Women who follow vegan diets during pregnancy may face higher risks of developing preeclampsia and of giving birth to newborns with lower birth weight, suggests a recent study published in Acta Obstetricia et Gynecologica Scandinavica.
For the study, 65 872 women identified themselves as omnivorous, 666 as fish/poultry vegetarians, 183 as lacto/ovo vegetarians, and 18 as vegans. Based on a questionnaire completed mid-pregnancy, investigators found that protein intake was lower among lacto/ovo vegetarians (13.3%) and vegans (10.4%) compared with omnivorous participants (15.4%). Micronutrient intake was also much lower among vegans, but when dietary supplements were considered, no major differences were observed.
Compared with omnivorous mothers, vegan mothers had a higher prevalence of preeclampsia (a pregnancy complication characterised by high blood pressure), and their newborns weighed an average of 240 g less.
“Further research is needed regarding possible causality between plant-based diets and pregnancy and birth outcomes, to strengthen the basis for dietary recommendations,” the authors wrote.
Older adults require more protein but eat less than younger people, making it a challenge for them to maintain muscle mass. Eating a meal with meat ensures that muscle proteins are built faster than a vegan meal with the same amount of protein. This study, published in The Journal of Nutrition, was the first to compare the speed at which muscle proteins are being made after eating a complete meal with animal or plant proteins.
Every two to three months the proteins in human muscle are completely renewed. In order to make muscle proteins, we need protein from food, for example from animal sources such as meat, cheese and yoghurt, or from plant products such as beans, nuts and soymilk. Previous research on protein powders showed that animal proteins have better muscle-building properties than plant proteins. “But in reality, we do not get our proteins in powder form, but through complete meals,” says study author and PhD student Philippe Pinckaers. “Those meals contain different types of protein and other nutrients such as fibres, fats and carbohydrates. These nutrients affect how proteins are released from the diet and influences the making of muscle proteins.”
To investigate how muscles respond after eating a complete meal, Pinckaers asked 16 participants aged over 65 to come to the lab twice for a dinner meal.
Dining out in the lab
On one day, the participants sat down to a meal with quinoa with chickpeas, broad beans, soy beans and soy sauce was on the menu, while on the other day the menu consisted of a beef tartlet, potatoes, green beans, apple sauce and herb butter. Both meals had similar amounts of protein, fat, carbohydrates and calories. Prior to the meals, participants were administered an infusion of special amino acids.
“The amino acids administered via the infusion were marked, as it were with a flag,” Pinckaers explains. “We took small pieces of muscle tissue from the participants and were able to measure the amount of ‘flags’ in them. If more flags are measured, it means that muscle proteins are built up faster, which is beneficial for muscles. In this way, we found that after eating a meal with animal protein, muscle protein was built up faster than after eating a vegan meal. This means that a vegan meal does not have the same capacity to make muscle proteins as a meal that includes animal proteins.” This difference arises partly because plant-based foods are harder to digest, and because they naturally contain fewer essential amino acids.
Context is key
The results do not mean that everyone should eat meat or other animal products, clarifies professor of exercise science and lead researcher Luc van Loon. “Healthy people can very well compensate for the lower quality of plant proteins by eating more of them.” For elderly or frail patients it is a bit more complicated. “Elderly people actually need more protein in order to reach the same level of muscle protein synthesis, when compared to young individuals. However, they actually eat less. Also, patients with reduced appetite or who do not exercise much, for example during hospitalisation, may have trouble consuming a sufficient amount of protein. For them, it is therefore important to choose protein sources that stimulate the making of muscle proteins as much as possible. The best sources in this situation would be proteins from animal products.”
A systematic review has revealed that plant-based or plant-heavy diets may offer a level of protection against prostate cancer and other male sexual health issues according.
The analysis included 23 studies, 12 of which included prostate cancer, and suggested a link between a plant-based diet and reduced prostate cancer risk. Some evidence also suggested benefits for erectile dysfunction and benign prostate hyperplasia. The findings were reported at the Sexual Medicine Society of North America (SMSNA) annual meeting.
“Medicine has moved to a more holistic approach overall, and with that, more researchers have started to look into [the question of] ‘Can we use these plant-based diets to help manage and prevent conditions like prostate cancer, erectile dysfunction [ED], and benign prostate hyperplasia [BPH]?’ Nathan Feiertag, MD, a medical student at Albert Einstein College of Medicine in New York City, told MedPage Today. “There were relatively few studies that we were able to find for this literature review, but that’s the current state.”
With the growing popularity of plant-based diets, studies have shown their benefits for patients with hypertension or diabetes. Dr Feirtag said that less is known about their effect on prostate cancer, ED and BPH.
Dr Feiertag told MedPage Today that “Urologists can maybe consider our review as an opportunity to incorporate or modify existing diet counselling for their patients, especially the ones who are eager to implement lifestyle changes, particularly as it pertains to prostate hyperplasia, ED, and prostate cancer.”
The review mostly consisted of cohort studies, along with cross-sectional studies, and a handful of randomised controlled trials. Studies included those on vegan diets, vegetarian diets, and plant-heavy diets, such as the Mediterranean diet. In a number small cohort studies, there was a significant decrease in prostate cancer velocity, though not sustained at six months, Dr Feiertag said.
Two of the five ED studies found a link between plant-based diets and improved International Index of Erectile Function scores, though one reported worsening scores. The two studies included on ED reported a reduced relative risk of ED for patients on plant-based diets. For BPH, five of six studies reported an inverse relationship between plant-based diets and developing BPH.
Limitations including not being generalisable due to the number of observational and cohort studies that relied on patient-reported evaluations of diet. Additional high-quality studies are needed to confirm the link between diet and urological conditions.
Fortunately, the studies all reported no non-association or no harmful effects of following a plant-based or plant-forward diet. “For the patients who want to change their diet, this is useful for them. It definitely won’t hurt,” Dr Feiertag told MedPage Today.
A study comparing meat and plant-based burger patties has found significant differences in nutritional content.
As plant-based foods have improved in quality and availability, some have achieved a taste and texture remarkably similar to real beef, and they may even seem nutritionally equivalent in terms of items such as vitamins, fats and protein, based on their nutritional information labels.
But a Duke University research team’s deeper examination of the nutritional content of plant-based meat alternatives, using an analysis known as ‘metabolomics,’ shows they’re still quite different.
Manufacturers of meat substitutes have gone to great trouble to make their plant-based products as meaty as possible, such as adding leghemoglobin, a plant-derived iron-carrying molecule to simulate bloodiness. Indigestible fibres like methyl cellulose thicken the texture of the meat substitutes. And to bring the plant-based meat alternatives up to the protein levels of meat, they use isolated plant proteins. Some meat-substitutes also add vitamin B12 and zinc to further replicate meat’s nutrition.
However, many other components of nutrition do not appear on the labels, and that’s where the products differ widely from meat, according to the study, which appears this week in Scientific Reports.
The metabolites that the scientists measured are building blocks of the body’s biochemistry, crucial to the conversion of energy, signaling between cells, building structures and tearing them down, and a host of other functions. There are expected to be more than 100 000 of these molecules in biology and about half of the metabolites circulating in human blood are estimated to be derived from our diets.
“To consumers reading nutritional labels, they may appear nutritionally interchangeable,” said Stephan van Vliet, a postdoctoral researcher at the Duke Molecular Physiology Institute who led the research. “But if you peek behind the curtain using metabolomics and look at expanded nutritional profiles, we found that there are large differences between meat and a plant-based meat alternative.”
The researchers compared 18 samples of a popular plant-based meat alternative to 18 grass-fed ground beef samples from a ranch in Idaho. The analysis of 36 carefully cooked patties found that 171 out of the 190 metabolites they measured varied between beef and the plant-based meat substitute.
The beef contained 22 metabolites that the plant substitute did not, while the plant-based substitute contained 31 metabolites that meat did not. The greatest distinctions occurred in amino acids, dipeptides, vitamins, phenols, and types of saturated and unsaturated fatty acids found in these products.
A number of important metabolites were found only in beef, or in greater quantities, including creatine, spermine, anserine, cysteamine, glucosamine, squalene, and the omega-3 fatty acid DHA. “These nutrients have potentially important physiological, anti-inflammatory, and or immunomodulatory roles,” the authors wrote in the paper.
“These nutrients are important for our brain and other organs including our muscles” van Vliet said. “But some people on vegan diets (no animal products), can live healthy lives – that’s very clear.” Besides, the plant-based meat alternative contained several beneficial metabolites not found in beef such as phytosterols and phenols.
“It is important for consumers to understand that these products should not be viewed as nutritionally interchangeable, but that’s not to say that one is better than the other,” said van Vliet, who eats a plant-heavy diet which still includes meat. “Plant and animal foods can be complementary, because they provide different nutrients.”
More research is needed, he said, to determine whether the presence or absence of particular metabolites in meat and plant-based meat alternatives have any short- or long-term effects.
A Finnish study has found that increasing the share of dietary protein from plant versus animal sources leads to increased bone turnover and possible fracture risk.
The 136 adult participants followed one of three diets for a period of three weeks. One of them was modelled on the typical Finnish diet where 70% of protein came from animal sources and the rest from cereals. The second had half the protein come from animal sources and the other half from plants, and the third had 70% of protein from plants and the rest from animal sources
Dairy milk, which is fortified with vitamin D in Finland, was substituted with unfortified plant-based milk, which may have been a confounding variable. There was a marked increase in bone formation and resorption markers, which in the long term could indicate bone loss. These findings are in line with the Oxford-EPIC study, which followed participants for 18 years and found a higher rate of fractures in vegetarians compared to those on an omnivorous diet.
“The results could be different if fluid dairy products had been replaced with plant-based drinks fortified with vitamin D and calcium,” said Docent Suvi Itkonen, Department of Food and Nutrition, Faculty of Agriculture and Forestry, University of Helsinki. “Then again, the average vitamin D intake was also below the recommended level in the group where subjects consumed the animal protein-rich diet, but not to the same extent as in the other groups.”
Journal information: Itkonen, S. T., et al. (2021) Partial Replacement of Animal Proteins with Plant Proteins for 12 Weeks Accelerates Bone Turnover Among Healthy Adults: A Randomized Clinical Trial. The Journal of Nutrition.doi.org/10.1093/jn/nxaa264.
