Data presented at the three-day event at Loma Linda University in southern California also showed that despite lower energy intakes, non-meat eaters, including vegans, were more likely to meet government recommendations on micronutrients, including iron and calcium – with the exception of vitamin B12.
Vegans and vegetarians typically have lower blood pressure and lower LDL cholesterol. They also typically have a lower BMI, lower fasting blood glucose (resulting in a lower incidence of type 2 diabetes) and a lower risk of developing certain cancers (notably colorectal cancer), kidney stones, gout, and even cataracts, said successive speakers at the event, which is held every five years.
Precisely why remains the subject of debate, with some speakers suggesting that vegetarians’ lower calorie intake - and lower BMI - is the critical factor from which the other health benefits stem; and others claiming that higher levels of fiber and health-promoting phytochemicals, coupled with lower levels of saturated fat and other components found in red meat in particular may be responsible.
Speaking to FoodNavigator-USA during one of the breaks, Timothy Key, professor of epidemiology at Oxford University in the UK, said:
"There are a range of other outcomes [beyond cardiovascular disease and diabetes] that we've been looking at, for example some types of cancer where although we've seen interesting associations with vegetarian diets, we don't fully understand the mechanisms involved, so it's difficult to say whether meat is increasing risk, or if it's plant foods that are protective."
If everyone cut red meat to one serving every other day, almost 10% of premature deaths could be prevented
If you replace red meat with nuts, seeds and legumes (beans, chickpeas, lentils etc), the effects on cardiovascular disease risk are pronounced, said Frank Hu, professor of nutrition and epidemiology at Harvard Medical school, who said that even small changes could have a significant impact.
“If everyone could cut red meat consumption to one serving every other day, almost 10% of premature deaths could be prevented.”
“A plant-based diet is associated with a lower risk of hypertension, diabetes, cardiovascular disease, cancer and mortality [premature death].”
Frank Hu, professor of nutrition and epidemiology, Harvard Medical school
Nuts and gut bacteria
Once considered a fatty junk food to eat sparingly, nuts – a good source of healthy fats, protein, fiber, vitamins, minerals and antioxidants – meanwhile, are now recognized as a key component in a healthy diet pattern, said David Baer, PhD, research leaders at USDA’s agricultural research service, who highlighted nuts’ beneficial effects on weight management (read more HERE), cardiovascular health, cognition and some cancers, although research into the latter two areas is preliminary.
We don’t absorb all of the energy in some nuts - as when you bite into a nut and break it into smaller pieces, some of them pass through the digestive system intact, taking the energy contained in these fragments with them - which means we may be overstating their calorie content by up to 20%, said Dr Baer.
While this is interesting from a weight management perspective, it may also confer other benefits, said Dr Baer, noting that undigested nut fragments reach the large intestine, where they are associated with higher concentrations of the gram-positive anaerobic bacteria roseburia, which produce the beneficial short chain fatty acid butyrate (associated with reduced risk of cardiovascular disease and certain cancers), he added.
Beans instead of beef?
A growing body of research also shows that increased consumption of legumes – lentils, chickpeas, peas, beans, soybeans and peanuts – can help people manage their weight (they are satiating and can replace protein sources with more calories and saturated fats), and reduce the risk of cardiovascular disease (they lower LDL cholesterol and blood pressure) and type 2 diabetes (they are low-GI), said Jordi Salas-Salvadó, MD, PhD, professor of nutrition and Rovira i Virgili University in Spain.
According to a high-profile study (Micha et al JAMA, March 2017) published in JAMA (The Journal of the American Medical Association) last year, “dietary factors were estimated to be associated with a substantial proportion of deaths from heart disease, stroke, and type 2 diabetes,” said Brenda Rea, MD, PT, RDN.
A significant percentage of premature deaths could be prevented if Americans ate more polyunsaturated fats, wholegrains, nuts, seeds, and fruits and vegetables, and reduced intakes of processed meats, sodium and sugar sweetened beverages, she added.
Vegans and ‘complete’ protein
While some vegans worry about getting enough ‘complete’ protein, a growing number of vegan athletes from ultramarathoner Scott Jurek to ultra endurance athlete Rich Roll are competing at the highest level, said Matt Ruscigno, MPH, RD, chief nutrition officer at Nutrinic, a plant-based nutrition clinic serving clients in the Los Angeles area and beyond.
“I think this concern about complete proteins is a little misleading,” said Ruscigno, who pointed out that while not all plant-based proteins are ‘complete’ in the sense that they don't all have adequate levels of all nine essential amino acids (with some exceptions including soy), mixing and matching foods can easily ensure vegans get what they need.
For example, rice and beans work well together as rice is low in lysine and high in methionine, while beans are low in methionine and high in lysine). Peanut butter sandwiches or hummus and pita bread are also good choices as peanuts/chickpeas are lower in methionine, but high in lysine, while whole grain bread is high in methionine, but lacks lysine.
Pointing to a slide listing the amino acid levels in various plant sources of protein, he said: “None of these numbers are zero.”
While it is quite possible to eat a poor vegetarian diet (click HERE) with too many refined grains and saturated fats (the cheesy pizza, cookies and ice cream vegetarian diet), it’s a myth that vegans and vegetarians struggle to get enough protein, which can be found in beans, lentils, peas and peanuts, soy, whole grains, nuts, seeds and (for lacto-ovo vegetarians) low-fat or fat-free dairy and eggs, he said.
“Even a serving of spinach has protein in it, so it all adds up.”
In the PREDIMED study , a single-blind, randomized clinical trial, 7,447 volunteers aged 55-80 at high risk of cardiovascular disease but with no symptoms were divided into three groups.
The control group was put on a low-fat diet (as per American Heart Association guidelines), and the two intervention groups were both put on Mediterranean diets rich in fresh fruits and veg, seafood, whole grains, mono-unsaturated fats and very low in meat and dairy.
The diet of the first intervention group was supplemented with 30g nuts a day (15g walnuts, 7.5g almonds and 7.5g hazelnuts); and the second with 50ml of virgin olive oil a day.
There were no calorie restrictions for any volunteers, who were monitored regularly. Compliance with the olive oil and nut prescriptions was also tested via analysis of urine (for hydroxytyrosol from olives), and blood (for alpha-linolenic acid from the walnuts).
The resulted showed that people following an energy unrestricted Mediterranean primarily plant-based diet supplemented with extra-virgin olive oil or nuts (both high in healthy unsaturated fats and polyphenols) reduced their risk of a major cardiovascular event by 30% compared with people following a purely low-fat diet.
The results of the Spanish trial - which began in 2003 and ended in 2011 - were so dramatic that it was ultimately stopped ahead of time for ethical reasons, as the control group was clearly at such a disadvantage compared with volunteers in both intervention groups.
Asked whether it was accurate to describe the diet consumed by the intervention groups as ‘plant-based’ given that they ate meat, fish and dairy products, Dr Joan Sabaté, professor in the Dept of Nutrition at Loma Linda University and chair of the vegetarian nutrition congress, said volunteers typically ate small amounts of all three groups.
And asked whether the cardiovascular benefits enjoyed by the intervention groups could be explained by differences in consumption of fish (which is rich in heart-healthy omega-3 long chain fatty acids) vs the control groups, study leader Dr. Miguel Angel Martinez said this was unlikely as all three groups ate a similar amount of fish.
Meanwhile, individuals in the intervention groups with a diet scoring the highest on a pro-vegetarian index had the best outcomes of all, he said.
While nuts and virgin olive oil appeared to be key to the improved health outcomes, the take home message was that whole dietary patterns have to change to deliver results, said Dr Sabate.
“The message is not that you should add walnuts to your ice cream!”