Provitamin A Carotenoids, Tocopherols, Ascorbic Acid and Minerals in Indigenous Leafy Vegetables from Tanzania

Prospective Role of Indigenous Leafy Vegetables as Functional Food Ingredients

Indigenous leafy vegetables (ILVs) play a pivotal role in sustaining the lives of many people of low socio-economic status who reside in rural areas of most developing countries. Such ILVs contribute to food security since they withstand harsher weather and soil conditions than their commercial counterparts and supply important nutrients such as dietary fibre, vitamins and minerals. Furthermore, ILVs contain bioactive components such as phenolic compounds, flavonoids, dietary fibre, carotene content and vitamin C that confer health benefits on consumers. Several studies have demonstrated that regular and adequate consumption of vegetables reduces risks of chronic conditions such as diabetes, cancer, metabolic disorders such as obesity in children and adults, as well as cardiovascular disease. However, consumption of ILVs is very low globally as they are associated with unbalanced and poor diets, with being food for the poor and with possibly containing toxic heavy metals. Therefore, this paper reviews the role of ILVs as food security crops, the biodiversity of ILVs, the effects of processing on the bioactivity of ILVs, consumer acceptability of food derived from ILVs, potential toxicity of some ILVs and the potential role ILVs play in the future of eating.

Vitamin E and carotenoid profiles in leaves, stems, petioles and flowers of stinging nettle (Urtica leptophylla Kunth) from Costa Rica

BACKGROUND

Local leafy vegetables are gaining attention as affordable sources of micronutrients, including vitamins, pro-vitamin carotenoids and other bioactive compounds. Stinging nettles (Urtica spp.) are used as source of fibers, herbal medicine and food. However, despite the relatively wide geographical spread of Urtica leptophylla on the American continent, little is known about its content of vitamin E congeners and carotenoids. We therefore investigated the particular nutritional potential of different plant structures of wild Costa Rican U. leptophylla by focusing on their vitamin E and carotenoid profiles.

RESULTS

Young, mature and herbivore-damaged leaves, flowers, stems and petioles were collected and freeze-dried. Vitamin E and carotenoids were determined by high-performance liquid chromatography after liquid/liquid extraction with hexane. α-Tocopherol was the major vitamin E congener in all structures. Flowers had a high content of γ-tocopherol. Herbivore-damaged leaves had higher contents of vitamin E than undamaged leaves. Lutein was the major and β-carotene the second most abundant carotenoid in U. leptophylla. No differences in carotenoid profiles were observed between damaged and undamaged leaves.

CONCLUSION

The leaves of U. leptophylla had the highest nutritional value of all analyzed structures; therefore, they might represent a potential source of α-tocopherol, lutein and β-carotene. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Leaf elemental composition analysis in spider plant [Gynandropsis gynandra L. (Briq.)] differentiates three nutritional groups

Understanding the genetic variability within a plant species is paramount in implementing a successful breeding program. Spider plant (Gynandropsis gynandra) is an orphan leafy vegetable and an extraordinary source of vitamins, secondary metabolites and minerals, representing an important resource for combatting malnutrition. However, an evaluation of the leaf elemental composition, using a worldwide germplasm collection to inform breeding programs and the species valorization in human nutrition is still lacking. The present study aimed to profile the leaf elemental composition of G. gynandra and depict any potential geographical signature using a collection of 70 advanced lines derived from accessions originating from Asia and Eastern, Southern and West Africa. The collection was grown in a greenhouse using a 9 × 8 alpha lattice design with two replications in 2020 and 2021. Inductively coupled plasma-optical emission spectrometry was used to profile nine minerals contents. A significant difference (p < 0.05) was observed among the lines for all nine minerals. Microelements such as iron, zinc, copper and manganese contents ranged from 12.59-430.72, 16.98-166.58, 19.04-955.71, 5.39-25.10 mg kg-1 dry weight, respectively, while the concentrations of macroelements such as potassium, calcium, phosphorus and magnesium varied in the ranges of 9992.27-49854.23, 8252.80-33681.21, 3633.55-14216.16, 2068.03-12475.60 mg kg-1 dry weight, respectively. Significant and positive correlations were observed between iron and zinc and calcium and magnesium. Zinc, calcium, phosphorus, copper, magnesium, and manganese represented landmark elements in the genotypes. Eastern and Southern African genotypes were clustered together in group 1 with higher phosphorus, copper and zinc contents than Asian and West African lines, which clustered in group 2 and were characterized by higher calcium, magnesium and manganese contents. An additional outstanding group 3 of six genotypes was identified with high iron, zinc, magnesium, manganese and calcium contents and potential candidates for cultivar release. The genotype × year interaction variance was greater than the genotypic variance, which might translate to phenotypic plasticity in the species. Broad-sense heritability ranged from low to high and was element-specific. The present results reveal the leaf minerals diversity in spider plant and represent a baseline for implementing a minerals-based breeding program for human nutrition.

Anthropometrics, Hemoglobin Status and Dietary Micronutrient Intake among Tanzanian and Mozambican Pigeon Pea Farmers

Inadequate consumption of micronutrient-dense and protein-rich foods such as vegetables, legumes and meat is an important contributing cause for anemia and deficiencies of vitamin A and iron in rural communities of Tanzania and Mozambique. A cross-sectional study was conducted to assess the nutritional status (anthropometrics and hemoglobin) and diets in particular micronutrient intake of female and male pigeon pea farmers from Lindi, Tanzania, and Gurué, the Zambézia province of Mozambique. A total of 1526 farmers (669 from Tanzania, 857 from Mozambique) were studied, of whom 16% were overweight and 35% were anemic. The highest prevalence of overweight and anemia, at 35% and 48%, was observed in Tanzanian and Mozambican women, respectively. Overall, only a small proportion of women and men reached the recommended daily dietary intake of vitamin A (10%), iron (51%) and zinc (44%). Multiple regression models revealed that dark green leafy vegetables (DGLVs) highly predicted vitamin A intake, whereas legumes in Tanzania and starchy plants in Mozambique were actually the dominant sources of vitamin A. Cereals covered over half of the iron and the zinc intake in both countries. An increased consumption of micronutrient-rich DGLVs and legumes, while reducing the high amounts of refined maize or polished rice, is suggested to counteract the high prevalence of anemia and overweight among smallholder farmers in East and South Eastern Africa.

Effect of two postharvest technologies on the micronutrient profile of cashew kernels from Mozambique

The economics involved in processing cashew nuts (Anacardium occidentale) might alter micronutrient profiles and concentrations. We analyzed and evaluated carotenoids, tocopherols, tocotrienols, minerals, fatty acids, and amino acids in (1) cashew kernels with testa recovered from nuts dried with and without the apple, and (2) testa-free industrial grade baby butts, splits, and white whole kernels using HPLC, ICP-OES, and GC-MS techniques. The results indicated that drying cashews with the respective apple slightly decreased the concentration of some carotenoids and total fatty and amino acids, but increased the concentration of iron, magnesium, and total tocotrienols compared with the conventionally (sun-) dried kernels. We also found high concentrations of carotenoids in the testa-containing kernels. Among the industrially processed kernel, baby butt grade was associated with lower content of β-carotene, total tocopherols, and tocotrienols, but with significantly higher concentrations in minerals, fatty acids, and amino acids than in white wholes and split grades. Conventional sun drying of cashew nuts revealed results similar to drying with apples regarding micronutrient concentrations. The high micronutrient content of industrial grade BB is reflected in widespread human consumption and better market value.

High Prevalence of Overweight and Its Association with Mid-Upper Arm Circumference among Female and Male Farmers in Tanzania and Mozambique

The increasing prevalence of overweight/obesity may already have reached the farmers in Tanzania and Mozambique. Here, the measurement of the mid-upper-arm-circumference (MUAC) could become a simple and sensitive tool for early detection of at-risk groups of overweight as well as underweight. Body Mass Index (BMI) and MUAC of female and male farmers (n = 2106) from different regions of Tanzania and the Zambézia province, Mozambique, were analyzed by region, sex, age, and correlates. MUAC cut-offs, calculated via BMI cut-offs (<18.5, ≥25, and ≥30 kg/m²), and multiple linear regression (MLR), compared to those selected by highest Youden’s index (YI) value, were assessed. The study showed an overall higher prevalence of overweight (19%) than underweight (10%) due to the high number of overweight female farmers (up to 35%) in southern Tanzania. BMI, which was mainly and positively predicted by MUAC, was higher in Tanzania and among female farmers, and decreased significantly from the age of ≥65 years. MUAC cut-offs of <24 cm and ≥30.5 cm, calculated by MLR, detected 55% of farmers being underweight and 74% being overweight, with a specificity of 96%; the higher cut-off <25 cm and lower cut-off ≥29 cm, each selected according to YI, consequently detected more underweight (80%) and overweight farmers (91%), but on the basis of a lower specificity (87–88%). Overweight was evident among female farmers in East Africa. MUAC cut-offs, whether defined via linear regression or Youden’s Index, could prove to be easy-to-use tools for large-scale screenings of both underweight and overweight.

High Prevalence of Stunting and Anaemia Is Associated with Multiple Micronutrient Deficiencies in School Children of Small-Scale Farmers from Chamwino and Kilosa Districts, Tanzania

Inadequate macro- and micronutrient nutrition and its consequences, such as anaemia, iron and vitamin deficiency, and growth retardation, could particularly affect children of small-scale farmers. In the present cross-sectional study, 666 school children aged 5-10 years from villages of Chamwino and Kilosa districts were studied for associations between nutritional and micronutrient status and dietary intake. The overall prevalence of stunting, underweight, and overweight was 28.1, 14.4, and 5%, while that of anaemia and deficiency of iron (ID), vitamin A (VAD), and zinc (ZnD) was 42.9, 29.3, 24.9, and 26.4%, respectively. Dietary recalls (24h) revealed that, except of iron (74%), only small proportions of children reached the recommended daily micronutrient intakes: 4% for zinc, 19% for vitamin A, and 14-46% for B vitamins. Stunting was highly associated with wasting in both districts and with VAD in Chamwino. Anaemia was predicted by ID, VAD, and ZnD in Chamwino and by elevated infection markers, C-reactive protein (CRP) and α-1 glycoprotein (AGP), in Kilosa. Overall, elevated CRP and/or AGP increased the risk while higher serum carotenoids indicating a diet of more fruit and vegetables reduced the risk of VAD. The significantly lower prevalence of anaemia and ID in Chamwino was related to higher iron and vitamin A intake and the consumption of mainly bulrush millet with dark green leafy vegetables compared to maize or rice with legumes in Kilosa. Nutrition and hygiene education integrated with home and school garden programmes could reduce the multiple burdens of anaemia; micronutrient deficiencies and infections; and, in the long term, the prevalence of stunting.

African Leafy Vegetables for Improved Human Nutrition and Food System Resilience in Southern Africa: A Scoping Review

The economic potential of African leafy vegetables (ALVs) remains obscured by a poorly developed value chain. This scoping review assembled and examined scattered knowledge generated on ALVs across southern Africa, focusing on production, processing, marketing, and consumption. Two electronic databases (Scopus and Web of Science) were screened, and a total of 71 relevant studies were included and evaluated. The review provides a state of the art on knowledge related to utilisation of ALVs across the entire value chain. The findings show that functional properties are of prime importance in the production and consumption of ALVs. However, the lack of improved germplasm and a non-existent seed supply system are significant production bottlenecks. Pests and diseases affecting the productivity of ALVs remain mostly unexplored. Sun-drying and boiling were the most reported post-harvest processing methods, suggesting that traditional processing methods are still prominent. Many studies also confirmed the predominance of informal markets in the trading of ALVs as they fail to penetrate formal markets because of poor product positioning and exclusion from produce demand and supply forecasts. The inception of cultivar development, mechanised processing methods, and market linkages will enhance the profitability of ALVs in the region. This review enhances the gaining of insight into the state of different value chain components will assist in upscaling production, value addition of products, and enhance marketing efficiency. There is a great opportunity for basic and applied research into ALVs.

Environment-Based Impairment in Mineral Nutrient Status and Heavy Metal Contents of Commonly Consumed Leafy Vegetables Marketed in Kyrgyzstan: a Case Study for Health Risk Assessment

Leafy vegetables are important components of the human diet for providing mineral nutrients. However, due to the tendency of metal accumulation, metal contents of leafy vegetables need not only to be determined but also estimated health risk for revealing possible health effects on humans. The aims of this study are (I) to examine comprehensive concentrations of trace/heavy metals along with some macroelements including Ca, Cd, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, and Zn in selected leafy vegetables from Kyrgyzstan; (II) to assess recommended dietary allowances (RDA); and (III) to evaluate hazard quotient (HQ) and carcinogenic risk estimation with associated vegetable consumption. For this purpose, B, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, and Zn elements were quantified, utilizing an ICP-OES instrument, in 18 samples belonging to 12 different groups of leafy vegetables including celery, Chinese parsley, dill, garden sorrel, lettuce, parsley, purple basil, spinach, and white-red-napa cabbage collected from different bazaars of Kyrgyzstan. Average elemental contents of the analyzed vegetables were determined (in mg kg^-1) as follows: B (3.21-64.79), Ca (852.51-17,183.20), Cd (0.015-0.09), Cu (6.08-63.47), Fe (116.52-768.66), K (2347.04-17,305.42), Mg (136.34-1261.11), Na (54.75-526.42), Ni (0.09-1.3), Pb (1.91-9.54), and Zn (29.49-314.93). Estimated daily intake, recommended daily allowance, hazard quotients, and carcinogenic risk values of the vegetables were calculated with the help of these results. In considering HQ values, Chinese cabbage was determined to be safe for the consumption of both genders whereas parsley to be safe for only males. Based on the carcinogenic risk calculation, most of the vegetables examined in this study were categorized as moderately risky. It was inferred from the given results that airborne pollution has impaired/increased the mineral contents of vegetables for both genders. The findings obtained from this study were compared with international standards and will contribute to the data available on a global scale.

Occurrence of Tocols in Foods: An Updated Shot of Current Databases

Tocols are present in various foods, mostly in fruits and in plant seeds. Edible oils are the most important natural dietary sources of tocopherols and tocotrienols, collectively known as tocols. Tocopherols and tocotrienols are considered beneficial for their antioxidant effect which impacts on prevention of different health conditions. This perspective is addressed to give an updated picture of the tocol occurrence in foods. Moreover, the current state of the art of tocols in updated databases is explored and commented outlining their importance and future trends.

Nutritional, phytochemical and diverse health-promoting qualities of Cleome gynandra

Cleome gynandra (Syn. Gynandropsis gynandra) is fast emerging as one of the most widely consumed leafy vegetables due to its nutrition and health-promoting properties. In addition to its high nutritional content, the plant has a rich pool of diverse antioxidant phytochemicals. The current review provides a critical appraisal on the increasing nutritional significance of Cleome gynandra due to its rich pool of natural bioactive compounds and beneficial health-promoting qualities. The rich nutritional content especially the high levels of macro- and micronutrients is an indication of its potential to mitigate malnutrition and the increasing incidence of diet-related obesity and non-communicable diseases. The presence of health-promoting natural compounds, notably polyphenols, glucosinates and terpernoids has been confirmed in Cleome gynandra using different analytical methods. Cleome gynandra possesses high levels of α-tocopherol, β-tocopherol and γ-tocopherol, ascorbic acid, α-carotene, β-carotene, lutein, violaxanthin, and β-cryptoxanthin. These nutritional compounds could be useful in food applications as supplements, colorants and extending shelf-life of food products. Cleome gynandra extracts have demonstrated promising effects in several biological assays using in vitro and in vivo systems. Clearly, diversified diets that include a regular intake of dark green leafy vegetables including Cleome gynandra, holds great promise in ensuring food and nutrition security.

Consumption of Dark Green Leafy Vegetables Predicts Vitamin A and Iron Intake and Status among Female Small-Scale Farmers in Tanzania

Inadequate consumption of micronutrient-dense foods such as vegetables and meat are an important contributing cause for anemia and deficiencies of iron and vitamin A in rural communities of Tanzania. A cross-sectional study was conducted in 2016 to examine nutritional and micronutrient status and their associations to the diet of female small-scale farmers in the sub-humid Kilosa (n = 333) and the semi-arid Chamwino (n = 333) districts, in the Morogoro and Dodoma region. An overall higher prevalence of overweight (19.7%) and obesity (7.1%) than of underweight (5.9%) was detected. Significantly more women in the two villages of Kilosa (27-40%) than in the two villages of Chamwino district (19-21%) were overweight/obese, but also more frequently had anemia (34-41% vs. 11-17%), iron deficiency (24-32% vs. 15-17%), and low serum retinol (21-24% vs. 8-9%). Overall, only a small proportion of women reached recommended daily micronutrient intakes: 27% for vitamin A, 17% for iron, 7% for zinc, and 12-38% for B-vitamins. The amount of dark green leafy vegetables (DGLV) consumed was the main determinant of vitamin A and iron intake by women in Chamwino and corresponded to higher hemoglobin, serum retinol and iron status than in the villages of the Kilosa district; in agreement, DGLV consumption also predicted iron and vitamin A intake in Kilosa district. DGLV consumed with wholemeal millet was advantageous in terms of women's vitamin A and iron intake and status over the predominantly maize-rice-based diet lacking vegetables.