein (including amino nitrogen, monoamine nitrogen, non-amino nitrogen, arginine, humin, histidine, lysine and cysteine), 30.6g carbohydrate (glycoprotein and mucin), 4.9g iron, 2.5g inorganic salt (including potassium, sodium, calcium, magnesium, sulfur, phosphorus, silica and other trace elements), and 1.4g fiber (Dictionary of Traditional Chinese Medicine, The History of Chinese Medicine and the Nutrition Table).
The energy contained in 100g of swiftlet nest is 345 kcal (Wikipedia).
In fact, Birds Spit Soups contain high valued glycoprotein and are rich in minerals like amino acids, calcium, sodium, magnesium and potassium to name a few. Acting as the spark plugs of life, these minerals are essential as they are required to activate thousands of enzyme reactions within the body. For example, magnesium maintains the alkaline balance and control of neuromuscular activity while sodium balances the electrolyte, body fluid volume and maintains our bodies' nerve impulse condition. It is also free from fats and cholesterol.
In addition, some of the proteins and amino acid detected in edible Birds Spit Soup have known antioxidant properties. A highly plausible explanation for this antioxidant activity may be due to the hydroxyl and carboxyl groups in the amino acids. Active oxygen and related elements play a significant physiological role and have a good effect in a variety of diseases including heart conditions, cancer and ageing.

Epidermal Growth Factor (EGF)

Epidermal Growth Factor or EGF is a growth factor that plays an important role in the regulation of cell growth, proliferation, and differentiation by binding to its receptor EGFR. (Wikipedia)
The first scientific evidence that Birds Spit Soup contain EGF was given by Ng Et Al. (1986) in Hong Kong. Edible Birds Spit Soup aqueous extract was found to potentiate mitogenic response of human peripheral blood monocytes to stimulation with proliferative agents. It suggested that edible Birds Spit Soup does possess immune-enhancing 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 Birds Spit Soup that stimulated the normal cellular processes such as proliferation, differentiation and development. It offers a rationale for the medicinal use of edible Birds Spit Soup in ageing resistance.
In short, the presence of EGF in Birds Spit Soup stimulates the rejuvenation of cells in human body, aid in tissue growth and hastens the process of body repair.

Sialic Acid

Sialic acid found in Birds Spit Soups are rich glycoproteins that bind selectin in humans and other organisms. It plays an important role in human influenza infections.
In a research conducted by Guo et al (2005) at the University of Shizuoka, researchers found that Birds Spit Soups extract could strongly inhibit infection with influenza viruses in a host range-independent manner. The results suggest that Birds Spit Soup is a safe and valid natural source for the prevention of influenza viruses.
Sialic Acid is also an important sugar for the development of a baby's brain, immunity against infections, and development of their digestive system. Sialic acids in Birds Spit Soups can be considered the next alternative to human milk which predominantly contain high sialic acid levels.

Birds Spit Soup is regarded as having a wide range of tonic and medical values

Traditionally, it is believed that Birds Spit Soup can strengthen the lungs. Consumption of Birds Spit Soup is also recommended to complement other treatments to combat degenerative diseases such as cancer and also for recovering health after illness, or surgery. Recent studies in Hong Kong suggested that it may even be useful in the treatment of AIDS.
In respect to aesthetic industry, research shown that swiftlet nest consist of high DOSIS of Epidermal Growth Factor(EGF). Currently EGF is used in the cosmetic industry for skin whitening, reduce wrinkles, and prevent premature aging. EGF is known to be capable of penetrating into the skin dermis to stimulate the growth of new cells, replacing cells that are old or damaged, and controls the growth of skin cells. Consuming swiftlet nest routinely is a means of maintaining one's beauty from inside out.

Benefits of eating Birds Spit Soup

You would have heard by now that among the most popular Chinese medicinal food is the Birds Spit Soup. This type of food can be costly where it could start from hundreds and reaches to thousands of ringgit. Basically, Birds Spit Soup is known to be a very nutritional type of food which is very good for health.
So what makes Birds Spit Soup so popular. Why would people go to great lengths to find and enjoy bird's saliva? This is because research has shown that Birds Spit Soup contain a rich amount of nutrients that are very organic. This includes minerals like zinc, copper, sodium, calcium, potassium while it has a lot of soluble glycoprotein and amino acid.
Throughout history, it has been recorded that traditional Chinese medicine doctors have used Birds Spit Soup for various medicinal reasons. This includes using this highly beneficial product for the use of treating asthma and bronchitis while it is known to help rejuvenate the skin and for anti-aging purposes.
According to scientific research, it has been found that Birds Spit Soup can actually facilitate more than just skin rejuvenation. In fact, it can help in growth and provide the human body with vital energy it needs. It helps to accelerate any type of recovery from diseases while keeps the body strong in terms of immunity and metabolism.
Birds Spit Soup are so popular with its benefits so well known that other types of medicinal herbs like the abalone, eggs and sea cucumbers do not come close. For the pregnant woman, Birds Spit Soup is highly recommended because it helps to increase the overall health of both the mother and the child.
It helps to grow the brain of the baby while ensuring that the mother's general health and immune system is strong. On top of that, mother's who have given birth are encouraged to take Birds Spit Soup as it helps them to recover faster while maintaining their overall beauty and body shape.
In most cases, Birds Spit Soup can be consumed as they are while there are many instances when this type of food is served with other accompanying dishes like fresh milk, soup and others. This is most commonly done for the younger people as it helps to enhance their metabolism and immune system.