Plant sources of provitamin A and human nutriture

Uncovering Potential Applications of Cyanobacteria and Algal Metabolites in Biology, Agriculture and Medicine: Current Status and Future Prospects

Cyanobacteria and algae having complex photosynthetic systems can channelize absorbed solar energy into other forms of energy for production of food and metabolites. In addition, they are promising biocatalysts and can be used in the field of "white biotechnology" for enhancing the sustainable production of food, metabolites, and green energy sources such as biodiesel. In this review, an endeavor has been made to uncover the significance of various metabolites like phenolics, phytoene/terpenoids, phytols, sterols, free fatty acids, photoprotective compounds (MAAs, scytonemin, carotenoids, polysaccharides, halogenated compounds, etc.), phytohormones, cyanotoxins, biocides (algaecides, herbicides, and insecticides) etc. Apart from this, the importance of these metabolites as antibiotics, immunosuppressant, anticancer, antiviral, anti-inflammatory agent has also been discussed. Metabolites obtained from cyanobacteria and algae have several biotechnological, industrial, pharmaceutical, and cosmetic uses which have also been discussed in this review along with the emerging technology of their harvesting for enhancing the production of compounds like bioethanol, biofuel etc. at commercial level. In later sections, we have discussed genetically modified organisms and metabolite production from them. We have also briefly discussed the concept of bioprocessing highlighting the functioning of companies engaged in metabolites production as well as their cost effectiveness and challenges that are being addressed by these companies.

Plant-based diets are traditional in developing countries: 21st century challenges for better nutrition and health

The chronic degenerative diseases were virtually unknown in original hunter-gatherer societies. At the dawn of the 21st century, however, they represent the most important public health challenge to populations of both the industrialized, affluent nations of the temperate zones and the low-income developing countries of the tropics. The developing countries most closely reflect the legacy of our traditional foreparents while constituting threequarters of the world's populace and public health interest. For economic, traditional, religious and cultural reasons, the majority of the dietary fares in the developing world are largely plant based. This is associated with high prevalences of deficiency states in vitamin A, iron, zinc, riboflavin and vitamin B12. Poor linear growth and chronic energy deficiency are concomitant conditions. Conversely, the major chronic diseases have low prevalences among the rural peasantry and tribal groups, with the exception of gastro-esophageal cancer, osteoarthritis and cataract. As a site for intensive research in food and nutritional sciences, Guatemala provides important lessons about the origin and evolvement of a congruent plant-based diet within a food system and which factors of demographic expansion, urbanization, environmental stress and food technology will carry it through the 21st century. We can conclude that, whatever was the 'original' dietary pattern of pre-agricultural humankind, a plant-based diet regimen provides the lowest content of promoters and the highest content of inhibitors of metabolic dysregulation that lead to the major causes of disease and debility in adults over 40 years of age. For developing countries, the challenge is to maintain and reinforce the traditional eating patterns while improving their delivery of micronutrients and obviating any adverse environmental consequences in their traditional preparation patterns. For developed countries, there is an opportunity to find a 'road map' of guidelines to allow correction of current, pathogenic dietary and lifestyle patterns by examining the food-ways of traditional developing societies' cuisines.

Photoprotective compounds from marine organisms

The substantial loss in the stratospheric ozone layer and consequent increase in solar ultraviolet radiation on the earth's surface have augmented the interest in searching for natural photoprotective compounds in organisms of marine as well as freshwater ecosystems. A number of photoprotective compounds such as mycosporine-like amino acids (MAAs), scytonemin, carotenoids and several other UV-absorbing substances of unknown chemical structure have been identified from different organisms. MAAs form the most common class of UV-absorbing compounds known to occur widely in various marine organisms; however, several compounds having UV-screening properties still need to be identified. The synthesis of scytonemin, a predominant UV-A-photoprotective pigment, is exclusively reported in cyanobacteria. Carotenoids are important components of the photosynthetic apparatus that serve both light-harvesting and photoprotective functions, either by direct quenching of the singlet oxygen or other toxic reactive oxygen species or by dissipating the excess energy in the photosynthetic apparatus. The production of photoprotective compounds is affected by several environmental factors such as different wavelengths of UVR, desiccation, nutrients, salt concentration, light as well as dark period, and still there is controversy about the biosynthesis of various photoprotective compounds. Recent studies have focused on marine organisms as a source of natural bioactive molecules having a photoprotective role, their biosynthesis and commercial application. However, there is a need for extensive work to explore the photoprotective role of various UV-absorbing compounds from marine habitats so that a range of biotechnological and pharmaceutical applications can be found.

Nutritional vitamin A status in northeast Brazilian lactating mothers

BACKGROUND

Vitamin A deficiency is the major cause of morbidity and mortality among children and in women of reproductive age in developing countries. The present study aimed to assess maternal nutritional vitamin A status, as well as analyse the association of preformed vitamin A and pro-vitamin A consumption on the nutritional status of nursing mothers, based on serum retinol and retinol colostrum concentrations coupled with dietary intake.

METHODS

Serum and colostrums were collected from 86 healthy parturients, recruited within 16 h postpartum. Blood samples were obtained, the morning after an overnight fast. Retinol was analysed by high-performance liquid chromatography. Dietary vitamin A was assessed using a food frequency questionnaire and the women were separated into two groups according to the predominant dietary source of vitamin A: group A, > 50% preformed vitamin A (n = 37); and group B > 50% pro-vitamin A carotenoids, (n = 49).

RESULTS

Serum retinol and total vitamin A ingestion (mean +/- SD) were higher in group A than in group B (1.4 +/- 0.4 micromol L(-1) and 2072.0 +/- 1465.9 microg retinol activity equivalent (RAE) day(-1) versus 1.2 +/- 0.6 micromol L(-1) and 1051.6 +/- 920.4 microg RAE day(-1), respectively (P < 0.05), but colostrum retinol (3.4 +/- 1.7 micromol L(-1) and 3.6 +/- 1.9 micromol L(-1)) was similar in both groups. In group B, 36.7% (n = 18) of the nursing mothers presented a risk of developing vitamin A deficiency, based on their dietary intake.

CONCLUSIONS

On the basis of the intake of the pro-vitamin A carotenoids, some women may be at risk of vitamin A deficiency. However, their status is currently normal, as indicated by serum and milk retinol concentrations.

Metabolites from algae with economical impact

In order to survive in a highly competitive environment, freshwater or marine algae have to develop defense strategies that result in a tremendous diversity of compounds from different metabolic pathways. Recent trends in drug research from natural sources have shown that algae are promising organisms to furnish novel biochemically active compounds. The current review describes the main substances biosynthesized by algae with potential economic impact in food science, pharmaceutical industry and public health. Emphasis is given to fatty acids, steroids, carotenoids, polysaccharides, lectins, mycosporine-like amino acids, halogenated compounds, polyketides and toxins.

Plasma appearance of labeled beta-carotene, lutein, and retinol in humans after consumption of isotopically labeled kale

The bioavailability of carotenoids from kale was investigated by labeling nutrients in kale with 13C, feeding the kale to seven adult volunteers, and analyzing serial plasma samples for labeled lutein, beta-carotene, and retinol. Ingested doses of labeled carotenoids were 34 micromol for beta-carotene and 33 micromol for lutein. Peak plasma concentrations, areas under the plasma concentration-time curves (AUCs), and percentages of dose recovered at peak plasma concentrations were calculated. Average peak plasma concentrations were 0.38, 0.068, and 0.079 microM for [13C]lutein, [13C]beta-carotene, and [13C]retinol, respectively. Average AUC values (over 28 days) were 42.8, 13.6, 13.2 microM h for [13C]lutein, [13C]beta-carotene, and [13C]retinol, respectively. Percentages of dose recovered at peak plasma concentrations were 3.6, 0.7, and 0.7% for [13C]lutein, [13C]beta-carotene, and [13C]retinol, respectively. A positive relationship was observed between baseline plasma retinol levels and [13C]retinol plasma response. It is possible that this relationship was mediated either through some aspect of beta-carotene absorption or via the common pathways of metabolism for postdose and endogenous retinoid.

Use of the deuterated-retinol-dilution technique to monitor the vitamin A status of Nicaraguan schoolchildren 1 y after initiation of the Nicaraguan national program of sugar fortification with vitamin A

BACKGROUND

Nicaragua initiated a national program of vitamin A fortification of its domestic sugar supply starting with the 1999-2000 sugarcane harvest.

OBJECTIVE

This study was conducted to document any change in the vitamin A status of a cohort of children during the first year of the program.

DESIGN

The vitamin A status of 21 Nicaraguan schoolchildren (mean age: 6.7 y; range: 5.3-9.3 y) was assessed in March 2000 and in March 2001. Total-body vitamin A stores and liver vitamin A concentrations were estimated with the deuterated-retinol-dilution (DRD) technique at a dose of 5 mg [(2)H(4)]retinyl acetate at baseline and 5 mg [(2)H(8)]retinyl acetate during the repeat test 1 y later. Plasma retinol and carotenoids were measured by HPLC.

RESULTS

Median total-body vitamin A stores increased from 0.33 to 0.72 mmol (P = 0.0001), liver vitamin A concentrations from 0.52 to 0.78 mumol/g (P = 0.0003), and plasma retinol concentrations increased from 0.97 to 1.17 mumol/L (P = 0.01).

CONCLUSION

The vitamin A status of Nicaraguan schoolchildren improved during the year after the initial distribution of vitamin A-fortified sugar in Nicaragua.

Orientação sobre o uso de vitamina A na saúde escolar: comparação de técnicas pedagógicas

O trabalho tem por objetivo comparar a eficácia de técnicas de ensino em motivar a criança em assimilar a importância dos alimentos ricos em vitamina A, e as conseqüências da falta desses nutrientes para o organismo. Foi elaborado material didático com 2 técnicas pedagógicas: uma baseada em um texto de conotação literária e outra, em teatro de fantoches. O estudo foi desenvolvido com alunos da 3ª série do ciclo básico da Escola Municipal Orlando Paulino da Costa, na zona rural de Alfenas, através da aplicação de questionários. Os resultados demonstraram que as técnicas pedagógicas empregadas promoveram aprendizagem de conceitos em relação à vitamina A e incentivo para o consumo de alimentos ricos nesses nutrientes. Não se verificaram diferenças significativas entre as técnicas pedagógicas (Teste de Comparação das Proporções, com p<0,05), uma vez que ambas utilizam os mesmos princípios metodológicos. Concluímos que a aplicação de métodos lúdicos é um incentivador para a reeducação alimentar. Propõe-se, então, o uso desses recursos nas escolas para a aprendizagem de conteúdos de saúde e alimentação.

Supplementing lactating women with puréed papaya and grated carrots improved vitamin A status in a placebo-controlled trial

Doubts have been raised about the effectiveness of carotene-containing foods in improving the vitamin A status of populations at risk. We investigated the effect of papaya and carrots on the vitamin A status of lactating women with 2- to 12-mo-old infants in ZIMBABWE: The women were randomly assigned to three supplementation groups and a placebo group, and received 6 mg of beta-carotene capsules, 650 g puréed papaya, 100 g grated carrots or a placebo, daily for 60 d. All groups were given a meal containing 10 g of vegetable oil daily. Serum retinol, relative dose response, serum ferritin, hemoglobin and C-reactive protein were measured before and after the supplementation period. Mean serum retinol increased significantly after supplementation in the beta-carotene group (P < 0.001), the papaya group (P < 0.001) and the carrot group (P < 0.001), but not in the placebo group (P > 0.05). The relative dose response decreased significantly (P < 0.05) in the beta-carotene and papaya groups, but not in the carrot or placebo groups (P > 0.05). There was an increase in mean serum ferritin in all groups but the increase did not differ among groups. The hemoglobin increases in the beta-carotene and papaya groups were greater than that in the placebo group. We conclude that puréed papaya and grated carrots can improve the vitamin A and iron nutriture of lactating women. These findings reinforce the importance of plant food-based approaches in the control of vitamin A deficiency in low income countries.

Plant sources of vitamin A and human nutriture: how much is still too little?

In a randomized controlled 12-week feeding trial among malnourished, anemic, and largely vitamin A-deficient Ghanaian preschool children, the hypothesis that the ability of provitamin A carotenoids in dark green, leafy vegetables (DGLV) to raise vitamin A status in different formats--with or without fat and with fat plus anthelmintic treatment for intestinal worms--was tested by comparison with a low vitamin A fare and with pure chemical beta-carotene. The 12-week increments in retinol concentrations over baseline ranged from 5% to 44%, but over half of the DGLV-fed population had persistently low circulating retinol. The very modest impact on vitamin A status of these maneuvers to optimize dietary use of provitamin A in DGLV has major implications for public policy to eradicate hypovitaminosis A.

Micronutrient malnutrition: policies and programs for control and their implications

Global progress in social and economic development is occurring, although slowly, in the most needy parts of the nonindustrialized world, where nutritional deficiencies, including micronutrients, remain significant public health problems. Until empowering benefits accrue from development spin-offs, policy guidance for purposeful public health actions can help reduce the unconscionable toll on health and quality of life from micronutrient malnutrition and can interrupt its intergenerational debilitating effects on national development. Narrowly focused control programs including homestead production, plant breeding, fortification, and supplementation are in effect, but in general, they have not been holistically planned and integrated into overall development programs. Such integration is needed to ensure sustainability into the next century. A new paradigm is needed, including a new way of thinking by nutrition scientists and program implementers that includes partnerships with the poor in all aspects of program planning and implementation.

Maternal vitamin A nutriture and the vitamin A content of human milk

Because of the many functions of vitamin A in human physiology, deficiency or excess of the vitamin in lactating women or their infants can adversely affect their health. Infants are born with low body stores of vitamin A, and rely on vitamin A in milk to meet their needs. The vitamin A content of milk is related to maternal vitamin A status and maternal dietary vitamin A intake during lactation. Low-income lactating women in non-industrialized countries have lower milk vitamin A concentrations than lactating women in industrialized countries. Supplementation of lactating women in non-industrialized countries with vitamin A or beta-carotene has resulted in increased milk vitamin A concentrations. However, the optimal timing and dose for sustaining adequate levels of vitamin A in milk throughout the lactation period has not been determined. Further research is needed to understand factors affecting the transfer of vitamin A to milk, and to evaluate various strategies for improving the vitamin A status of mothers and infants.

Compartmental models of vitamin A and beta-carotene metabolism in women

We have developed compartmental models of vitamin A and beta-carotene (beta C) metabolism in women living under controlled conditions on diets with known concentrations of vitamins and carotenoids. Fourteen healthy adult women were given either retinyl-d4 acetate, or beta C-d8 before breakfast. Natural and stable-isotopes of retinol and beta C were collected in serum for up to 95 days or 20 days, respectively. Stable isotopes were separated from other components and measured by GC-MS or HPLC-UV. Preformed retinyl-d4 acetate metabolism in all women tested can be accurately described by a simple four-compartment model. However, the model did not fit one women initially, when she had marginal vitamin A status. We tested the hypothesis that dietary changes of beta C intake have important roles on the kinetics of vitamin A metabolism. Dietary changes of beta C intake did not influence the turnover rate of retinol in any compartment. However, it did result in changes in steady-state masses and residence times of retinol in several compartments. A working compartmental model for beta C metabolism was developed. The kinetics of retinol-d4 formed from beta C is more complicated than the pre-formed retinol-d4. Results suggest that beta C-d8 readily converts into retinol-d4 with high inter-individual variability.

Plant sources of vitamin A and human nutrition: red palm oil does the job

Studies in India demonstrate that the beta-carotene in red palm oil is as effective as high-dose retinyl palmitate as a supplement to restore and preserve vitamin A nutriture in schoolchildren and may be an effective food-based strategy to combat hypovitaminosis A.

Bioavailability of beta-carotene is lower in raw than in processed carrots and spinach in women

Populations at risk of vitamin A deficiency usually rely on dietary provitamin A carotenoids to meet vitamin A needs, yet bioavailability of these compounds is influenced by several factors as follows: location in the plant source, the presence of other influencing dietary components, and type and extent of processing. The purpose of this study was to examine the plasma beta-carotene response to raw vs. processed carrots and spinach. Subjects were eight healthy females aged 23-36 y who consumed approximately 9.3 mg beta-carotene daily from either raw or thermally processed and pureed vegetables in two 4-wk treatment periods in a crossover study. Plasma concentrations of total, all-trans-, and cis-beta-carotene and alpha-carotene were measured at base line and the end of each treatment period by using HPLC assays. Total and all-trans (but not cis) plasma beta-carotene concentrations were significantly greater than base-line concentrations in the processed feeding period (P < 0. 04) and tended to be greater in the raw feeding period (P = 0.08). Daily consumption of processed carrots and spinach over a 4-wk period produced an increase in plasma beta-carotene concentration that averaged three times that associated with consumption of the same amount of beta-carotene from these vegetables in the raw form (P = 0.09). Increased cis isomers provided in the processed vegetables did not result in significantly greater plasma cis-beta-carotene isomer concentrations. These results suggest that isomerization of beta-carotene by heat treatment does not negate the enhanced beta-carotene uptake associated with consuming commercially processed vegetables compared with raw vegetables.

Fortified foods contribute one half of recommended vitamin A intake in poor urban Guatemalan toddlers

Vitamin A intake from food sources, not including breast milk, was determined from seven consecutive 24-h recalls for 55 children (mean age 20.8 mo, SD 8.9) from two poor communities of Guatemala City. Not including vitamin A derived from fortified sugar or breast milk, the median daily vitamin A intake was 194 retinol equivalents (RE). Including vitamin A derived from fortified sugar but not including that derived from breast milk, the median total vitamin A intake (25th and 75th percentiles) was 338 RE (146 and 617 RE) of which 78% was preformed retinol and 22% provitamin A. More than 90% of total vitamin A intake from non-breast milk food sources was derived from only 10 items; over half came from three fortified foods: fortified sugar, Incaparina and margarine. Sugar samples from 91 households in 1991 had a median of 3.3 RE/g (range, 0.0-29.9 RE/g), <25% of the target level (13-17 RE/g); nevertheless, fortified sugar provided 25% of these children's total vitamin A intake (81 RE/d) from non-breast milk food sources and their intake approached the level recommended by the FAO/WHO (400 RE/d). These results show that fortified foods make an important contribution towards vitamin A intake in this sample of poor urban Guatemalan toddlers.

The mongolian gerbil (Meriones unguiculatus) is an appropriate animal model for evaluation of the conversion of beta-carotene to vitamin A

Vitamin A (VA) deficiency is the leading cause of blindness in children in developing countries. Dietary intervention with foods rich in provitamin A carotenoids, such as beta-carotene (betaC), has been suggested as one solution to this problem. The objective of the two studies described in this paper was to examine the utilization of betaC as a source of VA at different stages of VA depletion using the Mongolian gerbil as a model. Male 4- to 5-wk-old Mongolian gerbils were fed powdered betaC-free semipurified diets either with or without VA for 26 d (Study 1), or without VA for 8-10 wk (Study 2). Gerbils were then fed diets with or without VA (20.9 nmol/g diet) and/or betaC [(67.0 micromol/g diet (Study 1) and 145.9 micromol/g diet (Study 2)] for variable periods. Two (Study 1) or three (Study 2) days before termination of the study, 3-4 gerbils per group were dosed orally with 14C-betaC. Tissues were evaluated for VA and betaC content by HPLC. Liver was extracted with and without saponification to evaluate 14C-betaC and 14C-VA content. The results demonstrate the following: 1) the gerbil is an appropriate animal model to study betaC utilization; 2) 20.9 nmol VA/g diet is more than sufficient for this species; 3) the daily VA utilization rate for this species is calculated to be 3.1 microg/100 g body weight; 4) a highly bioavailable source of betaC at a 6:1 weight ratio of betaC:VA is sufficient to reverse marginal VA status in this model; and 5) a highly bioavailable source of betaC fed between a 6:1 and 13:1 weight ratio to VA provides equivalent VA status as preformed VA in Mongolian gerbils.

Ferrets (Mustela putoius furo) inefficiently convert beta-carotene to vitamin A

The ferret has recently been used as a model to evaluate the absorption and metabolism of several carotenoids; however, little is known about the vitamin A (VA) requirements of this species or the ability of ferrets to convert dietary beta-carotene (betaC) to VA. Three studies were conducted to estimate the daily utilization of VA in ferrets and to determine the effect of prior VA status on the ability of ferrets to utilize betaC as a source of VA. Weanling male ferrets were fed a pelleted, low carotenoid, semipurified diet either with (+VA) or without VA (-VA) for 21- to 35-d prefeeding periods. Upon initiation of the experiments, several ferrets were killed to determine base-line VA status. The remaining ferrets were fed VA, betaC, or VA and betaC in pelleted feed (Studies 1-3) or liquid carrier (Study 3) for 16-21 additional days. Hepatic VA and betaC concentrations were used as the primary indicators of VA status, although serum and adrenal VA and betaC also were measured. The results showed the following: 1) provision of betaC at up to a 15:1 weight ratio of betaC to VA in pelleted feed or liquid carrier was not sufficient to maintain hepatic VA stores after a -VA prefeeding period; 2) the daily utilization rate of VA by ferrets ranged from 80 to 171 microg in the three studies; 3) the ferret was confirmed to be a species that has the majority of its serum VA in ester form; and 4) feeding -VA diets significantly reduced serum retinyl esters but had less effect on serum retinol. We conclude that although ferrets can convert betaC to VA, the process is inefficient. The ferret model can be most appropriately used when studying the biological effect of tissue betaC stores on VA status and is less appropriate for the evaluation of dietary betaC conversion to VA.

The possible significance of parallel changes in plasma lutein and retinol in Pakistani infants during the summer season

Recent evidence suggests that plasma lutein is better correlated than either beta-carotene or lycopene with its respective carotenoid intake and therefore may be a better marker of vegetable intake than either beta-carotene or lycopene. In the study reported in this paper, measurements of plasma carotenes and retinol were made in infants from two villages near Peshawar in the North West Frontier Province, Pakistan, in July and November 1993. The approximate age at the start was 14 months, and 101 boys and ninety girls completed the study. Of the usual plasma carotenes, only lutein was measurable in all samples and was correlated with retinol in both boys (r 0.38, P < 0.0001; r 0.35, P < 0.001) and girls (r 0.21, P = 0.038; r 0.0307, P = 0.003) at the two time points respectively. In addition, the change in lutein was even more strongly correlated with the change in retinol in both boys (r 0.453, P < 0.0001) and girls (r 0.439, P < 0.0001). In August beta-carotene was measurable in approximately 8 % of samples and this increased to 31 % in November but there was no correlation between beta-carotene and retinol at any time. There were negligible amounts of lycopene and beta-cryptoxanthin in plasma at both time points. The mean concentration of plasma retinol in the infants was 0.66 mumol/l at baseline and 59% of the infants had retinol concentrations < 0.7 mumol/l. In addition, there were fifteen infants whose levels were below 0.35 mumol/l suggesting that vitamin A status in the population was marginal. Food intake of the infants was not monitored in the present study but breast feeding continues for up to 2 years in this part of Pakistan and most infants would be weaned onto selected foods eaten by the family. The close correlation between plasma lutein and retinol suggests that the increase in retinol over the summer season may be attributable to an increased availability of green vegetables to the families. The source of lutein to the infants is most likely to be the breast milk since such vegetables are unlikely to be given to infants except to suck as a weaning food. The results may indicate the potential usefulness of plasma lutein as a marker of changes in vegetable intake and changes in vitamin A status in Third World infants and children.

Carotenoids: biology and treatment

Carotenoids are pigments found in plants and microorganisms, but not synthesized in animals. Fewer than 10% of the carotenoids can function as vitamin A precursors in mammals. Carotenoids and retinoids have chemical and metabolic similarities and differences, and some overlap in biological activities. Carotenoids in tissues reflect food choices. Carotenoids exhibit biological activities as antioxidants, affect cell growth regulation, and modulate gene expression and immune response. Epidemiologic evidence links higher carotenoid intakes and tissue concentrations with reduced cancer and cardiovascular disease risk, although results from clinical trials do not support beta-carotene supplementation as a strategy to reduce risk. Continued research in this area is likely to stimulate better intervention strategies with clinical and public health applications.

Plant sources of vitamin A and human nutrition: renewed strategies

The ability of a supplement of local, cooked green leaves to support vitamin A nutriture of anemic, lactating rural Indonesian women was tested using increments in carotenoid and retinol content in plasma and breast milk as indices of bioavailability and bioconversion, respectively. While beta-carotene provided in a simple matrix of a fortified cracker produced substantial improvements in both vitamin A and carotenoid status, an equivalent amount from stir-fried vegetables had a negligible effect.