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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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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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Effects of ascorbic acid supplementation on oxidative stress markers in healthy women following a single bout of exercise.
Yimcharoen, M, Kittikunnathum, S, Suknikorn, C, Nak-On, W, Yeethong, P, Anthony, TG, Bunpo, P
Journal of the International Society of Sports Nutrition. 2019;16(1):2
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Moderately intense exercise often causes muscle damage, which initiates an acute inflammatory response. Vitamin C or ascorbic acid is suggested to provide antioxidant protection against oxidative stress. The efficacy of ascorbic acid supplementation on exercise-induced oxidative stress remains unclear. The aim of this crossover study was to determine the effects of ascorbic acid supplementation on circulating biomarkers of oxidative stress and muscle damage in 19 healthy women after a single bout of moderately-intense exercise. Participants performed 30 minutes of cycling after ingesting 1000 mg of ascorbic acid or placebo with a one-week washout period. Blood samples were taken before exercise, immediately after and 30 minutes post-exercise to determine various markers of oxidative stress and muscle damage. This study found ascorbic acid supplementation prior to moderately-intense exercise improves antioxidant capacity but does not prevent muscle damage. The exercise performed in this study did not induce systemic inflammation, only low-grade muscle damage. Based on these results, the authors suggest further investigation of the effects of ascorbic acid supplementation during exercise be done to better understand the molecular interactions of ascorbic acid during exercise.
Abstract
BACKGROUND Ascorbic acid is a water-soluble chain breaking antioxidant. It scavenges free radicals and reactive oxygen species (ROS), which are produced during metabolic pathways. Exercise can produce an imbalance between ROS and antioxidants, leading to oxidative stress-related tissue damages. This study was designed to determine the effects of ascorbic acid supplementation on circulating biomarkers of oxidative stress and muscle damage following a single bout of exercise. METHODS In a crossover design with a 1 wk. wash-out period, 19 healthy women performed 30 min moderate-intensity cycling after ingesting 1000 mg of ascorbic acid (AA) or placebo. Blood samples were taken immediately before, immediately after and 30 min post-exercise to determine plasma albumin, total protein, glucose, oxidative stress and muscle damage markers. RESULTS Plasma albumin and total protein levels increased immediately after exercise in placebo alongside slight reductions in glucose (p = 0.001). These effects were absent in AA cohort. Ferric reducing ability of plasma and vitamin C levels in AA cohort significantly increased after exercise (p < 0.05). Superoxide dismutase activity was significantly elevated after exercise (p = 0.002) in placebo but not AA. Plasma malondialdehyde did not change after exercise in placebo but was significantly decreased in AA (p < 0.05). The exercise protocol promoted slight muscle damage, reflected in significant increases in total creatine kinase in all subjects after exercise. On the other hand, plasma C-reactive protein and lactate dehydrogenase remained unchanged. CONCLUSION Supplementation with ascorbic acid prior exercise improves antioxidant power but does not prevent muscle damage.
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Associations between maternal antioxidant intakes in pregnancy and infant allergic outcomes.
West, CE, Dunstan, J, McCarthy, S, Metcalfe, J, D'Vaz, N, Meldrum, S, Oddy, WH, Tulic, MK, Prescott, SL
Nutrients. 2012;4(11):1747-58
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This research studied the maternal intake of antioxidants (carotene, vitamin C, vitamin E, copper and zinc) during pregnancy and the effect on allergic outcomes during early infancy (eczema, food allergies, allergic sensitisation and wheeze) at 1 year of age. The study included 300 mother and child pairs from a pregnancy cohort in Western Australia from 2005 to 2008. The pregnant women had a family history of allergic rhinitis, asthma, eczema, food or other allergy. A post-natal randomised trial allocated either 650mg fish oil (280mg docosahexaenoic acid (DHA) and 110mg eicosapentaenoic acid (EPA)) or a placebo of olive oil for the first 6 months of life. The study also examined the effect of maternal diet during pregnancy. Demographic information was collected, and a semi quantitative food frequency questionnaire covering 212 foods was completed during the final trimester of pregnancy. Clinical outcome measures of the infants were taken at 12 months of age via a detailed history and examination. Eczema, IgE mediated food allergies and allergic sensitisation were the most common clinical outcomes of the study. The majority of pregnant women met the recommended daily intakes of antioxidants apart from vitamin E and zinc. At 12 months of age there was no difference in the occurrence of clinical outcomes between the fish oil and placebo groups. Higher dietary vitamin C in the mothers was associated with reduced risk of any diagnosed allergic disease when children were a year old, and also a reduced risk of wheeze. Higher copper intake was related to reduced risk of wheeze and development of early allergic disease. However, this was only seen in relation to nutrients from food rather than supplements. It was noted that there were no significant associations between early allergic responses/disease and dietary intake of carotene, vitamin E and zinc. In the group studied, the majority of mothers used some vitamin/mineral supplementation during pregnancy. There was no statistically significant association between carotene, vitamin E and zinc intake in pregnancy and risk of developing any allergic disease. Women reported intakes of dietary vitamin C were above the daily recommended intake of 60mg, and authors noted that allergic outcomes were not affected by vitamin supplementation.
Abstract
Antioxidant intakes in pregnancy may influence fetal immune programming and the risk of allergic disease. We investigated associations between maternal intakes of β-carotene, vitamin C, vitamin E, copper and zinc, and infant allergic outcomes. Antioxidant intakes of pregnant women (n = 420) assessed prospectively by a food frequency questionnaire, were examined in relation to allergic outcomes at 1 year of age (n = 300). The main relationships with allergic outcomes were seen with dietary vitamin C and copper. Specifically, higher maternal dietary vitamin C intake was associated with a reduced risk of any diagnosed infant allergic disease and wheeze. After adjustment for potential confounders the relationship with wheeze remained statistically significant. There was also an inverse linear relationship between vitamin C and food allergy. Higher dietary copper intake was associated with reduced risk of eczema, wheeze and any allergic disease. The relationship with wheeze and any allergic disease remained statistically significant in multivariate analysis, and there was also an inverse linear relationship between copper and food allergy. However, these relationships were only seen for nutrients present in food. There were no relationships between β-carotene, vitamin E or zinc and any allergic outcomes. In summary, this study suggests that maternal diet of fresh foods rich in vitamin C is associated with reduced risk of infant wheeze, and that copper intake is associated with reduced risk of several allergic outcomes.
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Functional biochemical and nutrient indices in frail elderly people are partly affected by dietary supplements but not by exercise.
de Jong, N, Chin A Paw, MJ, de Groot, LC, de Graaf, C, Kok, FJ, van Staveren, WA
The Journal of nutrition. 1999;129(11):2028-36
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Elderly people are at risk of nutritional deficiencies for a variety of reasons including reduced appetite, increased medication, and alterations in the absorption and metabolism of vitamins and minerals with age. The aim of this study was to measure the influence of exercise, and supplementing the diet with vitamins and minerals, on indicators of nutritional and health status in frail elderly people. A 17-week randomised controlled trial was carried out on 145 frail elderly people living in the community. Participants were given either; 1) food products enriched with vitamins D, E, thiamine, riboflavin, B6, folic acid, B12, calcium, magnesium, zinc, iron and iodine; 2) an exercise programme; 3) both enriched food products and exercise programme; or 4) food products that had not been enriched and a social programme (the control group). At the end of the study, significant improvements in the blood levels of vitamins B6, B12, C and D were detected in the groups receiving the enriched food products compared to the controls. There was no additional benefit to be gained from exercise. The improvement in nutritional status did not appear to influence several other biological indicators of health, perhaps because these indicators were already within normal levels at the start of the study. Despite this, the authors concluded that long-term supplementation may help to maintain optimal vitamin and mineral levels in elderly people, and therefore reduce the chance of this population developing health problems related to malnutrition.
Abstract
A decline in dietary intake due to inactivity and, consequently, development of a suboptimal nutritional status is a major problem in frail elderly people. However, benefits of micronutrient supplementation, all-round physical exercise or a combination of both on functional biochemical and hematologic indicators of nutritional and health status in frail elderly subjects have not been tested thoroughly. A 17-wk randomized controlled trial was performed in 145 free-living frail elderly people (43 men, 102 women, mean age, 78 +/- 5.7 y). Based on a 2 x 2 factorial design, subjects were assigned to one of the following: 1) nutrient-dense foods, 2) exercise, 3) both (1) and (2) or 4) a control group. Foods were enriched with micronutrients, frequently characterized as deficient [25-100% of the recommended daily allowance (RDA)] in elderly people. Exercises focused on skill training, including strength, endurance, coordination and flexibility. Dietary intake, blood vitamin levels and nutritional and health indicators, including (pre)albumin, ferritin, transferrin, C-reactive protein, hemoglobin and lymphocytes were measured. At baseline, 28% of the total population had an energy intake below 6.3 MJ, up to a maximum of 93% having vitamin intakes below two thirds of the Dutch RDA. Individual deficiencies in blood at baseline ranged from 3% for erythrocyte glutathione reductase-alpha to 39% for 25-hydroxy vitamin D and 42% for vitamin B-12. These were corrected after 17 wk in the two groups receiving the nutrient-dense foods, whereas no significant changes were observed in the control or exercise group. Biochemical and hematologic indicators at baseline were within the reference ranges (mean albumin, 46 g/L; prealbumin, 0.25 g/L; hemoglobin, 8.6 mmol/L) and were not affected by any of the interventions. The long-term protective effects of nutrient supplementation and exercise, by maintaining optimal nutrient levels and thereby reducing the initial chance of developing critical biochemical values, require further investigation. Other indicative functional variables for suboptimal nutritional status, in addition to those currently selected, should also be explored.