Scientific Update
By Reed Mangels, PhD, RD
Vegan Pregnancy
Two recent studies from Israel examined the outcomes of vegan, vegetarian, and
non-vegetarian pregnancies. Both studies found that babies of vegans weighed
slightly less, on average, at birth than did babies of non-vegetarians, but birth
weights were generally within a normal range.
The vegan women had a slightly lower average BMI before they became pregnant and, on average, gained less weight in pregnancy than did nonvegetarians. The researchers from both studies reported that significantly more babies of vegans were classified as being small for gestational age (SGA) compared to babies of nonvegetarians. Babies who are classified as SGA are smaller than 90% of babies of the same gestational age and have a higher risk of problems like low blood sugar and difficulty maintaining body temperature after birth.
Many factors can cause an infant to be SGA, and it is not possible to determine why infants of vegans were more likely to be classified this way. Ways to reduce the risk of having an SGA baby include starting pregnancy at a healthy weight, gaining the recommended amount of weight in pregnancy, and eating a healthy diet throughout pregnancy.
Avnon T, Paz Dubinsky E, Lavie I, Ben-Mayor Bashi T, Anbar R, Yogev Y. The impact of a vegan diet on pregnancy outcomes. J Perinatol. 2020.
Kesary Y, Avital K, Hiersch L. Maternal plant-based diet during gestation and pregnancy outcomes. Arch Gynecol Obstet. 2020;302(4):887-898.
Bone Health
By Kavitha Shankar MS, MBA, VRG
Intern
A recent large study from the United Kingdom that included
vegetarians, vegans, fish-eaters, and meat-eaters asked subjects about their diet
and then, over the next 15 to 23 years, determined, via the National Health
Service's records, which study subjects had fractured a bone.
Compared with meat-eaters, vegetarians and vegans had a higher risk of total fractures and hip fractures and vegans had a higher risk of leg fractures and of vertebral fractures. Vegetarians had a 25% higher risk of hip fractures than did meat-eaters, while vegans had more than twice the risk. No significant differences were seen among the groups in the risk of wrist or ankle fractures or the risk of arm fractures after controlling for BMI.
One factor that accounts for some of the differences in fracture risk is BMI. Vegans, on average, had a lower BMI. While a lower BMI offers many health benefits, it is also associated with less dense bones that may be more likely to fracture. The groups differed in their intakes of protein and calcium with vegans having markedly lower average dietary calcium intakes than the other groups. However, the differences in dietary protein and calcium intake do not account for all the differences in fracture risk between the groups.
Although the investigators examined dietary calcium intake, they did not determine if there were differences in intake of calcium supplements, nor did they investigate vitamin D or vitamin B12 intake or status. Adequate vitamin D and vitamin B12 are needed for bone health.
Because of the observational nature of this study, it is not possible to say if changes in vegans' dietary or supplement practices (such as increased calcium, vitamin D, vitamin B12, or protein intake) could have affected their risk of fracture.
Vegans should follow general recommendations to promote healthy bones, including getting enough calcium, vitamin D, protein, and vitamin B12 and doing weight-bearing exercise regularly.
Tong TYN, Appleby PN, Armstrong MEG, et al. Vegetarian and vegan diets and risks of total and site-specific fractures: results from the prospective EPIC-Oxford study. BMC Med. 2020;18(1):353.
Fruits and Vegetables Offer Many Benefits
A couple of recent studies illustrate the important role that fruits
and vegetables play in promoting health. The first study focused on almost 9,000
breast cancer survivors and asked the women about their diet every four years after
their diagnosis. Over the follow-up period, averaging 11.5 years, women who ate more
fruits and vegetables and women who ate more vegetables had a lower risk of dying
from any cause than did women with lower intakes of these foods. Women with the
highest intakes of vegetables and fruits averaged 7.4 servings per day; those with
the lowest intake averaged 2.2 servings per day.
When the investigators examined specific foods, they determined that women with a greater intake of green leafy and cruciferous vegetables (vegetables in the cabbage family) had a lower risk of death than did women with lower intakes of these foods. Vegetables and fruits high in vitamin C and vegetables high in beta-carotene (like carrots, winter squash, and sweet potatoes) were associated with a lower risk of death.
Higher fruit juice consumption, but not higher orange juice consumption, was associated with a higher risk of death from breast cancer and from any cause.
The second study looked at frailty in older women. Frailty is a decline in physical function and is associated with an increased risk of illness and disability. This study followed more than 78,000 women aged 60 and older for up to 20 years. During that time, the women were regularly asked about their diet and health.
Frailty was defined as having three or more of the following self-reported issues: fatigue, inability to walk up a flight of stairs, inability to walk several blocks, significant weight loss, and a history of several chronic illnesses; 16% of the women were assessed as having frailty. Total fruit and vegetable intake was associated with a reduced risk of frailty with those averaging seven or more servings of fruits and vegetables daily having a lower risk than those averaging fewer than three servings a day. Leafy green vegetables, yellow and orange vegetables, and apples and pears were specific fruits and vegetables associated with a lower risk.
Farvid MS, Holmes MD, Chen WY, et al. Postdiagnostic fruit and vegetable consumption and breast cancer survival: prospective analyses in the Nurses' Health Studies. Cancer Res. 2020;80(22):5134-5143.
Fung TT, Struijk EA, Rodriguez-Artalejo F, Willett WC, Lopez-Garcia E. Fruit and vegetable intake and risk of frailty in women 60 years old or older. Am J Clin Nutr. 2020 [published online ahead of print].
Vegetarianism and Veganism in Canada
by Kavitha Shankar, VRG Volunteer
Canadian researchers analyzed the results of a 2015 health survey of Canadians from all 10 provinces. A section of the survey included questions about plant-based dietary practices (PBDP). To reduce ambiguity in respondents?€? perception or definition of PBDP, the scientists first categorized PBDP into vegan (abstinence from red meat, poultry, fish and shellfish, dairy, and eggs), vegetarian (avoidance of red meat, poultry, fish, and shellfish), pescatarian (restraint from red meat and poultry), red meat excluder, and non-PBDP. They then incorporated questions into the larger survey that asked the respondents to identify which categories of animal products they fully excluded from their diet.
The researchers surveyed about 20,400 men, women, and children (age >2 years). Overall, fewer than 5% of the survey respondents adhered to any category of PBDP. More specifically, the study showed that about 1.9% of the respondents were categorized as vegetarians not including vegans and 0.3% as vegans. In comparison, a 2020 poll sponsored by the Vegetarian Resource Group found that about 6% of adults in the United States are vegetarian (including vegan), while 3% of adults are vegan (vrg.org/nutshell/faq.htm#poll).
The Canadian researchers also observed that sex was not a significant predictor of veganism or vegetarianism. Respondents who identified themselves as people of South Asian origin living in Canada were approximately 20 times more likely than white-identifying respondents to report vegetarianism, possibly owing to their cultural and religious beliefs.
Valdes M, Conklin A, Veenstra G, Black JL. Plant-based dietary practices in Canada: Examining definitions, prevalence and correlates of animal source food exclusions using nationally representative data from the 2015 Canadian Community Health Survey-Nutrition. Public Health Nutr. 2020:1-10.
