Jan Frank

Jan Frank
University of Hohenheim · Institute of Nutritional Sciences

Professor, Ph.D.

About

226
Publications
50,743
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Introduction
As a nutritionist, I am interested in the bioavailability of phytochemicals and micronutrients and how these are affected by age and gender and, ultimately, how their bioavailabilities impact their biological activities. A micronutrient that features prominently in my research is vitamin E.
Additional affiliations
September 2013 - present
University of Hohenheim
Position
  • Professor (Full)
September 2012 - August 2013
University of Bonn
Position
  • Professor (Full)
September 2009 - August 2012
University of Hohenheim
Position
  • Group Leader
Education
February 2001 - July 2004
October 1993 - September 2000
University of Bonn
Field of study
  • Human Nutrition and Home Economics

Publications

Publications (226)
Article
Recent studies have shown that elevated concentrations of unconjugated bilirubin (UCB) may be a protective host factor against the development of noncommunicable diseases (NCDs), whereas low levels of UCB are associated with the opposite effect. The results of this European study, in which 2,489 samples were tested for their UCB concentration using...
Article
Low bioavailability of phenolic compounds (phenolics) results in low in vivo bioactivity, thus their co-encapsulation could enhance potential health benefits. In this study, reconstitutable nanoliposomes loaded with phenolics varying in solubility were fabricated using spray drying after stabilized by chitosan (CH) or whey protein (WP). The physico...
Article
Full-text available
Purpose The original aim of the study was to determine, in a double-blind 3-arm crossover human trial (n = 7), the effect of supplemental levels of iron (25 mg) and zinc (30 mg) on β-carotene (synthetic) bioavailability (10 h postprandial). However, despite the high dose of supplemental β-carotene (15 mg) consumed with the high fat (18 g), dairy-ba...
Article
Scope Tocomonoenols (T1) are little‐known vitamin E derivatives naturally occurring in foods. Limited knowledge exists regarding the cellular uptake and metabolism of α‐tocomonoenol (αT1) and none about that of γ‐tocomonoenol (γT1). Methods and results The study investigates the cytotoxicity, uptake, and metabolism of αT1 and γT1 in HepG2 cells co...
Article
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The aim of this study was to evaluate the accuracy of nutrient intake assessment with the food group-based algorithm "Calculator of Inadequate Micronutrient Intake" (CIMI) in comparison to the established nutrition software NutriSurvey. Using Food Frequency Questionnaires and 24-h dietary recalls of 1010 women from two rural districts in Tanzania,...
Article
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Spray drying is a well-established, energy efficient, and scalable process widely used in the food industry, however it may lead to thermal degradation of susceptible compounds, such as (poly)phenols, resulting in biological activity loss to some extent. In this study, we aimed to improve the physicochemical stability and bioaccessibility of (poly)...
Article
Scope Diets rich in fat and sugars evoke chronic low‐grade inflammation, leading to metabolic derangements. This study investigates the impact of fructose and galactose, two commonly consumed simple sugars, on exacerbation of the harmful effects caused by high fat intake. Additionally, the potential efficacy of fructooligosaccharides (FOS), a ferme...
Article
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Tomonoenols (αT1) are tocochromanols structurally related to tocopherols (T) and tocotrienols (T3), the bioactive members of the vitamin E family. However, limited evidence exists regarding the sources and biosynthesis of tocomonoenols. Nitrogen depletion increases the content of α‐tocopherol (αT), the main vitamin E congener, in microalgae, but li...
Article
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Aim This research aimed to evaluate health and nutritional practices of mothers during pregnancy and birth outcomes of their newborns in Bukavu, Democratic Republic of the Congo (DRC), comparing semi-urban and rural areas. Background Health and nutrition during pregnancy are crucial for adequate development of the fetus. Health care plays an impor...
Article
Scope Prenylated chalcones and flavonoids are found in many plants and are believed to have beneficial effects on health when consumed. Xanthohumol is present in beer and likely the most consumed prenylated chalcone, but poorly absorbed and rapidly metabolized and excreted, thus limiting its bioavailability. Micellar formulations of phytochemicals...
Article
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Beans (Phaseolus vulgaris L.) are a traditional food in Chile. This work aimed to determine the chemical composition, antioxidant capacity, and enzyme inhibition effect of secondary metabolites-enriched extracts (SMEE) of thirteen Chilean bean landraces before and after boiling. The SMEE composition was assessed by HPLC-DAD-MS/MS, and the main comp...
Article
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The fruits of Rosa pimpinellifolia are rich sources of (poly)phenols, however they are underutilized due to the limited information available. The influence of the pressure, temperature, and co-solvent concentration (aqueous ethanol) of the supercritical carbon dioxide extraction (SCO2-aqEtOH) on the extraction yield, total phenolic-, total anthocy...
Article
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Globally, the prevalence of anemia among children during the period of complementary feeding is high. A cross-sectional, mixed-methods study was conducted to examine the main determinants of anemia among Syrian refugee children aged 6 to 23 months (n = 215) and to illuminate the knowledge, attitudes and perceptions of their mothers and Lebanese hea...
Article
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Background Bread is a major source of grain-derived carbohydrates worldwide. High intakes of refined grains, low in dietary fiber and high in glycemic index, are linked with increased risk for type 2 diabetes mellitus (T2DM) and other chronic diseases. Hence, improvements of the composition of bread could influence population health. Objective Thi...
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Dietary supplements that promote healthy aging are mostly warranted in an aging society. Because of age-related risks, anti-inflammatory and anti-oxidative agents such as mi-croalgae are potential candidates for intervention. In a randomized controlled trial, we tested Phaeodactylum tricornutum (PT), a microalgae rich in eicosapentaenoic acid (EPA)...
Article
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Syrian refugees in Lebanon are facing vulnerabilities that are affecting their food insecurity levels. The objectives of this study were to measure dietary diversity, food insecurity (FI), and mental health status of Syrian refugee mothers in Lebanon and to explore its associations with their anemia and nutritional status. A cross-sectional study w...
Article
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The objective was to describe infant feeding practices, nutrition and related health aspects of infants under six months among Syrian refugees in Greater Beirut, Lebanon. A cross-sectional study was conducted among Syrian refugee mothers with infants under six months in July–October 2018 (N = 114). Additionally, eleven focus group discussions were...
Article
Scope: 20-hydroxyecdysone (20E) is the main phytochemical present in the fresh arils of Prumnopitys andina. 20E was reported to have anabolic effects by modulation of gene transcription by interaction with nuclear receptors. Our aim was to evaluate in vitro bioaccessibility, transepithelial transport of 20E and the capacity of P. andina fruit extr...
Article
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In this work, pressurized hot water extraction (PHWE) of hydrophilic polyphenols from black rosehip fruit was maximized using response surface methodology for simultaneous optimization in terms of extraction yield, total antioxidant capacity, total (poly)phenols, catechin, total monomeric anthocyanins, and cyanidin-3-O-glucoside. Extraction paramet...
Preprint
Full-text available
The objective is to describe infant feeding practices and the nutritional status of infants under six months among Syrian refugees in Greater Beirut, Lebanon. A cross-sectional study was conducted among Syrian refugee mothers with children under five years (July-October 2018), mothers with infants under six months were included in the analysis (n=1...
Article
Scope: Preclinical models have demonstrated the anti-inflammatory and lipid-lowering effects of curcumin. Innovative formulations have been developed to overcome the poor bioavailability of native curcumin. The study hypothesizes that the bioavailability of micellar curcumin is superior to native curcumin and investigates the potential anti-inflam...
Article
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Recent studies suggest that a diet rich in sugars significantly affects the gut microbiota. Adverse metabolic effects of sugars may partly be mediated by alterations of gut microbiota and gut health parameters, but experimental evidence is lacking. Therefore, we investigated the effects of high intake of fructose or galactose, with/without fructool...
Article
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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 di...
Article
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Background Urinary metabolites of vitamin E, i.e., α- and γ-carboxyethyl hydroxychroman (α- and γ-CEHC), have gained increasing attention and have been proposed as novel biomarkers of vitamin E intake and status. However, there are insufficient data on the relationship of plasma α-tocopherol and γ-tocopherol and dietary vitamin E intake with 24 h u...
Article
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Objectives A high intake of sugars is associated with adverse metabolic effects in animal models and humans. However, little is known about the potential of simultaneously ingested dietary fibers to attenuate the negative effects of sugars. The current study thus aimed to investigate the effects of high intakes of fructose or galactose with or with...
Article
Über ein Viertel der Bevölkerung in Deutschland nimmt regelmäßig Nahrungsergänzungsmittel ein, von denen wiederum 11% Vitamin E enthalten [1]. Diese Supplemente können bis zu 1000 I.E. pro Dosis enthalten, was ca. 60-mal höher ist als die empfohlenen 16–22 I.E. pro Tag [2]. Da gerade ältere Menschen häufig Medikamente einnehmen müssen, sind möglich...
Article
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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 Ameri...
Article
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Mesenchymal stem cells (MSC) have many roles that are important for the body’s proper functioning. When the MSC pool is damaged, it is often correlated with impaired development or health of the organism. MSC are known for their anti-inflammatory, immunomodulatory and trophic characteristics that play an important role in the physiological homeosta...
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(1) Background: Mitochondria are the cells' main source of energy. Mitochondrial dysfunction represents a key hallmark of aging and is linked to the development of Alzheimer's disease (AD). Maintaining mitochondrial function might contribute to healthy aging and the prevention of AD. The Mediterranean diet, including walnuts, seems to prevent age-r...
Article
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Hop prenylated flavonoids have been investigated for their in vivo activities due to their broad spectrum of positive health effects. Previous studies on the metabolism of xanthohumol using untargeted methods have found that it is first degraded into 8-prenylnaringenin and 6-prenylnaringenin, by spontaneous cyclisation into isoxanthohumol, and subs...
Article
Grass silage is barely used in intensive beef production, but it is unclear if its lower energy supply compared to maize-silage feeding really impairs growth performance. Diets with 100, 300, 500 or 750 g grass silage/kg dry matter replacing maize silage and concentrate were tested with or without dried corn-cob mix (CCM). Performance, carcass and...
Article
Uptake into intestinal cells and intracellular distribution into metabolically competent organelles, such as the endoplasmic reticulum, are important processes potentially limiting the bioavailability of xenobiotics. The incorporation of curcumin into polysorbate 80 micelles improves its naturally low oral bioavailability in humans. Here, we invest...
Article
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11′-α-Tocomonoenol (11′-αT1) is structurally related to vitamin E and has been quantified in the microalgae Tetraselmis sp. and Nannochloropsis oceanica. However, it is not known whether 11′-αT1 is present in other microalgae independent of species and origin. The aim of this study was to analyze the tocochromanol profiles of Chlorella sorokiniana,...
Poster
Full-text available
Study on the Dietary Diversity, and Nutritional Status of Mother child Pairs by Season in Enset Cultivating Areas of Southern Ethiopia
Article
Phytic acid, the main storage form of phosphate in maize (Zea mays L.) grains, is known as antinutrient due to its chelating properties but may also prevent oxidation. Thus, the impact of phytic acid on the degradation of tocochromanols, carotenoids, fatty acids, and oxidation products in maize during cooking and subsequent in vitro digestion was e...
Article
Xanthohumol is the main prenylflavonoid in hops and has been associated with a wide range of health benefits, due to its anti-inflammatory, anti-oxidative, and cancer-preventive properties. Increasing evidence suggests that xanthohumol positively affects biomarkers associated with metabolic syndrome and cardiovascular diseases (CVDs). This review s...
Article
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The microalgae Phaeodactylum tricornutum (PT) contains valuable nutrients such as proteins, polyunsaturated omega-3 fatty acids (n-3 PUFA), particularly eicosapentaenoic acid (EPA) and some docosahexaenoic acid (DHA), carotenoids such as fucoxanthin (FX), and beta-glucans, which may confer health benefits. In a randomized intervention trial involvi...
Article
α-Tocomonoenols are vitamin E-derivatives with a single double-bond in the tocochromanol sidechain. Currently, two congeners are known: 11'-α-tocomonoenol and 12'-α-tocomonoenol, the later better known as “marine-derived tocopherol” (MDT). Information regarding their presence in photosynthetic aquatic organisms is scarce. We thus determined vitamin...
Article
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Commercially produced complementary foods are inaccessible to rural households in Ethiopia. This study aimed to optimize the nutritional and functional properties of local complementary foods using flours of the following locally available crops: maize, red kidney bean, kocho, and pumpkin fruit. Ten formulations were generated using a customized mi...
Article
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Self-rated health (SRH) is associated with higher risk of death. Since low plasma levels of fat-soluble vitamins are related to mortality, we aimed to assess whether plasma concentrations of vitamins A, D and E were associated with SRH in the MARK-AGE study. We included 3158 participants (52% female) aged between 35–75 years. Cross-sectional data w...
Article
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The biological activities of curcumin in humans, including its antioxidative and anti-inflammatory functions, are limited by its naturally low bioavailability. Different formulation strategies have been developed, but the uptake of curcumin from these galenic formulations into and efflux from intestinal cells, which may be critical processes limiti...
Article
Contrary to the major vitamin E congener α-tocopherol, which carries a saturated sidechain, and α-tocotrienol, with a threefold unsaturated sidechain, little is known about the intracellular fate of α-tocomonoenol, a minor vitamin E derivative with a single double bond in C11′-position of the sidechain. We hypothesized that, due to structural simil...
Article
Scope: Different mechanistic approaches to improve the low oral bioavailability of curcumin have been developed, but not yet directly compared in humans. Methods and results: In a randomized, double-blind, cross-over trial with 12 healthy adults, the 24 h pharmacokinetics of a single dose of 207 mg curcumin is compared from the following formula...
Article
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Resveratrol, a natural plant phytoalexin, is produced in response to fungal infection or− UV irradiation. It exists as an isomeric pair with cis- and trans-conformation. Whereas multiple physiological effects of the trans-form, including a pronounced anti-tumoral activity, are nowadays elucidated, much less knowledge exists concerning the cis-isome...
Article
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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 farmer...
Article
Berries are rich food sources of potentially health-beneficial (poly)phenols. However, they may undergo chemical modifications during gastrointestinal digestion. The effect of simulated gastrointestinal digestion on the content and composition of secondary metabolites from Gaultheria phillyreifolia and G. poeppigii berries was studied. The influenc...
Article
Grains of three specialty maize varieties and one conventional maize variety cultivated in China were collected and dissected to obtain the germ, endosperm, and pericarp fraction, and then determined for distribution pattern of phosphorus, carotenoids, and tocochromanols. The results showed that phytochemical contents varied significantly among dif...
Article
Full-text available
The objective was to assess the prevalence of anemia and nutritional status of mothers and children under five years among Syrian refugees in Lebanon and to identify nutritional deficiencies among pregnant, lactating, and non-pregnant non-lactating (NPNLM) mothers. A cross-sectional study was conducted among Syrian refugee mothers with children und...
Thesis
Full-text available
Bitter acids are produced in the glands of the female inflorescence of hop and cause the characteristic bitter taste of most beer styles. The bitter acid biosynthesis is an enzymatic process in which three enzymes are mainly responsible for bitter acid production: valerophenone synthase (VPS) and prenyltransferases 1 and 2 (PT1 and PT2). PT1 is, in...
Article
Acrocomia aculeata is a promising crop for agroforestry systems in subtropical regions and investigated as an alternative to oil palm. Since significant regional differences in morphology and chemical composition have been reported for Acrocomia fruits, we aimed to determine the vitamin E profiles of Costa Rican Acrocomia aculeata from three differ...
Article
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The present demographic changes toward an aging society caused a rise in the number of senior citizens and the incidence and burden of age-related diseases (such as cardiovascular diseases [CVD], cancer, nonalcoholic fatty liver disease [NAFLD], diabetes mellitus, and dementia), of which nearly half is attributable to the population ≥60 years of ag...
Article
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Epidemiological studies frequently rely on a single biomarker measurement to assess the relationship between antioxidant status and diseases. This bears an inherent risk for misclassification, if the respective biomarker has a high intra-individual variability. The present study investigates the intra-individual variation and reliability of enzymat...
Article
Phosphate is a limiting plant nutrient and essential for corn growth and development. Thus, the impact of phosphate fertilization, location, and the variety of modern corn (Zea mays L.) hybrids on the profiles of fatty acids, carotenoids, and tocochromanols (vitamin E) was assessed in corn grains. Eight different corn hybrids were grown with (52.9...
Article
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Non-alcoholic fatty liver disease (NAFLD) is the most common liver disorder in Western nations and characterized by excessive accumulation of lipids in the liver. In this narrative review, we summarize the evidence from human trials that free radical-induced oxidation of macromolecules, in particular of lipids, is a characteristic feature of NAFLD...
Article
Scope A high fructose and galactose intake have shown adverse metabolic effects in animal models and in humans, but it is yet unknown if addition of fermentable dietary fiber could mitigate such effects. This study investigated the effects of high intakes of fructose and galactose, with/without added fructooligosaccharides (FOS), on metabolic facto...
Article
The effects of single and twofold continuous pressure change technology (PCT) applications on the volatiles and sensory characteristics of pineapple juice were studied. Fresh and thermally pasteurised juices were additionally characterised. 128 volatiles were tentatively assigned in the four juices. Thermal pasteurisation and a single PCT treatment...