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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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Plain language summary
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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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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Effect of double-blind crossover selenium supplementation on biological indices of selenium status in cystic fibrosis patients.
Portal, B, Richard, MJ, Ducros, V, Aguilaniu, B, Brunel, F, Faure, H, Gout, JP, Bost, M, Favier, A
Clinical chemistry. 1993;39(6):1023-8
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Plain language summary
Previous studies have found that cystic fibrosis (CF) patients have lower blood selenium concentrations than healthy individuals. It is thought that this is likely to be an effect of the disease, rather than a cause. Selenium is needed for the production of glutathione peroxidase, an antioxidant enzyme that protects cells from oxidative damage. The purpose of this study was to investigate the selenium status of CF patients before and after supplementation with selenium. In this double-blind, cross-over trial, patients were given 2.8 micrograms of sodium selenite per kg of bodyweight per day for 5 months. At the start of the trial, selenium concentrations in the blood of CF patients were about the same as those seen in healthy people. After supplementation, both selenium and glutathione peroxidase levels increased. One explanation for the apparently normal levels of selenium seen in CF patients before the start of the study was that many of the patients had been self-supplementing with selenium before the study began. The authors recommend that the selenium status of every CF patient should be checked, and supplementation given where needed.
Abstract
Twenty-seven cystic fibrosis patients received selenium supplementation (2.8 micrograms of sodium selenite per kilogram of body weight per day) or a placebo. This 5-month trial was conducted as a double-blind, placebo-controlled study. After an interval of 2 months, treatments of the two groups were interchanged (crossed over) for another 5-month period. A group of healthy subjects, living in the same area, was investigated simultaneously. No selenium deficiency was found either in plasma or in erythrocytes before the supplementation. This result was inconsistent with a previous study performed in 1988 in our laboratory. This change in selenium status can be explained by progress in the nutritional nursing care of children and by the addition of selenium to the diet. During the study, selenium concentrations in plasma decreased when patients received placebo treatment and increased during selenium intake. In one of the two groups a similar variation was found for glutathione peroxidase activities in plasma and erythrocytes, whereas erythrocyte selenium was normal and did not change in any group. Nowadays, in the Grenoble area, the selenium status of cystic fibrosis patients is close to normal. Nevertheless, this study indicates a fragile equilibrium, given that selenium concentrations cn be lowered by placebo or mildly increased by supplementation.