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Vegetarian Diet

physician assistant

Feta SaladIntroduction:

A vegetarian diet focuses on plant foods which may include fruits, vegetables, beans, peas, grains, seeds and nuts. There is no single type of vegetarian diet. Instead, vegetarian eating patterns usually fall into the vegan diet (excludes all meat and animal products), the lacto-vegetarian diet (includes plant foods plus dairy products), or the lacto-ovo vegetarian diet, which includes both dairy products and eggs. There are overwhelming health benefits to a vegetarian diet over a mixed diet with meats and vegetables documented in research. These benefits include a lower risk or developing cancers, heart disease, diabetes, obesity, and high blood pressure. People who follow vegetarian diets can get all the nutrients they need, however, they must be careful to eat a wide variety of foods to meet all nutritional needs. Nutrients which vegetarians may need to ensure adequate intake of include protein, iron, calcium, iodine, zinc and vitamin B12.

 

Vegetables, fruits, legumes, and cancer:

Cancer incidence among meat eaters, fish eaters, and vegetarians: A 12-year study investigated the relationship between diet and risk of certain cancers. Researchers followed 61,566 British men and women, which included 32,403 meat eaters, 8,562 non-meat eaters who ate fish but not meat (the “fish eaters”) and 20,601 vegetarians (ate neither fish nor meat). Over the follow-up period there were 3,350 incident cancers, including 2,204 among the meat eaters, 317 among the fish eaters and 829 among the vegetarians. In other words, in this study, cancer among meat eaters was 3.8%, among fish-eaters, 0.5%, and among vegetarians, 1.3%. The study found that compared to meat-eaters, vegetarians had a 53%, 45% and 74% reduced risk in bladder, leukemia, lymphoma, and stomach cancers, respectively. Looking at all cancers combined, vegetarians were 12 per cent less likely to develop cancer than meat eaters, while fish eaters were 18 per cent less likely to develop cancer. (1)

 

Meat consumption, legume intake, and colon cancer:

The risk of colon cancer was found to be increased in individuals with a high meat consumption, a low legume consumption, and a high body mass index compared to their low meat consumption, high legume consumption and low body mass counterparts in this 6 year prospective study examining 32,051 white participants. Compared to non-meat eaters, individuals eating meat at least 1 time per week had an 85% increased risk of colon cancer. Participants who ate red meat at least 1 time per week had a risk 1.9 times that of those who abstained from eating red meat. Those who ate white meat at least 1 time per week had a risk 3.2 times that of those who abstained from eating white meat. Legume consumption of >2 times/week compared to <1 time/week was associated with a 47% reduction in risk of colon cancer. Finally, a body mass index >25.6 kg/m2 was associated with a risk 2.63 times that of a body mass index less than 22.5 kg/m2. (2)

 

Red meat consumption and cancer:

Red meat consumption has been found to be associated with various forms of cancer in a multisite case-control study of 11 cancer sites in Uruguay. High consumption of red meat was associated with an increased cancer risk of the oral cavity and pharynx (odds ratio [OR]= 3.65), esophagus (OR= 3.36), larynx (OR=2.91), stomach (OR= 2.19), colorectum (OR= 3.83), lung (OR= 2.17), breast (OR= 1.97), prostate (OR= 1.87), bladder (OR= 2.11) and kidney (OR= 2.72). Lamb was also associated with increased cancer risk. Eating a lot of processed meat was also linked to an increased risk of cancers of the esophagus (OR= 1.63), larynx (OR= 1.84), stomach (OR= 1.62), colorectum (OR= 2.15), lung (OR= 1.70) and breast (OR= 1.53). (3)

 

Vegetables and prostate cancer:

A population-based, case–control study, performed on 238 patients with prostate cancer and 471 male control subjects in China, investigated the association between intake of allium vegetables including garlic, scallions, onions, chives, and leeks, and the risk of prostate cancer. It was found that men in the category of highest intake of allium vegetables (>10 g day-1) had a 49% risk reduction of developing prostate cancer than did those in the category of lowest intake (2.2 g day-1).  Reductions in risk for men in the highest intake categories (compared to the lowest intake categories) for garlic was 53% (OR = 0.47) and 70% for scallions consumption (OR = 0.30). These benefits were more significant in men with localized, rather than advanced prostate cancer and were independent of body size, intake of other foods and total calorie intake. These results suggest that the allium group of vegetables has some cancer preventative properties and it may be worthwhile to increase their intake. (4)

 

Disease in animal based foods vs. strict plant based diet:

In multiple, peer-reviewed animal studies, researchers discovered that they could actually turn the growth of cancer cells on and off by raising and lowering doses of casein, which is the type of protein found in milk. This result was not found in all proteins. The safe proteins were from plants, including wheat and soy. In the largest comprehensive study of human nutrition ever conducted, Campbell examined mortality rates from 48 forms of cancer and other chronic diseases from 1973–75 in 65 counties in China, and correlated them with 1983–84 dietary surveys and blood work from 6,500 people, 100 from each county. He concluded that countries with a high consumption of animal-based foods were more likely to have had higher death rates from “Western” diseases, while the opposite was true for counties that ate more plant foods. Highly processed, refined carbohydrates and sugar intake resulted in poor health outcomes. Plant foods were found to possess many health benefits. Research shows that low-carbohydrate diets like the Atkins or South Beach can actually cause dangerous side effects. People who eat a plant-based/vegan diet—avoiding animal products such as beef, pork, poultry, fish, eggs, cheese, and milk, and reducing their intake of processed foods and refined carbohydrates—will escape, reduce, or reverse the development of chronic diseases according to this author. Sufficient levels of vitamin D, and supplements of vitamin B12 are recommended if a strict plant-based diet is followed. In conclusion, people who ate the most animal-based foods developed the most chronic disease. Those who ate the most plant-based foods were the healthiest. Therefore, a whole foods, plant-based diet is advocated by this research. (5)

 

Fruit, vegetable intake, and kidney cancer:

Eating fruits and vegetables was linked with a reduced risk of kidney cancer (RCC, renal cell carcinoma) in men (n=116), but not women (n=132). Men who consumed at least 6 servings of fruits and vegetables per day had a 55% reduced risk of RCC compared to men who had less than 3 servings per day. Vitamins A, C, and carotenoids from food were found to be inversely associated with RCC in men. Vitamin E had no clear link to RCC in either men or women. (6)

 

Vegetarian diet, fiber intake and diverticular disease:

A comparison of the effects of diet on diverticular disease, a medical condition where pouches (diverticula) form in the colon wall, found that a lower fiber intake is associated with the presence of diverticular disease. Results show that among vegetarians with a reported average fiber intake of 41.5 g/day the rate of diverticular disease is 12%. In contrast, non-vegetarians had an average fiber intake of 21.4 g/day and diverticular disease was found in 33%. (7)

 

Semi-vegetarian diet and Crohn’s disease:

A semi-vegetarian diet can prevent relapse of symptoms of Crohn’s disease. Crohn’s disease is a type of inflammatory bowel disease. The semi-vegetarian diet includes daily portions of brown rice, miso soup made from fermented bean paste, brown rice, plain yogurt, eggs, vegetables, fruits, legumes, potatoes, algae and other plant foods. Fish was eaten once per week and meat once every two weeks. Remission from symptoms of Crohn’s disease was maintained in about 94% of patients on this semi-vegetarian diet during the two-year study. (8)

 

Weight Loss on a Vegetarian Diet

Many people believe that eating a vegetarian diet will help them to lose weight. While this statement may raise the hackles of most vegetarians, the truth of the matter is that weight loss requires a negative calorie balance. This means that an individual who wishes to lose weight must eat less calories than they burn. For a healthy adult, with no other underlying medical conditions, who receives a moderate amount of exercise daily, a calorie is a calorie. Research has shown that individuals who follow a typical vegetarian diet will consume approximately 500 fewer calories daily than those individuals who eat meat. Individuals who eat a vegetarian diet will actually consume a greater volume of food than nonvegetarians.

This is because vegetarian foods contain higher bulk resulting in more food consumption but with less calories. The foods are less calorie dense, have a higher number of vitamins and minerals and generally healthier. The definition of a vegetarian diet is the consumption of vegetable based products and no meat or meat products. However, this does not mean that white flour, sugar or processed foods are completely removed from the diet, all of which are high in dense calories and are related to disease and illness. Even vegetarians can eat the wrong types of food which can lead to weight gain. For instance, chips, cookies, power bars and candy all qualify as vegetarian foods and yet are high in calories, sugar and processed chemicals.

Research has also shown that individuals who follow a low fat, plant-based diet plan will have a greater degree of success at weight loss and improve their insulin sensitivity than those who follow a diet which includes both meat and vegetables. This research was published in the September issue of The American Journal of Medicine. Other studies show that obesity and individuals who suffer from being overweight are less prevalent in populations which follow a plant-based diet. (45,46,47)

On a worldwide basis researchers have found that vegetarian populations experience lower rates of heart disease, diabetes, high blood pressure, cardiovascular disease, peripheral vascular disease and other life-threatening illnesses. Because the vegetarian diet consists of complex carbohydrates the individuals who eat a vegetarian diet often feel full longer than those who eat simple carbohydrates. By enjoying an unlimited servings of fruits, vegetables, whole grains and other healthy foods individuals who eat a vegetarian diet often are able to lose weight without feeling hungry.

However, it is still important to remember that even vegetarians who enjoy pasta, crackers, cookies, chocolate, sweets and large amounts of soda will also suffer from being overweight and obesity. The real benefit from eating a vegetarian diet does not come just from eliminating meat but also from eliminating processed foods, simple sugars and incorporating a greater number of complex carbohydrates into the diet plan.

 

Vegan diet, weight loss, and diabetes:

A prospective clinical intervention study of diet and its effects on body weight and other cardiovascular risk factors recruited 113 workers aged 21 to 65 years with a BMI≥25 kg/m2 or with a diagnosis of type 2 diabetes. Workers at the intervention site were instructed to follow a low-fat vegan diet. At the end of the 22 weeks, the intervention group lost on average 5.1 kg (vs a gain of 0.1 kg in the control group; P<0.0001) as well as an average of 4.7 cm from their waist (vs gain of 0.8 cm in the control group). Among the intervention group, 48.5% had a weight loss of 5% body weight compared to only 11.1% among the control group. (9)

 

Bean consumption and weight loss:

Papanikolaou and Fulgoni reported on the association of consumption of beans with dietary quality and obesity risk in 1,475 adult participants in the NHANES 1999–2002 in this cross-sectional study. They found that bean consumers had a higher consumption of dietary fiber, potassium, magnesium, iron, and copper (p< 0.05), lower body weight (p = 0.008), and a smaller waist size (p = 0.043) relative to non-consumers. Additionally, they had a significantly reduced their risk of increased waist size and obesity by 23% and 22%, respectively. This study showed that bean consumption is associated with an overall dietary pattern and lifestyle that tends to be associated with relative leanness. (10)

 

Vegetarian diet and diabetes:

Vegetarian diet may lower the risk of developing diabetes. In a two-year study of non-diabetic participants, 15,200 men and 26,187 women were followed for 2 years. It was inclusive of 17.3% African Americans. During that time period the development of diabetes cases were significantly reduced in vegans, lacto ovo, and semi vegetarians compared to non-vegetarians. It was proven that vegetarian diets are associated with reduction in diabetes incidence. Those with black ethnicity on vegetarian diets also were found to have lower incidence of diabetes. The vegetarian diets appeared to negate the higher risk of diabetes present in blacks due to their ethnicity. (11)

 

Vegetarian diet, diabetes, weight loss, and cholesterol:

The effects of diet on blood glucose, weight, and plasma lipids (fatty molecules in blood) were examined among individuals with type 2 diabetes for 74 weeks. Participants were randomly assigned to a low-fat vegan diet (n=42) or a standard diabetes diet based on the 2003 American Diabetes Association guidelines (n=50). Glycated hemoglobin (Hb A1c), plasma lipids, and weight were measure. At the end of the study period, HbA1C was reduced by 0.34 in vegetarians and 0.14 in the ADA diet group. Weight significantly decreased by 4.4 kg and 3.0 kg in the vegan and conventional groups, respectively. For participants on the vegan diet, total cholesterol and LDL (bad) cholesterol decreased by 20.4 mg/dL and 13.5 mg/dL, respectively. Corresponding values for those on the conventional diet was a decrease of 6.8 mg/dL and 3.4 mg/dL. In conclusion changes in overall lifestyle that include a vegan or nearly-vegan diet may be effective in improving the health of people with diabetes. (12)

 

Fruits, vegetables, and blood pressure:

Obesity, high salt intake, and the consumption of alcohol are leading factors in the development of hypertension. The effect of diet on blood pressure (bp) was put to the test. Research of 133 adults with hypertension and 326 without hypertension showed that a diet low in both saturated and unsaturated fats, yet rich in fruits and vegetables, can greatly lower bp. As a control, the subjects were first provided a typical American diet for 3 weeks with average fruit, vegetable and fat intake. Following a diet rich in fruits, vegetables, and low fat dairy products, bp in subjects without hypertension improved from an average bp of 131.3/84.7 at baseline to an average of 125.8/81.7. In those with hypertension (bp over 140/90), systolic and diastolic bp improved by 11.4 and 5.5 points respectively over the control diet. (13)

 

Vegetarian diet and iodine deficiency:

Vegetarian diets may result in higher iodine requirement and have been found to be associated with iodine (I) deficiency. Six healthy individuals were analyzed in four separate 5-day diet periods (diets included normal, protein-rich, lactovegetarian [includes dairy products, vegetables, fruits, grains, and nuts] and normal diet with no fish, sea food, iodized salt or processed foods fortified with I). Results show the iodine levels in urine were significantly lower in the lactovegetarian diet (36.6 mcg/d) than in the normal (50.2 mcg/d) or protein-rich diets (61.0 mcg/d). Corresponding to findings that show iodine consumption was lowest for the lactovegetarian diet (15.6 mcg/d) compared to the normal (35.2 mcg/d) or protein-rich diets (44.5 mcg/d). (14)

Vegetarians and vegans have a higher risk of iodine deficiency than people who had a mixed diet that includes meat. Urine analysis of study participants showed an iodine excretion of 172 microg/l in vegetarians (n=31) and 78 microg/l in vegans (n=15) compared to 216 microg/l in subjects on a mixed diet (n=35). Only 9% of those on a mixed diet were reported to have iodine deficiency (iodine excretion value below 100 microg/l) compared to 25% and 80% of vegetarians and vegans, respectively. (15)

Iodine requirements for vegetarians: Iodine recommendations may be found at: Nutritive Value of Foods, United States Department of Agriculture, Agricultural Research Service, Home and Garden Bulletin Number 72. May be accessed at (38): http://www.nal.usda.gov/fnic/foodcomp/Data/HG72/hg72_2002.pdf  and http://www.ars.usda.gov/Services/docs.htm?docid=22769

 

Vegetarian diet and iron intake:

Food and Nutrition Board Institute of Medicine recommendations for iron intake: According to the Food and Nutrition Board Institute of Medicine, recommendations for iron intake has been proposed based on estimates of the maximum rates of absorption attainable by individuals in order to maintain a serum ferritin concentration of 15 mg/L, considered an adequate level of iron. Ferritin is a level in the blood checked by doctors to determine adequate iron stores. Those eating a mixed diet with meat contain heme iron (the hemoglobin found in the blood of animals). The iron bioavailability in these sources is much higher and therefore incidence of iron deficiency may be lower than vegetarians. It was suggested by this literature source that iron present in vegetarian foods requires to be consumed in 2-fold greater amounts than those eating a non-vegetarian diet to meet requirements. Vegetarian diets contain non-heme iron which is the type of iron present in fruits, vegetables, bread, cereal, and grains and are sometimes fortified with iron by food companies. This source recommends the following amounts of iron per day for each of the mentioned age groups: infants 0-6 months, 0.27 mg; 7-12 month olds, 11 mg; children 1-3 years old, 7 mg; 4-8 year olds, 10 mg;  9-13 year olds, 8 mg; males 14-18 years old, 11 mg; females 14-18 years old, 15 mg; all males over 18 years old, 8 mg, females age 19-50, 18 mg; females over age 50, 8 mg; all pregnant women, 27 mg; lactating females under age 18, 10mg; and lactating females over age 18, 10 mg. As noted above, vegetarians of the corresponding age groups are encouraged to obtain twice the amount of iron recommended. (16)

 

Vegetarian men, women, and iron needs:

According to this study, Vegetarian men were found to easily obtain the recommended 14mg/d of iron from diet alone. However, vegetarian women of childbearing age in developed countries, on average, did not obtain a recommended iron (Fe) intake of 33 mg/d from diet alone. Many were found to consume only about 11-18 mg/d. To ensure adequate intake of 32-36 mg/d of iron from food, vegetarians on a 2000 kcal diet should have 8 servings of grains, 3 of vegetables, 2.5 of green leafy vegetables, 1.5 of fruit, 1.5 of dried fruit, 2.5 of beans and protein foods, 3 of dairy or fortified nondairy, 1.5 of nuts and seeds, and 2.5 of oils. Modifying food preparation techniques (such as using iron cookware), food selection (such as limiting foods such as coffee and tea until after a meal), and food combinations (such as eating iron-containing foods along with foods that contain ascorbic acid or vitamin C) may improve iron absorption. It is also suggested vegetarian women of childbearing age may need routine iron supplementation to ensure the recommended amount but there is controversy regarding iron supplements in vegetarians. Long term effects have not been studied and iron supplementation over time reduces iron absorption from vegetarian dietary sources. Long-term continuous iron supplementation is required to influence levels of ferritin, a protein that stores iron and is a level checked by doctors to determine adequate iron stores. Also, iron supplementation may increase oxidative stress (a harmful imbalance of pro-oxidants and antioxidants) by the unabsorbed iron in the lower intestine. Excess iron is thought to increase risk of colorectal cancer. Compared to lacto-ovo-vegetarians (people who eat eggs and dairy products, but not meat), higher ferritin levels found in meat eaters has been associated with reduced insulin sensitivity. An increased risk of heart disease has been found among people with hemochromatosis, a gene mutation resulting in excessive iron in the body. Approximately 1 out of 1000 of US non-Hispanic whites are susceptible to this disease. Therefore, it is important to be screened for excess iron stores by your physician before starting iron supplements. Information in this study supports that vegetarians attempt to maintain iron intake using iron rich vegetarian foods rather than iron supplements due to unknown risk of using iron supplements long term. (17)

 

Vegetarians and zinc requirement:

Vegetarians may require 50% more zinc than non-vegetarians based on research in phytate-zinc molar ratios. Phytate is a nondigestible salt responsible for the storage of phosphorus. Phytate in plant tissues reduces the bioavailability of zinc and iron in humans. Therefore, the higher the amount of phytate consumed, the higher the ratio of phytate will be to zinc and iron resulting in less absorption. Compared to non-vegetarian diets, lacto-ovo-vegetarian diets (which includes consumption of eggs and dairy products, but not meat) were associated with a reduced zinc absorption of about 35%. Meat was replaced by legumes, whole grains, seeds, and nuts, resulting in phytate-zinc molar ratios of 14 and 5 for the lacto-ovo-vegetarian and non-vegetarian diets, respectively. After 4 weeks, women on the vegetarian diet absorbed less zinc (2.4 mg Zn/d) than their non-vegetarian counterparts 3.7 mg Zn/d (26% vs 33%). After about 8 weeks, this difference was associated with a 5% reduction in zinc in the blood. The information in this study supports that vegetarians would benefit from zinc supplementation. (18)

 

Recommendation for zinc:

Food and Nutrition Board Institute of Medicine recommendation for zinc in vegetarians is as follows. According to the Food and Nutrition Board Institute of Medicine, zinc intake was suggested to be consumed in 2-fold greater amounts than those eating a non-vegetarian diet to meet requirements. The Food and Nutrition Board, Institute of Medicine recommends the following daily zinc requirement for each of the mentioned age groups: infants 0-6 months, 2 mg; 7-12 month olds, 3 mg; children 1-3 years old, 3 mg; 4-8 year olds, 5 mg;  9-13 year olds, 8 mg; all males over 14 years old, 11 mg; females 9-13 years old, 8 mg; females age 14-18, 9 mg; females over age 18, 8 mg; all pregnant women under 18 years old, 12 mg, all pregnant women age 19-50, 11 mg; lactating females under age 18, 13mg; and lactating females over age 18, 12 mg. As noted above, vegetarians of the corresponding age groups are encouraged to obtain twice the amounts recommended. Daily allowance of zinc may be found at the following link for all ages: http://iom.edu/~/media/Files/Activity%20Files/Nutrition/DRIs/DRI_Elements.pdf (19)

 

Vegetarian diet and vitamin B12 deficiency:

In vegetarian women, supplementation of vitamin B12 is required due to the lack of this vitamin in vegetarian foods. (20)

Vegetarians, B12, and coronary artery disease (CAD): In a study involving 816 subjects (368 with coronary artery disease [CAD] and 448 controls) in India, levels of vitamin B12 were found to be significantly lower in patients with CAD, as compared to controls. In this study interestingly, vegetarians who were found to have lower levels of vitamin B12 were noted to have a higher incidence of coronary artery disease compared to non-vegetarians. (21)

 

Beta-carotene and cancer:

Cancer risk is lower in those who consume beta-carotene containing foods but not beta-carotene supplements according to the National Research Council, Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. (22)

High blood concentrations of beta-carotene and other carotenoids, plant pigments found in carrots, sweet potatoes, spinach, kale, collard greens, papaya, bell peppers, tomatoes, have been linked to a lower risk of cancer, especially lung, mouth, throat, and cervical cancers.

A blood beta-carotene concentration less than 0.28 micromol/L has been linked with a higher risk of several cancers, while a concentration of more than 0.28 to 0.37 micromol/L have been associated with a reduced risk of several cancers in prospective blood concentration studies. However, three other large randomized studies reported no cancer benefit from beta-carotene supplements given at 20, 30, or 50 mg/d for 4 to 12 years.

A word of caution regarding beta-carotene supplements. Beta-carotene supplements are not advised among healthy individuals, unless they suffer from or are at risk of vitamin A deficiency. Beta-carotene supplementation results in a greater increase of beta-carotene blood concentration than beta-carotene rich foods. A 20 mg/d supplement of beta-carotene is associated with blood concentrations high enough to increase a patient’s risk of lung cancer, while the same quantity obtained from foods was not associated with lung cancer risk. Additionally, 30 mg/d of beta-carotene supplement was associated with blood concentrations 5 times greater than that of 29 mg/d of beta-carotene from carrots.

National Cancer Institute Five-A-Day for a Better Health program and Canada’s Food Guide for Healthy Eating:  The consumption of 5 or more daily servings of fruits and vegetables is recommended by the National Cancer Institute’s Five-A-Day for a Better Health program and Canada’s Food Guide for Healthy Eating. Eating a variety of 5 fruits and vegetables per day provides the individual with about 5.2 to 6 mg/day of food based beta-carotene. This allows plasma carotenoid levels to rise above a range represented in studies which were associated with a lower risk of cancer and all-cause mortality compared to those with a lower food based carotenoid levels.

Beta-carotene levels have been found to be associated with a lower risk of mortality. Intake of vegetables containing beta carotene was associated with a lower risk for all causes of death including cancer but no benefit was seen with taking beta-carotene supplements. Greenberg ER et al tested beta carotene levels in subjects prior to being randomized to take beta carotene supplements. Subjects with an intial beta carotene level of 0.34 to 0.52 umol/L had a 51% less risk of dying from cancer when compared to subjects with the lowest intial beta carotene levels of under 0.21 umol/L. Those subjects with an intitial beta carotene level of over 0.52 umol/L had a lower risk of death from all causes. There was no reduced risk of disease or mortality benefit in subjects who took beta carotene supplements in pill form. (23)

Beta-carotene intake from food is required to establish a lower risk of mortality. According to Martini et al in the University of Minnesota Cancer Prevention Research Unit Feeding Studies, an intake of 5 mg per day of beta carotene was required to establish beta carotene levels to a plasma level of 0.37 umol/L. When food based beta carotene was consumed in amounts over 42 mg per day, levels increased to 0.83 umol/L. (25)

Beta-carotene, cancer and mortality was evaluated in the Beta-Carotene and Retinol Efficacy Trial (CARET). This trial showed that among 18,314 men and women who smoked heavily or were exposed to asbestos, daily intake of 30 mg (100,000 IU) of beta-carotene and 25,000 IU vitamin A failed to decrease the risk of cancer. The study was stopped early because it showed that beta-carotene/vitamin A takers who were heavy smokers, ex-smokers or asbestos workers were showing a 28% increased risk of lung cancer in smokers (versus placebo) and a 17% more likely chance of dying, mostly of lung cancer or heart disease.  Results of a 6-year follow-up of study participants showed that compared to the placebo or no intervention group, participants who had taken the intervention had a 12% and 8% increase in relative risk of lung cancer and all-cause mortality among the intervention group, respectively. They found that women were more affected by the supplements with a larger relative risk of lung cancer mortality (1.33 versus 1.14; P = .36), and all-cause mortality (1.37 versus 0.98; P = .001) than males. (24)

For a breakdown of concentration of beta-carotene in foods, please see: Nutritive Value of Foods, United States Department of Agriculture, Agricultural Research Service, Home and Garden Bulletin Number 72. This may be accessed at: (26) https://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/SR25/nutrlist/sr25w321.pdf and http://www.nal.usda.gov/fnic/foodcomp/Data/HG72/hg72_2002.pdf

A meta-analysis that included 78 randomized clinical trials was conducted to determine the relationship of oral antioxidant supplementation (beta-carotene, vitamin A, vitamin C, vitamin E, and selenium) and mortality. Mean duration of supplementation was 3 years. When all of the trials were combined, and the analysis that is typically used when similarity is present was conducted (fixed-effect model), antioxidant use did slightly increase mortality. When the trials with low risks of bias were considered, the patients consuming the antioxidants had a 4% higher risk of death compared to those taking placebo or no intervention (relative risk [RR]=1.04). The increased risk of mortality was significantly associated with use of beta-carotene (death rate: 13.8% on supplement vs 11.1% on placebo; RR=1.05) and vitamin E (12.0% vs 10.3%; RR=1.03) and possibly vitamin A, though the relationship was not significant with a 14.0% death rate among those taking vitamin A compared to a 13.6% death rate among placebo subjects. The current evidence does not support the use of these antioxidant supplements in the general population or in patients with various diseases. (27)

For the prevention of cancer or cardiovascular disease, the U.S. Preventive Services Task Force (USPSTF) recommends against the use of beta-carotene supplements, alone or in combination. According to the USPSTF, the is insufficient evidence to recommend for or against the use of vitamins A, C, or E supplements or multivitamins with folic acid or antioxidant combinations for the prevention of cancer or cardiovascular disease. (28)

A lower risk of mortality appears to be related to beta carotene intake from food sources but not beta-carotene supplements. The benefit may also come from other phytonutrients in the vegetable food source and not necessarily the beta carotene itself.

 

Vegetarian diet and heart disease:

A vegetarian diet may prove a beneficial intervention for patients with heart disease. A randomized, single-blind prospective trial by Singh et al tested a vegetarian diet intervention on 406 patients for 6 weeks starting 24-48 hours after having an acute myocardial infarction (acute MI). A vegetarian diet group compared to a control diet showed a decrease of total cardiac disease events of 34.5% which included fatal acute MI, non-fatal acute MI, and sudden cardiac death. (44)

 

Fruit, vegetable intake, and mortality:

An analysis was conducted on 19,496 men and women, ages 45 to 79, in the U.K. The participants’ blood was tested for ascorbic acid (a form of vitamin C) and they were placed in five groups (quintiles) according to their serum ascorbic acid levels. Men and women were tracked separately. The researchers observed how many people died of cardiovascular disease, ischemic heart disease, cancer, and all causes in each of the blood ascorbic acid quintiles. In every case (except for women at risk of cancer), death rates were significantly lower among those with higher blood ascorbic acid levels. People with the highest ascorbic acid levels had half the risk of dying from all causes combined. Additionally, a 20 micromol/L increase in blood ascorbic acid concentration, the same as a 50 g per day increase in fruit and vegetable intake, was associated with about a 20% reduction in risk of all-cause mortality. (29)

 

Mortality in vegetarians and non-vegetarians:

A meta-analysis consisting of 7 studies with a total of 124,706 participants from the UK, Germany, USA, Netherlands and Japan was conducted to investigate cardiovascular disease mortality and cancer incidence among vegetarians and non-vegetarians. All-cause mortality, mortality from circulatory diseases, and mortality from cerebrovascular diseases in vegetarians were lower when compared to non-vegetarians by 9%, 16%, and 12%, respectively. Researchers also found a statistically reduced rate for vegetarians in terms of ischemic heart disease mortality (29%) and cancer incidence (18%). This study suggests vegetarians have a mortality advantage compared to non-vegetarians. (30)

 

Ideal amount of fruit and vegetable intake:

The ideal amount of fruits and vegetables required to reduce the risk of ischemic heart disease was studied. A Danish review of cohort studies by Ovesen LF examined the relationship between consumption of fruit and vegetables (including nuts) and the risk of ischemic heart disease (IHD). Eight published cohort studies were located which documented that the overall reduction in the risk of developing IHD was approximately 20%. It was determined that the risk reduction was associated with the quantity of fruits and vegetables consumed. The maximum benefit of eating fruits and vegetables toward reduction of ischemic heart disease was reached at a maximum intake of 800 grams of fruits and vegetables per day according to this review. This data has led to a public recommendation in Denmark to consume 600 grams and fruits and vegetables per day. (31)

 

Green and yellow vegetable intake and skin health:

Researchers measured skin hydration, surface lipids, skin elasticity and wrinkling in 716 Japanese women. Differences based on dietary habits were determined by evaluating usual eating patterns with a food frequency questionnaire. The researchers noted that: Higher dietary intake of total fat, saturated fat, and monounsaturated fat was associated with improved skin elasticity. Decreased skin wrinkling around the corners of the eyes was observed in women with higher intakes of green and yellow vegetables. After adjustment for intake of green and yellow vegetables, higher levels of saturated fat were associated with worse skin wrinkling. (32)

 

Phytochemicals in fruits and vegetables and LDL:

In total 115 women participated in a cross-sectional study investigating the intake of the phytochemicals flavonols, flavones and isoflavones with blood chemistry data. Flavonoids (flavonols, flavones) and isoflavones are the anti-oxidant phytochemicals, chemical compounds produced by plants, found in many foods such as apples, cabbage, onions, parsley, pinto beans, and tomatoes. The main sources of flavonoid consumption in this study were vegetables (72.3%), fruits (15.6%), green tea (5.4%), potatoes (3.8%) and pulses (tofu) (2.9%). A 3-day dietary intake was recorded and urine and blood samples were taken after that period. Researchers found that the mean intake of flavonoids was 16.7 mg/d and the mean intake of isoflavones was 47.2 mg/d. The following phytochemicals were determined to make up the total flavonoid intake: quercetin (55.9%), kaempferol (35.3%), fisetin (4.6%), myricetin (2.5%), and luteolin (1.7%). Most of the flavonoids came from onion consumption 45.9%, 23.1 g/d) followed by molokheya, a dark leafy green, (9.7%, 4.6 g/d), apples (7.2%, 22.2 g/d) and green tea (5.4%, 206 mL/d). The study concluded that the intake of flavonoids was inversely related with LDL levels. Intake of other phytochemicals was not correlated with lipid levels. In this particular study, there was no correlation between green tea consumption and plasma lipids. (33)

 

Vegetarian diet and mood:

The link between diet composition and mood in women on weight-reducing diets of a 1,000 kcal per day for 6 weeks was examined. Researchers found that mood during the last 3 weeks of the diet were significantly better in the “vegetarian” than in the “mixed” diet group. A significant relationship was also observed between low carbohydrate intake and decline in mood (r = -0.74; p less than 0.01) and between the ratio of plasma tryptophan to other large neutral amino acids (a predictor of tryptophan flow into brain) and global mood (r = -0.52; p less than 0.05). These findings suggest that group differences are related to differences in carbohydrate intake. The authors propose that in situations of relatively low carbohydrate intake serotonin levels are low due to reduced tryptophan availability which can prompt a decline in mood. (34)

 

Vegetarian diet and abdominal aortic aneurysm:

The consumption of nuts, vegetables, fruits and risk of abdominal aortic aneurysm was evaluated in a cohort study. Kent et al retrospectively analyzed medical and questionnaire data from 3.1 million patients screened with ultrasound for abdominal aortic aneurysm (AAA) from 2003 to 2008. The analysis affirmed well-known risk factors—male, age, family history, cardiovascular disease, and past smoker—but also discovered new markers of higher or lower risk. Excess weight was associated with increased risk, whereas exercise and consumption of nuts, vegetables, and fruits were associated with reduced risk. Blacks, Hispanics, and Asians had lower risk of AAA than whites and Native Americans. The study also found that the risk of AAA increased with more years of smoking and total cigarettes smoked (based on packs-per-day estimates), while the risk went down the longer the patient lived after quitting smoking. Based on their findings from the database, Kent et al created a new scoring system that would assign points to different risk factors, with negative points for factors that decrease AAA risk. For example, in their scoring system, smoking could add between 1 to 26 points to the patient’s risk score, depending on the duration and severity of their habit, and points are taken off for years since quitting. Being Hispanic or Asian subtracts four points, while being aged 80 to 84 adds 35 points. The authors suggest that patients with a score of 42 or above should be screened for AAA. This is also the point where the system has the best discriminative ability and would identify 88.6% of all AAAs, if applied to a population aged 50 to 84 years, or 59%, if applied to people 50 to 75 years old. (35)

 

Vegetarian diet and rheumatoid arthritis:

The effect of diet on patients with rheumatoid arthritis (RA) or inflammation of the joints was studied in a controlled, single-blind trial. Participants in the treatment group (n=27) fasted for 7-10 days, followed by an individually adjusted gluten-free vegan diet for 3.5 months, followed by a 9-month lactovegetarian diet. The control subjects consumed an ordinary mixed food diet. Compared to the control group, those on the specified diet had a significant improvement in all clinical variables and most laboratory variables measured. A year later, the patients were re-examined. Researchers found that vegetarians who had benefited from the diet showed a significantly greater benefit than diet non-responders or control subjects. This suggests that the vegetarian diet positively influenced measures of inflammation and disease activity. (36)

 

Vegetarian diet and use of health services:

Vegetarian diet may reduce the use of health services, rates of allergic disease, and use of medications. A study looked at diet, lifestyle and disease in 1976 with 27,766 participants, of which 15,228 (55%) were vegetarians. Among female participants, researchers found a higher rate of reported overnight hospitalizations and surgeries among non-vegetarian females compared to vegetarian females. Non-vegetarian males reported more overnight hospitalizations and x-rays. When comparing the rates of disease between non-vegetarian and vegetarians, non-vegetarian females were 1.3 times more likely to report a chemical allergy, 1.2 times more likely to report asthma, 1.17 times more likely to report drug allergy, 1.17 times more likely to report bee-sting allergy, 1.15 times more likely to report hay-fever. Among non-vegetarian males, they were more likely to report chemical and drug allergy. Additionally, use of medication increased by 70-115% in non-vegetarian females and more than doubled in non-vegetarian males. (37)

 

Summary and Conclusion: Vegetarian diet

 

 

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