Biofortification is the process by which the nutrient density of food crops is increased through conventional plant breeding, and/or improved agronomic practices and/or modern biotechnology without sacrificing any characteristic that is preferred by consumers or most importantly to farmers (1). It is recognized as a nutrition-sensitive-agriculture intervention that can reduce vitamin and mineral deficiency (2). Iron-biofortification of beans, cowpea and pearl millet, zinc-biofortification of maize, rice, and wheat, and pro-vitamin A carotenoid-biofortification of cassava, maize, rice, and sweet potato are currently underway and at different stages of development (3, 4).

The biological mechanism for biofortified crops improving nutritional status is simple: biofortified crops are more nutrient-dense than non-biofortified varieties. Therefore, assuming similar micronutrient bioavailability (5) and retention (6) after cooking or processing and storage, persons will consume (7) and absorb (8) more micronutrients from eating biofortified crops than from the same amount of non-biofortified crops. In populations with a diet limited in these micronutrients, the consumption of biofortified staple crops can improve micronutrient intake.

Results are promising for iron-biofortified crops, as partially iron-biofortified rice has improved the iron stores of reproductive-age women in the Philippines (9), iron-biofortified pearl millet has increased the iron stores and reversed iron deficiency in school children in India (10) and iron-biofortified beans have improved the iron stores in women in Rwanda (11). Evidence for pro-vitamin A rich crops is more difficult to interpret as pro-vitamin A carotenoids are first absorbed in the body and then converted into the active form of vitamin A according to the body’s need for the nutrient. There is broad evidence (both efficacy and effectiveness) that provitamin A biofortified orange sweet potato reduces vitamin A deficiency in children in Mozambique (12,13), Uganda (14) and in South Africa (15), with an additional study in Bangladesh showing increased pro-vitamin A concentration but not vitamin A status (16). A study with pro-vitamin A biofortified yellow cassava in Kenya showed an increase in vitamin A status and a greater increment in pro-vitamin A concentrations in school children (17). For biofortified orange maize the results are ambiguous because the laboratory tests used display different degrees of sensitivity and accuracy. Therefore, the two studies conducted in independent population groups in Zambia showed different results: pro-vitamin A concentrations increased in both (18, 19); the active form of vitamin A did not increase in either study partly because vitamin A deficiency was initially low; and only the study that used a more sensitive test for vitamin A status proved increased vitamin A stores in the school children who consumed the biofortified maize (18). Moreover, the study that did not improve the levels of vitamin A in the blood of the children found a positive effect in visual adaptation to twilight conditions (dusk/dawn) of ambient light illumination, which is a functional indicator of improved vitamin A status in the body (20). While more trials with biofortified crops with higher provitamin A densities in other populations are being conducted, evidence is accumulating in favour of biofortified crops being able to improve the micronutrient status of different populations.

There are two main behavioural issues related to biofortification: one for the farmer and one for the consumer. Farmers are interested in planting new varieties that are agronomically superior to the current varieties they plant, for example cultivars that are more drought resistant, have more yield or less susceptibility to diseases (21). Crops with improved micronutrient concentration with the same or poorer agronomic performance will not be accepted and adopted by farmers (3, 4). Therefore, biofortified varieties must be agronomically equivalent or preferably superior to the less nutrient dense market and traditional varieties with which they will compete.

Provitamin A carotenoids impart colour to foods; therefore, biofortification with these carotenoids will change the colour of crops. Thus, motivating consumers to change their buying and eating habits from white- to orange-fleshed maize, cassava, or sweet potato can be a challenge (22). However, other sensory properties like taste are also affected by improved pro-vitamin A concentrations and can result in an overall better rating, as was shown with school children in Kenya who particularly liked the taste and colour of the yellow cassava (23). Furthermore, acceptability has been shown to be improved by providing information about the health benefits of the biofortified crop to the consumer (24).

Biofortified crops are often assumed to be transgenic or genetically modified crops. While the thrust of biofortification activities through international projects (3,4) focused on the production of nutritionally enhanced crops through conventional breeding, increasingly, more efforts are using genetic modification to add value to staple and non-staple crops. Therefore, consumer education and a functional regulatory framework to assess the benefits and risks of genetically modified crops will be needed to increase consumer confidence in biofortified crops developed through genetic modification long before these products reach the local markets.

The long-term nature of developing biofortified crops and its relation to agriculture (and not to health as more well-known strategies such as industrial micronutrient fortification and supplementation), mean that most programme activities have traditionally centred on speeding up the process of selective plant breeding. However, this is changing with the use of cheaper and more efficient laboratory tests to identify the promising varieties and because biofortification is being recognized as a sustainable strategy to be included in various country programmes on food and nutrition security (i.e. Colombia, Kenya, Nicaragua, Nigeria, Panama). Additionally, the focus is shifting towards improving seed systems, demand and supply creation, diffusion, and marketing as part of the biofortification package (3, 4, 24). Efforts are underway around the world to create demand for high yielding biofortified crops and to develop healthy food products from biofortified crops so that non-farmers and urban consumers can also benefit.

References

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Conflict of interest statements were collected from all named authors and no conflicts were identified.