1.
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
-
-
-
-
Free full text
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:
-
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
-
X
B: Systematic reviews including RCTs of limited number
-
C: Non-randomized trials, observational studies, narrative reviews
-
D: Case-reports, evidence-based clinical findings
-
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.
2.
Alternate Day Fasting Improves Physiological and Molecular Markers of Aging in Healthy, Non-obese Humans.
Stekovic, S, Hofer, SJ, Tripolt, N, Aon, MA, Royer, P, Pein, L, Stadler, JT, Pendl, T, Prietl, B, Url, J, et al
Cell metabolism. 2019;30(3):462-476.e6
-
-
-
-
Free full text
Plain language summary
Intermittent fasting and calorie restriction are believed to reduce cardiometabolic risk factors and increase longevity. Fasting alternate days (ADF) involves fasting for 36 hours and eating ad libitum for 12 hours. Thirty healthy participants were randomly assigned to a long-term ADF intervention group for ≥6 months against sixty participants in the control group. After completing the cross-sectional study arm, sixty healthy participants in the control group were randomly assigned to either a four-week short-term ADF intervention group or a control group with an ad libitum diet. Study participants adhered well to the fasting regimen. Both short-term and long-term ADF intervention groups showed a significant reduction in calorie intake, improvements in anthropometric and cardiovascular parameters including reduced BMI, substantial reduction in trunk fat, lower heart rate, increased serum β-hydroxybutyrate which is cardioprotective and anti-ageing, reduced circulating triiodothyronine (fT3) levels which indicate longevity. Short-term ADF reduced systolic and diastolic pressure, mean arterial pressure, pulse pressure, and pulse wave velocity. Long-term ADF intervention reduced circulating total cholesterol, low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and triglycerides, the age-related biomarker sICAM-1 for disease and inflammation, and improved lipid and amino acid metabolites. ADF did not affect insulin sensitivity. Although red blood cells and iron levels were altered, ADF interventions were not associated with iron deficiency. Healthcare professionals can use the results of this study to understand the cardioprotective and anti-ageing properties of ADF. However, further long-term robust studies are required to evaluate the effect of long-term ADF on bone health.
Expert Review
Conflicts of interest:
None
Take Home Message:
- Short duration (<4 weeks) alternate day fasting may be an effective way to implement caloric restriction, improve body composition and reduce cardiovascular disease risk in healthy non-overweight adults.
- >6 months alternate fasting does not appear to be associated with reduced bone mass, bone mineral density of the lumbar spine region, white blood cell counts, ferritin and transferrin when compared to healthy controls.
- Both short term and long term alternate day fasting may reduce triiodothyronine in healthy adults. Low levels of fT3 without thyroid gland dysfunction has been associated with longevity in humans.
- Alternate day fasting should be performed alongside a trained clinician to reduce the risk of adverse effects due to critical medical conditions.
Evidence Category:
-
X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
-
B: Systematic reviews including RCTs of limited number
-
C: Non-randomized trials, observational studies, narrative reviews
-
D: Case-reports, evidence-based clinical findings
-
E: Opinion piece, other
Summary Review:
Introduction
Animal models have consistently demonstrated the healthspan and lifespan benefits of caloric restriction. However, chronic caloric restriction in humans has proven difficult to maintain.
Intermittent fasting may serve as a more manageable alternative to continuous caloric restriction. This randomised controlled trial and cross sectional analysis aimed to investigate the effects of alternate day fasting (ADF) on heart rate, blood pressure, cholesterol levels, CVD risk, body composition, and the metabolome and proteome of healthy, non-overweight adults (cohort median age between 48 and 52 years).
Methods
Prior to the enrollment of the study a cross sectional analysis was conducted on healthy adults engaged in long term (>6 months) alternate day fasting (n=30) and a control group (n=60).
The 60 participants from the cross sectional analysis control group were then randomised to either a 4 week ADF group or a control group. In both the >6 months and 4 weeks of ADF groups, participants were instructed to eat every second-day ad libitum, but to completely exclude solid and liquid foods and caloric beverages on fasting days.
Results
The cross sectional analysis identified that the alternate day fasting group:
- Consumed fewer calories vs the control group (−28.56%, p=0.0002).
- Had lower levels of circulating total cholesterol (p=0.004), LDL (p=0.011), VLDL (p=0.009), triglycerides (p=0.010) and a lower heart rate (p=0.040) vs the control group.
- Lower levels of soluble intercellular adhesion molecule-1 (sICAM-1) (p value 0.048), an age-associated inflammatory marker.
- Reduced circulating triiodothyronine (p<0.001) compared to the control group.
- In the metabolome, 54 out of 113 detected significantly modified metabolites (p value < 0.05) were at least 20% higher after 36 h of fasting, of which the majority (>95%) were lipids or free fatty acids, including polyunsaturated free fatty acids (PUFAs), α-tocopherol, and a type of vitamin E. 49 metabolites were at least 20% lower, consisting mainly (44.9%) of amino acids or related metabolites. Low levels of circulating amino acids have been found to increase lifespan in model organisms. The authors concluded that the elevation in fatty acids may be due to increased lipolysis from adipose tissue while the reduction in amino acids may be the result of increased gluconeogenesis.
- 13 out of 2,089 significantly (p value < 0.05) modulated protein hits within the PBMC proteome showed an increase of ≥15%, while the remaining proteins were downregulated after 36 h of fasting. Gene set enrichment analysis (GSEA) performed on the PBMC proteome unveiled changes in pathways related to lipid metabolism, pathways related to energy metabolism and stress response.
Following the 4 week intervention the alternate day fasting group demonstrated:
- Reduced caloric intake from baseline vs. the control group (−37.40% vs. −8.22%, p=0.0012).
- Greater reductions in body weight (−3.5kg vs −0.2kg, p<0.0001), BMI (−1.23kg/m2 vs −0.02kg/m2, p<0.0001) and improvements in their fat to lean mass ratio (−6.3% ± 5.0 percentage points, p value < 0.0001).
- Reduced systolic (−4.5mmHg, p=0.006) and diastolic (−2.5mmHg, p=0.03) blood pressure, heart rate (-4.5 b/min, p=0.0019), arterial (−3mmHg, p=0.0087) and pulse pressure (−2.5mmHg, p=0.0088) as well as pulse wave velocity (−1.538%, p=0.0362). Pulse wave velocity measures the rate at which pressure moves down the vessel wall and is a measure of arterial stiffness.
- Reduced circulating triiodothyronine (p<0.001) from baseline values.
Clinical practice applications:
The cross sectional analysis did not identify any differences in the long-term (>6 months) alternate day fasting group and control group in bone mass, bone mineral density of the lumbar spine region, white blood cell counts, ferritin and transferrin when compared to healthy controls. RBC counts and iron metabolism markers in the blood plasma (hematocrit, haemoglobin, iron, and transferrin saturation), were lower in the >6 months of ADF group but stayed within the reference range.
The randomised controlled trial demonstrated that alternate day fasting may be an effective intervention to reduce caloric intake, improve body composition and reduce cardiovascular disease risk in healthy non-overweight adults within 4 weeks.
Compliance rate was high with only 1 drop out in the alternate day fasting group of the randomised controlled trial.
Both the 4 week intervention and long-term (>6 month) analysis identified a reduction in triiodothyronine amongst the ADF groups. Low levels of triiodothyronine in absence of thyroid gland dysfunction has been associated with longevity in humans.
Considerations for future research:
- Future larger studies in non-healthy and/or overweight/obese populations would be useful to determine safety and efficacy of alternate day fasting within that population group.
- Further studies comparing alternate day fasting with continuous caloric restriction would be useful to identify which intervention is most beneficial for body composition and cardioprotection.
- Subgroup analysis of diet composition and diet quality may help to identify the most appropriate/inappropriate diet to compliment alternate day fasting.
- Longer duration randomised controlled trials are needed to identify any health risks or deficiencies which may develop with long term caloric restriction and alternate day fasting.
Abstract
Caloric restriction and intermittent fasting are known to prolong life- and healthspan in model organisms, while their effects on humans are less well studied. In a randomized controlled trial study (ClinicalTrials.gov identifier: NCT02673515), we show that 4 weeks of strict alternate day fasting (ADF) improved markers of general health in healthy, middle-aged humans while causing a 37% calorie reduction on average. No adverse effects occurred even after >6 months. ADF improved cardiovascular markers, reduced fat mass (particularly the trunk fat), improving the fat-to-lean ratio, and increased β-hydroxybutyrate, even on non-fasting days. On fasting days, the pro-aging amino-acid methionine, among others, was periodically depleted, while polyunsaturated fatty acids were elevated. We found reduced levels sICAM-1 (an age-associated inflammatory marker), low-density lipoprotein, and the metabolic regulator triiodothyronine after long-term ADF. These results shed light on the physiological impact of ADF and supports its safety. ADF could eventually become a clinically relevant intervention.
3.
Effect of 12-Week Daily Intake of the High-Lycopene Tomato (Solanum Lycopersicum), A Variety Named "PR-7", on Lipid Metabolism: A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group Study.
Nishimura, M, Tominaga, N, Ishikawa-Takano, Y, Maeda-Yamamoto, M, Nishihira, J
Nutrients. 2019;11(5)
-
-
-
-
Free full text
Plain language summary
Tomatoes are a rich source of lycopene, a compound believed to have many health benefits. Researchers in Japan conducted a randomised, double-blind, placebo-controlled trial to investigate the effects of eating a type of tomato bred to be high in lycopene on 74 healthy volunteers with raised cholesterol levels. Participants were given 50g per day of either semi-dried high-lycopene tomato or lycopene-free tomato. Those eating the high-lycopene tomatoes significantly reduced their levels of LDL cholesterol over 12 weeks. The researchers concluded that their findings support the health benefits of eating tomatoes rich in lycopene.
Expert Review
Conflicts of interest:
None
Take Home Message:
- Lycopene, a carotenoid, has antioxidant effects and exhibits the highest physical quenching rate constant for singlet oxygen.
- Lycopene has also been reported to inhibit the production of serum lipid peroxide and oxidize low-density lipoprotein (LDL)
- This study reported that the intake of 50g of high-lycopene (lycopene, 22.0-27.8mg) for 12 weeks significantly decreased LDL-C in subjects with LDL-C ranging from 120–139 mg/dL.
Evidence Category:
-
X
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
-
B: Systematic reviews including RCTs of limited number
-
C: Non-randomized trials, observational studies, narrative reviews
-
D: Case-reports, evidence-based clinical findings
-
E: Opinion piece, other
Summary Review:
A Randomized, Double-Blind, Placebo-Controlled, Parallel-Group study was conducted to investigate the effects of the regular and continuous intake of high-lycopene tomato, a variety named PR-7, for 12 weeks on 74 healthy Japanese subjects with low-density lipoprotein cholesterol (LDL-C) levels > 120 to <160mg/dL.
The subjects were randomly assigned to either the high-lycopene tomato or placebo (lycopene-free tomato) group. Each subject in the high-lycopene group ingested 50g of semi-dried PR-7 (lycopene, 22.0-27.8mg) per day. Medical interviews were conducted, vital signs were monitored, and blood and saliva samples were taken at 0 (baseline) and at 4, 8 and 12 weeks.
Primary clinical outcomes were:
- The intake of high-lycopene tomato improved LDL-C at week 12 when compared to the placebo group (Week 12: placebo, 4,1 +- 15.7mg/dL; high-lycopene tomato, -3.7 +- 13.8.mg/dL; p=0.027).
- Based on a subgroup analysis, the ingestion of high-lycopene tomato significantly decreased LDL-C in subjects with LDL-C ranging from 120–139 mg/dL at week 12 (Week 12: placebo, 4.3 15.1 mg/dL; high-lycopene tomato, +- 5.1 9.5 mg/dL; p = 0.030).
Secondary clinical outcomes were:
- There were no significant differences between the high-lycopene tomato and placebo groups in terms of lipid profiles comprising of total cholesterol (TC), HDL-C, triglycerides (TG), LDL-C/HDL-C ratio, and non-HDL, and adiponectin.
- The intake of high-lycopene tomato increased lycopene levels compared to the placebo group (Week 12: placebo,
+-24.2 49.3 g/dL; high-lycopene tomato, 22.7 47.9 g/dL; p < 0.001).
- In addition, beta-carotene levels increased in the high-lycopene tomato group compared to those in the placebo group at week 12 (Week 12: placebo, 0.9 13.6 g/dL; high-lycopene tomato, 12.0 24.5 g/dL; p = 0.009).
Clinical practice applications:
- A previous meta-analysis demonstrated that LDL-C decreases when more than 25 mg per day of lycopene is ingested. The biological mechanism was associated with a reduction in 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase activity in the liver, activation of LDL-receptors, and increased expression of the ABCA1 transporter gene, the key component of HDL-C production.
- This study also suggests that there is a decrease in LDL-C at 12 weeks in subjects with LDL-C ranging from 120–139 mg/dL.
- Based on these findings, a practitioner could therefore consider recommending 25mg of lycopene to help reduce LDL-C in patients with an LDL-C range of 120–139 mg/dL for at least 12 weeks.
Considerations for future research:
- Lycopene has been reported to possess the strongest singlet oxygen scavenging ability among the eight carotenoids, as measured by the singlet oxygen absorption capacity method, and some researchers have found that lycopene and tomato display antioxidant effects. However, other reports suggest that ingesting lycopene does not affect oxidative markers. These findings suggest that further investigation is needed to evaluate the effect of lycopene on oxidative markers.
- The LOX index is a biomarker for the early risk of arteriosclerosis, cerebral infarction, and myocardial infarction. Lycopene might be ineffective against LOX-1 which is a product of the peroxidation reaction. Additional studies with a longer intake period are required to investigate the effect of lycopene on the risk of arteriosclerosis.
- The subjects in this study were asked to avoid cooking the test food (semi-dried tomato). It is, therefore, necessary to investigate the differences in the effect of the high-lycopene tomato based on various cooking methods.
Abstract
Tomato (Solanum lycopersicum) is a rich source of lycopene, a carotenoid that confers various positive biological effects such as improved lipid metabolism. Here, we conducted a randomized, double-blind, placebo-controlled, parallel-group comparative study to investigate the effects of regular and continuous intake of a new high-lycopene tomato, a variety named PR-7, for 12 weeks, based on 74 healthy Japanese subjects with low-density lipoprotein cholesterol (LDL-C) levels ≥120 to <160 mg/dL. The subjects were randomly assigned to either the high-lycopene tomato or placebo (lycopene-free tomato) group. Each subject in the high-lycopene group ingested 50 g of semidried PR-7 (lycopene, 22.0-27.8 mg/day) each day for 12 weeks, while subjects in the placebo group ingested placebo semidried tomato. Medical interviews were conducted, vital signs were monitored, body composition was determined, and blood and saliva samples were taken at weeks 0 (baseline), 4, 8, and 12. The primary outcome assessed was LDL-C. The intake of high-lycopene tomato increased lycopene levels in this group compared to levels in the placebo group (p < 0.001). In addition, high-lycopene tomato intake improved LDL-C (p = 0.027). The intake of high-lycopene tomato, PR-7, reduced LDL-C and was confirmed to be safe.
4.
Cardiovascular Health Benefits of Specific Vegetable Types: A Narrative Review.
Blekkenhorst, LC, Sim, M, Bondonno, CP, Bondonno, NP, Ward, NC, Prince, RL, Devine, A, Lewis, JR, Hodgson, JM
Nutrients. 2018;10(5)
-
-
-
-
Free full text
Plain language summary
Diets high in vegetables are linked with a lower incidence of chronic disease. Some vegetables may have much larger health benefits in comparison to others, and therefore dietary guidelines could be developed to include targeted advice on consuming specific types of vegetables with the greatest health benefits. This review of observational studies focused on the cardiovascular health benefits of specific vegetable types. Vegetables discussed in this review were grouped into the following types: leafy green, cruciferous, alliums, yellow-orange-red and legumes. These vegetables contain many nutrients and phytochemicals that have been proposed to have benefits for cardiovascular health. The authors looked at the results from nearly 100 observational studies. Most of the studies were carried out on older adults; some were focussed on a single gender (male or female), and some were mixed. Follow up periods in the studies ranged from 3 years to 28 years. Most of the studies relied on food frequency questionnaires (FFQs) to estimate vegetable consumption, and many did not define the size of a vegetable portion in grams. The percentage of studies demonstrating significant benefits of vegetable consumption on CVD ranged from 25% for legumes to 43% for leafy greens. The strongest beneficial effects on CVD risk were seen for leafy green and cruciferous vegetables. The authors concluded that the evidence in this review suggests intake of leafy green and cruciferous vegetables may confer strong cardiovascular health benefits. Increasing vegetable intake, with a focus on leafy green and cruciferous vegetables may provide the greatest benefits.
Expert Review
Conflicts of interest:
Educator for various organizations, such as Institute for Functional Medicine, American Academy for Anti-Aging Medicine
Take Home Message:
- Green leafy vegetables and cruciferous vegetables were found to most impactful for cardiovascular health.
Evidence Category:
-
A: Meta-analyses, position-stands, randomized-controlled trials (RCTs)
-
B: Systematic reviews including RCTs of limited number
-
X
C: Non-randomized trials, observational studies, narrative reviews
-
D: Case-reports, evidence-based clinical findings
-
E: Opinion piece, other
Summary Review:
This review highlights the role of specific types of vegetables based on color and nutrients for cardiovascular health benefit.
Clinical practice applications:
The authors investigated whether some vegetable types were more relevant for cardiovascular-related issues than others. Based on their review of the scientific literature, green, leafy vegetables and cruciferous vegetables were found to be most impactful.
Considerations for future research:
This review suggests that more research is needed to understand how certain plant foods, vegetables, and phytochemicals may be functionally important for certain organ systems.
Abstract
Adequate vegetable consumption is one of the cornerstones of a healthy diet. The recommendation to increase vegetable intake is part of most dietary guidelines. Despite widespread and long-running public health messages to increase vegetable intake, similar to other countries worldwide, less than 1 in 10 adult Australians manage to meet target advice. Dietary guidelines are predominantly based on studies linking diets high in vegetables with lower risk of chronic diseases. Identifying vegetables with the strongest health benefits and incorporating these into dietary recommendations may enhance public health initiatives around vegetable intake. These enhanced public health initiatives would be targeted at reducing the risk of chronic diseases, such as cardiovascular diseases (CVD). Specific vegetable types contain high levels of particular nutrients and phytochemicals linked with cardiovascular health benefits. However, it is not clear if increasing intake of these specific vegetable types will result in larger benefits on risk of chronic diseases. This review presents an overview of the evidence for the relationships of specific types of vegetables, including leafy green, cruciferous, allium, yellow-orange-red and legumes, with subclinical and clinical CVD outcomes in observational epidemiological studies.