Grazing cattle on alfalfa (Medicago sativa L.) would be economically beneficial, but its rapid initial rate of protein degradation results in pasture bloat, low efficiency of protein utilization and excessive N pollution into the environment. Introducing a gene that stimulates the accumulation of mono/polymeric anthocyanidins might reduce the ruminal protein degradation rate and reduce bloat related foam stability. The overall objective of this thesis was to evaluate newly developed anthocyanidin-accumulating Lc-alfalfa progeny for nutritional properties (composition, site of degradation and molecular structure), environmental emissions and bloat characteristics. The objective of the first study was to determine survival and phytochemical and chemical profiles of Lc-alfalfa progeny (BeavLc1, RambLc3 and RangLc4) and their non-transgenic (NT) parental cultivars (Beaver, Rambler and Rangelander). Lc-alfalfa forage accumulated enhanced amounts of anthocyanidin, with an average concentration of 197.4 µg/g DM, while proanthocyanidin (i.e. condensed tannins) were not detected. Both of these metabolites were absent in the NT-parental varieties. Lc-alfalfa progeny had ~3 % less crude protein (CP) and ~3 % more carbohydrates (CHO), which resulted in their 11 g/kg lower N:CHO ratio compared with NT-alfalfa. Total rumen-degradable N:CHO ratio based on chemical analysis was 12.9 g/kg lower in Lc-alfalfa compared with NT-alfalfa. The objective of the second study was to evaluate in vitro degradation, fermentation and microbial-N partitioning of three forage color phenotypes [green, light purple-green (LPG) and purple-green (PG)] within Lc-progeny and their parental green NT-alfalfa varieties. Purple-green-Lc alfalfa accumulated more anthocyanidin than Green-Lc with LPG-Lc intermediate. Gas, methane and ammonia accumulation rates were slower for the two purple-Lc phenotypes compared with NT-alfalfa with Green-Lc intermediate. Effective degradable DM and N were lower in the three Lc-phenotypes compared with NT-alfalfa. Anthocyanidin concentration correlated negatively with gas and methane production rates and effective degradability of DM and N. The objectives of the third study were to evaluate in situ ruminal degradation characteristics and synchronization ratios, and to model protein availability to dairy cattle and net energy for lactation of three Lc-alfalfa progenies, BeavLc1, RambLc3 and RangLc4 and the cultivar AC Grazeland (selected for a low initial rate of ruminal degradation). Anthocyanidin accumulation was on average 163.4 ìg/g DM in the three Lc-progeny while AC Grazeland did not accumulate anthocyanidin. The basic chemical composition of the original samples, soluble and potentially degradable fractions and degradation characteristics of crude protein and carbohydrates were similar in Lc-alfalfa and AC Grazeland. The undegradable in situ crude protein and neutral detergent fiber fraction were, respectively, 1.3 %CP and 4.8 %CHO lower in the three Lc-progeny compared with AC Grazeland. Lc-alfalfa had a 0.34 MJ/kg DM higher net energy for lactation and tended to have a 11.9, 6.9 and 8.4 g/kg DM higher rumen degradable protein, rumen degraded protein balance and intestinal available protein, respectively, compared with AC Grazeland,. The hourly rumen degraded protein balance included an initial and substantial peak (over-supply) of protein relative to energy which was highest in RangLc4 and lowest in RambLc3. The hourly rumen degraded protein balance between 4 and 24 h was similar and more balanced for all four alfalfa populations. The objective of the fourth study was to determine foam formation and stability in vitro from aqueous leaf extracts of three Lc-alfalfa progeny (BeavLc1, RambLc3, RangLc4), parental NT-alfalfa and AC Grazeland (bloat reduced cultivar) harvested in the field at 07:00 or 18:00 h. Anthocyanidin accumulation averaged 247.5 ìg/g DM in the leaves of the three Lc-progeny. There was an interaction between population and harvest time for the foam parameters. Initial foam volume (0 min) and final foam volume (150 min) at 07:00 h were lower for AC Grazeland compared with all other treatments and lower for RangLc4 compared with the other two Lc-progeny at 0 min and NT-alfalfa at 150 min; while from the 18:00 h harvest, initial foam volume was larger for NT-alfalfa and final foam volume was larger for RambLc3 compared with AC Grazeland, BeavLc1 and RangLc4. Foam formation correlated positively (R = 0.30 to 0.44) with leaf DM content, leaf extract protein and ethanol-film content, spectroscopic vibration intensity due to all carbohydrates (CHOVI) and amide I:amide II ratio and negatively (R = -0.33 and -0.34; P<0.05) with á-helix:â-sheet ratio and amide I:CHOVI. Final foam volume correlated negatively (R = -0.53 to -0.25; P<0.05) with leaf extract pH, spectroscopic vibration intensity due to all protein structures, structural carbohydrates (SCVI) and lipids (CH2 and CH3 asymmetric stretching) and amide I:CHOVI ratio and corelated positively (R = 0.39 to 0.44; P<0.05) with CHOVI, amideI:SCVI ratio and CHOVI:SCVI ratio. In conclusion, all Lc-alfalfa progeny and phenotypes accumulated anthocyanidin in their forage. Lc-alfalfa progeny had lower protein and higher carbohydrate content which improved the nitrogen to carbohydrate balance compared to their parental NT-alfalfa cultivars. Rate of fermentation and effective degradability in vitro reduced for both purple anthocyanidin-accumulating Lc-alfalfa phenotypes compared with NT-alfalfa. Intestinal protein availability tended to be higher and net energy for lactation was higher from Lc-alfalfa progeny for dairy cattle compared with AC Grazeland. Foaming properties were reduced in Lc-alfalfa progeny compared with parental non-transgenic alfalfa but not compared with AC Grazeland. However, differences between the Lc-alfalfa progeny and other cultivars were small. Therefore, further increases in mono/polymeric anthocyanidin accumulation in alfalfa are required in order to develop an alfalfa cultivar with superior nutritional and bloat preventing characteristics compared to currently available alfalfa cultivars.

Grazing cattle on alfalfa (Medicago sativa L.) would be economically beneficial, but its rapid initial rate of protein degradation results in pasture bloat, low efficiency of protein utilization and excessive N pollution into the environment. Introducing a gene that stimulates the accumulation of mono/polymeric anthocyanidins might reduce the ruminal protein degradation rate and reduce bloat related foam stability. The overall objective of this thesis was to evaluate newly developed anthocyanidin-accumulating Lc-alfalfa progeny for nutritional properties (composition, site of degradation and molecular structure), environmental emissions and bloat characteristics. The objective of the first study was to determine survival and phytochemical and chemical profiles of Lc-alfalfa progeny (BeavLc1, RambLc3 and RangLc4) and their non-transgenic (NT) parental cultivars (Beaver, Rambler and Rangelander). Lc-alfalfa forage accumulated enhanced amounts of anthocyanidin, with an average concentration of 197.4 µg/g DM, while proanthocyanidin (i.e. condensed tannins) were not detected. Both of these metabolites were absent in the NT-parental varieties. Lc-alfalfa progeny had ~3 % less crude protein (CP) and ~3 % more carbohydrates (CHO), which resulted in their 11 g/kg lower N:CHO ratio compared with NT-alfalfa. Total rumen-degradable N:CHO ratio based on chemical analysis was 12.9 g/kg lower in Lc-alfalfa compared with NT-alfalfa. The objective of the second study was to evaluate in vitro degradation, fermentation and microbial-N partitioning of three forage color phenotypes [green, light purple-green (LPG) and purple-green (PG)] within Lc-progeny and their parental green NT-alfalfa varieties. Purple-green-Lc alfalfa accumulated more anthocyanidin than Green-Lc with LPG-Lc intermediate. Gas, methane and ammonia accumulation rates were slower for the two purple-Lc phenotypes compared with NT-alfalfa with Green-Lc intermediate. Effective degradable DM and N were lower in the three Lc-phenotypes compared with NT-alfalfa. Anthocyanidin concentration correlated negatively with gas and methane production rates and effective degradability of DM and N. The objectives of the third study were to evaluate in situ ruminal degradation characteristics and synchronization ratios, and to model protein availability to dairy cattle and net energy for lactation of three Lc-alfalfa progenies, BeavLc1, RambLc3 and RangLc4 and the cultivar AC Grazeland (selected for a low initial rate of ruminal degradation). Anthocyanidin accumulation was on average 163.4 ìg/g DM in the three Lc-progeny while AC Grazeland did not accumulate anthocyanidin. The basic chemical composition of the original samples, soluble and potentially degradable fractions and degradation characteristics of crude protein and carbohydrates were similar in Lc-alfalfa and AC Grazeland. The undegradable in situ crude protein and neutral detergent fiber fraction were, respectively, 1.3 %CP and 4.8 %CHO lower in the three Lc-progeny compared with AC Grazeland. Lc-alfalfa had a 0.34 MJ/kg DM higher net energy for lactation and tended to have a 11.9, 6.9 and 8.4 g/kg DM higher rumen degradable protein, rumen degraded protein balance and intestinal available protein, respectively, compared with AC Grazeland,. The hourly rumen degraded protein balance included an initial and substantial peak (over-supply) of protein relative to energy which was highest in RangLc4 and lowest in RambLc3. The hourly rumen degraded protein balance between 4 and 24 h was similar and more balanced for all four alfalfa populations. The objective of the fourth study was to determine foam formation and stability in vitro from aqueous leaf extracts of three Lc-alfalfa progeny (BeavLc1, RambLc3, RangLc4), parental NT-alfalfa and AC Grazeland (bloat reduced cultivar) harvested in the field at 07:00 or 18:00 h. Anthocyanidin accumulation averaged 247.5 ìg/g DM in the leaves of the three Lc-progeny. There was an interaction between population and harvest time for the foam parameters. Initial foam volume (0 min) and final foam volume (150 min) at 07:00 h were lower for AC Grazeland compared with all other treatments and lower for RangLc4 compared with the other two Lc-progeny at 0 min and NT-alfalfa at 150 min; while from the 18:00 h harvest, initial foam volume was larger for NT-alfalfa and final foam volume was larger for RambLc3 compared with AC Grazeland, BeavLc1 and RangLc4. Foam formation correlated positively (R = 0.30 to 0.44) with leaf DM content, leaf extract protein and ethanol-film content, spectroscopic vibration intensity due to all carbohydrates (CHOVI) and amide I:amide II ratio and negatively (R = -0.33 and -0.34; P<0.05) with á-helix:â-sheet ratio and amide I:CHOVI. Final foam volume correlated negatively (R = -0.53 to -0.25; P<0.05) with leaf extract pH, spectroscopic vibration intensity due to all protein structures, structural carbohydrates (SCVI) and lipids (CH2 and CH3 asymmetric stretching) and amide I:CHOVI ratio and corelated positively (R = 0.39 to 0.44; P<0.05) with CHOVI, amideI:SCVI ratio and CHOVI:SCVI ratio. In conclusion, all Lc-alfalfa progeny and phenotypes accumulated anthocyanidin in their forage. Lc-alfalfa progeny had lower protein and higher carbohydrate content which improved the nitrogen to carbohydrate balance compared to their parental NT-alfalfa cultivars. Rate of fermentation and effective degradability in vitro reduced for both purple anthocyanidin-accumulating Lc-alfalfa phenotypes compared with NT-alfalfa. Intestinal protein availability tended to be higher and net energy for lactation was higher from Lc-alfalfa progeny for dairy cattle compared with AC Grazeland. Foaming properties were reduced in Lc-alfalfa progeny compared with parental non-transgenic alfalfa but not compared with AC Grazeland. However, differences between the Lc-alfalfa progeny and other cultivars were small. Therefore, further increases in mono/polymeric anthocyanidin accumulation in alfalfa are required in order to develop an alfalfa cultivar with superior nutritional and bloat preventing characteristics compared to currently available alfalfa cultivars.

Aim Nutrient profiling is defined as “the science of classifying or ranking food items according to their nutritional composition for reasons related to preventing disease and promoting health, and can be used to govern the criteria under which nutrient and/or health claims may be made”. The validation of a nutrient profiling model (NPM) is an essential part of the model development process, and is extremely important for the model to meet basic scientific criteria. This mini-dissertation investigated the content and convergent validity of a suitable NPM for South Africa. Method Content validity was tested for by comparing the NPM classification of 131 “indicator” foods with the classification of the “indicator” foods by the Food Based Dietary Guidelines (FBDGs). Convergent validity was tested for by comparing the standard ranking of a representative data set of food items (n = 128) by nutrition experts with the classification of the food items by the NPM. The questionnaire asked respondents to rank 40 foods (electronically generated from a master list of 128 foods) according to the nutritional information provided from “more healthy” to “less healthy” using a six point Likert scale. The 128 foods were selected to be representative of the South African diet. These questionnaires were sent via e-mail to all full members (n = 1105) of the Association of Dietetics in South Africa. The draft “Guiding principles and framework manual for the development or adaptation of nutrient profile models” dated 22 February 2011 (WHO, 2011), was used as a guide in the validation process of the NPM. Results The NPM showed good content validity: the way that the NPM categorises foods correspond well with that of the FBDGs (kappa statistic = 0.73). Two hundred and ninety two responses were received (26.4%) from the nutrition experts, these responses were used to rank the 128 foods by the average score which they received from the nutrition experts. The NPM also showed good convergent validity: the NPM classification of foods had a good correlation with the standard ranking of foods by dietitians (r = 0.853; p = 0.0001). Conclusion The NPM demonstrated good content validity by classifying food items in way that supports the FBDGs with the exception of a few processed food items and combined food items. The NPM also demonstrated good convergent validity by classifying food items in accordance with the views of nutrition experts in South Africa. / Thesis (MSc (Dietetics))--North-West University, Potchefstroom Campus, 2013.

Aim Nutrient profiling is defined as “the science of classifying or ranking food items according to their nutritional composition for reasons related to preventing disease and promoting health, and can be used to govern the criteria under which nutrient and/or health claims may be made”. The validation of a nutrient profiling model (NPM) is an essential part of the model development process, and is extremely important for the model to meet basic scientific criteria. This mini-dissertation investigated the content and convergent validity of a suitable NPM for South Africa. Method Content validity was tested for by comparing the NPM classification of 131 “indicator” foods with the classification of the “indicator” foods by the Food Based Dietary Guidelines (FBDGs). Convergent validity was tested for by comparing the standard ranking of a representative data set of food items (n = 128) by nutrition experts with the classification of the food items by the NPM. The questionnaire asked respondents to rank 40 foods (electronically generated from a master list of 128 foods) according to the nutritional information provided from “more healthy” to “less healthy” using a six point Likert scale. The 128 foods were selected to be representative of the South African diet. These questionnaires were sent via e-mail to all full members (n = 1105) of the Association of Dietetics in South Africa. The draft “Guiding principles and framework manual for the development or adaptation of nutrient profile models” dated 22 February 2011 (WHO, 2011), was used as a guide in the validation process of the NPM. Results The NPM showed good content validity: the way that the NPM categorises foods correspond well with that of the FBDGs (kappa statistic = 0.73). Two hundred and ninety two responses were received (26.4%) from the nutrition experts, these responses were used to rank the 128 foods by the average score which they received from the nutrition experts. The NPM also showed good convergent validity: the NPM classification of foods had a good correlation with the standard ranking of foods by dietitians (r = 0.853; p = 0.0001). Conclusion The NPM demonstrated good content validity by classifying food items in way that supports the FBDGs with the exception of a few processed food items and combined food items. The NPM also demonstrated good convergent validity by classifying food items in accordance with the views of nutrition experts in South Africa. / Thesis (MSc (Dietetics))--North-West University, Potchefstroom Campus, 2013.

Introdução: A introdução da agricultura e pecuária foram muito recentes para que o genoma humano se adaptasse e a tecnologia avançada pós revolução Industrial foi ainda mais. Segundo Cordain, a substituição de alimentos minimamente processados por alimentos pós-agrícolas e pós-industriais influenciaram os indicadores nutricionais: carga glicêmica, composição de ácidos graxos e macronutrientes, densidade de micronutrientes, equilíbrio ácido-base, relação sódio/potássio e teor de fibras, levando a um desequilíbrio que é causa de várias doenças atuais da civilização. A Protein Leverage Hypothesis (PLH) propõe que a queda na ingestão de proteínas possa levar a obesidade e doenças cardiometabólicas associadas. Objetivos: Estudar o efeito do consumo de alimentos ultraprocessados nos indicadores nutricionais na população dos EUA, incluindo a composição de macronutrientes, densidade de fibras e micronutrientes e fitoestrógenos urinários; avaliar se a contribuição calórica de alimentos ultraprocessados é determinante para a qualidade nutricional das dietas contemporâneas; e finalmente estudar se a associação entre o consumo de alimentos ultraprocessados, proteína e energia correspondem às previsões do modelo PLH. Métodos: Foram avaliados os participantes do National Health and Nutrition Examination Survey 2009-2010, com pelo menos um recordatório alimentar de 24 horas. Os itens foram classificados em: alimentos in natura ou minimamente processados, processados, ultraprocessados e ingredientes de uso culinário. O manuscrito 1 examina a relação entre a contribuição calórica de alimentos ultraprocessados e qualidade nutricional da dieta, avaliando individual e globalmente a contribuição de cada ingrediente crítico, usando a análise de componentes principais (ACP). O manuscrito 2 estuda a associação entre a contribuição calórica dos alimentos ultraprocessados e consumo de açúcares de adição. O manuscrito 3 avalia como o consumo de alimentos ultraprocessados influencia o conteúdo proteico relativo da dieta e as ingestões absolutas de energia e proteína, e se essas relações se encaixam nas previsões da PLH. O manuscrito 4 avalia a relação entre a contribuição calórica de alimentos ultraprocessados e níveis de fitoestrógenos urinários. Resultados: O teor médio de proteínas, fibras, vitaminas A, C, D e E, zinco, potássio, fósforo, magnésio e cálcio na dieta diminuiu ao longo dos quintis de contribuição calórica de alimentos ultraprocessados, enquanto o de carboidratos, açúcares de adição e gordura saturada aumentou. Uma associação inversa de dose-resposta foi encontrada entre o consumo de alimentos ultraprocessados e qualidade nutricional total, medida através de um escore de padrão balanceado de nutrientes derivado usando ACP. Consistente com a PLH, a contribuição calórica de alimentos ultraprocessados foi inversamente associada à densidade proteica e diretamente ao consumo energético total, enquanto a ingestão absoluta de proteínas permaneceu constante com aumento do consumo de alimentos ultraprocessados. Os níveis médios de enterolignanos urinários diminuíram ao longo dos quintis de consumo de alimentos ultraprocessados, enquanto os níveis de isoflavonas permaneceram inalterados. Conclusões: Este estudo mostra que a diminuição da contribuição calórica de alimentos ultraprocessados é um meio racional e eficaz de melhorar a qualidade nutricional das dietas dos EUA / Background: The introduction of agricultural and animal husbandry has not provided the human genome time enough to adapt, much less the advancing technology after Industrial Revolution. According to Cordain et al., displacement of minimally processed foods by post-agricultural and post-industrial food items adversely affected the following dietary indicators: glycemic load, fatty acid and macronutrient compositions, micronutrient density, acid-base balance, sodium-potassium ratio and fiber content. Many current diseases of civilization, in turn may be ascribable to those unbalanced dietary indicators. Indeed, Raubenheimer and Simpson have proposed the Protein Leverage Hypothesis (PLH) to explain how a drop in dietary protein content might lead to obesity and associated cardiometabolic disease. Objective: This thesis aims to study the effect of an increased consumption of ultra-processed foods on dietary indicators in the US population, including macronutrient composition, micronutrient and fiber densities, and urinary phytoestrogens. It also explores whether the dietary share of ultra-processed foods, expressed as a percentage of total energy intake, is a meaningful determinant of overall nutritional quality of contemporary diets. Lastly, it also looks into whether the association between ultra-processed food, protein and energy consumptions fit predictions of the PLH model. Methods: Participants from cross-sectional 2009-2010 National Health and Nutrition Examination Survey with at least one 24-hour dietary recall were evaluated. Food items were classified according to extent and purpose of industrial food processing as: unprocessed or minimally processed foods, processed culinary ingredients, processed foods and ultra-processed foods. Manuscript 1, examines the relationship between dietary contribution of ultra-processed foods and nutritional quality of US diet through the evaluation of dietary contents of critical nutrients individually and also overall, using Principal Component Analysis (PCA). Manuscript 2 studies the association between dietary contribution of ultra-processed foods and energy intake from added sugars. Manuscript 3 examines how consumption of ultra-processed food influences relative dietary protein content and, absolute energy and protein intakes; it furthermore, tests whether the relationships fit PLH predictions. Manuscript 4 assesses the relationship between dietary contribution of ultra-processed foods and urinary levels of phytoestrogens. Results: The average content of protein, fiber, vitamins A, C, D and E, zinc, potassium, phosphorus, magnesium and calcium in US diet decreased significantly across quintiles of energy contribution of ultra-processed foods, while carbohydrate, added sugars and saturated fat contents increased. An inverse dose-response association was found between ultra-processed food consumption and overall dietary quality measured through a Nutrient balanced pattern PCA derived factor score. Consistent with PLH, dietary contribution of ultra-processed foods was inversely associated with protein density and directly associated with total energy intake, while absolute protein intake remained relatively constant with increases in ultra-processed food consumption. Average urinary mammal lignan levels decreased across quintiles of ultra-processed food consumption, while isoflavone levels remained unchanged. Conclusions: This study suggests that decreasing the dietary share of ultra-processed foods is a rational and effective way to improve the nutritional quality of US diets

Introdução: A introdução da agricultura e pecuária foram muito recentes para que o genoma humano se adaptasse e a tecnologia avançada pós revolução Industrial foi ainda mais. Segundo Cordain, a substituição de alimentos minimamente processados por alimentos pós-agrícolas e pós-industriais influenciaram os indicadores nutricionais: carga glicêmica, composição de ácidos graxos e macronutrientes, densidade de micronutrientes, equilíbrio ácido-base, relação sódio/potássio e teor de fibras, levando a um desequilíbrio que é causa de várias doenças atuais da civilização. A Protein Leverage Hypothesis (PLH) propõe que a queda na ingestão de proteínas possa levar a obesidade e doenças cardiometabólicas associadas. Objetivos: Estudar o efeito do consumo de alimentos ultraprocessados nos indicadores nutricionais na população dos EUA, incluindo a composição de macronutrientes, densidade de fibras e micronutrientes e fitoestrógenos urinários; avaliar se a contribuição calórica de alimentos ultraprocessados é determinante para a qualidade nutricional das dietas contemporâneas; e finalmente estudar se a associação entre o consumo de alimentos ultraprocessados, proteína e energia correspondem às previsões do modelo PLH. Métodos: Foram avaliados os participantes do National Health and Nutrition Examination Survey 2009-2010, com pelo menos um recordatório alimentar de 24 horas. Os itens foram classificados em: alimentos in natura ou minimamente processados, processados, ultraprocessados e ingredientes de uso culinário. O manuscrito 1 examina a relação entre a contribuição calórica de alimentos ultraprocessados e qualidade nutricional da dieta, avaliando individual e globalmente a contribuição de cada ingrediente crítico, usando a análise de componentes principais (ACP). O manuscrito 2 estuda a associação entre a contribuição calórica dos alimentos ultraprocessados e consumo de açúcares de adição. O manuscrito 3 avalia como o consumo de alimentos ultraprocessados influencia o conteúdo proteico relativo da dieta e as ingestões absolutas de energia e proteína, e se essas relações se encaixam nas previsões da PLH. O manuscrito 4 avalia a relação entre a contribuição calórica de alimentos ultraprocessados e níveis de fitoestrógenos urinários. Resultados: O teor médio de proteínas, fibras, vitaminas A, C, D e E, zinco, potássio, fósforo, magnésio e cálcio na dieta diminuiu ao longo dos quintis de contribuição calórica de alimentos ultraprocessados, enquanto o de carboidratos, açúcares de adição e gordura saturada aumentou. Uma associação inversa de dose-resposta foi encontrada entre o consumo de alimentos ultraprocessados e qualidade nutricional total, medida através de um escore de padrão balanceado de nutrientes derivado usando ACP. Consistente com a PLH, a contribuição calórica de alimentos ultraprocessados foi inversamente associada à densidade proteica e diretamente ao consumo energético total, enquanto a ingestão absoluta de proteínas permaneceu constante com aumento do consumo de alimentos ultraprocessados. Os níveis médios de enterolignanos urinários diminuíram ao longo dos quintis de consumo de alimentos ultraprocessados, enquanto os níveis de isoflavonas permaneceram inalterados. Conclusões: Este estudo mostra que a diminuição da contribuição calórica de alimentos ultraprocessados é um meio racional e eficaz de melhorar a qualidade nutricional das dietas dos EUA / Background: The introduction of agricultural and animal husbandry has not provided the human genome time enough to adapt, much less the advancing technology after Industrial Revolution. According to Cordain et al., displacement of minimally processed foods by post-agricultural and post-industrial food items adversely affected the following dietary indicators: glycemic load, fatty acid and macronutrient compositions, micronutrient density, acid-base balance, sodium-potassium ratio and fiber content. Many current diseases of civilization, in turn may be ascribable to those unbalanced dietary indicators. Indeed, Raubenheimer and Simpson have proposed the Protein Leverage Hypothesis (PLH) to explain how a drop in dietary protein content might lead to obesity and associated cardiometabolic disease. Objective: This thesis aims to study the effect of an increased consumption of ultra-processed foods on dietary indicators in the US population, including macronutrient composition, micronutrient and fiber densities, and urinary phytoestrogens. It also explores whether the dietary share of ultra-processed foods, expressed as a percentage of total energy intake, is a meaningful determinant of overall nutritional quality of contemporary diets. Lastly, it also looks into whether the association between ultra-processed food, protein and energy consumptions fit predictions of the PLH model. Methods: Participants from cross-sectional 2009-2010 National Health and Nutrition Examination Survey with at least one 24-hour dietary recall were evaluated. Food items were classified according to extent and purpose of industrial food processing as: unprocessed or minimally processed foods, processed culinary ingredients, processed foods and ultra-processed foods. Manuscript 1, examines the relationship between dietary contribution of ultra-processed foods and nutritional quality of US diet through the evaluation of dietary contents of critical nutrients individually and also overall, using Principal Component Analysis (PCA). Manuscript 2 studies the association between dietary contribution of ultra-processed foods and energy intake from added sugars. Manuscript 3 examines how consumption of ultra-processed food influences relative dietary protein content and, absolute energy and protein intakes; it furthermore, tests whether the relationships fit PLH predictions. Manuscript 4 assesses the relationship between dietary contribution of ultra-processed foods and urinary levels of phytoestrogens. Results: The average content of protein, fiber, vitamins A, C, D and E, zinc, potassium, phosphorus, magnesium and calcium in US diet decreased significantly across quintiles of energy contribution of ultra-processed foods, while carbohydrate, added sugars and saturated fat contents increased. An inverse dose-response association was found between ultra-processed food consumption and overall dietary quality measured through a Nutrient balanced pattern PCA derived factor score. Consistent with PLH, dietary contribution of ultra-processed foods was inversely associated with protein density and directly associated with total energy intake, while absolute protein intake remained relatively constant with increases in ultra-processed food consumption. Average urinary mammal lignan levels decreased across quintiles of ultra-processed food consumption, while isoflavone levels remained unchanged. Conclusions: This study suggests that decreasing the dietary share of ultra-processed foods is a rational and effective way to improve the nutritional quality of US diets