Template:Chapter 9.3

9.3 - Reducing vitamin A deficiencies by eating colorful foods and leafy greens

Nick Moroz, University of Guelph, Canada

Suggested citation for this chapter.

Moroz,N(2022) Human nutrition, The Encyclopedia for Small Scale Farmers. Editor, M.N. Raizada, University of Guelph, Canada. http://www.farmpedia.org

Health Issues Resulting from Vitamin A Deficiencies

In 2013, 29 percent of children aged 6 to 59 months were vitamin A deficient, nearly one in three (UNICEF, 2016). VAD is caused by a diet that is insufficient in vitamin A, a necessary micronutrient that is needed to maintain the body’s physiological functions, leading to adverse health affects (WHO, 2009). A diet that is chronically lacking in vitamin A can lead to low tissue concentrations of vitamin A and the failure of normal human development, metabolism, and a properly functioning immune system. (WHO, 2009; NIH, 2016). Vitamin A is needed in sustained small amounts or it can be administered in high does supplements to those in critical states, if needed (UNICEF, 2007). However, insufficient levels the vitamin A in periods of life with high metabolic demands (infancy, childhood, and pregnancy) can greatly impair cell functioning and vision processes (WHO, 2009). This is why VAD is the leading cause of preventable blindness in children, as well as a major contributor to childhood mortality under 5 years of age (UNICEF, 2007). Chronic VAD can lead to conditions such as childhood blindness, xeropthalmia, anaemia, and increased susceptibility to infectious diseases due to weakened immunity (WHO, 2009).

Vitamin A is also necessary for the healthy development of the fetus during pregnancy, as well as for the health of the mother, who requires the nutrient in excess to sustain fetus growth (WHO, 2011; NIH, 2016). Unfortunately, about 19 million pregnant women are impacted by VAD, and the majority of these women are from Sub-Saharan Africa and South-Asia (UNICEF, 2007). The WHO also estimates that 9.8 million pregnant women have xerophthalmia, the most common indicator of VAD, as a result of VAD (NIH, 2016). Human immunodeficiency virus (HIV) affects pregnant women and children through the mother-to-child transmission of the disease, and is a risk factor for VAD (WHO, 2011). Mother-to-child HIV transmission is the primary route for child HIV, with 1000 new cases occurring worldwide each day (WHO, 2011). Thus, HIV positive women should be included in interventions that aim to address VAD (WHO, 2011). It must be noted that vitamin A supplementation is not a WHO-recommended intervention to prevent mother-to-child transmission of HIV – but rather that HIV and pregnancy are risk factors for VAD (WHO, 2011). Because the greatest prevalence and severity of VAD complications are in young children and pregnant women, these groups carry the greatest burden of disease and require specific attention in alleviating VAD in South-Asia, Sub-Saharan Africa, and beyond.

Absorption of Vitamin A

Understanding how different forms of vitamin A impact their absorbance into the body is of great importance in order to address VAD. Two forms of vitamin A meet dietary needs: preformed vitamin A (retinol) and pro-vitamin carotenoid (i.e. β-carotene) sources (FAO/WHO, 2002). Preformed Vitamin A is found almost exclusively in the fat-storage cells of animal foods, such as the milk, beef, eggs, and fish (FAO/WHO, 2002). The pro-vitamin carotenoid form is found in vegetables and fruits, but this form is held in more complex lipid matrix structures within these plants cells, impacting the bioavailability of this form (FAO/WHO, 2002). The form of vitamin A great influences uptake: about 90 percent of ingested preformed vitamin A is absorbed into human metabolism, whereas pro-vitamin A carotenoid absorption greatly depends on the plant source and the amount of fats consumed in the person’s diet (FAO/WHO, 2002). The amount of vitamin A obtained from plant sources depends on the conversion factor of the pro-vitamin A carotenoid plant source, and this reflects the bioefficacy of the organism’s carotenoids (de Pee & Bloem, 2007). Vitamin A is a fat-soluble compound, meaning that fats assist in the uptake of both forms of vitamin A into human metabolism (FAO/WHO, 2002). It is important to note that a diet of less than 5-10 grams of fat daily can greatly reduce the absorption of these metabolites (FAO/WHO, 2002). Increasing the amounts of fats consumed in one’s diet is likely to increase vitamin A uptake. However, this is not the only hurdle. As vitamin A is fat-soluble, its absorption is poor when diseases that prevent healthy fat uptake, such as chronic diarrhea, impact peoples’ livelihoods (Merck Manuel, 2016; NIH, 2016). Chronic VAD frequently coexists with infectious diseases, leading to less vitamin A absorption into the body (WHO, 2009). Indeed, populations that acquire vitamin A from pro-vitamin carotenoid sources and lack adequate fat intake face a very high risk of VAD (FAO/WHO, 2002).

It is important to understand the different forms of vitamin A provide alternate levels of Retinol Equivalence (RE), the amount of compound that can be converted into preformed vitamin A (retinol) and absorbed adequately (FAO/WHO, 2002, NIH). A joint FAO/WHO Expert Group in 1967 introduced the concept of Retinol Equivalence (RE) and showed the relationship among the different forms of vitamin A, shown in table 1.1 (FAO/WHO, 2002). This table outlines the concept of the retinol equivalence (RE), with one RE being equal to 1 µg retinol, as a convention for comparing food sources of vitamin A. What can be seen in this table is that the absorption of carotenoids and their bioconversion to vitamin A (retinol) is less efficient than preformed vitamin A, which is already supplied in an adequate form (FAO/WHO, 2002). These conversion factors help to understand that bioefficacy of carotenoids and why preformed vitamin A is so advantageous.

Access to High Levels of Vitamin A through Orange-Yellow Fruits and Vegetables

In regions endemic for VAD, such as South-Asia and sub-Saharan Africa, shortages of vitamin A-rich foods correlates with the highest incidences of childhood infection (FAO/WHO, 2002). The prevalence of VAD in South Asian and Sub-Saharan African countries is the result of a number of factors, including insufficient access to proper dietary nutrients, economic constraints, and poor absorption of vitamin A (Akhtar et al., 2013). The situation is further complicated by low sources of preformed vitamin A (FAO/WHO, 2002).

In South Asia and sub-Saharan Africa where VAD is most prevalent, vegetable sources contribute up to 80% or more of the available supply of retinol equivalents (FAO/WHO, 2002). Seasonal food availability can result in changes and also scarcity of plant sources high in pro-vitamin A carotenoids and this availability influence the prevalence of VAD (FAO/WHO, 2002). For example, one should consider the scarcity of orange fruits in hot arid months in regions endemic for VAD (FAO/WHO, 2002). Thus, there is a need to balance vitamin A availability and need throughout the year in countries that experience dry seasons and limited resources. In order to address VAD using accessible interventions, it is important to use the materials that are readily available to the public. Table 1.2 outlines some household interventions to help reduce VAD (de Pee & Bloem, 2007).

Foods that include a rich source of preformed vitamin A, such as fish, beef, and milk products, are sometimes not readily accessible in the regions endemic with VAD. Pro-vitamin A carotenoids are sometimes more accessible in these regions. They are found in yellow vegetables, orange-yellow non-citrus fruits, and leafy green vegetables (FAO/WHO, 2002). These orange-yellow vegetables and fruits can sometimes be more easily accessible and supported in regions endemic with VAD. A comprehensive list of orange-yellow products available in endemic areas can be found in table 1.3, along with their corresponding IU values. Red palm oil is also especially rich in pro-vitamin A carotenoids (FAO/WHO, 2002). From these results it can be seen that carefully cooking certain items such as sweet potato and carrots increases the IU of these items. This shows how cooking (but not too much heating) may break down plant matrixes and increase uptake of carotenoids into human metabolism. Indigenous plants in Africa and South Asia also produce many fruits, vegetables and leafy greens with many micronutrients, often including pro-vitamin A carotenoids (FAO/WHO, 2002).

Access to Vitamin A Through Leafy Greens

Pro-vitamin A carotenoids can also be found in green leafy vegetables, such as spinach, amaranth, and various other sources (FAO/WHO, 2002). The majority of the literature supports the consumption of eating dark green leafy vegetables to manage and prevent VAD (Müller & Krawinkel, 2005). A comprehensive list of pro-vitamin A carotenoid-rich leafy greens is seen in table 1.4, along with their corresponding IU values. It is important to recognize that although it may appear as though the leafy greens are very high in Vitamin A IU, 100 grams of leafy greens requires a lot of leafs, whereas for fruits and vegetables 100 grams may be one large carrot or mango. From these results it can be seen that cooking certain items such as Spinach, Collards, and mustard greens increases the IU of these items. Again, this shows how careful cooking may break down the matrixes and increase uptake of carotenoids into human metabolism. However, overcooking can damage the vitamin A content of the meal (de Pee & Bloem, 2007).

Many of these varieties of leafy greens are important sources of micronutrients to sub-Saharan Africa. For example, leafy greens such as Amaranth are eaten across the continent (NRC, 2006). To visualize why leafy greens would have a high content of carotenoids that often give an orange or red color, one can imagine leaves during the fall season in the northern hemisphere, as these leaves turn from green to orange-yellow pigments before falling to the ground. The potential of these leafy green products to aid in alleviating micronutrient deficiencies merits greater scientific attention

Short Term and Long Term Interventions to Address VAD

Children need additional vitamin A because of high metabolic demands during growth, especially between 6-59 months old (UNICEF, 2016). VAD is a major contributor to child mortality under five in many high priority countries (UNICEF, 2007). To compensate for these needs in regions lacking in reliable vitamin A-rich food sources throughout the year, three specific interventions to improving vitamin A status are possible. These interventions are supplementation, fortification, and homestead food production/dietary diversification.

1. Supplementation:

High supplement coverage, defined by the WHO’s UNICEF supplement project, is the administration of two high dose vitamin A supplements, provide in small capsules, spread over 4-6 months (UNICEF, 2007). This coverage is the principle strategy to eliminate VAD because of its feasibility as well as its ability to ensure adequate biological supply of vitamin A. This coverage can simultaneously eliminate VAD in endemic regions while reducing childhood mortality under five by approximately 23 percent because of enhanced resistance to disease (UNICEF, 2016). It can also reduce mortality in babies younger than 6 months by 21 percent (Bhutta, Darmstadt, Hasan, Haws, 2005; Bhutta et al., 2008). Currently, the delivery of these supplements occurs through various national immunization or health days as well as routine health services. However, there are concerns that integrating supplementation into routine health services has not yet provided full coverage and so outreach initiatives must continue, such as delivery of supplements through outreach campaigns (UNICEF, 2007). Finally, the WHO recommends immediate supplementation for women in the post-partum period, and this should be coupled with the child’s first immunization (UNICEF, 2007).

2. Food fortification:

Two high-dose supplementations of vitamin A capsules is the principle strategy to fight VAD and it is the most effective (UNICEF, 2007). However, food-based approaches, including food fortification and dietary diversification to eat foods rich in vitamin A are increasingly feasible options (UNICEF, 2007). When foods are fortified or bio-fortified to address micronutrient deficiencies as public health initiatives, foods such as sugar, cereals, fats, and oils are enriched with certain vitamins or minerals (FAO/WHO, 2002). Food fortification of local staple crops in regions is the especially beneficial. Food fortification requires a significant amount of technological capital, distribution, and political commitment to reach VAD-affected areas and to be effective over the long time span needed to address micronutrient deficiencies (UNICEF, 2007).

3. Homestead food production/dietary diversification:

In order to have a sustained source of vitamin A in endemic regions for VAD, sustainable community-based solutions are essential. An example of dietary diversification, Homestead food production (HFP) - increasing vitamin A-rich cultivar production and consumption - is generally successful in increasing vitamin A intake in regions with limited access to dietary diversity (de Pee & Bloem, 2007). Introducing vitamin A-rich cultivars and improving breeds through the interventions outlined in this book will create lasting solutions for communities, especially those that are the most remote (de Pee & Bloem, 2007). Dietary diversification is especially successful when coupled with nutrition education (de Pee & Bloem, 2007). Although progress has been made, these three major interventions have not solved the problem in priority countries, such as South Asian countries, because of poor governmental support and supervision (Akhtar et al., 2013). Impacts can be maximized when all of these interventions are supported together.

Cultural Relativity

Culture plays an important role in the foods consumed in certain regions. Good source of vitamin A, including the orange-yellow fruits and vegetables, can at times be restricted due to culturally related factors, such as food taboos (FAO/WHO, 2002). In many traditional cultures, certain foods are prescribed during illness and childbirth, influencing the nutrition that individuals experience at unique times (FAO/WHO, 2002). Furthermore, culture impacts foods freely consumed by children and pregnant women (FAO/WHO, 2002).

An example of how cultural factors can impact initiatives that reduce VAD is the case of Golden Rice (GR). GR is genetically modified rice that is concentrated with pro-vitamin A carotenoids as a public health initiative to address VAD (Al-Babili & Beyer 2005). The name GR comes from the yellow colour of the grains visible during milling and resulting from the substantial carotenoid concentration (Al-Babili & Beyer 2005). However, yellow rice is associated with disease in rice in some countries, leading some farmers to refuse to plant these cultivars. Although GR and its overall impacts are still being researched and considered, cultural acceptance of interventions must be considered (Al-Babili & Beyer 2005).

References

1. Al-Babili, S., & Beyer, P. (2005). Golden Rice–five years on the road–five years to go?. Trends in plant science, 10(12), 565-573.

2. Akhtar, S., Ahmed, A., Randhawa, M. A., Atukorala, S., Arlappa, N., Ismail, T., & Ali, Z. (2013). Prevalence of vitamin A deficiency in South Asia: causes, outcomes, and possible remedies. Journal of Health, Population and Nutrition, 31(4), 413-423.

3. Bhutta, Z. A., Darmstadt, G. L., Hasan, B. S., & Haws, R. A. (2005). Community-based interventions for improving perinatal and neonatal health outcomes in developing countries: a review of the evidence. Pediatrics, 115(Supplement 2), 519-617.

4. Bhutta, Z. A., Ahmed, T., Black, R. E., Cousens, S., Dewey, K., Giugliani, E., ... & Shekar, M. (2008). What works? Interventions for maternal and child undernutrition and survival. The lancet, 371(9610), 417-440.

5. de Pee, S., & Bloem, W. (2007). The bioavailability of (pro) vitamin A carotenoids and maximizing the contribution of homestead food production to combating vitamin A deficiency. International Journal for Vitamin and Nutrition Research, 77(3), 182-192.

6. de Pee, S., West, C. E., Hautvast, J. G., & Karyadi, D. (1995). Lack of improvement in vitamin A status with increased consumption of dark-green leafy vegetables. The Lancet, 346(8967), 75-81.

7. FAO/WHO, Joint (2002). Human vitamin and mineral requirements. Chapter 7. Rome, Food and Agriculture Organization of the United Nations and World Health Organization.

8. Merck Manuel, Professional Version. (2016). Vitamin A (Retinol), Nutritional Disorders. Merck & Co., Inc. Retrieved from: http://www.merckmanuals.com/en-ca/professional/nutritional-disorders/vitamin-deficiency,-dependency,-and-toxicity/vitamin-a

9. Müller, O., & Krawinkel, M. (2005). Malnutrition and health in developing countries. Canadian Medical Association Journal, 173(3), 279-286.

10. NIH, National Institute of Health. (2016 – last update). Vitamin A Fact Sheet for Health Professionals. NIH, Office of Dietary Supplements. Retrieved from: https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/

11. NRC, National Research Council. (2006). Lost Crops of Africa: Volume II: Vegetables. National Academy of Sciences. Washington, DC, USA.

12. UNICEF. (2016). Vitamin A supplementation: a statistical snapshot, February 2016. New York, UNICEF.

13. UNICEF. (2007). Vitamin A supplementation: a decade of progress. New York, UNICEF.

14. WHO. (2009). Global prevalence of vitamin A deficiency in populations at risk 1995–2005. WHO Global Database on Vitamin A Deficiency. Geneva, World Health Organization.

15. WHO. (2011) Guideline: Vitamin A supplementation in pregnancy for reducing the risk of mother-to-child transmission of HIV. Geneva, World Health Organization.