SCIENTIFIC UPDATE
By Reed Mangels, PhD, RD, FADA
Survey of Vegans in the U.S.
A survey of 100 adult vegans from across the U.S. provided a snapshot of behaviors and motivations. Although this was a small study, it adds to what we know about vegan practices. About half of the study subjects, all of whom had been vegan for at least 9 months, reported health beliefs as their main reason for being vegan. Animal welfare concerns were the main motivation for 40% of subjects. The majority had BMIs in the normal weight range; those for whom health was their primary motivator were more likely to be classified as overweight or obese than those motivated by animal welfare. Few subjects (1%) reported eating fast food meals. Health-motivated vegans were more likely to choose lower fat products than vegans who were motivated by animal welfare. Subjects typically ate almonds, flaxseeds, and peanut butter at least twice weekly. Three-quarters of subjects ate tofu at least twice a week; almost 60% used soymilk that often. Commonly eaten vegetables included tomatoes, carrots, leaf and romaine lettuce, and broccoli. Commonly eaten fruits included apples, bananas, and oranges. All nutrients except vitamin D were adequate. Cigarettes and alcohol were rarely used and the majority of subjects exercised at least 3 times per week. These results show that the vegans surveyed were likely to practice health-supporting behaviors.
Dyett PA, Sabaté J, Haddad E, Rajaram S, Shavlik D. 2013. Vegan lifestyle behaviors. An exploration of congrunce with ealth-related beliefs and assessed health indices. Appetite 67:119-24.
Heart Disease - Could Causes Include Carnitine or Choline?
Cholesterol and saturated fat have long been thought to be related to the higher risk of heart disease seen in those eating more red meat. New research suggests that carnitine and choline may play a role. Carnitine is made from lysine, an amino acid. Red meat is an especially good source of carnitine, as are energy drinks and supplements. Most people make enough choline and do not need to have a dietary source. Apparently, bacteria that live in the intestines of humans digest dietary carnitine and turn it into another substance, TMAO, which can lead to blocked arteries. When vegetarians or vegans are given carnitine, they produce less TMAO than meat eaters, suggesting that vegetarians and vegans have fewer bacteria in their intestines that can convert carnitine to TMAO. This could help to explain why heart disease rates are lower in vegetarians.
As an aside, media reports of this study said that 77 vegetarians and vegans were fed red meat. The published study actually said that one long-term (>5 years) vegan male agreed to eat an 8-ounce sirloin steak and that a small group of vegetarians and vegans was given carnitine supplements but was not given meat. This shows how information gets distorted; if a story sounds off, it's necessary to read the original study.
Choline, an essential nutrient, may also be associated with increased risk of heart disease. Choline is also involved in TMAO production. Researchers fed 40 healthy adults two hard-boiled eggs. Eggs are high in choline. Blood TMAO levels of study subjects increased after they ate the eggs. These researchers also examined more than 4000 adults and found that those whose blood levels were highest in TMAO were at highest risk of having a heart attack or stroke or of dying from heart disease. These results are preliminary but could help to explain the lower risk of heart disease seen in vegetarians.
Koeth RA, Wang Z, Levison BS, et al. 2013. Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis. Nat Med 19:576-85.
Tang WH, Wang Z, Levison BS, et al. 2013. Intestinal microbial metabolism of phosphatidylcholine and cardiovascular risk. N Engl J Med 368:1575-84.
Vegetarian Companion Animals
How do vegetarians deal with the issue of animal-based pet foods? Are vegetarians more or less likely to have a companion animal (identified by this study as a "pet")? A researcher at Bellarmine University recruited study participants mainly through the VRG's blog and newsletters. The final survey included 515 participants, 61% vegan, and 39% vegetarian. Close to three-quarters of respondents had at least one companion animal. Those abstaining from meat for ethical reasons were more likely to have a dog or cat than those who avoided meat for health reasons. There was no difference between vegans and vegetarians in terms of having companion animals. Subjects who avoided meat for ethical reasons were more likely to avoid feeding their companion animal(s) a high-meat diet compared to those avoiding meat for health reasons. Vegans were more likely to avoid high-meat diets for companion animals. Vegans and ethical vegetarians/vegans were more likely to feel guilty about feeding their companion animals diets based on animal products than non-vegans and health vegetarians/vegans. These differences in guilt were not due to differences in perception of how healthy vegetarian diets are for companian animals. The author stated that vegans and ethical vegetarians/vegans find it more objectionable to use animals for pet food because they see other animals as similar to humans. These groups were more likely to feed their companion animals a predominantly vegetarian diet.
Rothgerber H. 2013. A meaty matter. Pet diet and the vegetarian's dilemma. Appetite 68:76-82
Vegetarians and Phytates
Phytates, substances found in whole grains, dried beans, nuts, and seeds, interfere with the absorption of minerals like iron and zinc. Bacteria in our intestines can produce phytases — enzymes which partially digest phytates and could reduce their impact on mineral absorption. Phytase activity is very low in humans. Polish researchers wondered if vegetarians, whose diets are typically higher in phytates, would have a greater ability to digest phytates. They studied 4 lacto-ovo vegetarians, 4 vegans, and 6 non-vegetarians. Bacteria collected from the vegans/vegetarians' intestines were the most effective at digesting phytates. This suggests that intestinal bacteria may be able to adapt to their environment so that bacteria in a high-phytate environment (like vegetarians' intestines) are better able to break down phytates. This could mean that phytates wouldn't interfere with iron and zinc absorption in vegetarians and vegans as much as was previously thought. This was a small study; additional research is needed.
Markiewicz LH, Honke J, Haros M, Swiatecka D, Wróblewska B. 2013. Diet shapes the ability of human intestinal microbiota to degrade phytate - invitro studies. J Appl Microbiol 115:247-59
Smile - You're a Vegetarian
German researchers examined dental health of 100 vegetarians (89 lacto-ovo vegetarians and 11 vegans) and 100 non-vegetarians. Subjects received a complete dental exam. Vegetarians had better gum health and were less likely to have inflamed or bleeding gums. Plaque accumulation was lower in the vegetarian group. They also had fewer missing teeth but were more likely to have decayed teeth. The vegetarians practiced oral hygeine more often. The results of this study suggest that a vegetarian diet has a positive effect on dental health.
Staufenbiel I, Weinspach K, Förster G, Geurtsen W, Günay H. 2013. Periodontal conditions in vegetarians: a clinical study. Eur J Clin Nutr [Epub ahead of print]
Lower Risk for GERD
GERD (gastroesophageal reflux disease) is a condition that affects the esophagus. Normally, stomach acid does not move up into the esophagus. The opening between the esophagus and the stomach does not close properly in people with GERD. This means that stomach acid can irritate the esophagus and cause symptoms like heartburn and hoarseness. Obesity, smoking, and alcohol are risk factors for GERD. Researchers from South Korea wondered if a vegetarian diet would reduce the risk of GERD. They studied 148 vegetarian Buddhist priests and 148 non-vegetarians. About half of each group was male. The Buddhist priests were heavier and had a higher BMI. None of the priests smoked or used alcohol. The incidence of GERD, determined by endoscopic exam, was lower in the vegetarian priests than in the nonvegetarians. Risk factors for GERD in this study included being male, smoking, using alcohol, and not following a vegetarian diet. The researchers theorized that the higher amount of fruits and vegetables in many vegetarians' diets may be protective because of these foods' antioxidant content.
Jung JG, Kang HW, Hahn SJ, et al. 2013. Vegetarianism as a protective factor for reflux esophagitis: a retrospective, cross-sectional study between Buddhist priests and general population. Dig Dis Sci [Epub ahead of print]
