The effect of vegetarian diets on iron status in adults: A systematic review and meta-analysis

Background: Vegetarian diets exclude meat, seafood, and products containing these foods. Although the vegetarian lifestyle could lead to a better health status in adults, it may also bear risks for certain nutritional deficiencies. Cross-sectional studies and narrative reviews have shown that the iron status of vegetarians is compromised by the absence of highly bioavailable haem-iron in meatless diets and the inhibiting effect of certain components present in plant foods on non-haem iron bioavailability.

Methods: The databases Pubmed, Scopus, Embase, and Cochrane CentralRegister of Controlled Trials were searched for studies comparing serum ferritin, as the major laboratory parameter for iron status of adult vegetarians with non-vegetarian control groups. A qualitative review was conducted as well as an inverse-variance random-effects meta-analysis to pool available data. In addition the effect of vegetarian diets according to gender was investigated with a subgroup analysis. The results were validated using a sensitivity analysis.

Results: A total of 27 cross-sectional studies and three interventional studies were selected for the systematic review. The meta-analysis which combined data of 24 cross-sectional studies showed that adult vegetarians have significantly lower serum ferritin levels than their non-vegetarian controls (?29.71 µg/L, 95% CI [?39.69, ?19.73], p < 0.01). Inclusion of semi-vegetarian diets did not change the results considerably (?23.27 µg/L, 95% CI [?29.77, ?16.76], p < 0.01). The effects were more pronounced in men (?61.88 µg/L, 95% CI [?85.59, ?38.17], p < 0.01) than in both premenopausal women (?17.70 μg/L, 95% CI [?29.80, ?5.60], p < 0.01) and all women (?13.50 μg/L, 95% CI [?22.96, ?4.04], p < 0.01), respectively.

Conclusions: In conclusion our results showed that vegetarians are more likely to have lower iron stores compared with non-vegetarians. However, since high iron stores are also a risk factor for certain non-communicable diseases, such as type 2 diabetes, it is recommended that not only vegetarians but also non-vegetarians should regularly control their iron status and improve their diet regarding the content and bioavailability of iron by consuming more plants and less meat.     

Sodium status and the metabolic syndrome: A systematic review and meta-analysis of observational studies

The prevalence of metabolic syndrome (MetS) has been greatly increased, worldwide. In recent years, investigators have proposed that sodium might contribute to the development of metabolic syndrome; however, the published data were conflicting. The present systematic review aimed to summarize the evidence from observational studies in this regard. We conducted a systematic search for relevant observational studies investigating the association between sodium status and MetS, published until June 2017 in electronic databases including PubMed, EMBASE, Scopus and Google Scholar. Summary effects were derived using random effects model. After screening the records, seventeen publications with 66,274 participants were eligible to be included in the systematic review and meta-analysis. The analysis revealed that subjects with MetS have significantly higher levels of sodium compared to healthy controls (Hedges' g = 0.21, 95% CI: 0.12, 0.29, I² = 68.6). Subgroup analyses revealed that the difference was significant when the sodium status was assessed using urinary sodium levels. The random effects meta-regression analysis also revealed that body sodium level increases with the number of MetS components. Furthermore, participants with highest dietary/urinary or serum sodium levels had 37% higher chance of developing MetS when compared with participants with the lowest sodium levels (OR = 1.37 95%CI: 1.31, 1.42, I² = 86.9). The current meta-analysis revealed that higher sodium input into the body is directly associated with the likelihood of MetS. Prospective cohort studies and well-designed randomized clinical trials considering the effect of sodium restricted diets on the risk of MetS as an outcome are necessary to represent the causal association.     

Effect of vitamin A supplementation on iron status in humans: A systematic review and meta-analysis

Anemia is a worldwide public health problem that can be related to many causes, including vitamin A deficiency. The aim of this study was to assess and estimate the effect of vitamin A supplementation (VAS) on iron status biomarkers and anemia in humans. Six databases, including Cochrane, EMBASE, LILACS, Pubmed, Scopus and Web of Science, were searched for clinical trials and cohort studies that investigated the effect of vitamin A supplementation alone on iron status and anemia, without time-restriction. The search yielded 23 eligible studies, 21 clinical trials and 2 cohort studies, with children, teenagers, pregnant or lactating women. The meta-analysis of the clinical trials showed that VAS reduces the risk of anemia by 26% and raises hemoglobin levels, compared to non-treated group, independent of the life stage. VAS did not alter the prevalence of iron deficiency among the clinical trials conducted with children and teenagers (RR 0.82, 95% CI 0.60 to 1.12, p = 0.204), whereas a significant increase in serum ferritin levels was observed in trials conducted with pregnant and lactating women (WMD 6.61 μg/L; 95% CI 6.00 to 7.21 μg/L; p < 0.001). Therefore, vitamin A supplementation alone may reduce the risk of anemia, by improving hemoglobin and ferritin levels in individuals with low serum retinol levels.     

Calcium bioavailability of vegetarian diets in rats: potential application in a bioregenerative life-support system

Calcium bioavailability of vegetarian diets containing various proportions of candidate crops for a controlled ecological life-support system (CELSS) was determined by femur 45Ca uptake. Three vegetarian diets and a control diet were labeled extrinsically with 45Ca and fed to 5-wk old male rats. A fifth group of rats fed an unlabeled control diet received an intraperitoneal (IP) injection of 45Ca. There was no significant difference in mean calcium absorption of vegetarian diets (90.80 +/- 5.23%) and control diet (87.85 +/- 5.25%) when calculated as the percent of an IP dose. The amounts of phytate, oxalate, and dietary fiber in the diets did not affect calcium absorption.     

Assessment of zinc deficiency and effect of dietary carrot, amchur and onion on zinc status during repletion in zinc-deficient rats

BACKGROUND: Food acidulants, β‐carotene‐rich vegetables and sulfur compound‐rich Allium spices are known to improve zinc bioaccessibility from food grains. This animal study evaluated the positive influence of these promoters of zinc bioaccessibility on zinc status during zinc repletion in Wistar rats previously rendered zinc‐deficient by feeding a zinc‐deficient semi‐synthetic diet for 4 weeks. Groups of these zinc‐deficient animals were subsequently maintained on a zinc‐containing grain‐based diet for 2 weeks. Various experimental diets consisted of the grain‐based diet supplemented with (1) carrot, (2) onion, (3) amchur, (4) carrot + amchur and (5) onion + amchur. RESULTS: Zinc deficiency was confirmed by lower zinc concentration in tissues and bones and lower activity of zinc‐containing enzymes. Zinc concentration was 10–15% lower in serum, liver and kidney of zinc‐deficient rats. Bone weight in zinc‐deficient rats was 20% lower than that in normal rats. Activities of zinc‐containing enzymes (hepatic superoxide dismutase and alcohol dehydrogenase and serum alkaline phosphatase) were lower in the zinc‐deficient group. Animals fed diets supplemented with these promoters of zinc bioaccessibility showed better zinc status in tissues and bones compared with those repleted with the control stock diet. CONCLUSION: This animal study supports the claim of promoters of zinc bioaccessibility for improving zinc status, which may find practical application. Copyright © 2011 Society of Chemical Industry     

Effect of the vegetarian diet on non‐communicable diseases

A vegetarian diet generally includes plenty of vegetables and fruits, which are rich in phytochemicals, antioxidants, fiber, magnesium, vitamins C and E, Fe³⁺, folic acid and n‐6 polyunsaturated fatty acid (PUFA), and is low in cholesterol, total fat and saturated fatty acid, sodium, Fe²⁺, zinc, vitamin A, B₁₂ and D, and especially n‐3 PUFA. Mortality from all‐cause, ischemic heart disease, and circulatory and cerebrovascular diseases was significantly lower in vegetarians than in omnivorous populations. Compared with omnivores, the incidence of cancer and type 2 diabetes was also significantly lower in vegetarians. However, vegetarians have a number of increased risk factors for non‐communicable diseases such as increased plasma homocysteine, mean platelet volume and platelet aggregability compared with omnivores, which are associated with low intake of vitamin B₁₂ and n‐3 PUFA. Based on the present data, it would seem appropriate for vegetarians to carefully design their diet, specifically focusing on increasing their intake of vitamin B₁₂ and n‐3 PUFA to further reduce already low mortality and morbidity from non‐communicable diseases. © 2013 Society of Chemical Industry     

The sensory acceptance of fibre‐enriched cereal foods: a meta‐analysis

Improved understanding of the sensory responses to fibre fortification may assist manufacturers and health promotion efforts. The effects of fibre fortification (or modified ingredients) on sensory acceptability of baked cereal foods (bread, cookies, muffins) were estimated by linear random‐effects meta‐analysis of twenty eligible studies (869 panellists, 34% male). As little as 2 g per 100 g fortification caused moderate–large reductions in overall acceptability, flavour acceptability, and appearance acceptability in most items, with cookies most negatively affected. Fortification of base nonfortified foods with low initial acceptability improved acceptability; however, at higher basic levels, fortification lowered acceptability. Fortification improved texture acceptability of muffins and bread with low base acceptability, but lowered texture acceptability when base acceptability was high. Flavour improvement of muffins with fortification decreased with increasing base food acceptability. Fibre fortification of baked cereal foods lowers acceptability, but food format and base food acceptability affect the magnitude and direction of responses. Refining fibre fortification approaches could improve consumer uptake.     

Effect of dietary cation-anion difference on acid-base status and dry matter intake in dry pregnant cows

The objective was to determine if the reduction in dry matter (DM) intake of acidogenic diets is mediated by inclusion of acidogenic products, content of salts containing Cl, or changes in acid-base status. The hypothesis was that a decrease in intake is mediated by metabolic acidosis. Ten primigravid Holstein cows at 148 ± 8 d of gestation were used in a duplicated 5 × 5 Latin square design. The dietary cation-anion difference (DCAD) of diets and acid-base status of cows were manipulated by incorporating an acidogenic product or by adding salts containing Cl, Na, and K to the diets. Treatments were a base diet (T1; 1.42% K, 0.04% Na, 0.26% Cl; DCAD = 196 mEq/kg); the base diet with added 1% NaCl and 1% KCl (T2; 1.83% K, 0.42% Na, 1.23% Cl; DCAD = 194 mEq/kg); the base diet with added 7.5% acidogenic product, 1.5% NaHCO₃, and 1% K₂CO₃ (T3; 1.71% K, 0.54% Na, 0.89% Cl; DCAD = 192 mEq/kg); the base diet with added 7.5% acidogenic product (T4; 1.29% K, 0.13% Na, 0.91% Cl; DCAD = ?114 mEq/kg); and the base diet with 7.5% acidogenic product, 1% NaCl, and 1% KCl (T5; 1.78% K, 0.53% Na, 2.03% Cl; DCAD = ?113 mEq/kg). Periods lasted 14 d with the last 7 d used for data collection. Feeding behavior was evaluated for 12 h in the last 2 d of each period. Reducing the DCAD by feeding an acidogenic product reduced blood pH (T1 = 7.450 vs. T2 = 7.436 vs. T3 = 7.435 vs. T4 = 7.420 vs. T5 = 7.416) and induced a compensated metabolic acidosis with a reduction in bicarbonate, base excess, and partial pressure of CO₂ in blood, and reduced pH and strong ion difference in urine. Reducing the DCAD reduced DM intake 0.6 kg/d (T1 = 10.3 vs. T4 = 9.7 kg/d), which was caused by the change in acid-base status (T2 + T3 = 10.2 vs. T4 + T5 = 9.6 kg/d) because counteracting the acidifying action of the acidogenic product by adding salts with strong cations to the diet prevented the decline in intake. The decline in intake caused by metabolic acidosis also was observed when adjusted for body weight (T2 + T3 = 1.75 vs. T4 + T5 = 1.66% BW). Altering the acid-base status with acidogenic diets reduced eating (T2 + T3 = 6.7 vs. T4 + T5 = 5.9 bouts/12 h) and chewing (T2 + T3 = 14.6 vs. T4 + T5 = 13.5 bouts/12 h) bouts, and extended meal duration (T2 + T3 = 19.8 vs. T4 + T5 = 22.0 min/meal) and intermeal interval (T2 + T3 = 92.0 vs. T4 + T5 = 107.7 min). Results indicate that reducing the DCAD induced a compensated metabolic acidosis and reduced DM intake, but correcting the metabolic acidosis prevented the decline in DM intake in dry cows. The decrease in DM intake in diets with negative DCAD was mediated by metabolic acidosis and not by addition of acidogenic product or salts containing Cl.     

Is a vegan or a vegetarian diet associated with the microbiota composition in the gut? Results of a new cross-sectional study and systematic review

Abstract

It is assumed that diet influences the composition of gut microbiota, which in turn may affect human health status. This systematic review aimed to summarize associations of a vegan or vegetarian diet with the composition of microbiota. A literature search was conducted in PubMed and Embase for eligible human studies with vegan or vegetarian diets as an exposure and microbiota composition as an outcome in healthy adults. Furthermore, data from our cross-sectional study with vegan participants were included. Out of sixteen included studies, six investigated the association between gut microbiota composition in both vegans and in vegetarians, six in vegans and four studies in vegetarians compared to omnivores, respectively. Among 5 different phyla, 28 families, 96 genera and 177 species, Bacteroides, Bifidobacterium and Prevotella were the most reported genera, followed by the species Prevotella copri, Faecalibacterium prausnitzii and Escherichia coli in all diets. No consistent association between a vegan diet or vegetarian diet and microbiota composition compared to omnivores could be identified. Moreover, some studies revealed contradictory results. This result could be due to high microbial individuality, and/or differences in the applied approaches. Standardized methods with high taxonomical and functional resolutions are needed to clarify this issue.     

Graduate Student Literature Review: A scoping review on the impact of consumption of dairy products on phosphatidylcholine and lysophosphatidylcholine in circulation and the liver in human studies and animal models

Dairy consumption is inversely related to the risk of developing type 2 diabetes in epidemiological research. One proposed hypothesis is that phospholipid (PL) species associated with dairy consumption mediate this relationship. This scoping review aimed to identify the existing literature in animal and human trials investigating the impact of dairy products, including milk, yogurt, and cheese as well as dairy-derived PL supplementation on PL and its species in the circulation, summarizing the characteristics of these studies and identifying research gaps. A systematic search was conducted across 3 databases (PubMed, Scopus, and Web of Science) in March 2021. Of 2,427 identified references, 15 studies (7 humans and 8 animal studies) met the eligibility criteria and were included in the final narrative synthesis. The evidence base was heterogeneous, involving a variety of clinical and preclinical studies, metabolically healthy or obese/diabetic participants or animal models, and displayed mixed findings. Circulating postprandial concentrations of total PL were elevated acutely but unchanged after longer intervention with dairy products. The PL concentration remained stable even after a high dosage of milk supplemented with dairy-derived PL, which may be related to increased fecal excretion; however, certain phosphatidylcholine (PC) or lysophosphatidylcholine species were increased in circulation by interventions. These include several PC species with 32 to 38 total carbons in addition to the dairy biomarkers C15:0 and C17:0. The results of this scoping review demonstrate a small body of literature indicating that dairy products can influence blood concentrations of PC and lysophosphatidylcholine species in both rodents and humans without alteration of total PL and PC. There is a lack of well-designed trials in humans and animals that explore the potential differences between individual dairy foods on PL species. In addition, trials to understand the bioactive properties of PC and lysophosphatidylcholine species on cardiometabolic risk are needed.     

Effect of natural fermentation on in vitro zinc bioavailability in cereal–legume mixtures

There is increasing concern about zinc availability from cereal-based vegetarian diets and the need to improve its native bioavailability. Effects of natural fermentation on zinc availability were assessed by in vitro assay with a ⁶⁵Zn extrinsic tag on four cereals (rice, wheat, sorghum and pearl millet), four decorticated legumes (red gram, bengal gram, green gram and black gram) and their 16 binary combinations. Fermentation significantly increased zinc solubility (2–28%) and zinc uptake by intestinal segment (1–16%). Two-way ANOVA indicated significant effects of combinations on zinc solubility but not on zinc uptake in both fermented and unfermented states. Levels of phytate-P were reduced while titratable acid and ascorbic acid levels were increased by fermentation. However, tannins were unchanged.     

Nitrogen fertilisation in coriander (Coriandrum sativum L.): a review and meta‐analysis

Nitrogen (N) fertilisation is one of the most important external inputs in assessing coriander seed yield and plant growth. Recent concerns related to the misuse of N fertilisers in agricultural environments, however, stress the opportunity for a fine‐tuning of N management in order to optimise the use of this element, avoiding losses and reducing environmental hazards. In this study, some results from the literature concerning N fertilisation in coriander are reviewed and, by means of statistical analysis, an attempt is made to derive from them some general suggestions about practices of N fertilisation. In most cases examined, N fertilisation allowed a 10–70% increase in seed yields in comparison with each respective untreated control. The efficiency of use of this element, however, has proven to be greatly dependent on the overall fertility conditions of the growing site. The greatest yield advantages were actually found in more favourable environments, whereas in low‐yielding environments plants reached their maximum yield with a comparatively reduced N supply. In low‐yielding environments a careful risk/benefit assessment of this practice is therefore advisable. No definite conclusion could be drawn at this stage about essential oil yield and composition in relation to N fertilisation. Copyright © 2009 Society of Chemical Industry     

盘龙区9岁及以上社区居民膳食营养素摄 入状况分析

目的 分析2010年昆明市盘龙区9岁及以上居民膳食与营养素摄入状况。方法 采用整群随机抽样的方法,在盘龙区抽取180户334名9岁及以上居民开展连续3天24小时膳食回顾调查。 结果 2010年盘龙区9岁及以上居民谷类及制品每日平均摄入量为485.4g,豆及其制品摄入量为19.1g,动物性食物摄入量为185.8g(猪肉91.4g、其他畜肉31.0g、内脏4.9g、禽肉类18.4g、蛋类20.5g、鱼虾贝壳类19.6g),乳及其制品50.6g,蔬菜及制品321.6 g,水果及其制品61.8g,油脂类食物39.0 g,调味品24.7g(盐8.8g,酱类7.7g、酱油0.4g),坚果及种子类2.9g,糕点糖果类26.4g。居民每标准人日能量摄入为1960.9Kcal,蛋白质摄入70.4g/d,脂肪摄入为82.5 g/d,碳水化合物摄入235.5 g/d,胆固醇为281.3,膳食纤维为12.5 g/d,灰分摄入为20.7 g/d,维生素A视黄醇当量561.9ug /d,胡萝卜素2074.2 ug/d,视黄醇213.6 ug/d,维生素E总量29.7 mg/d,硫胺素1.0 mg/d,核黄素0.9 mg/d,维生素C104.3 mg/d,尼克酸19.5 mg/d,α维生素E9.3 mg/d,钙403.1mg/d,磷1018.9mg/d,钾1789.1mg/d,钠4957.1mg/d,镁278.3mg/d,铁23.5mg/d,锌12.3mg/d,硒44.1mg/d,铜1.7mg/d,锰5.4mg/d。盘龙区居民蛋白质、脂肪和碳水化合物提供能量比例分别为14.6%、36.1%和49.9%;谷类、豆类、薯类、动物性食物、纯热能食物、其他食物等各类食物提供的能量分别占总能量的42.2%、3.9%、1.8%、23.0%、16.0%和13.1%。膳食蛋白质来源于谷类、豆类、动物性食物、其他食物分别为32.3%、8.5%、42.7%和16.6%。脂肪来源于动物性食物和植物性食物的脂肪分别为43.5%和56.5%。 结论 2010年盘龙区居民膳食情况较2002年全国平均水平的摄入状况有较大变化。盘龙区居民的膳食结构不合理,营养素摄入不平衡,蛋类、鱼虾贝壳类、干豆及其制品、乳及其制品等摄入不足,均低于我国居民膳食营养素参考摄入量,而油脂类食物和食盐的摄入量均高于我国居民膳食营养素参考摄入量。     

Impact of food consumption habits on the pesticide dietary intake: Comparison between a French vegetarian and the general population

This study aims to compare the pesticide residue dietary intake of the French general population and the vegetarian population, separated into five specific diets: omnivorous (OMN), lacto-vegetarian (LV), ovo-lacto-vegetarian (OLV), pesco-lacto-vegetarian (PLV) and vegan (VG). Theoretical Maximum Daily Intakes (TMDIs) based on Maximum Residue Levels (MRLs) were calculated as a percentage of the Acceptable Daily Intake (ADI). Among the 421 pesticides studied, only 48 had TMDI above ADI for at least one population subgroup. An excessive exposure was noticed for 44, 43, 42, 41 and 30 pesticides in the OLV, VG, OMN, LV and PLV groups, respectively, versus 29 in the general population. Meat and egg products consumption was responsible for higher intakes of organochlorine pesticides in the general population than in the vegetarian population (TMDI = 348% versus 146–183% ADI for aldrin). However, as the limited consumption of animal-origin commodities was largely offset by a higher fruit, vegetable and cereal intake in the vegetarian diets, vegetarians appear to be preferentially exposed to pesticides, for which fruit, vegetables and cereals are the main contributors, such as tri-allate, chlorpyrifos-methyl and diazinon. This study illustrates that consumption habits have a real impact on pesticide exposure in terms of intake levels, number and type of pesticides, representing a potential risk of dietary exposure. Except for organochlorine compounds, the vegetarian population may be more exposed to pesticide residues than the general population due to specific dietary habits. Thus, this population should be considered for risk assessment of pesticide residues.