The Therapeutic Effects of Camel Milk: A Systematic Review of Animal and Human Trials

Camel milk and D-allulose synergistically improved camel dairy flavor and alleviated insulin resistance of human HepG2 cells

Camel milk is a dairy product widely consumed in desert and semi-arid areas, with high nutritional value and potential for auxiliary medical treatment. It has unique efficacy and a gamey taste, and exploring its functional factors and making camel milk more easily accepted by the public has become a research hotspot. This study mainly investigated the protein components in camel milk that may play a role in alleviating insulin resistance by observing the cell activity, glucose consumption, and morphological changes of the treatment group. Further research was conducted on the potential synergistic hypoglycemic effect of camel milk and D-allulose, and a formula was ultimately determined to enhance the flavor of camel milk through a series of sensory evaluation experiments. The optimal concentration for the treatment of insulin resistance (IR) was identified as 4 mg/mL of CWP4 combined with 1 mg/mL of D-allulose for a period of 12 h. The addition of D-allulose at a ratio of 1:36 in camel milk has been observed reduce the odoriferous properties of the camel milk, while simultaneously retaining the majority of other desirable flavors. This research helps to concentrate the functional protein factors in camel milk, promote the intensive processing of camel milk, and develop new camel milk health products. These products may help patients with diabetes stabilize their blood sugar levels in daily life, thus enriching their diet, and may expand the market of camel milk.

Valorizing date seeds through ultrasonication to enhance quality attributes of dough and biscuit: Part 2 - Study on bioactive properties, sensory acceptance, in vitro gastrointestinal digestion and shelf life of biscuits

Aligning with sustainable food system development, in this study, date seeds derived compounds were utilized as functional ingredient to formulate value-added biscuits. Ultrasound-assisted extraction (UAE) was employed as a non-thermal method to extract polyphenolic compounds from small, medium and large particles of defatted date seed powder (DDSP). The remaining fiber-rich fraction (residue) was further utilized. Water content in biscuit formulation was replaced by the extract, and the fiber-rich fraction was substituted at three substitution levels; 2.5 %, 5 % and 7.5 %. Effects of baking on bioactive properties of dough, nutrient composition, sensory analysis, bioaccessibility of polyphenols, and shelf-life of biscuits were analyzed. Total phenolic content (TPC) increased in dough and biscuit with incorporated fiber-rich fraction. TPC of dough decreased with increasing particle size of fiber-rich fraction while biscuits exhibited an opposite trend. Similar tendency was observed with antioxidant activity of dough and biscuit. TPC was higher in biscuits than dough, with the highest values of 0.46 mg gallic acid equivalents (GAE)/g and 2.26 mg GAE/g in dough and biscuit, respectively. Fiber and moisture contents in biscuits increased while protein content decreased with fortification. Consumers showed moderate acceptance of fortified biscuits with overall acceptability comparable with the control biscuits. Bioaccessibility index of polyphenols upon gastrointestinal digestion was high in biscuits with 5 % and 7.5 % substitution of small and medium sized particles of fiber-rich fraction. Phenolic retention increased with fiber fortification and at the end of 6 months the lowest thiobarbituric acid reactive substances (TBARS) value of 18.23 nmol malondialdehyde (MDA)/g sample, was observed in 7.5 % large particle substituted biscuit. Thus, utilizing date seeds in the form of green extracted polyphenols and fiber-rich fraction, as functional and bioactive ingredients highlight sustainable processing and utilization of date-fruit processing by-products which is in line with the circular economy approach.

Anti-breast cancer effects of dairy protein active peptides, dairy products, and dairy protein-based nanoparticles

Breast cancer is the most frequently diagnosed and fatal cancer among women worldwide. Dairy protein-derived peptides and dairy products are important parts of the daily human diet and have shown promising activities in suppressing the proliferation, migration, and invasion of breast cancer cells, both in vitro and in vivo. Most of the review literature employs meta-analysis methods to explore the association between dairy intake and breast cancer risk. However, there is a lack of comprehensive summary regarding the anti-breast cancer properties of dairy protein-derived peptides, dairy products, and dairy protein-based nanoparticles as well as their underlying mechanisms of action. Therefore, the present study discussed the breast cancer inhibitory effects and mechanisms of active peptides derived from various dairy protein sources. Additionally, the characteristics, anti-breast cancer activities and active components of several types of dairy products, including fermented milk, yogurt and cheeses, were summarized. Furthermore, the preparation methods and therapeutic effects of various dairy protein-containing nanoparticle delivery systems for breast cancer therapy were briefly described. Lastly, this work also provided an overview of what is currently known about the anti-breast cancer effects of dairy products in clinical studies. Our review will be of interest to the development of natural anticancer drugs.

Detection of 11 carbamate pesticide residues in raw and pasteurized camel milk samples using liquid chromatography tandem mass spectrometry: Method development, method validation, and health risk assessment

This study aimed to use ultra-high-performance liquid chromatography coupled to a triple-quadrupole mass spectrometer to detect 11 carbamate pesticide residues in raw and pasteurized camel milk samples collected from the United Arab Emirates. A method was developed and validated by evaluating limits of detection, limits of quantitation, linearity, extraction recovery, repeatability, intermediate precision, and matrix effect. Due to the high protein and fat content in camel milk, a sample preparation step was necessary to avoid potential interference during analysis. For this purpose, 5 different liquid-liquid extraction techniques were evaluated to determine their efficiency in extracting carbamate pesticides from camel milk. The established method demonstrated high accuracy and precision. The matrix effect for all carbamate pesticides was observed to fall within the soft range, indicating its negligible effect. Remarkably, detection limits for all carbamates were as low as 0.01 μg/kg. Additionally, the coefficients of determination were >0.998, demonstrating excellent linearity. A total of 17 camel milk samples were analyzed, and only one sample was found to be free from any carbamate residues. The remaining 16 samples contained at least one carbamate residue, yet all detected concentrations were below the recommended maximum residue limits set by Codex Alimentarius and the European Union pesticide databases. Nonetheless, it is worth noting that the detected levels of ethiofencarb in 3 samples were close to the borderline of the maximum residue limit. To assess the health risk for consumers of camel milk, the hazard index values of carbofuran, carbaryl, and propoxur were calculated. The hazard index values for these 3 carbamate pesticides were all below 1, indicating that camel milk consumers are not at risk from these residues.

Invited review: Camel milk-derived bioactive peptides and diabetes-Molecular view and perspectives

In dairy science, camel milk (CM) constitutes a center of interest for scientists due to its known beneficial effect on diabetes as demonstrated in many in vitro, in vivo, and clinical studies and trials. Overall, CM had positive effects on various parameters related to glucose transport and metabolism as well as the structural and functional properties of the pancreatic β-cells and insulin secretion. Thus, CM consumption may help manage diabetes; however, such a recommendation will become rationale and clinically conceivable only if the exact molecular mechanisms and pathways involved at the cellular levels are well understood. Moreover, the application of CM as an alternative antidiabetic tool may first require the identification of the exact bioactive molecules behind such antidiabetic properties. In this review, we describe the advances in our knowledge of the molecular mechanisms reported to be involved in the beneficial effects of CM in managing diabetes using different in vitro and in vivo models. This mainly includes the effects of CM on the different molecular pathways controlling (1) insulin receptor signaling and glucose uptake, (2) the pancreatic β-cell structure and function, and (3) the activity of key metabolic enzymes in glucose metabolism. Moreover, we described the current status of the identification of CM-derived bioactive peptides and their structure-activity relationship study and characterization in the context of molecular markers related to diabetes. Such an overview will not only enrich our scientific knowledge of the plausible mode of action of CM in diabetes but should ultimately rationalize the claim of the potential application of CM against diabetes. This will pave the way toward new directions and ideas for developing a new generation of antidiabetic products taking benefits from the chemical composition of CM.

Role of gastrointestinal health in managing children with autism spectrum disorder

Children with autism spectrum disorders (ASD) or autism are more prone to gastrointestinal (GI) disorders than the general population. These disorders can significantly affect their health, learning, and development due to various factors such as genetics, environment, and behavior. The causes of GI disorders in children with ASD can include gut dysbiosis, immune dysfunction, food sensitivities, digestive enzyme deficiencies, and sensory processing differences. Many studies suggest that numerous children with ASD experience GI problems, and effective management is crucial. Diagnosing autism is typically done through genetic, neurological, functional, and behavioral assessments and observations, while GI tests are not consistently reliable. Some GI tests may increase the risk of developing ASD or exacerbating symptoms. Addressing GI issues in individuals with ASD can improve their overall well-being, leading to better behavior, cognitive function, and educational abilities. Proper management can improve digestion, nutrient absorption, and appetite by relieving physical discomfort and pain. Alleviating GI symptoms can improve sleep patterns, increase energy levels, and contribute to a general sense of well-being, ultimately leading to a better quality of life for the individual and improved family dynamics. The primary goal of GI interventions is to improve nutritional status, reduce symptom severity, promote a balanced mood, and increase patient independence.

Invited review: Bovine colostrum, a promising ingredient for humans and animals-Properties, processing technologies, and uses

Mammalian colostrum, known as "liquid gold," is considered a valuable source of essential nutrients, growth factors, probiotics, prebiotics, antibodies, and other bioactive compounds. Precisely for this reason, bovine colostrum (BC) is an emerging ingredient for the feed, food, and pharmaceutical industries, being nowadays commercially available in a variety of forms in several countries. Moreover, quite a large number of functional foods and supplements for athletes, human medicines, pet nutrition plans, and complementary feed for some livestock categories, such as piglets and calves, contain BC. The amount of BC yielded by a cow after calving represents approximately 0.5% of the yearly output in dairy breeds. For its nutritional properties and low availability, BC is characterized by a greater market value and an increasing demand compared with other by-products of the dairy sector. However, information regarding the market size of BC for the food and pharmaceutical industries, as well as future developments and perspectives, is scarcely available in the scientific literature. This lack can be attributed to industrial secrecy as well as to the relatively small scale of the BC business when compared with other dairy products, which makes the BC market limited, specific, and intended for a restricted audience. From a legal perspective, regulations assign BC to the large family of milk-derived powders; thus, collecting specific production data, as well as import-export trend information, is not straightforward and can result in unprecise estimates. Given that the interest in BC is increasing in different fields, it is important to have an overview of the production steps and of pros and cons of this emerging ingredient. The present narrative review discloses why BC has started to be considered a product rather than a by-product of the dairy industry. Moreover, the present document aims to summarize the existing methodologies used to assess BC quality in terms of immunoglobulin concentration, the different applications of BC in the industry, and the BC processing technologies. Finally, a panoramic view of the current international market is provided for the first time for this dairy product.

Prospective nutritional, therapeutic, and dietary benefits of camel milk making it a viable option for human consumption: Current state of scientific knowledge

For over five thousand years, people in Asia and Africa have known about the health benefits of camel milk. Thus, it is used not only as a food source but also as a medicine. The similarities between camel milk and human milk have been scientifically proven. Camel milk is unique among ruminant milk because it is high in vitamins C and E and low in sugar and cholesterol. Still, it contains a wide variety of beneficial minerals (including sodium, potassium, iron, copper, zinc, and magnesium), besides being rich in several nutrients, including monounsaturated and polyunsaturated fatty acids, serum albumin, lactoferrin, immunoglobulins, lysozyme and the hormone insulin. Because of these components, many medical professionals now recommend camel milk as a treatment for various human ailments. It has been demonstrated to be effective in treating gastrointestinal issues, Type 1 diabetes, and food allergies. As a bonus, camel milk has been utilized to cure autism, lower cholesterol, prevent psoriasis, heal inflammation, aid tuberculosis patients, boost the body's natural defences, and impede the spread of cancer cells. Those who have problems digesting lactose may still be able to tolerate it. Conversely, camel milk can also help reduce an excessively high bilirubin, globulin, and granulocyte count. Drinking camel milk does not affect the erythrocyte sedimentation rate, hemoglobin concentration, and leukocyte count. The proteins in camel milk have an adequate ratio of critical amino acids. Immunoglobulins, which fight disease, are contained inside, and their small size allows antigens to penetrate and boosts the immune system's efficacy. This article highlights the health benefits and medicinal uses of camel milk.

Camel (Camelus dromedarius) raw milk’s hypotensive roles within chemical induced hypertension model in rats

Dromedary camels (Camelus dromedarius) inhabit not only arid areas but are among common domestic animals that are normally kept for numerous uses. It’s raw milk (CM) is believed to have exceptional nutraceutical value in addition to it’s other uses similar to camel itself. This study aimed to evaluate hypotensive efficacy of raw CM within context of chemical induced hypertension model in albino rats. Rats received the chemical; L-NAME (50 mg/kg body weight/day, p.o.) and amlodipine (10 mg/kg/day, p.o.) as negative and positive controls for 4 weeks. Rats of treatment group received concurrently L-NAME (50 mg/kg body weight /day, p.o.) and raw milk of camel at (100, 300, and 500 mg/kg body weight/day p.o.) respectively for 4 weeks. Result showed significant decrease (p <  0.001) in treatment relative to negative control in all measured parameters viz systolic, diastolic and mean arterial blood pressures in accordance to the used dosages. Also elevated levels of liver/kidney biomarkers in negative control became reduced compared to normal and positive controls courtesy of CM treatment. In conclusion, obtained data revealed CM to be effective in controlling hypertension. The bioactive constituents present in CM appeared likely to be responsible for the observed effect of antioxidant action and ACE inhibition. Evidence is thus provided from research findings that raw CM can afford efficient hypotensive effect.

Camel milk products: innovations, limitations and opportunities

Camel milk is the mainstay for millions of people in arid and semi-arid environments. In these areas, it is mainly consumed raw or after it spontaneously turns sour. Although some attempts have been made to produce dairy products from camel milk, processing of camel milk is generally considered to be difficult and the quality of the final products made from camel milk do not correspond to their bovine milk counterparts. This paper reports a comprehensive analysis of the literature on camel milk products and presents synthesis of the latest developments, limitations pertaining processing and opportunities for development of new and improved camel milk products. The protein composition and colloidal structure of camel milk differs from cow milk. It is characterized by absence of β-lactoglobulin, low κ-casein content, high proportion of β-casein, larger casein micelles and smaller fat globules. These differences lead to the difficulty of making dairy products from camel milk using the same technologies as for bovine milk. Some of the challenges of camel milk processing include poor stability of the milk during UHT treatment, impaired rennetability, formation of weak and fragile curd during coagulation, longer fermentation time, and low thermal stability of the milk during drying. Despite these difficulties, it has now become possible to produce a range of commercial and traditional dairy products from camel milk. Some of the strategies that could be applied to improve the quality and characteristics of camel milk products are discussed.

Graphical Abstract

Caseins: Versatility of Their Micellar Organization in Relation to the Functional and Nutritional Properties of Milk

The milk of mammals is a complex fluid mixture of various proteins, minerals, lipids, and other micronutrients that play a critical role in providing nutrition and immunity to newborns. Casein proteins together with calcium phosphate form large colloidal particles, called casein micelles. Caseins and their micelles have received great scientific interest, but their versatility and role in the functional and nutritional properties of milk from different animal species are not fully understood. Caseins belong to a class of proteins that exhibit open and flexible conformations. Here, we discuss the key features that maintain the structures of the protein sequences in four selected animal species: cow, camel, human, and African elephant. The primary sequences of these proteins and their posttranslational modifications (phosphorylation and glycosylation) that determine their secondary structures have distinctively evolved in these different animal species, leading to differences in their structural, functional, and nutritional properties. The variability in the structures of milk caseins influence the properties of their dairy products, such as cheese and yogurt, as well as their digestibility and allergic properties. Such differences are beneficial to the development of different functionally improved casein molecules with variable biological and industrial utilities.

Establishment of Bactrian Camel Induced Pluripotent Stem Cells and Prediction of Their Unique Pluripotency Genes

Induced pluripotent stem cells (iPSCs) can differentiate into all types of cells and can be used in livestock for research on biological development, genetic breeding, and in vitro genetic resource conservation. The Bactrian camel is a large domestic animal that inhabits extreme environments and holds value in the treatment of various diseases and the development of the local economy. Therefore, we transferred four mouse genes (Oct4, Sox2, Klf4, and c-Myc) into Bactrian camel fetal fibroblasts (BCFFs) using retroviruses with a large host range to obtain Bactrian camel induced pluripotent stem cells (bciPSCs). They were comprehensively identified based on cell morphology, pluripotency gene and marker expression, chromosome number, transcriptome sequencing, and differentiation potential. The results showed the pluripotency of bciPSCs. However, unlike stem cells of other species, late formation of stem cell clones was observed; moreover, the immunofluorescence of SSEA1, SSEA3, and SSEA4 were positive, and teratoma formation took four months. These findings may be related to the extremely long gestation period and species specificity of Bactrian camels. By mining RNA sequence data, 85 potential unique pluripotent genes of Bactrian camels were predicted, which could be used as candidate genes for the production of bciPSC in the future. Among them, ASF1B, DTL, CDCA5, PROM1, CYTL1, NUP210, Epha3, and SYT13 are more attractive. In conclusion, we generated bciPSCs for the first time and obtained their transcriptome information, expanding the iPSC genetic information database and exploring the applicability of iPSCs in livestock. Our results can provide an experimental basis for Bactrian camel ESC establishment, developmental research, and genetic resource conservation.

The Flourishing Camel Milk Market and Concerns about Animal Welfare and Legislation

The worldwide dromedary milk production has increased sharply since the beginning of this century due to prolonged shelf life, improved food-safety and perceived health benefits. Scientific confirmation of health claims will expand the market of dromedary milk further. As a result, more and more dromedaries will be bred for one purpose only: the highest possible milk production. However, intensive dromedary farming systems have consequences for animal welfare and may lead to genetic changes. Tighter regulations will be implemented to restrict commercialization of raw milk. Protocols controlling welfare of dromedaries and gene databases of milk-dromedaries will prevent negative consequences of intensive farming. In countries where dromedaries have only recently been introduced as production animal, legislators have limited expertise on this species. This is exemplified by an assessment on behalf of the Dutch government, recommending prohibiting keeping this species from 2024 onwards because the dromedary was deemed to be insufficiently domesticated. Implementation of this recommendation in Dutch law would have devastating effects on existing dromedary farms and could also pave the way for adopting similar measures in other European countries. In this paper it is shown that the Dutch assessment lacks scientific rigor. Awareness of breeders and legislators for the increasing knowledge about dromedaries and their products would strengthen the position of dromedaries as one of the most adapted and sustainable animals.

Camel milk consumption patterns and perceptions in the UAE: a cross-sectional study

Camel milk has been consumed for centuries due to its medicinal and healing properties. The present study aims to investigate the consumption patterns of camel milk and perceived benefits and risks among adults in the United Arab Emirates. A self-administered online questionnaire was developed in English and Arabic languages and was completed online by 852 adults. Socio-demographic characteristics, camel milk consumption patterns and perceived knowledge of the benefits and risks of camel milk were investigated. About 60 % of the participants have tried drinking camel milk, but only a quarter (25⋅1 %) were regular consumers. The most consumed camel milk products after fresh milk were yoghurt and flavoured milk. The most popular additions to camel milk were honey, turmeric and sugar. Most consumers had less than one cup of camel milk per day (57⋅0 %). Camel milk consumers preferred it over other types of milk due to its nutritional value (66⋅4 %) and medicinal properties (39⋅3 %). Among consumers, 58⋅4 % reported consuming unpasteurised camel milk. Reasons included the belief that it is fresher (87⋅2 %), better for the immune system (41⋅6 %), and higher in nutrients (39⋅2 %). Overall, participants had inadequate knowledge about the health benefits of camel milk (7⋅11 ± 5⋅3 out of 25). Males and camel milk consumers had a significantly higher knowledge about the health benefits of camel milk compared to females and non-consumers (P < 0⋅05). Although positive perceptions were common, misperceptions appear to be prevalent among non-consumers. Consuming unpasteurised camel milk is a major public health concern, thus national regulations are essential.

The antiplatelet activity of Camel milk in healthy and aluminum chloride-intoxicated rats

This study examined the effect of camel milk on some marker of blood coagulation markers in aluminum chloride (ALCl₃)-treated rats. Rats (n = 6) were assigned as control, control + fresh camel milk (1 ml), ALCl₃ (0.5 mg/kg), and ALCl₃ + fresh camel milk (1 ml and 0.5 mg/kg, respectively). Treatments were conducted orally for 30 days and daily. Administration of camel milk to control and ALCl₃-intoxicated rats significantly increased platelet count, bleeding time, and collagen epinephrine (CEPI)-induced platelet aggregation. It also lowered plasma levels of thromboxane B2 and hepatic levels of glutathione (GSH) and the activities of antioxidant enzymes, catalase (CAT) and superoxide dismutase (SOD). While the treatment with camel milk has no effect on the liver structure, values of activated partial prothrombin time (aPPT), and levels of prothrombin time (PT) in control rats, it improved liver architectures and decreased serum levels alanine and aspartate aminotransferases (ALT and AST, respectively), and reduced values of both aPTT and PT in ALCl₃-intoxicated rats. In conclusion, camel milk inhibits platelets activity and aggregation in both control and ALCl₃-intoxicated rats.

The Application of Natural Camel Milk Products to Treat Autism-Spectrum Disorders: Risk Assessment and Meta-Analysis of Randomized Clinical Trials

Camel milk is better tolerated than the milk of other ruminants, potentially expanding its consumer appeal. It also contains essential vitamins, minerals, and immunoglobulins, providing the milk with antioxidant, antibacterial, and antiviral properties. These properties may reduce oxidative stress in camel milk consumers, ameliorating many conditions, including those of the CNS, such as autism spectrum disorders (ASDs). We performed a meta-analysis of randomized controlled trials (RCTs) in which camel milk administration (boiled or raw) was examined as an ASD treatment intervention. The primary endpoint was participants' total autism scores, determined using the Childhood Autistic Responsiveness Scale (CARS). A comparison of the responsiveness in these ASD intervention groups yielded a mean difference (MD) of 1.99 (0.89, 3.08) in those consuming boiled camel milk, MD = 2.77 (1.92, 3.61) in raw camel milk consumers, and MD = -1.02 (-0.10, 2.13) in cow milk consumers. Heterogeneity was notably low among the examined studies. Treatment of ASD with raw and boiled camel milk resulted in significantly lower CARS scores than the placebo. Our findings support the development of larger, more populated RCTs to establish camel milk's overall potential as a therapeutic intervention for CNS disorders.

Effect of Camel Milk on Glucose Homeostasis in Patients with Diabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

The effects of camel milk (CM) intake on glycemic control in patients with diabetes are controversial. This systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to summarize the effect of CM intake on glucose homeostasis parameters in patients with both types of diabetes mellitus; T1DM and T2DM. We searched Google Scholar, PubMed/MEDLINE, EBSCO host, CINAHL, ScienceDirect, Cochrane, ProQuest Medical, Web of Science, and Scopus databases from inception until the end of November 2021. Relevant RCTs were identified, and the effect size was reported as mean difference (MD) and standard deviation (SD). Parameters of glycosylated hemoglobin (HbA1c), fasting blood glucose (FBG), postprandial blood glucose (PBG), fasting serum insulin (FI), insulin resistance (expressed in terms of HOMA-IR), insulin dose (ID) received, serum insulin antibody (IA), and C-peptide (CP) were tested. Out of 4054 collected articles, 14 RCTs (total 663 subjects) were eligible for inclusion. The pooled results obtained using a random-effects model showed a statistically significant decrease in HbA1c levels (MD, −1.24, 95% confidence interval (CI): −2.00, −0.48, p < 0.001 heterogeneity (I2) = 94%) and ID received (MD, −16.72, 95% CI: −22.09, −11.35 p < 0.00001, I2 = 90%), with a clear tendency was shown, but non-significant, to decrease FBG (MD, −23.32, 95% CI: −47.33, 0.70, p = 0.06, I2 = 98%) in patients with diabetes who consumed CM in comparison to those on usual care. Conversely, the consumption of CM did not show significant reductions in the rest of the glucose homeostasis parameters. Subgroup analysis revealed that patients with T2DM were more beneficially affected by CM intake than those with T1DM in lowering FBG, while patients with T1DM were more beneficially affected by CM intake than those with T2DM in lowering HbA1c. Both fresh and treated (pasteurized/fermented) CM gave similar beneficial effects in lowering HbA1c. Lastly, a relatively superior effect for longer duration on shorter duration (>6 months, ≤6 months, respectively) of CM intake is found in lowering HbA1c. To conclude, long-term consumption of CM by patients with diabetes could be a useful adjuvant therapy alongside classical medications, especially in lowering the required insulin dose and HbA1c. Due to the high heterogeneity observed in the included studies, more controlled trials with a larger sample size are warranted to confirm our results and to control some confounders and interfering factors existing in the analyzed articles.

Camel Milk Targeting Insulin Receptor—Toward Understanding the Antidiabetic Effects of Camel Milk

Camel milk (CM) is known for its beneficial virtues in the human diet and health. This includes its antidiabetic properties demonstrated in many in vitro and in vivo studies. Nevertheless, the scientific rationale behind the molecular and cellular basis of such beneficial effects and the exact antidiabetic agent(s)/mechanism(s) are still elusive. In this review, we focused on the recent advances supporting the targeting of insulin receptor (IR) by CM components. Indeed, our recent work reported that CM proteins and derived peptides pharmacologically target IR in vitro leading to its activation and potentiation of insulin-mediated responses. The review describes the experimental approaches used to investigate the effects of CM on IR in vitro based on the fractionation of CM whey proteins to purify functional proteins and their hydrolysis by gastric proteases to generate bioactive peptides. In addition, we illustrated our cellular and molecular model consisting of studying the functional activity of CM fractions on IR and its downstream signaling pathways in the hepatocarcinoma (HepG2) and the human embryonic kidney (HEK293) cells using the bioluminescence resonance energy transfer (BRET), phosphorylation, and glucose uptake assays. Overall, our work demonstrated for the first time that CM lactoferrin and CM-derived bioactive peptides positively modulate IR and its related signaling pathways in HepG2 and HEK293 cells. As a conclusion, the pharmacological targeting of IR by CM sheds more light on the antidiabetic properties of CM by providing its molecular basis that may constitute a solid rationale for the development of new generation of antidiabetic tools from CM-derived proteins and peptides and the utilization of CM in the management of diabetes. The sequencing and the synthesis of the potent bioactive CM peptides may open promising perspectives for their application as antidiabetic agents.

Camel and bovine milk lactoferrins activate insulin receptor and its related AKT and ERK1/2 pathways

Lactoferrin (LF) is a milk protein that may be an interesting candidate for the antidiabetic properties of milk due to its well-documented bioactivity and implication in diabetes. Here, we investigated the functional action of LF purified from camel and bovine milk (cLF, bLF) on insulin receptors (IR) and their pharmacology and signaling in hepatocarcinoma (HepG2) and human embryonic kidney (HEK293) cells. For this, we examined IR activation by bioluminescence resonance energy transfer (BRET) technology and the phosphorylation of its key downstream signaling kinases by western blot. The purified cLF and bLF induced phosphorylation of IR, AKT, and ERK1/2 in HepG2 and HEK293 cells. The BRET assays in HEK293 cells confirm the pharmacological action of cLF and bLF on IR, with a possible allosteric mode of action. This reveals for the first time the bioactivity of LF toward IR function, indicating it as a potential bioactive protein behind the antidiabetic properties of camel milk.

Molecular detection and identification of Babesia bovis and Trypanosoma spp. in one-humped camel (Camelus dromedarius) breeds in Egypt

Background and Aim:

Camels are a unique source of milk and meat, which helps recover from several diseases that affect humans worldwide. In Egypt, one of the great obstacles for this industry is tick-borne diseases. This study aimed to characterize blood parasite infections, such as Babesia (B.) bovis and Trypanosoma (T.) spp. in one-humped camel (Camelus dromedarius) (n=142) breeds in Halayeb and Shalateen, Egypt, through phylogenetic analysis.

Materials and Methods:

The prevalence of B. bovis and Trypanosoma spp. was identified in camels using polymerase chain reaction (PCR) assays targeting the Rhoptry-Associated Protein-1 and internal transcribed spacer 1 genes, respectively. A nested PCR technique was conducted to detect B. bovis. At the same time, KIN multispecies PCR assay was employed to diagnose and classify trypanosome DNA in camels.

Results:

B. bovis was detected in 4/142 camels with an infection rate of 2.81%. Sequencing and phylogenetic analyses revealed that the strain of B. bovis isolated from this population was closely related to strains isolated from Argentine, the United States, and Brazil. Moreover, Trypanosoma evansi was detected in 8/142 camels with an infection rate of 5.63%. Sequencing and phylogenetic analyses revealed that this isolated strain T. evansi was closely related to Trypanosoma theileri detected from cattle in Brazil.

Conclusion:

The obtained data indicated the existence of B. bovis and T. evansi in camels from two provinces of Egypt. The obtained findings have economic significance and reflect the importance of implementing effective prevention and control methods across Egypt to reduce the incidence of B. bovis and T. evansi in camels.

Hydrolyzed camel whey protein alleviated heat stress-induced hepatocyte damage by activated Nrf2/HO-1 signaling pathway and inhibited NF-κB/NLRP3 axis

Liver damage is the most severe complication of heat stress (HS). Hydrolyzed camel whey protein (CWP) possesses bioactive peptides with obviously antioxidant and anti-inflammatory activities. The current study aims to investigate whether CWP that is hydrolyzed by a simulated gastrointestinal digestion process, named S-CWP, protects BRL-3A hepatocytes from HS-induced damage via antioxidant and anti-inflammatory mechanisms. BRL-3A cells were pretreated with S-CWP before being treated at 43 °C for 1 h, and the levels of the cellular oxidative stress, inflammation, apoptosis, biomarkers for liver function, the activities of several antioxidant enzymes, and the cell viability were analyzed. The expression level of pivotal proteins in correlative signaling pathways was evaluated by western blotting. We confirmed that S-CWP alleviated HS-induced hepatocytes oxidative stress by decreased reactive oxygen species (ROS), nitric oxide (NO), 8-Hydroxy-2'-deoxyguanosine (8-OHdG), lipid peroxidation (LPO), protein carbonylation (PCO), and the activities of NADPH oxidase while enhanced superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), heme oxygenase-1 (HO-1) activities, and GSH content. S-CWP suppressed HS-induced inflammatory response by reducing the phosphorylation of NF-κB p65, the expression of NLRP3, and caspase-1 and finally alleviated caspase-3-mediated apoptosis. S-CWP also alleviated HS-induced hepatocyte injury by reducing alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) levels and restoring Heat Shock Protein 70 (HSP70) expression. Furthermore, S-CWP treatment significantly enhanced the expression of NF-E2-related nuclear factor erythroid-2 (Nrf2) and HO-1. The antioxidant and anti-inflammatory effects of S-CWP were weakened by ML385, a specific Nrf2 inhibitor. Additionally, zinc protoporphyrin (ZnPP), a specific HO-1 inhibitor, significantly reversed S-CWP-induced reduction in the phosphorylation of NF-κB p65. Thus, our results revealed that S-CWP protected against HS-induced hepatocytes damage via activating the Nrf2/HO-1 signaling pathway and inhibiting NF-κB/NLRP3 axis.

The gut microbiota and its metabolites in mice are affected by high heat treatment of Bactrian camel milk

Heat treatment is the most common method used to make milk safe; however, it leads to changes in the organoleptic and nutritional properties of milk. This study aimed to investigate the effects of different heat treatments on nutrients and microbiota of camel milk. The results showed that the nutrient composition of camel milk could be influenced by heat treatment. Ultra-high-temperature treatment of samples significantly reduced levels of camel milk proteins, vitamin C, and lactose, but did not significantly alter the amino acids content. Analysis of 16S rRNA amplicon sequences demonstrated that the composition of the intestinal microbiota of mice fed different heat-treated camel milks changed, as did the production of short-chain fatty acids as determined by gas chromatography-mass spectrometry. High temperature/short time treatment had similar effects to UHT treatment on microbial diversity of camel milk; however, the low temperature/long time treatment had different effects. In addition, higher-temperature treatments changed the abundance of key bacteria at the genus level. These results demonstrated that different heat treatments not only resulted in some nutrient loss, but also changed the proliferation of some probiotic genera. Our results could provide the basis for the potential industrial application of camel milk processing technologies.

Triplex real-time PCR assay for the authentication of camel-derived dairy and meat products

Authentication of dairy and meat products is important to ensure fair competition, consumer benefit, and food safety. The large difference in price between camel and cow milk may be an incentive to adulterate camel dairy products with cow-derived foodstuffs. However, no studies so far have used triplex real-time PCR with an endogenous control to identify camel and cow origins in dairy and meat products. In this study, we developed a triplex real-time PCR assay based on amplification of mitochondrial 12S ribosomal DNA for the authentication of camel-derived dairy and meat products. This method was applied to identify camel and cow DNA in milk, yogurt, cheese, milk powder, milk beverage, meat products, and mixtures with milk and meat. Concentrations as low as 1 to 5% and 0.1% camel milk and meat, respectively, were detected in the mixtures, and 1 to 5% and 0.1% cow milk and meat, respectively, were identified via this approach. The limits of detection were 0.005 to 0.0025 ng, 0.05 to 0.001 ng, 0.001 to 0.0005 ng, and 0.00025 to 0.0001 ng of DNA in camel milk, camel yogurt, commercial camel milk beverage, and camel meat, and from 0.0025 to 0.001 ng, 0.5 to 0.001 ng, 1 to 0.05 ng, 0.01 ng, 0.001 ng, 0.0005 to 0.00025 ng, 0.0005 to 0.00025 ng, and 0.005 ng of DNA from cow milk, yogurt, cheese, acidic whey, milk powder, beef, beef jerky, and beef sausage, respectively. Different dairy and meat samples of camel and cow origins had a range of authentication limits and limits of detection. The designed triplex real-time PCR assay was shown to be a specific, sensitive, and efficient technique for the identification of camel and cow DNA in foodstuffs.

Distinct Effects of Milks From Various Animal Types on Infant Fecal Microbiota Through in vitro Fermentations

Human milk is compatible with infant intestinal microbiota and is vital for infant health. However, most infants do not receive sufficient exclusive breastfeeding, and the effects of including other types of animal milk on the gut microbiota of infants are unclear. Therefore, the objective of this study was to elucidate the impact of milk from various animal sources on infant fecal microbiota through in vitro fermentation. The types of milk assessed include cow milk, goat milk, camel milk, mare milk, human milk, and infant formula milk. Here we determined the gas pressure, pH, and microbiota after 24 h fermentation. Results showed that mare milk had the lowest gas pressure rating, with levels similar to human milk. More so, pH analysis demonstrated that other milk types were identical to human milk. Bacterial 16S rRNA gene sequence analysis revealed that all milk types increased the abundance of Bifidobacterium and Lactobacillus, which was proportional to the lactose content of milk. Moreover, mare milk also significantly increased the relative abundance of Akkermansia. Collectively, results from mare milk (gas pressure, pH, and microbiota) were comparable to that of human milk, and thus support the theoretical basis for exploring the development of a mare milk-based infant formula.

Marked variability in bioactivity between commercially available bovine colostrum for human use; implications for clinical trials

Background

Colostrum, the milk produced during first few days after birth, is rich in immunoglobulins, antimicrobial peptides & growth factors. Multiple clinical trials using bovine colostrum are ongoing but with no assessment of test product bioactivity.

Objectives

To examine variability of bioactivity between 20 commercial colostrum products, contribution of TGFβ and EGFR in mediating effects, heat sensitivity of bioactivity and changes in bioactivity of colostrum milkings in the days following calving.

Design

In vitro bioactivity used AGS, RIE-1 and Caco-2 cell proliferation (Alamar blue) and migration (wounded monolayers) assays. Changes in colostrum bioactivity determined following addition of TGFβ-neutralising antibody, EGFR blocker (Typhostin) and after heating (40–60°C, 60 min). In vivo bioassay assessed ability of colostrum gavage (2ml, 7mg/ml) to reduce gastric damage (NSAID + restraint) in rats. Milkings from 6 cows, days 0–3 post calving were assessed for bioactivity and growth factor concentrations.

Result

Six-fold differences in pro-proliferative and migratory activity were seen comparing commercial products. Comparison of most- and least-active samples from in vitro studies showed two- to three-fold differences in ability to reduce gastric injury (86% reduction using most-active vs 48% using least-active, p<0.01). Tyrphostin reduced pro-migratory and proliferative activity by 23% and 55%. TGFβ neutralisation reduced migratory activity by 83% but did not affect proliferation Heating colostrum powder to 50°C did not affect immunoactivity of haptoglobin, EGF, TGFβ, IgG, IGF-1 or betacellulin but decreased bioactivity by >40%. Milking studies showed high bioactivity during first and second milkings on day 0 but 77% reduction by day 3. Changes in total protein, haptoglobin, EGF, TGFβ, IgG and IGF-1 paralleled falls in bioactivity.

Conclusion

Commercial colostrum products possess widely different bioactivity. Variation in heat exposure and/or proportion of day 0 colostrum content may contribute to this. Assessment of colostrum bioactivity has advantages to growth factor quantitation for quality control.

Comparative Analysis of Milk Fat Globular Membrane (MFGM) Proteome between Saudi Arabia Camelus dromedary Safra and Wadha Breeds

Camel milk is traditionally known to have medicinal properties and many potential health benefits. Natural milk contains many soluble proteins and nanoparticles, such as a milk fat globule membrane (MFGM), a three-layered membrane covering of milk fat globule mainly composed of proteins and lipids, which plays an important role in human health. MFGM proteins account for 1%-4% of total milk proteins, and their nutritive value and distribution depends on the different breeds. The differential composition of these membrane proteins among different camel breeds has not been explored. The current study, therefore, aimed to quantitatively analyze and compare the MFGM proteome between the milk produced by the two most common Saudi camel breeds, Camelus dromedarius: Safra and Wadha. Two-dimensional difference in gel electrophoresis (2D-DIGE) and mass spectrometry analysis revealed a total of 44 MFGM proteins that were identified with a significant difference in abundance (p ≤ 0.05; fold change ≥ 1.5) between the two breeds. Thirty-one proteins were up-regulated and 13 proteins were down-regulated in the Safra breed compared to the Wadha breed. The proteins identified with an increased abundance included α-lactalbumin, lactadherin, and annexin a8, whereas the down-regulated proteins included butyrophilin subfamily 1 member a1, lactotransferrin, and vinculin. The differentially abundant proteins were analyzed by the UNIPROT system and gene ontology (GO) to reveal their associations with known biological functions and pathways. Enzyme-linked immunosorbent assay (ELISA) confirmed the 2D-DIGE findings of butyrophilin (BTN) and α-lactalbumin (α-LA) levels obtained from Safra and Wadha breeds.

Prevalence of methicillin-resistant (mecA gene) and heat-resistant Staphylococcus aureus strains in pasteurized camel milk

Staphylococcus aureus is a significant opportunistic pathogen in humans, dairy cattle, and camels. The presence of antibiotic-resistant and heat-resistant bacteria in camel milk has become a potential public health issue. The phenotypic and molecular characterization of methicillin-resistant staphylococcal strains recovered from pasteurized camel milk distributed in retail markets of Saudi Arabia was assessed. A total of 100 samples were collected between March and May 2017. Out of the 20 S. aureus isolates that were recovered from the pasteurized camel milk, 10 were found to be resistant to cefoxitin (30 µg) and, thus, were designated as methicillin-resistant strains. The resistance ratio of methicillin-resistant S. aureus isolates for a different class of antibiotics was determined by performing the antimicrobial susceptibility test and was estimated to be approximately 60%. Polymerase chain reaction assay was performed to amplify the methicillin-resistant gene mecA, and furthermore, nucleotide sequencing was performed to detect and verify the presence of methicillin-resistant strains. Upon sequencing the putative S. aureus methicillin-resistant strains, we obtained 96 to 100% similarity to the penicillin-binding protein 2a gene (mecA) of the S. aureus strain CS100. Moreover, the 10 methicillin-resistant S. aureus isolates were also identified to be heat resistant and were stable at temperatures up to 85°C for 60 s, with 3 isolates being heat resistant even at 90°C for 60 or 90 s. The mean decimal reduction time (D₈₅ value) was 111 s for all the 10 isolates. No difference was observed in the profile of total protein between the 10 methicillin- and heat-resistant S. aureus isolates and the S. aureus strain ATCC 29737, which was determined by sodium dodecyl sulfate-PAGE analyses. Therefore, we could conclude that a relatively high percentage of the tested pasteurized camel milk samples were contaminated with S. aureus (20%) and methicillin- and heat-resistant S. aureus (10%).

Effects of Geographic Region on the Composition of Bactrian Camel Milk in Mongolia

Summary

Camels are known to occupy arid and desert countries. These pastoralist areas and conditions make it difficult to estimate camel milk production. Camel milk is considered to have anti-cancer, hypo-allergic and anti-diabetic properties. A high content of unsaturated fatty acids contributes to its overall dietary quality. The low quantity of β-casein and the lack of β-lactoglobulin are linked to the hypo-allergic effect of camel milk. Although the Bactrian camel is an important domestic animal in Mongolia, few studies have focused on Bactrian camel milk in this country. Our study characterizes the amino acid and fatty acid compositions of Bactrian camel milk collected from several geographical areas in Mongolia. The findings establish a theoretical basis for additional studies on the composition of milk from Bactrian camels in Mongolia.

Abstract

Camel milk is considered as an essential source of nutrition for desert people. However, few studies have investigated how geography affects Bactrian camel milk in Mongolia. In this study, we evaluated the differences in gross composition, fatty acid composition, and amino acid composition among Bactrian camel milk samples collected from 102 Bactrian camels in five different Mongolian regions. The proportion of long-chain fatty acids, out of total fatty acids, was high in all samples of Bactrian camel milk. The primary fatty acids detected in the samples were palmitic acid (23.99–30.72%), oleic acid (17.21–24.24%), and stearic acid (11.13–16.49%), while the dominant amino acids were leucine, lysine, valine, and aspartic acid. Cysteine was the least common amino acid detected in the Bactrian camel milk samples. Considerable differences in the fatty acid and amino acid compositions were observed among Bactrian camel milk from different regions of Mongolia. The findings suggest that geography strongly affects the composition of camel milk.

Challenges of managing food allergy in the developing world

Food allergy (FA) is currently a significant health care problem in the developing world. Widely varying study populations and methodologies, the use of surrogate markers such as self report or hospitalization rates due to anaphylaxis rather than objective methods, limits robust estimation of FA prevalence in low income settings. Also, allergy is under-recognized as a clinical specialty in the developing world which compromises the chance for accurate diagnosis. In this review, most published data on food allergens from developing or low income countries are displayed. The diagnostic challenges and limitations of treatment options are discussed. It seems that FA is an under-appreciated health care issue in the developing world, and accurate determination of its burden in low-income settings represents an important unmet need. Multicenter surveillance studies, using standardized methodologies, are, therefore, needed to reveal the true extent of the problem and provide epidemiological clues for prevention. Preventive strategies should be tailored to fit local circumstances in different geographic regions. In addition, studying the gene environment interactions and impact of early life microbiota on the expression of FA in developing communities would be worthwhile. Efforts and resources should be directed toward public health education and training of health care providers dealing with food allergic patients.

The molecular basis of the anti-diabetic properties of camel milk

Over the years, strong evidence have been accumulated in favor of the beneficial effects of camel milk on glucose homeostasis with significant anti-diabetic properties in both human and animal diabetic models. However, the cellular and molecular mechanisms involved in such effects remain not understood. In this review, we speculated about the potential mechanisms and summarized few mechanistic-based studies that investigated the biological activity of camel milk and its protein components on the different aspects that may be involved in the anti-diabetic effects. A special emphasis is given to the molecular events engaged by camel milk proteins/peptides on two key aspects: insulin secretion and insulin receptor activity. Thus, the review gives a molecular rationale to the anti-diabetic effects of camel milk. This will help to identify the anti-diabetic agent(s) contained in camel milk and to understand better its mechanism of action in order to use it for the management of diabetes mellitus.

Potential antioxidant bioactive peptides from camel milk proteins

Camel milk is traditionally considered to have medicinal characteristics that it has potential health benefits and could help to treat several illnesses. Particularly, it is closest to human breast milk and has high levels of nutrients and bioactive components. The aim of this study was to explore the antioxidant peptides derived from protein fractions of camel milk. Camel milk proteins (CMP) were fractionated into camel casein protein (CCP) and camel whey protein (CWP), which were hydrolyzed with pepsin to produce peptic digests P-CCP and P-CWP, respectively. RP-HPLC was used for fractionation of the peptides from the P-CCP and P-CWP. The antioxidant activities were evaluated using superoxide anion generating system of xanthine oxidase (XOD) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay. Active peptides were analyzed using matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS) whereas a number of antioxidant peptides, with masses ranging from 913 to 2,951 Da, derived mainly from alpha-casein, lactophorin and lactoferrin, were identified. When yeast cells are used as a system for modeling mitochondrial disease, the peptides in caseins and whey fractions significantly enhanced the tolerance of yeast cells against peroxide-induced oxidative stress. The results show that both caseins and whey proteins of camel milk possess bioactive peptides with significant radical-scavenging activities and thus herald a fascinating opportunity for their potential as nutraceuticals or therapeutic peptides for prevention and treatment of oxidative stress-associated diseases.

Influence of Bactrian camel milk on the gut microbiota

Bactrian camel milk has become popular in the market as an important source of nutrients with diverse functional effects. In this study, the influence of Bactrian camel milk on the gut microbiota of mice was studied using metagenomic-based sequencing of the V3 and V4 hypervariable regions of the 16S rRNA gene. Bioinformatics analysis showed that Firmicutes and Bacteroidetes were the predominant phyla, accounting for more than 80% of the bacteria present. At the genus level, Allobaculum, Akkermansia, Romboutsia, Bifidobacterium, and Lactobacillus were most abundant in the gut microbiota; of these, Allobaculum and Akkermansia were the predominant genera, representing 40.42 and 7.85% of all the bacteria present, respectively. Camel milk was found to reduce relative abundance of Romboutsia, Lactobacillus, Turicibacter, and Desulfovibrio (decreased by 50.88, 34.78, 26.67, and 54.55%, respectively) in the gut microbiota compared with the control. However, some genera such as Allobaculum, Akkermansia, and Bifidobacterium in the gastrointestinal flora increased in abundance in the presence of camel milk; these genera are correlated with beneficial effects for organisms. Our research suggests that the gut microbiota should be taken into account when conducting functional studies on camel milk, and this work provides a useful foundation for further study on functions of camel milk.

In vitro investigation of anticancer, antihypertensive, antidiabetic, and antioxidant activities of camel milk fermented with camel milk probiotic: A comparative study with fermented bovine milk

This study aimed to investigate in vitro anticancer activity by antiproliferative activity, antihypertensive activity by angiotensin-converting enzyme inhibition, antidiabetic activity by α-amylase and α-glucosidase inhibitions, and antioxidant activities of camel milk fermented with camel milk probiotic compared with fermented bovine milk. The camel milk probiotic strain Lactococcus lactis KX881782 (Lc.K782) and control Lactobacillus acidophilus DSM9126 (La.DSM) were used to prepare fermented camel and bovine milks separately. The proteolytic activities of water-soluble extract (WSE) in all fermented camel milk were higher than those in fermented bovine milk. The α-glucosidase inhibitions in both milk types fermented by Lc.K782 ranged from 30 to 40%. Camel milk fermented by Lc.K782 had the highest antioxidant activity by 2,2'-azino-bis(3-ethylbenzo-thiazoline-6-sulphonic acid). The highest angiotensin-converting enzyme inhibition of WSE in camel milk fermented by Lc.K782 was >80%. The proliferations of Caco-2, MCF-7, and HELA cells were more inhibited when treated with WSE of fermented camel milk extracts.

Processing Challenges and Opportunities of Camel Dairy Products

A review on the challenges and opportunities of processing camel milk into dairy products is provided with an objective of exploring the challenges of processing and assessing the opportunities for developing functional products from camel milk. The gross composition of camel milk is similar to bovine milk. Nonetheless, the relative composition, distribution, and the molecular structure of the milk components are reported to be different. Consequently, manufacturing of camel dairy products such as cheese, yoghurt, or butter using the same technology as for dairy products from bovine milk can result in processing difficulties and products of inferior quality. However, scientific evidence points to the possibility of transforming camel milk into products by optimization of the processing parameters. Additionally, camel milk has traditionally been used for its medicinal values and recent scientific studies confirm that it is a rich source of bioactive, antimicrobial, and antioxidant substances. The current literature concerning product design and functional potential of camel milk is fragmented in terms of time, place, and depth of the research. Therefore, it is essential to understand the fundamental features of camel milk and initiate detailed multidisciplinary research to fully explore and utilize its functional and technological properties.

Environmental risk factors for autism: an evidence-based review of systematic reviews and meta-analyses

BACKGROUND

According to recent evidence, up to 40-50% of variance in autism spectrum disorder (ASD) liability might be determined by environmental factors. In the present paper, we conducted a review of systematic reviews and meta-analyses of environmental risk factors for ASD. We assessed each review for quality of evidence and provided a brief overview of putative mechanisms of environmental risk factors for ASD.

FINDINGS

Current evidence suggests that several environmental factors including vaccination, maternal smoking, thimerosal exposure, and most likely assisted reproductive technologies are unrelated to risk of ASD. On the contrary, advanced parental age is associated with higher risk of ASD. Birth complications that are associated with trauma or ischemia and hypoxia have also shown strong links to ASD, whereas other pregnancy-related factors such as maternal obesity, maternal diabetes, and caesarian section have shown a less strong (but significant) association with risk of ASD. The reviews on nutritional elements have been inconclusive about the detrimental effects of deficiency in folic acid and omega 3, but vitamin D seems to be deficient in patients with ASD. The studies on toxic elements have been largely limited by their design, but there is enough evidence for the association between some heavy metals (most important inorganic mercury and lead) and ASD that warrants further investigation. Mechanisms of the association between environmental factors and ASD are debated but might include non-causative association (including confounding), gene-related effect, oxidative stress, inflammation, hypoxia/ischemia, endocrine disruption, neurotransmitter alterations, and interference with signaling pathways.

CONCLUSIONS

Compared to genetic studies of ASD, studies of environmental risk factors are in their infancy and have significant methodological limitations. Future studies of ASD risk factors would benefit from a developmental psychopathology approach, prospective design, precise exposure measurement, reliable timing of exposure in relation to critical developmental periods and should take into account the dynamic interplay between gene and environment by using genetically informed designs.