Nori

A type of seaweed widely used in cookery. In Japan, rice is wrapped up in sheets of nori to make sushi. In Wales this seaweed is known as laver, and is mixed with oatmeal and fried to make laverbread.

Nucleic acids

Two complex compounds known as DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) which contain purines, pyrimidines, sugars and phosphoric acid, and are involved in the determination and transmission of genetic characteristics.

Molecules of DNA contain instructions coded into their molecular structure for the synthesis of cell proteins, ensuring that cells will reproduce correctly. Genes are those parts of a DNA molecule which contain the information determining how proteins will be formed. One DNA molecule contains many genes.

The transfer of information from DNA in the cell nucleus to the site of protein synthesis is carried out by RNA. RNA synthesis is in turn determined by DNA.

One of the richest sources of nucleic acids in animals is the thymus gland. 12 per cent of dried yeast consists of nucleic acids.

It is widely believed that nucleic acids found in the diet or taken as dietary supplements are broken down in the intestines and that their components are not available for the synthesis of RNA and DNA in the human body.

Nutrient density

According to conventional nutritionists, foods with a nutrient density of less than one are poor sources of this nutrient and a value of more than one is satisfactory. Nutrient-poor foods are often described as 'empty-calorie' foods - those consisting of mainly fat, sugar and refined starch. Nutrient-dense foods are usually those described as 'nutritious' in ordinary terminology: wholefoods, fruit, vegetables, fish, nuts etc. However scientists use the term 'nutritious' to refer to all foods, even those with a very poor content of vitamins and minerals. This is because sugar, fat and refined starch are also nutrients.

Nutrients

Components of the diet which are essential to life and health. Nutrients are classified as macronutrients (carbohydrates, fat and protein, dietary fibre and essential fatty acids) and micronutrients (vitamins, minerals and trace elements).