The nutritional importance of plants

Plants are the staple food for the vast majority of the world’s population. It is known that many staple plant foods are deficient in essential nutrients and, consequently, malnutrition is widespread. It has been estimated that over 100 million children worldwide are vitamin A deficient and improving the vitamin A content of their food could prevent as many as two million deaths annually in young children [4]. This is apart from the deficiencies in iodine intake, resulting in goitre, and in iron-deficient an aemia which are estimated to affect millions in the developing world. There is also an important need to improve the amino acid content of legume proteins that are deficient in essential sulphur amino acids. Nutritional deficiencies can lead to a reduction in immune responsiveness, rather than a specific attributable disorder, making it difficult clearly to establish how many people are suffering from malnutrition [5].

In the developed world all public health authorities are urging consumers to consume more plant-based foods as part of a healthy diet. There is a significant body of evidence to suggest that the traditional Mediterranean diet, rich in plant foods, reduces the risk of many age-related diseases. Epidemiological studies show a strong and consistent inverse relationship between fruit and vegetable intake and the risk of cardiovascular diseases and some cancers [2]. An explosion of interest in trying to define what are the factors in fruit and vegetables which might be responsible for these observations has not yet led to a clear set of explanations although many theories abound.

Plants contain 17 mineral nutrients, 13 vitamins and numerous phytochemicals that have been shown to have potentially beneficial effects on health especially against the initiation or progression of degenerative diseases. Almost all human nutrients can be obtained from plant foods, the exceptions are vitamins B₁₂ and D. However, the adequacy of a plant diet in delivering a health benefit from a specific component will depend on the amount ingested, and its bioavailability. Many beneficial plant compounds that are associated with the plant cell wall are not easily bioavailable. Any way in which overall levels can be increased will help overcome this difficulty.