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 doctors and therapists 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
Excretory System
Heart Health
Immune System
Men's Health
Mitos & Energy
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

Webseite: www.dermallegra.de/aerzte

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.

Hormones

Dr. Katharina Burkhardt

Graz, Austria

Fields of expertise: Hormone scientist, PhD in Public Health, holistic health practitioner for psychotherapy

Website: www.hormon-netzwerk.at

Dr. Katharina Maria Burkhardt is a hormone scientist (research and development), lecturer, supervisor and author. She holds a master's degree and a PhD in public health with a focus on human hormones and is also a holistic health practitioner for psychotherapy. With more than 20 years of experience in medical practice, she is particularly dedicated to the research, application and further development of bioidentical hormones.

As part of her academic career, Dr. Burkhardt first conducted a study on hormones and their effect on physical and mental well-being (master's thesis 2018/2019) and expanded on these findings in her dissertation (2020/2021), which focused on in-depth case studies of bioidentical hormones. Currently (2022–2025), she is supervising a clinical study and a preliminary study on measurement methods (serum, saliva LCMS) for transdermal hormone delivery.

In addition to her research, Dr. Burkhardt is heavily involved in the development and design of micronutrient food supplements (including Sunday Natural and Vita Libra), hormone cosmetics and essence complexes. She founded and heads the Network for Bioidentical Hormones (www.hormon-netzwerk.at) and regularly gives lectures and seminars on the topic of human-identical hormones in German-speaking countries (further information on her website).

In addition, Dr. Burkhardt designed and leads the three-year specialist training programme for doctors in integrative bioidentical hormone therapy. Here, she shares her expertise with professionals whose aim it is to gain comprehensive qualifications in the field of hormone medicine.

Heart Health

Christian W. Engelbert M. A.

Berlin, Germany

Field of expertise: Integrative medicine

Website: www.integrative-medizin-beelitz.de

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.

Heart Health

Dr. med. univ. Manuela Hanke

Vienna, Austria

Fields of expertise: Internal medicine, cardiology, nutritional medicine and orthomolecular medicine

Website: www.kardiologie-hanke.wien

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 3 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: Gynäkologische Endokrinologie und Reproduktionsmedizin

Website: www.kinderwunschzentrum.de

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.

Heart Health

Dr. med. Ralf Heinrich

Berlin, Germany

Field of expertise: Integrative medicine

Website: www.theraklinik.de

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

Website: www.drlessenich.com

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

Website: vitalpraxis-musil.at

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

Webseit: www.anthronuk.de

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 6 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.

Bladder

Marcel Riffel

Ostfildern, Germany

Field of expertise: Complementary medicine

Website: www.riffels.net, www.riffel-dienstleistungen.de

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

Website: www.intestinal-health.com

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

Website: www.paleo-mama.de

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.