Are Meat Alternatives Healthier Than Cow And Pig Meat?

An increasing amount of peer-reviewed research is showing that a plant-based diet is one of the healthiest options for many people. However, there are many ways to ‘go plant-based’, and some will be healthier than others. A balanced diet of whole vegetables will keep the doctor away, but a diet of French fries and ketchup? Not so much! With the rise of realistic meat substitutes like the Impossible Burger and the Beyond Burger across the world, some are questioning what this means for the healthiness of the plant-based diet. These products are highly processed, and often contain higher levels of salt and similar levels of fats to regular meat. In that context, are they still the healthier option? This study, published in The American Journal of Clinical Nutrition in late 2020, set out to do just that. The project was amusingly called: The ‘Study With Appetizing Plantfood—Meat Eating Alternatives Trial’ or SWAP-MEAT.

The study was a randomized, clinical crossover trial with no washout period. That’s a mouthful of jargon, so let’s carve it up and take it one bite at a time:

• A clinical trial means that the study plan was registered on the US government’s database before it was carried out. This ensures that the study is reliable, because we can see what the researchers intended to do, and then see what they did. We can compare them to see if any funny business has gone on. Anyone can go and see here. 
• In a Randomized trial, people in the study are randomly divided into 2 groups. 
• Because it was a crossover trial, Group 1 gets the meat diet for 8 weeks then the plant protein diet for 8 weeks, whereas group 2 gets the plant diet first, then swaps to the meat diet. They crossover during the course of the study. This is different from a randomized control trial where subjects are randomly assigned to 16 weeks of only plant-based or 16 weeks of only meat. The advantage of the crossover trial is that we compare the same people when they ate the plant diet to when they ate the animal protein diet. We can see how a person’s health changes, rather than comparing 2 groups of different people. By mixing up the order (plant –> animal for one group, animal –> plant for the other), we know that any changes in health are not just due to the order that they got the diet. Imagine if all of them ate meat in November, then all ate plant in December. If they gained weight on the plant diet, would it really be caused by a plant based diet? No! It would probably be the Christmas period. The crossover design cancels out issues like this.
• No washout period: crossover trials sometimes have a washout period, where the study pauses for a few weeks in the middle. E.g. group 1 might have 8 weeks of a plant-based diet, 4 week washout where they eat normally and then 8 weeks of an animal-based diet. Group 2 does the same, but animal first and plant second. Washout periods are normally used for clinical trials involving comparing drugs, so that there aren’t 2 drugs churning around in the patient’s system at the same time. In this study, it wasn’t really necessary to have a washout period, so they didn’t have one.

36 omnivores participated in the study. During the plant phase, subjects ate 2 or more portions of Beyond Meat products per day (e.g. burgers, brat-style sausages, fake chicken strips). In the animal phase, they were told to eat 2 meat products per day. Otherwise, they were told to keep their diet as similar as possible in the 2 phases. 

What Did They Find?

The subjects’ health was assessed before the study, and after each 8-week diet phase. 

Firstly, after eating plant-based meat alternatives for several weeks, subjects’ TMAO (trimethylamine-N-oxide) levels dropped, meaning their heart health improved. This makes sense, as other studies have found that TMAO levels are higher in people who eat more red meat. When the researchers dug into the data however, they found something strange: the subjects who had the plant diet first, then the meat, showed no changes over the study. Those who had the animal diet first saw their TMAO levels rise (heart health got worse), then a steep drop once they switched to the plant based-diet. 

We don’t know what is causing this, but as the study did not test a large number of subjects (remember the meat-first, plant-second group was only 18 people), it could just be the result of random chance. Looking at the graph in the paper, it seems that 1 or 2 people showed very large increases in TMAO on the animal diet, which might be responsible for the trend. One possibility is that these people were flexitarians who ate very little meat before the study, so when the study required them to up their meat intake, their bodies reacted badly.

Second, on average subjects also lost 1kg on the plant diet, and their LDL cholesterol (bad cholesterol) levels dropped (i.e. LDLs improved). The researchers confirmed that these results were not due to differences in exercise between the groups, and subjects were not eating fewer calories in the plant phase either. It is interesting that the subjects lost weight eating plant-based alternatives despite not eating fewer calories. This may have been because the plant-based meat alternatives the researchers used in the study were higher in fiber and lower in saturated fat. 

Some things did not change, however: IGF-1 levels, HDL levels, triglycerides, insulin, glucose levels, and blood pressure. There was also no change in the gut microbiome as measured from feces. However, everyone’s gut microbiome is unique, and the science about it is relatively new, so it may be difficult to detect changes unless we test a large group of people. On this point, we should take this finding with a grain of salt and say more research is needed.

What’s The Verdict? 

The study shows that switching out meat for meat alternatives can boost some aspects of heart health (i.e. better TMAO and LDL levels) in as little as 2 months. The study was more rigorous than many we’ve seen, and the researchers even brought in an independent statistician to analyze their data. However, the small number of people means that more subtle health effects of the plant-based diet might have gone undetected. Still, overall, this study adds another line of evidence indicating that a plant-based diet can make us healthier.

Extra details on the methods of the study for the interested reader

• All were healthy weight, had no heart problems or were on any medications that affected their gut bacteria. 
• The clinicians measuring their health during the study did not know what diet they were on when they tested the subjects.
• The researchers provided all subjects with the food. All meat was organic and all beef was grass-fed. 
• They were asked to record their diet for 3 days each week and were randomly quizzed on their diet to ensure they were following the rules.