Different foods and food groups are good sources for various macro- and micronutrients, so a diverse diet best ensures nutrient adequacy. The principle of dietary diversity is embedded in evidence-based healthy diet patterns, such as the Mediterranean diet and the “DASH” diet (Dietary Approaches to Stop Hypertension), and is affirmed in all national food-based dietary guidelines. The World Health Organization (WHO) notes that a healthy diet contains fruits, vegetables, legumes, nuts and whole grains.

A diverse diet is most likely to meet both known and as yet unknown needs for human health. In addition to our knowledge of protein, essential fatty acid, vitamin and mineral requirements, new knowledge about health effects of a wider range of bioactive compounds continues to grow. Considering plant foods alone, it is currently estimated that there are approximately 100,000 bioactive phytochemicals and that “observed health effects associated with vegetable, fruit, berry, and whole grain consumption can likely be explained by the combined action of many different phytochemicals and other nutrients” (Nordic Nutrition Recommendations 2012. Copenhagen: Nordic Council of Ministers).