principleintopractice

Happy New Year!

2012 was a whirlwind year for me. I defended my PhD at the beginning of 2012 and am now almost finished with all the required clerkships of third-year medical school. Phew!

I spent my winter holiday visiting my brother in Dubai, exploring many sites of the United Arab Emirates (UAE). I got to see a lot during my stay, and I’ve been writing a post on some of the interesting things I saw there.  As I was writing about the traditional dietary staples of the Middle East, I took a foray through a lot of literature that is available on camel milk.  It’s interesting stuff, and I found myself heading off on a tangent that I thought I should post as a stand-alone article.

So here we go…

Ship of the desert
Camels were (and still are, but for different reasons) an important part of life in the Middle East. The Arabian camel (the dromedary Camelus dromedarius) is a one-humped beast, and should not be confused with the 2-humped Bactrian camel (Camelus bactrianus) of central Asia.  Dromedaries were the only mode of transportation in the desert before motorized vehicles (walking any substantial distance on foot is out of the question and horses need too much water), and they also were an important form of wealth and source of food. Camel meat was a rare delicacy, while camel milk was a staple of the Bedouin diet. Camel hair was also used to make household necessities and camel dung was often used as fuel (a nice argument against the calories in calories out argument- if biological creatures were bomb calorimeters there wouldn’t be anything worth burning coming out the other end…).

Camel meat was not a staple of the Bedouin diet.  In fact, most nomadic people are reluctant to kill their subsistence animals for meat. Female camels were used for dairy and some males were kept for breeding purposes, but extra young male camels would be slaughtered and eaten for special occasions.

Though definitely not a traditional dish, this seems to be the most popular way to eat camel meat today

Camels are uniquely able to provide sustenance for humans in an environment that is generally rather inhospitable. Camels are able to not only survive, but thrive, on the limited and harsh forages that are available in the desert. She-camels can produce enough milk to nurse their offspring and provide liters of milk per day for their owner.

Camel in its native environment. These beasts thrive on the coarse and sparse forage of the desert.

Camels’ milk is interesting stuff. Unlike the milk of cows, goats, and sheep, it cannot be easily made into cheese.  It doesn’t coagulate with bovine rennet, however recombinant camel rennet is incredibly efficient at coagulating cow milk and can also coagulate camel milk (there is a difference in the camel kappa-casein that makes it more resistant to cleavage) [1, 2].  With the right enzyme the job can be done, and there is at least one company that makes a camel cheese (nicknamed Camelbert!).

Camel milk isn’t much good for making yoghurt either, being much more resistant to lactic acid fermentation than cow milk. The result of camel milk lactic fermentation is very runny, with little microbial growth [3]. Gariss, a traditional Sudanese fermented camel’s milk product, is made with a mixed culture including Lactobacillus, Streptococcus, and yeast [4]. Here’s how it was traditionally made:

fermentation is carried out in two leather bags of tanned goat skin embedded in green or wet grass carried on the bag of camels and subjected to continuous shaking by the jerky walk inherent to camels. Whenever part of the product is withdrawn for consumption, a portion of fresh camel’s milk is added to make up volume and this continues for months [4].

According to one paper I spotted, food scientists can thicken fermented camel milk with gelatin or alginate (a thickener made from seaweed) in order to make a yoghurt-like product that consumers might find acceptable, but I didn’t spot any on the shelves in the stores of Dubai [5].

It seems to me that when it comes to camel milk it might be best to just keep it simple. Plain old milk.

But camel milk may not be such simple stuff.  There is growing research that explores the use of camel milk for medicinal purposes.

I haven’t gone into the research in depth, but there are a number of small studies looking at the benefits of camel milk for people with diabetes (type 1 and type 2), with rather remarkable results. The addition of 500mL of camel milk on top of usual care for patients with type 1 diabetes resulted in significant improvements in a number of parameters in comparison to people who just received standard care. The camel milk group had a decrease in mean blood glucose levels and hemoglobin A1c.  The study was small, but 3 of the 12 participants in the camel milk group were able to completely stop using insulin (an almost unheard of occurrence for those with type 1 DM).  While the mean amount of insulin used in the control group remained constant, the amount used in the camel milk group dropped rapidly [4].

Abdelgadir et al [4]

It hasn’t been determined how camel milk affects those with diabetes, but there are a number of hypotheses. Some sources think that insulin from camel milk is uniquely able to escape digestion when ingested or that camel milk contains a unique insulin-like small peptide that is bioavailable when consumed [6]. This is unlikely to be the whole story, however, as camel milk is able to increase endogenous insulin secretion in type 1 diabetics (individuals in standard of care + camel milk groups have higher levels of C-peptide, showing an increase in insulin production) [7].

Some readers may know that I have a fondness for fatty liver disease, so I was particularly interested to learn that, in a rat study, camel milk reversed alcohol-induced liver injury. This was seen histologically, where there was minimal fatty accumulation in the livers of alcohol-treated animals supplemented with camel milk in comparison to those just treated with alcohol alone, and serologically, where animals that were treated with ethanol alone had significantly increased liver enzymes in comparison to controls and those fed alcohol and camels milk [8]. I would postulate that it might have something to do with the high levels of carnitine found in camel milk [9], but that’s a story for another day.

Nutritionally, camel milk is unique. As I just mentioned, it has a more free carnitine as a percentage of total carnitine than other species and higher total carnitine than cow or human milk (though lower than sheep and goat milk) [9]. Camel milk has three-times the vitamin C of cow milk, but a similar amount of vitamin E and considerably less vitamin A and riboflavin [10]. Camel milk is low in short chain fatty acids in comparison to other milks and it has primarily long chain fatty acids, a significant portion of which is linoleic acid [11].  I tend to avoid this omega-6 FA, but I suspect that as part of a traditional diet the amount found in camel milk does not cause a problem.
Camels can carry a number of zoonotic organisms, including Coxiella burnetii (which causes Q fever) and Brucella sp. (which causes brucellosis), which can be transmitted through the milk. In fact, there was a recent brucellosis outbreak in Israel caused by raw camel milk [12].  If you’re drinking milk from an untested camel, it’s probably best to have it pasteurized. All the milk that’s available in Dubai supermarkets is pasteurized and homogenized. There are a variety of brands, and you can get milk in an array of flavors!

I spied plain, chocolate, strawberry, saffron, rose, cardamom, and date flavor! In this pic there’s saffron, chocolate, strawberry, date, and plain.

Of course I had to try some… I opted for plain milk, and found it slightly sour in comparison to cow’s milk, with a watery mouthfeel. It’s been at least a decade since I drank skim milk, but as I remember the mouthfeel is similar.

Sculptors of human evolution

Camels have played central roles in the lives of desert dwelling people for millennia. They are the “ship of the desert” and their milk has nourished and sustained generations.  Their milk has also shaped the human genome…

The predominance of lactase persistence in populations is a well-known and well-studied example of human evolution. In populations that had access to animal milk, a mutation that allowed for the production of lactase past the age of weaning gave humans access to a rich food source. This was a huge advantage to those that had such a mutation.  Those that could easily consume milk were able to have more children, and the mutation spread throughout the population.  The advantage of having persistent lactase expression is so advantageous it has occurred independently in multiple populations over time.  While some mutations are linked back to the domestication of the cow, there are novel mutations found in Middle Eastern populations that are linked to the domestication of, and subsequent milk consumption from, Arabian camels [13].

The advantage of camel domestication is still present today.  A paper from 1996 looked at child health in three populations of Rendille pastoralists in Northern Kenya. Two of the groups had abandoned their nomadic roots to become settled, while one group remained nomadic.  In wet years (good years) there was a similar number of malnourished children in the three groups; however in a drought year, the children of the nomadic group faired significantly better.  The differences in malnutrition were attributed to food- specifically camels milk.  In drought years, the children in the nomadic group consumed three times as much milk as those from the sedentary group, where the children got more starches and sugar.  Other studies have found that nomadic groups generally do poorly during drought years (because of decreased production of milk from their herd), but because the Rendille maintain a large number of camels, they faired better during hard times [14].

So there you have it… I went diving into pubmed looking for a few fun facts to incorporate into a blog post on my trip to Dubai and found myself swept up in a mess of Dromedary data… I hope you found it as interesting as I did!

1.            Kappeler, S.R., H.J. van den Brink, H. Rahbek-Nielsen, Z. Farah, Z. Puhan, E.B. Hansen, and E. Johansen, Characterization of recombinant camel chymosin reveals superior properties for the coagulation of bovine and camel milk. Biochem Biophys Res Commun, 2006. 342(2): p. 647-54.

2.            Sorensen, J., D.S. Palmer, K.B. Qvist, and B. Schiott, Initial stage of cheese production: a molecular modeling study of bovine and camel chymosin complexed with peptides from the chymosin-sensitive region of kappa-casein. J Agric Food Chem, 2011. 59(10): p. 5636-47.

3.            Attia, H., N. Kherouatou, and A. Dhouib, Dromedary milk lactic acid fermentation: microbiological and rheological characteristics. J Ind Microbiol Biotechnol, 2001. 26(5): p. 263-70.

4.            Abdelgadir, W., D.S. Nielsen, S. Hamad, and M. Jakobsen, A traditional Sudanese fermented camel’s milk product, Gariss, as a habitat of Streptococcus infantarius subsp. infantarius. Int J Food Microbiol, 2008. 127(3): p. 215-9.

5.            Hashim, I.B., A.H. Khalil, and H. Habib, Quality and acceptability of a set-type yogurt made from camel milk. J Dairy Sci, 2009. 92(3): p. 857-62.

6.            Malik, A., A. Al-Senaidy, E. Skrzypczak-Jankun, and J. Jankun, A study of the anti-diabetic agents of camel milk. Int J Mol Med, 2012. 30(3): p. 585-92.

7.            Mohamad, R.H., Z.K. Zekry, H.A. Al-Mehdar, O. Salama, S.E. El-Shaieb, A.A. El-Basmy, M.G. Al-said, and S.M. Sharawy, Camel milk as an adjuvant therapy for the treatment of type 1 diabetes: verification of a traditional ethnomedical practice. J Med Food, 2009. 12(2): p. 461-5.

8.            Darwish, H.A., N.R. Abd Raboh, and A. Mahdy, Camel’s milk alleviates alcohol-induced liver injury in rats. Food Chem Toxicol, 2012. 50(5): p. 1377-83.

9.            Alhomida, A.S., Total, free, short-chain and long-chain acyl carnitine levels in Arabian camel milk (Camelus dromedarius). Ann Nutr Metab, 1996. 40(4): p. 221-6.

10.            Farah, Z., R. Rettenmaier, and D. Atkins, Vitamin content of camel milk. Int J Vitam Nutr Res, 1992. 62(1): p. 30-3.

11.            Gorban, A.M. and O.M. Izzeldin, Fatty acids and lipids of camel milk and colostrum. Int J Food Sci Nutr, 2001. 52(3): p. 283-7.

12.            Shimol, S.B., L. Dukhan, I. Belmaker, S. Bardenstein, D. Sibirsky, C. Barrett, and D. Greenberg, Human brucellosis outbreak acquired through camel milk ingestion in southern Israel. Isr Med Assoc J, 2012. 14(8): p. 475-8.

13.            Enattah, N.S., T.G. Jensen, M. Nielsen, R. Lewinski, M. Kuokkanen, H. Rasinpera, H. El-Shanti, J.K. Seo, M. Alifrangis, I.F. Khalil, A. Natah, A. Ali, S. Natah, D. Comas, S.Q. Mehdi, L. Groop, E.M. Vestergaard, F. Imtiaz, M.S. Rashed, B. Meyer, J. Troelsen, and L. Peltonen, Independent introduction of two lactase-persistence alleles into human populations reflects different history of adaptation to milk culture. Am J Hum Genet, 2008. 82(1): p. 57-72.

14.            Nathan, M.A., E.M. Fratkin, and E.A. Roth, Sedentism and child health among Rendille pastoralists of northern Kenya. Soc Sci Med, 1996. 43(4): p. 503-15.