Vegan & vegetarian diet

Peer-Reviewed Scientific Articles​

Effects of an omnivorous diet compared with a lactoovovegetarian diet on resistance-training-induced changes in body composition and skeletal muscle in older men

URLhttps://academic.oup.com/ajcn/article/70/6/1032/4729141

The American Journal of Clinical Nutrition

Publication Date: 12/1999

Summary: Very limited data suggest that meat consumption by older people may promote skeletal muscle hypertrophy in response to resistance training (RT). The objective of this study was to assess whether the consumption of an omnivorous (meat-containing) diet would influence RT-induced changes in whole-body composition and skeletal muscle size in older men compared with a lactoovovegetarian (LOV) (meat-free) diet. Nineteen men aged 51–69 y participated in the study. During a 12-wk period of RT, 9 men consumed their habitual omnivorous diets, which provided ≈50% of total dietary protein from meat sources (beef, poultry, pork, and fish) (mixed-diet group). Another 10 men were counseled to self-select an LOV diet (LOV-diet group). Maximal strength of the upper- and lower-body muscle groups that were exercised during RT increased by 10–38% (P < 0.001), independent of diet. The RT-induced changes in whole-body composition and skeletal muscle size differed significantly between the mixed- and LOV-diet groups (time-by-group interactions, P < 0.05). With RT, whole-body density, fat-free mass, and whole-body muscle mass increased in the mixed diet group but decreased in the LOV- diet group. Type II muscle fiber area of the vastus lateralis muscle increased with RT for all men combined (P < 0.01), and the increase tended to be greater in the mixed-diet group (16.2 ± 4.4 %) than in the LOV diet group (7.3 ± 5.1%). Type I fiber area was unchanged with RT in both diet groups. Consumption of a meat-containing diet contributed to greater gains in fat-free mass and skeletal muscle mass with RT in older men than did an LOV diet.

Key Takeaways

Resistance training increased strength in both meat containing and lactoovovegetarian diets of men aged 51-69, but the exclusion of meat from the diet resulted in a decrease in lean mass compared to the increase in lean muscle mass of the meat containing diet. Fast-twitch (type II) muscle fiber area also increased in both groups, however meat in the diet led to a greater increase.

Excluding Meat from the Diet Diminishes Returns of Strength Training

Veganism, vegetarianism, bone mineral density, and fracture risk: a systematic review and meta-analysis

URL: https://academic.oup.com/nutritionreviews/advance-article-abstract/doi/10.1093/nutrit/nuy045/5146363?redirectedFrom=fulltext

Journal: Nutrition Reviews

Publication Date: 10/2018

Summary: The numbers of vegans and vegetarians have increased in the last decades. However, the impact of these diets on bone health is still under debate. This systematic review and meta-analysis sought to study the impact of vegetarian and vegan diets on bone mineral density (BMD) and fracture risk. A systematic search was conducted of PubMed, Scopus, and Science Direct, covering the period from the respective start date of each database to November 2017. Two investigators evaluated 275 studies against the inclusion criteria (original studies in humans, written in English or Spanish and including vegetarian or vegan diets and omnivorous diets as factors with BMD values for the whole body, lumbar spine, or femoral neck and/or the number of fractures as the outcome) and exclusion criteria (articles that did not include imaging or studies that included participants who had suffered a fracture before starting the vegetarian or vegan diet). The quality assessment tool for observational cohort and cross-sectional studies was used to assess the quality of the studies. Twenty studies including 37 134 participants met the inclusion criteria. Compared with omnivores, vegetarians and vegans had lower BMD at the femoral neck and lumbar spine and vegans also had higher fracture rates. Vegetarian and vegan diets should be planned to avoid negative consequences on bone health.

Key Takeaways

An aggregation of 275 studies with 37134 total participants showed vegetarians and vegans have lower bone mineral density than omnivores. Vegans also had higher rates of fractures than vegetarians and omnivores.

Veganism Leads to Frailty and Fractures

Bioavailability of iron, zinc, and other trace minerals from vegetarian diets

URL: https://academic.oup.com/ajcn/article/78/3/633S/4690005

Journal: The American Journal of Clinical Nutrition

Publication Date: 09/2003

Summary: Iron and zinc are currently the trace minerals of greatest concern when considering the nutritional value of vegetarian diets. With elimination of meat and increased intake of phytate-containing legumes and whole grains, the absorption of both iron and zinc is lower with vegetarian than with nonvegetarian, diets. The health consequences of lower iron and zinc bioavailability are not clear, especially in industrialized countries with abundant, varied food supplies, where nutrition and health research has generally supported recommendations to reduce meat and increase legume and whole-grain consumption. Although it is clear that vegetarians have lower iron stores, adverse health effects from lower iron and zinc absorption have not been demonstrated with varied vegetarian diets in developed countries, and moderately lower iron stores have even been hypothesized to reduce the risk of chronic diseases. Premenopausal women cannot easily achieve recommended iron intakes, as modified for vegetarians, with foods alone; however, the benefit of routine iron supplementation has not been demonstrated. It may be prudent to monitor the hemoglobin of vegetarian children and women of childbearing age. Improved assessment methods are required to determine whether vegetarians are at risk of zinc deficiency. In contrast with iron and zinc, elements such as copper appear to be adequately provided by vegetarian diets. Although the iron and zinc deficiencies commonly associated with plant-based diets in impoverished nations are not associated with vegetarian diets in wealthier countries, these nutrients warrant attention as nutritional assessment methods become more sensitive and plant-based diets receive greater emphasis.

Key Takeaways

Vegetarian dieters tend to have lower iron and zinc stores likely due to the phytates present in legumes and grains that prevents the body from absorbing the minerals. There haven't been any negative health outcomes associated with these reductions in developed countries.

Vegetarians May Be Iron and Zinc Deficient

Vitamin D deficiency in mothers, neonates and children

URL: https://www.ncbi.nlm.nih.gov/m/pubmed/28179126/

Journal: The Journal of Steroid Biochemistry and Molecular Biology

Publication Date: 01/2018

Summary: Vitamin D deficiency mainly occurs if strict vegetarian diet is followed as mostly the source of vitamin D is animal based. Low vitamin D levels results in increased possibility of gestational diabetes among pregnant women, low birth weight and pre-eclampsia in infants, and mothers may suffer bone impairment, osteoporosis, hypocalcaemia, and hypertension. Vitamin D deficiency is directly linked with severe complication in mothers and neonates, causing rickets, poor fetal growth and infantile eczema in neonates.

Key Takeaways

Strict vegan diets can lead to low Vitamin D, which can result in gestational diabetes, low birth weight, and high blood pressure during pregnancy. Mothers can also experience low calcium and osteoporosis. Newborns may also experience rickets, poor growth, and eczema due to Vitamin D deficiency.

Vegan Diets, Vitamin D, and Problems During Pregnancy and Birth

Food intake diet and sperm characteristics in a blue zone: a Loma Linda Study

URL: https://www.ncbi.nlm.nih.gov/m/pubmed/27280539/

Journal: European Journal of Obstetrics & Gynecology and Reproductive Biology

Publication Date: 08/2016

Summary: Observational study of males in Loma Linda. The study showed that the vegetables-based food intake decreased sperm quality

Key Takeaways

Loma Linda is a "Blue Zone" and a significant portion of the population consumes a plant based diet. Men in Loma Linda have decreased sperm quality.

Do Plant Based Diets Lead to Low Sperm Counts?

Status of 25(OH)D levels in pregnancy: A study from the North Eastern part of India

URL: https://www.ncbi.nlm.nih.gov/m/pubmed/23565444/

Journal: Indian Journal of Endocrinology and Metabolism

Publication Date: 12/2012

Summary: Study of Vitamin D levels in pregnant Indian women. Vitamin D deficient women were significantly more likely to be vegetarian

Key Takeaways

Pregnant women on vegetarian diets are more likely to be vitamin D deficient, which can lead to complications with the pregnancy and development of the child.

Vegetarians Have Low Vitamin D

Vegetarian diet and mental disorders: results from a representative community survey

URL: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3466124/

Journal: International Journal of Behavioral Nutrition and Physical Activity

Publication Date: 06/2012

Summary: In Western cultures vegetarian diet is associated with an elevated risk of mental disorders. However, there was no evidence for a causal role of vegetarian diet in the etiology of mental disorders.

Key Takeaways

Vegetarian diets are associated with increased mental disorders, but it has not been proven that the vegetarian diet is the cause of these disorders.

Will a Vegetarian Diet Make You Crazy?

Oral implications of the vegan diet: observational study

URL: https://www.ncbi.nlm.nih.gov/pubmed?term=oral%20implications%20of%20the%20vegan%20diet%5BTitle%5D

Journal: Minerva Stomatol

Publication Date: 11/2010

Summary: The study revealed greater incidence of demineralization and white spots in the vegan subjects compared to the omnivorous ones localized at the neck of the teeth and on the vestibular surfaces of dental elements (with the exception of the lower anterior group). The saliva pH, more acid in the omnivorous patients, ranged between four and six. Changes in oral conditions in both groups of subjects were observed.

Key Takeaways

In this study vegans were found to have more demineralization and white spots on the teeth than omnivores.

What is the Vegan Diet Doing To Your Teeth?

Maternal and gestational risk factors for hypospadias

URL: https://www.ncbi.nlm.nih.gov/m/pubmed/18709149/

Journal: Environmental Health Perspectives

Publication Date: 08/2008

Summary: A pregnancy diet lacking meat and fish appears to increase the risk of hypospadias in the offspring

Key Takeaways

Hypospadias in a congenital malformation in a child's penis that may occur due to the lack of meat and fish in the mother's diet during pregnancy.

This Can Happen To Your Child's Penis If You Don't Eat Meat While Pregnant

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