This is an excerpt of the GDI Study "European Food Trends Report". The study is available for download.

The spectrum of nutritional teachings is enormous. On the one hand, there is nutrition science, which is located between the fields of medicine and biochemistry and deals with the principles, composition and effects of nutrition on humans. Between food and pharmaceuticals, there are also nutrition-based disease therapies and functional foods to be found. Examples of this are probiotic yoghurts or fruit juices enriched with vitamins.

On the opposite side, the teachings are based less on scientific knowledge and more on experience or tradition. They provide guidance on “proper” nutrition in line with religious or philosophical systems. Examples include the Bircher-Benner diet, the Paleo diet and macrobiotics. In between are ancient teachings such as Ayurveda or traditional Chinese medicine (TCM), along with more recent concepts such as superfoods or light products. While these nutritional teachings may have a scientific background, they do not provide sufficient evidence – from the Western scientific standpoint – to be considered “true”.

The graph from the "European Food Trends Report" provides a rough overview of the current nutritional teachings, arranged according to their evidence:
 
Nutrition science
A natural science concerned with the principles, composition and effects of nutrition.

Functional food
Foods that are enriched with additional ingredients and promoted as having a positive effect on health.

Traditional Chinese medicine (TCM)
A style of medicine developed in China over a period of more than 2000 years. TCM is considered an alternative or complementary approach to medicine.

Ayurveda
A traditional Indian healing art. Ayurveda is not a single therapeutic method, but rather a holistic system within the realm of traditional alternative medicine.

Free-from-products
Foods containing no lactose or gluten. For people with food intolerances.

Light products
Foodstuffs, drinks and tobacco with a reduced content of ingredients regarded as unhealthy, such as fat, sugar, ethanol or nicotine.

Organic food
Eschewal of conventionally produced foods in favour of bio-products from organic farming. Positive effects on health have not yet been demonstrated.

Superfood
Marketing term for foodstuffs with alleged health benefits. In some cases, the positive effects on health are based on scientifically proven associations.

Five elements cuisine
The transfer of parts of traditional Chinese medicine to the customary diet in the Western world. It is based on the theory of the five elements: wood, fire, earth, metal and water. However, it differs significantly from dietetics according to the principles of TCM.

Paleo diet
A form of nutrition based on the presumed diet of the Paleolithic period. The Stone Age diet consists exclusively of foodstuffs that are assumed to have been available as early as the Paleolithic – with no milk products, no cereal grains, no processed foods.

Macrobiotics
An approach to diet and lifestyle founded by Japanese author Georges Ohsawa and based on Taoist teachings and Asian traditions. Macrobiotics contradicts accepted scientific and medical knowledge. Its claim to be able to heal all diseases is considered to be refuted.

Bircher-Benner diet
Max Bircher-Benner, a Swiss doctor and nutrition reformer, developed Bircher muesli and is considered a pioneer in the area of wholefoods. Even as it was being developed, Bircher-Benner’s nutritional doctrine was met with scepticism and rejection among doctors and scientists, as it contradicted biochemical knowledge.

Food combining
A form of nutrition developed by William Howard Hay at the beginning of the 20th century in which protein-rich foods and carbohydrate-rich foods are not eaten together at the same meal. The theory underlying is considered “scientifically untenable”.

Humoral pathology
A medical doctrine that was first developed in the Corpus Hippocraticum around 400 BC as an explanation of general bodily functions and a conception of disease. Until the advent of cellular pathology in the 19th century, it remained the dominant approach to medicine.
    
For further explanations consult the GDI Study “European Food Trends Report“. It is available for download.