The way that crops are processed, stored, and cooked affects the nutritional value they provide when eaten.

A new analysis shows biofortified crops add more micronutrients into diets than non-biofortified crops, even when accounting for the nutrients that are lost after harvesting due to crop handling, storage, processing, and cooking. Results vary by crop variety and processing method.

The systematic review, published today in Nature Food, analyzed 67 publications to identify best practices relevant for households, national regulatory bodies, and value chain actors for ways to prepare biofortified crops and products for maximal nutrition impact.

Improving dietary quality is a globally urgent issue. One in two children and two in three women worldwide are affected by preventable micronutrient deficiencies. Low- and middle-income countries (LMICs) suffer disproportionately, due in part to their reliance on traditional staple food crops that are energy-dense but low in micronutrients essential for good health and development.

Biofortification breeds increased amounts of micronutrients into the staple food crops most widely grown and eaten by smallholder famers in LMICs—and is proven to reduce micronutrient deficiencies. For many smallholder populations, diverse and nutrient-rich foods like fruits and vegetables and animal-based products are often inaccessible.

Nutrients can be lost from crops post-harvest because vitamins like vitamin A break down when exposed to heat from cooking, sun when drying, or oxygen during storage, for example. Minerals like zinc and iron can be unintentionally stripped out of crops like rice or maize when refined or milled, as these processes remove the most nutritious parts of the grain.

The evidence in the paper provides households with guidance to improve their dietary quality, including:

• Vitamin A orange sweet potato should be eaten soon after harvest or solar dried unpeeled;
• Vitamin A cassava should be baked or boiled whole then peeled, which will provide more vitamin A than when eaten as a refined fermented paste such as chikwangue or fufu;
• Vitamin A maize should either be eaten soon after harvest, boiled, or roasted in its husk. If being stored, use of aluminum packaging is ideal;
• Iron pearl millet’s iron and zinc contents are relatively unaffected by cooking and preparations like parboiling, oven-drying, or storage;
• Zinc rice and zinc wheat should be eaten as whole grains. Polishing to white rice or milling to refined white flour removes the nutritious, zinc- and iron-containing outer layers and germ of the grains.

National regulatory bodies and technical institutions should encourage manufacturers of processed biofortified food products to provide instructions to consumers on how to prepare their product to retain maximum micronutrient content.

Across the biofortification value chain, actors should choose varieties of crops that contain a high baseline micronutrient level and are amenable to their processing and storage techniques to prioritize the nutritional value of products that reach vulnerable consumers.

The systematic review includes an online, interactive dashboard that offers an at-a-glance view of how different processing methods affect the micronutrient content of biofortified crop varieties, so value chain actors can take informed decisions about their businesses.

By providing evidence to smallholder farmers, value chain actors, and national regulatory bodies on ways to handle, store, process, and cook biofortified crops in optimal ways, nutrient-enriched crops can contribute meaningfully to the urgent need to improve dietary quality.

Learn more:

Samantha L Huey et al. A systematic review of the impacts of post-harvest handling on provitamin A, iron and zinc retention in seven biofortified crops. Nature Food. Nov 9, 2023. DOI: 10.1038/s43016-023-00874-y

Cornell Human Ecology and Center for Precision Nutrition and Health Dashboard for Micronutrient Retention of Biofortified Foods and Food Products.

Center for Precision Nutrition and Health, directed by Saurabh Mehta