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Intake and adequacy of the vegan diet. A systematic review of the evidence.
Bakaloudi, DR, Halloran, A, Rippin, HL, Oikonomidou, AC, Dardavesis, TI, Williams, J, Wickramasinghe, K, Breda, J, Chourdakis, M
Clinical nutrition (Edinburgh, Scotland). 2021;40(5):3503-3521
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This systematic review investigated vegan diets in the European populations and their adequacy of macro-and micronutrient intake, compared to the recommendations of the World Health Organization. Included were 48 studies and their outcomes regarding protein, carbohydrates, fats and micronutrients summarized. The overall results and their impact on health are discussed in the later sections of the paper. Adequate intake amongst vegans was seen with carbohydrates, fats, Vitamin A, B1, В6, C, E, iron, phosphorus, magnesium, copper and folate. Sodium exceeded recommended intake, whilst protein, Vitamin B2, B3, B12, D, iodine, zinc, calcium, potassium, selenium was of low consumption in a vegan diet. The bioavailability of some nutrients was also acknowledged. In summary, following a vegan diet appears to have positive and negative aspects. A vegan diet profile can contribute to disease prevention with lower incidence rates of obesity, Type 2 diabetes, and cardiovascular disease. Yet veganism appears to increase the risk for mental health conditions, bone fractures, immune system impairments, anaemias and deficiencies from low nutrient intake. This review yields a comprehensive overview of the positive and negative health consequences of a vegan diet. It may be a useful reference for those looking to support vegans or individuals considering adopting a vegan diet pattern.
Expert Review
Conflicts of interest:
None
Take Home Message:
- Vegan diets in European populations tend to be lower in protein intake, particularly amino acids lysine, methionine and tryptophan.
- Other micronutrients that tend to lower in vegan diets are Vitamin B12, zinc, calcium and selenium.
- Healthcare practitioners should be aware of these potential deficiencies when working with vegan clients.
Evidence Category:
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A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
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X
B: Systematic reviews including RCTs of limited number
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C: Non-randomized trials, observational studies, narrative reviews
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D: Case-reports, evidence-based clinical findings
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E: Opinion piece, other
Summary Review:
Vegan diets have become increasingly popular in the last ten years. This systematic review of 48 studies investigated the adequacy of vegan diets in European populations. It compared their macro- and micronutrient intakes compared to World Health Organization recommendations. It found that vegan diets tend to be lower in protein and in essential amino acids (lysine, methionine and tryptophan). They can also be lower in micronutrients especially vitamin B12, zinc, calcium and selenium. However, the lower intakes are not always associated with health impairments.
Clinical practice applications:
Practitioners should be aware of the potential deficiencies in a vegan diet.
Considerations for future research:
More research is needed to determine whether lower nutrient intakes in vegans correlated with poor health outcomes.
Abstract
BACKGROUND Vegan diets, where animal- and all their by-products are excluded from the diet, have gained popularity, especially in the last decade. However, the evaluation of this type of diet has not been well addressed in the scientific literature. This study aimed to investigate the adequacy of vegan diets in European populations and of their macro- and micronutrient intakes compared to World Health Organization recommendations. METHODS A systematic search in PubMed, Web of Science, IBSS, Cochrane library and Google Scholar was conducted and 48 studies (12 cohorts and 36 cross-sectional) were included. RESULTS Regarding macronutrients, vegan diets are lower in protein intake compared with all other diet types. Veganism is also associated with low intake of vitamins B2, Niacin (B3), B12, D, iodine, zinc, calcium, potassium, selenium. Vitamin B12 intake among vegans is significantly lower (0.24-0.49 μg, recommendations are 2.4 μg) and calcium intake in the majority of vegans was below recommendations (750 mg/d). No significant differences in fat intake were observed. Vegan diets are not related to deficiencies in vitamins A, B1, Β6, C, E, iron, phosphorus, magnesium, copper and folate and have a low glycemic load. CONCLUSIONS Following a vegan diet may result in deficiencies in micronutrients (vitamin B12, zinc, calcium and selenium) which should not be disregarded. However, low micro- and macronutrient intakes are not always associated with health impairments. Individuals who consume a vegan diet should be aware of the risk of potential dietary deficiencies.
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Thyroid-Gut-Axis: How Does the Microbiota Influence Thyroid Function?
Knezevic, J, Starchl, C, Tmava Berisha, A, Amrein, K
Nutrients. 2020;12(6)
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Thyroid and gut disease often coexist together. This literature review highlights the strong interplay between gut, microbiota and thyroid disease. In autoimmune thyroid disease (AITD) gut bacteria imbalances, bacterial overgrowth, Coeliac's disease or non-coeliacs wheat sensitivity, increased gut permeability and resulting deficiency of thyroid nutrients are not uncommon. Inflammation and intestinal wall damage that lead to increased permeability are thought to be one of the driving factors for autoimmune activity. Allergens, certain drugs, impaired gut flora and nutrient deficiencies are some of the contributors to heightened intestinal permeability. Furthermore, the gut walls host deiodinase enzymes that convert thyroid hormone to its active form. The gut microbiota however influence thyroid function in their own rights. The bacteria are crucial for nutrient synthesis, absorption and availability, including those essential for thyroid health. Gut bacteria and their metabolites also play a significant role in the regulation, development and training of immune cells, relevant to AITD. After all, the gut also houses a large proportion of the immune system known as gut-associated lymphatic tissue (GALT). Besides, some bacteria species seem to be capable of balancing fluctuating thyroid hormone levels in the blood. The writings further elaborate on thyroid-essential nutrients and the gut such as iodine, iron, zinc, selenium and Vitamin D. And the impact of bariatric surgery on thyroid function and the presence of certain gut bacteria in thyroid cancers. In summary, the authors concluded that the thyroid-gut axis seems to exhibit a strong connection. Limited evidence from human studies showed promising results of probiotics and synbiotics on thyroid function and targeting the microbiota as a novel strategies for the management of thyroid disease is encouraged to be explored further. This article may be of interest to those looking for an informative summary on the many ways in which the gut influences thyroid function in health and disease.
Abstract
A healthy gut microbiota not only has beneficial effects on the activity of the immune system, but also on thyroid function. Thyroid and intestinal diseases prevalently coexist-Hashimoto's thyroiditis (HT) and Graves' disease (GD) are the most common autoimmune thyroid diseases (AITD) and often co-occur with Celiac Disease (CD) and Non-celiac wheat sensitivity (NCWS). This can be explained by the damaged intestinal barrier and the following increase of intestinal permeability, allowing antigens to pass more easily and activate the immune system or cross-react with extraintestinal tissues, respectively. Dysbiosis has not only been found in AITDs, but has also been reported in thyroid carcinoma, in which an increased number of carcinogenic and inflammatory bacterial strains were observed. Additionally, the composition of the gut microbiota has an influence on the availability of essential micronutrients for the thyroid gland. Iodine, iron, and copper are crucial for thyroid hormone synthesis, selenium and zinc are needed for converting T4 to T3, and vitamin D assists in regulating the immune response. Those micronutrients are often found to be deficient in AITDs, resulting in malfunctioning of the thyroid. Bariatric surgery can lead to an inadequate absorption of these nutrients and further implicates changes in thyroid stimulating hormone (TSH) and T3 levels. Supplementation of probiotics showed beneficial effects on thyroid hormones and thyroid function in general. A literature research was performed to examine the interplay between gut microbiota and thyroid disorders that should be considered when treating patients suffering from thyroid diseases. Multifactorial therapeutic and preventive management strategies could be established and more specifically adjusted to patients, depending on their gut bacteria composition. Future well-powered human studies are warranted to evaluate the impact of alterations in gut microbiota on thyroid function and diseases.
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The Effect of a Multivitamin and Mineral Supplement on Immune Function in Healthy Older Adults: A Double-Blind, Randomized, Controlled Trial.
Fantacone, ML, Lowry, MB, Uesugi, SL, Michels, AJ, Choi, J, Leonard, SW, Gombart, SK, Gombart, JS, Bobe, G, Gombart, AF
Nutrients. 2020;12(8)
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Vitamins and minerals are essential for a healthy immune system. The prevalence of vitamin and mineral deficiencies increases with age, and this may contribute to age-related decline of the immune system. The aim of this study was to investigate whether a daily multivitamin and mineral (MVM) supplement could improve the immune function of older people. 42 healthy adults aged between 55 and 75 took part in this single-centre, two-armed, parallel, randomised, double-blinded study. Half of the group was given a MVM supplement called Redoxon Vita Immune (VI) containing the vitamins A, D, E, C, B6, B12 and folate plus iron, copper, zinc and selenium daily for 12 weeks, whilst the other half was given placebo tablets for 12 weeks. Participants were instructed to avoid certain foods high in vitamins and minerals such as oily fish, red meat, liver, and citrus fruits during the study period. Blood and saliva samples were taken from all participants at the beginning and end of the study period, to measure vitamin and mineral status and markers of immune function. Participants also kept a diary to record any illnesses or symptoms. At the end of the study, participants given the MVM supplement had increased their blood levels of vitamin C by 126% and zinc by 43%. There was no significant change in blood levels of vitamin D. There was no significant difference in the potential of blood to kill the introduced bacteria Staphylococcus aureus, or in neutrophil activity, nor were there any significant changes in blood levels of cytokines and chemokines. Participants taking the supplement did however report a shorter length, and lower severity of illnesses compared to those taking the placebo. The authors concluded that their findings support further research to test whether MVM supplementation can improve immune outcomes in older adults.
Abstract
Older adults are at increased risk for vitamin and mineral deficiencies that contribute to age-related immune system decline. Several lines of evidence suggest that taking a multi-vitamin and mineral supplement (MVM) could improve immune function in individuals 55 and older. To test this hypothesis, we provided healthy older adults with either an MVM supplement formulated to improve immune function (Redoxon® VI, Singapore) or an identical, inactive placebo control to take daily for 12 weeks. Prior to and after treatment, we measured (1) their blood mineral and vitamin status (i.e., vitamin C, zinc and vitamin D); (2) immune function (i.e., whole blood bacterial killing activity, neutrophil phagocytic activity, and reactive oxygen species production); (3) immune status (salivary IgA and plasma cytokine/chemokine levels); and (4) self-reported health status. MVM supplementation improved vitamin C and zinc status in blood and self-reported health-status without altering measures of immune function or status or vitamin D levels, suggesting that healthy older adults may benefit from MVM supplementation. Further development of functional assays and larger study populations should improve detection of specific changes in immune function after supplementation in healthy older adults. Clinical Trials Registration: ClinicalTrials.gov #NCT02876315.