As one of the market leaders in the online world of food supplements, Sunday Natural is committed to ensuring that our products always meet the highest standards of quality. That is why we pursue the True Clean Label philosophy – without compromise – while developing our products. Every product must meet the requirements of the 10,000 healthcare professionals we collaborate with. These partnerships allow us to gain valuable insights from therapeutic practice and research; in turn, we can continuously improve our products to be even more innovative and effective.
Our Product Development Partners
Our innovative formulations are made possible by leveraging the unique expertise of leading specialists, working side-by-side. These partnerships have resulted in a wide range of unique functional blends, enabling us to provide even more targeted micronutrient support. A selection of our partners:
Specialisation
All specialties
Brain & Nerves
Gut Health
Heart Health
Immune System
Joints & Bones
Liver & Cleansing
Men's Health
Microorganisms
Mitos & Energy
Strengthening the Immune System
Thyroid & Autoimmunity
Women's Health
Skin Diseases
Prof. Dr. med. habil. Ulrich Amon
Pommelsbrunn, Germany
Fields of expertise: Dermatology and allergology, specialist in micronutrient medicine
Prof. Dr. med. habil. Ulrich Amon is a specialist in dermatology and allergology with a focus on autoimmune diseases, micronutrient therapy and the Coimbra Protocol. He studied law and human medicine in Innsbruck, Freiburg, Marburg and London. As part of his specialist training and post-doctoral qualification at the Medical University of Luebeck, he headed a laboratory for experimental allergology.
From 1996 to 2011, Dr. Amon was chief physician at the PsoriSol Skin Clinic in Hersbruck near Nuremberg. Since 2005, he has been managing the International Skin Centre DermAllegra in Hohenstadt/Nuremberg. He has many additional qualifications, including laser therapy and quality management, and has gained international experience in London and Australia, among other places.
Prof. Amon has received numerous awards and publishes regularly. His areas of expertise are autoimmune diseases, surgical dermatology, laser surgery and micronutrient medicine.
Genetics & immunology, functional medicine
Dr. Petra Buchanan
Freiburg, Germany
Fields of expertise: Genetics & immunology, functional medicine
Dr. Petra Buchanan holds a PhD in biology (genetics & immunology) and has been a holistic practitioner specialising in functional medicine for over 7 years. She has a particular interest in treating Down's syndrome as a metabolic and neurodegenerative disease in addition to her focus on optimising the gut microbiome and utilising personalised micronutrient therapy.
Since 2019, Dr. Buchanan has supported over 800 families in her clinic – Praxis 321 – from pregnancy to adulthood, where she combines holistic approaches with a deep scientific understanding of the molecular processes within the body. She is also actively committed to education and research in the fields of childhood developmental disorders and modern functional therapeutic approaches.
Hormones
Dr. Katharina Maria Burkhardt, MSc
Fischbach, Austria
Fields of expertise: Hormone science, public health, female health, bioidentical hormones, micronutrient medicine
Dr. Katharina Maria Burkhardt is an independent scientist, speaker, author and developer of evidence-based concepts in the fields of female health, bioidentical hormones and micronutrient medicine.
She has focused on hormonal imbalances and their effects on physical and mental well-being for over 20 years. Her work lies at the intersection of research, laboratory analytics, clinical practice and product development, which includes designing studies, developing diagnostic and therapeutic concepts and managing scientific projects in the fields of integrative hormone medicine and female health.
At the beginning of her academic career, Dr. Burkhardt investigated hormones and their effects on physical and mental well-being (master's thesis 2018/2019) and expanded on these findings in her doctorate dissertation (2020/2021). Since 2022, she has been involved in research that evaluates various measurement methods for transdermal hormone therapy.
In addition, she develops concepts regarding female health and micronutrients during the various stages of a woman's life – from menstrual health and perimenopause to healthy ageing and longevity. Her work combines scientific research with clinical experience, laboratory analytics and practical healthcare.
Alongside her scientific work, Dr. Burkhardt is the author of several books, serves as a keynote speaker at professional events and develops numerous health and product concepts in the fields of hormones, micronutrients and female health.
From 2022 to 2025, she was the founder, scientific director and conceptual developer of the Network for Bioidentical Hormones Austria. In addition, she developed and managed a 3-year specialist training programme in integrative bioidentical hormone therapy for medical professionals in Germany, Austria and Switzerland.
Joint & Bone Health
Prof. Dr. med. habil. Philip Catalá-Lehnen
Hamburg, Germany
Fields of expertise: Orthopaedics, trauma surgery, sports medicine
Prof. Dr. med. habil. Philip Catalá-Lehnen has served as the Medical Director and owner of LANS Medicum in Hamburg since 2016. He completed his specialist training in orthopaedics and trauma surgery at the University Medical Centre Hamburg-Eppendorf and obtained additional qualifications in special trauma surgery and sports medicine. As the founder and Medical Director of UKE Athleticum, he successfully established an interdisciplinary centre of excellence for athletic medicine between 2011 and 2014. He was Chief Physician at Lanserhof Hamburg from 2014–2016 before setting up his own practice, LANS Medicum, in 2016.
Prof. Catalá-Lehnen was the team doctor for the German first league handball team of the HSV from 2011 to 2014.
Prof. Catalá-Lehnen and his team currently work with the German first league handball team of the HSV, the regional football league teams FC Eintracht Norderstedt and FC Altona 93 as well as John Neumeier's Hamburg Ballet.
Additionally, Prof. Catalá-Lehnen organises and chairs scientific symposia and conferences, including ORTHOBIOLOGICA Hamburg, where he initiates innovative developments in new therapeutic approaches to the treatment of osteoarthritis and cartilage damage.
Since 2018, Prof. Philip Catalá-Lehnen has been teaching orthopaedics, sports medicine and bone pathology at the University Medical Centre Hamburg-Eppendorf as well as training UKE medical students in conservative sports orthopaedics at LANS Medicum. Since the winter semester of 2023, he has also been working at the Medical School Hamburg as a professor of clinical medicine with a focus on orthopaedics.
Christian W. Engelbert has been running a practice for integrative medicine in Berlin since 2007 and in Beelitz-Heilstaetten since 2025 (www.integrative-medizin-beelitz.de). As a specialist in general and emergency medicine, acupuncture and naturopathy, he bases his therapy on state-of-the-art diagnostics, particularly in the cardiovascular field, the latest scientific findings and experience in naturopathy. In addition to symptoms, he also considers the background and interconnections of diseases and symptoms.
In addition to many publications in specialist journals, Mr. Engelbert is the author of two books entitled "Heart Balance" and "Diagnosing High Blood Pressure" (published by Herbig Verlag) as well as a book/audiobook "Understanding and Protecting My Heart" (published by Tropical Verlag). He has been a lecturer at the universities of Milan, Viadrina Frankfurt (Oder) and Urania in Berlin. In addition, he was head of the "Further Training in Naturopathic Medicine for Doctors" programme in Berlin for many years. He lectures both in Germany and abroad and also hosts numerous webinars.
Gut Health
Dr. med. Thomas Fielder
Berlin, Germany
Fields of expertise: Internal medicine, gastroenterology
Dr. Thomas Fiedler, MBA completed just over eight years of specialist training in internal medicine at several clinics affiliated with Charité University Medicine Berlin, spending most of that time in the gastroenterology department (specifically digestive medicine). Together with Dr. Georgi, he has been running what is likely Berlin's largest specialist practice for patients with irritable bowel syndrome and functional bowel disorders for more than 13 years.
Four years ago, Dr. Fielder co-founded the website www.reizdarm-SOS.de where patients can buy diagnostic tests online. These tests are evaluated by Dr. Fiedler's and Dr. Georgi's team of nutritionists, who then provide targeted follow up.
Dr. Fiedler has been integrating herbal and orthomolecular remedies into his holistic and naturopathic approach to therapy for years; he is highly experienced in evaluating the effects and efficiency of both single and combination formulas.
Through appearances in and contributions to podcasts, magazines and social media, he has developed a reputation as an expert on irritable bowel syndrome and, in particular, small intestinal bacterial overgrowth (SIBO). In October 2025, his book "SIBO and Irritable Bowel Syndrome" was published by TRIAS Verlag as part of their "Expert Knowledge" series.
Gut Health
Dr. med. Sven Georgi
Berlin, Germany
Fields of expertise: General medicine, gastroenterology
Dr. Sven Georgi has been in private practice for 20 years and specialises in functional bowel disorders. He has been running a large internal and general medicine practice with Dr. Thomas Fiedler and six other doctors in Berlin since 2012, focusing on irritable bowel syndrome, SIBO and functional bowel disorders. Through their targeted diagnostics and customised therapy, they have provided relief for thousands of patients suffering from long-term symptoms.
For more than five years, Dr. Fiedler and Dr. Georgi have been running the website www.reizdarm-SOS.de where patients can buy diagnostic tests (with a focus on small intestinal bacterial overgrowth (SIBO)) online. These tests are evaluated by their team of nutritionists, who then provide targeted follow up. Dr. Georgi has been integrating herbal and orthomolecular remedies into his holistic and naturopathic approach to therapy for years; he is highly experienced in evaluating the effects and efficiency of both single and combination formulas.
Through appearances in and contributions to TV shows, podcasts, magazines and social media, Dr. Georgi has developed a reputation as an expert on holistic approaches to irritable bowel syndrome. In particular, he specialises in the treatment of bacterial overgrowth in the small and large intestines (SIBO, IMO, ISO).
Heart Health
Dr. med. univ. Manuela Hanke
Vienna, Austria
Fields of expertise: Internal medicine, cardiology, nutritional medicine and orthomolecular medicine
Dr. Hanke completed her medical studies in Vienna and spent over 20 years in Athens, where she successfully completed her specialist training as an internist and cardiologist. During this time, she worked for over 10 years as head of preventive cardiology at the Biomedicine Group of Companies Athens and also took on the medical management and expansion of the KEPY Marousi civil prevention centre for three years.
From 2016 to 2018, Dr. Hanke worked as a senior physician at Mistelbach Hospital; she has been running her own practice in Vienna since 2017, specialising in internal medicine, cardiology, nutritional medicine and orthomolecular medicine. She also offers genetic testing for various medical analyses. She is a member of the German and Austrian Society of Cardiology, the Austrian Academy of Nutritional Medicine and the Medical Platform for Orthomolecular Medicine.
Women's & Men's Health / Fertility
Dr. Reinhard Hannen
Berlin, Germany
Fields of expertise:Gynaecological endocrinology and reproductive medicine
Dr. Hannen has been working as a gynaecologist in Berlin for 28 years, specialising in gynaecological endocrinology and reproductive medicine.
He has been head of the CERES Fertility Centre in Berlin since 1997, where he has treated over 50,000 patients. Dr. Hannen also supports couples trying to conceive with a holistic approach for over 10 years.
In addition to fertility treatment, Dr. Hannen offers innovative and supportive measures at the CERES Fertility Centre, including NAD+ infusions for mitochondrial therapy and individualised micronutrient therapies. He has also been a psychotherapist since 1997. In 2005, he was trained as a medical quality manager in healthcare by the Berlin Medical Association. In 2000, he was authorised by the Berlin Medical Association to train prospective specialists in gynaecology and obstetrics. Since 2003, this authorisation has also included gynaecological endocrinology and reproductive medicine.
Dr. Hannen has laboratory expertise in gynaecology and obstetrics (OBGYN) and has been running his own laboratory at the CERES Fertility Centre since 1997. In 2017, he passed the exam to become an orthomolecular therapist, followed by qualification as a micronutrient physician in 2018.
Dr. Heinrich has been working with a holistic approach to health and illness since 1984. He initially pursued a psychotherapeutic approach, then increasingly focused on physical aspects, working as a therapist in naturopathy, homeopathy and holistic medicine.
Since 2005, Dr. Heinrich has been working in his own medical practice in Berlin, which initially developed as a Holistic Medicine Clinic and subsequently became the current THERA Clinic. Currently, 12 doctors and 30 other employees work there.
The THERA Clinic focuses on the prevention and treatment of chronic diseases and stress: Biological oncology Hyperthermia centre Apheresis centre Fertility Stem cell therapy Integrative cardiac medicine (Prof. Dohmen)
All treatments aim to restore a healthy balance in the most natural and gentle way possible, within the framework of an individualised and holistic therapy approach.
Mitochondria & Brain Health
Dr. Alina Lessenich
Fields of expertise: Orthomolecular medicine, brain health, mitochondriopathy, detoxification and longevity
After studying veterinary medicine at the University of Veterinary Medicine Hannover, Dr. Alina Lessenich obtained a PhD in neuroscience with a focus on neuropharmacology and Parkinson's research before fulfilling her lifelong dream of caring for sport horses in her own veterinary practice.
Dr. Lessenich experienced the limitations of conventional medicine firsthand with health challenges of her own. This motivated her to search for alternative healing methods and to study micronutrient medicine, mitochondrial medicine and detoxification therapies as well as new therapeutic approaches from longevity research and neuroscience.
Dr. Lessenich immersed herself in new studies, attended international conferences and seminars and collaborated with experts from various disciplines. The knowledge she gained during this time is now reflected in her work as a health mentor.
In 2020, Dr. Lessenich founded the Body-Mind-Soul Academy and has been helping people on their journey to holistic health ever since. She shares her wide-ranging knowledge in online courses, seminars and interviews. Through her work, Dr. Lessenich aims to support people in taking responsibility for their own health by offering them holistic approaches.
Dr. Lessenich developed several product lines in collaboration with Sunday Natural, including the "Long C" products to support recovery from viral diseases, the "Mito" products to promote mitochondrial health and special brain complexes to support cognitive performance and brain health. These products are based on natural ingredients and reflect her philosophy of holistic health promotion.
Vein Health
Dr. med. univ. Cornelia Musil-Domenig
Klagenfurt, Austria
Fields of expertise: General practitioner with a focus on holistic medicine and health
Dr. Musil-Domenig is a general practitioner specialising in holistic medicine and health. Since completing her studies at Karl-Franzens University, she has been involved in alternative healing methods. She is particularly fascinated by herbal medicine, acupuncture and homeopathy, which have been an integral part of her therapeutic work for over 20 years. She has a particular focus on sclerotherapy, an effective method for treating venous disorders.
The healing power of nature plays a central role in her life. She is constantly amazed by the diverse possibilities of plant-based medicine – knowledge that influences both her medical practice and her family's everyday life.
At her practice in Klagenfurt, Dr. Musil-Domenig uses holistic methods to treat vein problems, varicose veins, spider veins and a wide range of other conditions. Her areas of expertise include laboratory diagnostics, orthomolecular medicine, infusion therapies, bioidentical hormone therapy, acupuncture and homeopathy. She holds diplomas in sclerotherapy and homeopathy & acupuncture (Diploma of the Austrian Medical Chamber) as well as additional training in herbal medicine, mesotherapy and micro-immunotherapy.
Thyroid
Dr. med. Johannes-Paul Richter
Berlin, Germany
Fields of expertise: Specialist in radiology and nuclear medicine, medical physics expert
Dr. Richter has been a qualified physicist for 20 years and has been practising medicine in the fields of radiology and nuclear medicine for over 15 years.
Dr. Richter has been the medical director and owner of MVZ AnthroNUK – Berlin Thyroid Centre (www.anthronuk.de) and the nuclear medicine department at the Bundeswehr Hospital in Berlin for over six years. He combines holistic medicine with state-of-the-art diagnostic technology and the latest methods for treating thyroid disorders and diseases of various organ systems, such as radiofrequency ablation of thyroid nodules (www.123schilddrüse.de) as an alternative to conventional surgery.
As a medical physics expert, radiologist and nuclear medicine specialist, Dr. Richter is generally in high demand as a speaker at many conferences and training courses.
He has partnered with Sunday Natural for more than 10 years now and works closely with us to develop products for thyroid disorders and their accompanying symptoms.
Marcel Riffel is a trained physiotherapist and holistic health practitioner with additional training as a Building Biology Consultant. He has been running his own practice with his wife Bettina Riffel in 73760 Ostfildern Nellingen since 2000.
When he first started his own practice, his treatment focused on physiotherapy and osteopathy, but he quickly added naturopathy and complementary medicine to his repertoire.
His therapeutic focus is now on BICOM bioresonance therapy, osteopathy and cupping treatments, ozone-oxygen and infusion therapy and treatment with bioidentical hormones.
He has also started working with micronutrients since collaborating with Sunday Natural.
His slogan for Sunday products is: "Sustainable philosophy, organic product diversity at fair prices – micronutrients of the highest quality."
Marcel Riffel is currently developing a webinar for Sunday Academy about the diverse therapeutic applications of Sunday Natural's essential oils.
This will soon be available for download to all Sunday therapists.
Since 2007, Marcel Riffel has been a consultant for REGUMED and holds national and international seminars on the subject of BICOM bioresonance therapy.
Acid–Base Balance
Prof. Dr. med. univ. Harald Stossier
Klagenfurt, Austria
Fields of expertise: General medicine, orthomolecular medicine, manual medicine, nutritional medicine, functional myodiagnostics, modern Mayr medicine
Dr. Stossier has been working as a doctor in the field of complementary medicine for over 35 years, specialising in functional myodiagnostics, orthomolecular medicine and modern Mayr medicine. For 17 of those years, he was head of the medical department at the VIVAMAYR Medical Health Resort at various locations worldwide.
In addition to his work as a doctor, Prof. Stossier's current achievements include setting up a health centre in Armenia and acting as a speaker and testimonial for the continuing education series on orthomolecular medicine (www.dieplattform.info).
In addition, Prof. Stossier is the author of several books and a trainer in modern Mayr medicine and additional training for autoimmune therapists.
Women's & Men's Health / Fertility
Dr. Darja Wagner
Berlin, Germany
Fields of expertise: Molecular biology, reproductive medicine and micronutrient therapy
Dr. Darja Wagner is a biologist, fertility consultant and author of the fertility blog paleo-mama.de, which focuses on natural methods for improving fertility for women over 35. Since completing her doctoral thesis, Dr. Wagner has been conducting research in the field of adult stem cell regeneration and differentiation and the control of cell behaviour through vitamins and hormones. Her research has taken her to the University Hospital Frankfurt, the Max Planck Institute in Munich and the Institute of Biochemistry at the Free University of Berlin, amongst other places.
Dr. Wagner is the author of the best-selling book "Improving Egg Quality: Getting Pregnant Over 35".
For over 10 years, Dr. Wagner has been helping women and couples prepare their bodies for pregnancy. In her online consultations, she helps patients understand hormone data and tailor their micronutrient intake and diet to their individual needs. Together with other fertility experts, she has created a digital video course called "Baby Joy – Pimp My Eggs" on topics close to her heart.
Together with Sunday Natural and fertility specialist Dr. Reinhard Hannen, Dr. Wagner is responsible for a range of micronutrients and herbal mixtures for fertility and sexuality.
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