Plant-Based Protein: A Real Game Changer?
With the movie "Game Changers" having come out, a lot of people are interested in the health value of plant-based diets. The American Journal of Medicine did a study comparing those getting their protein sources from plant-based sources vs animal sources. The study consisted of 85,013 women and 46,329 men from the Nurses’ Health Study (1980–2012) and Health Professionals Follow-up Study (1986–2012). You can find the article in the link below: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5048552/
They compared diets based on percentage of Calories from protein, looking at the number of deaths from all-cause mortality, but they also separated by deaths by cardiovascular deaths and other diseases. The article gives data sets but no visualizations, so I visualized the data with Tableau. You can look at the data sets on the article, but for simplicity, let's just look at all-cause mortality. They also separated by healthy lifestyle and unhealthy lifestyle. For now, lets look at unhealthy lifestyles such as those consisting of smoking, lack of exercise, unhealthy diet, etc.
It seems that the highest number of deaths was from between 12% to 15% of Calories from animal protein. The group that consumed the most animal protein was 18% Calories from animal protein, and it was slightly below the middle rather than near the top. Consuming 10% of Calories from animal protein had much lower number of deaths, which would give the impression that that the more animal protein, the higher risk of death. However, the highest intake of animal protein was 15%-18% of total Calories. Also, if the assumption is that a plant-based diet causes lower risk of death than one from animal sources, the data shows that the second and third highest rates of death were from the groups that had 4%-5% and 3% to 4% of Calories from plant protein, respectively. The group with the lowest number of deaths consumed 6% of total Calories from plant protein, while the second lowest risk came from those consuming 10% of Calories from animal protein. So given the data, what can we conclude? It is difficult to come to a conclusion. Now it does seem that although some of the highest deaths came from those relying on plant protein, those were ones consuming between 3% to 5% of Calories from animal protein. Groups consuming 5% to 6% or more of Calories form animal protein were closer to the bottom. In fact, the group that had the lowest death rate had more than 6% of Calories from plant protein. As the study didn't compare apples to apples in terms of percentage of Calories from protein (10% animal protein vs 10% plant protein), due to the fact that on average, plant-based diets have a lower percentage of Calories from protein, we can make a few guesses. Maybe the plant-based groups on the higher end of the number of deaths were not getting sufficient protein, or lack of total Calories. While not a perfect association, it does seem that more plant protein resulted in fewer deaths while less animal protein resulted in more deaths. On the other hand, more animal protein overall had a higher association with death. But if that is the case, why is the group with over 18% of Calories from animal protein somewhat close to the bottom in terms of number of deaths, only slightly above the 10%-12% of Calories from protein group? It is hard to say. As high-protein diets are often low-carbohydrate diets, it may be possible that this group also consumed less carbohydrates. Now this may be overall carbs, consisting of whole grains but also refined grains and sugar. Also, as the animal protein group didn't rely only on an all animal food diet, but rather an omnivorous diet of both plants and animals, it may be that this group also consumed plants high in protein such as legumes and whole grains, which also tend to be high in fiber, while the 10% to 12% animal protein group consumed less legumes and whole grains. The study doesn't make this clear, so it is hard to tell.
Now what about the healthy lifestyle group? I analyzed that data as well. Here is what the results showed.
There was a somewhat similar pattern, such as the highest number of deaths being from people who consumed 12% to 15% of their Calories from protein relying on animal sources of protein. However, the lowest deaths came from those consuming less than or equal to 3% of their Calories from plant protein. So the group consuming more than 6% of Calories from plant sources of protein was 4th from the bottom rather than at the very bottom. As getting 3% or less of Calories is very low, it is surprising that this group had the lowest death rate. The second lowest death rate came from the group with the most animal protein. Now the healthy population would consist of physically active people, and maybe athletes as well. It is possible that more exercise reduces the potential negative effects of animal protein, and it also increases the need for protein. Just like the unhealthy lifestyle group, it may also be possible that this group added high-fiber plant proteins along with the animal proteins. But the 15% to 18% Calories from protein relying on animal sources, was 4th from the top among the healthy lifestyles. So why would there be so much difference between both of these groups? Did the 15% to 18% consume almost identical animal protein and very little or no legumes and whole grains, while the 18% group included it, and thus offset some of the negative effects? Maybe the 12% to 15% protein group relying on animal protein, had no whole grains and legumes at all, while the 15% to 18% group relied on some legumes and whole grains, while the more than 18% group relied on even more? But the 10% Calories from protein relying on animal sources was near the bottom? Maybe they consumed plenty of fruits and vegetables, which had a protective effect, but didn't get as much of a protective effect as the more than 18% animal protein group due to that group also including legumes and whole grains? As the study data set doesn't separate by food groups, it really is hard to compare, and my ideas may be mere speculation. As it is highly unlikely that the animal protein groups went on an animal-only diet, and thus likely to have consumed plant foods as well, we would also have to look at those plant foods and not just the animal sources of protein. Maybe the groups relying on animal protein all ate lots of fruits and vegetables, and animal protein, or plant protein, had no effect. In this case, I may be completely wrong about consumption of legumes, whole grains, fruits, and vegetables. While the data sets themselves did not separate by food groups, the study itself did contrast different types of animal foods. They put fish and chicken in the health lifestyle while they put red meat and processed meat in the unhealthy lifestyle group. Now this still doesn't help a lot because it lumps fish with exercising and smoking, and thus blurs the comparison of plant vs animal protein. It would have been easier if they did not put any food source, plant or animal, in the healthy group. Also, it does not compare these food sources in the data set (e.g. have a column for fish, another for red meat, etc). It also fails to compare food groups for animal protein such as fruits, vegetables, legumes, whole grains, etc. It doesn't compare carbohydrate intake either, making it hard to make certain conclusions. To be fair, it is impossible to look at all factors in a single study. The article does site other sources. It is always good to look at multiple sources. Here is what American Medical Association stated in their study:
"Those with unhealthy lifestyles consumed more processed and unprocessed red meat, whereas the healthy-lifestyle group consumed more fish and chicken as animal protein sources, suggesting that different protein sources, at least partly, contributed to the observed variation in the protein-mortality associations according to lifestyle factors. This hypothesis is supported by our substitution analysis results. Although substituting plants for various animal foods was all associated with a lower mortality, red meat, especially processed red meat, showed a much stronger association than fish and poultry, which themselves were not associated with mortality. In fact, protein from certain fish, such as cod, has been suggested to improve lipid profile, glycemic control and insulin sensitivity." In their conclusion, they further added: "In summary, while higher intake of animal protein was associated with higher mortality and plant protein was associated with lower mortality, these associations were confined to participants with at least one lifestyle risk factor. Substitution of plant protein for animal protein, especially from processed red meat, may confer a substantial health benefit. Therefore, public health recommendations should focus on improvement of protein sources" While the article does discuss the different plant foods, it doesn't compare and contrast them as they did with animal sources. "Major food contributors to plant protein included bread, cereals, pasta, nuts, beans, and legumes. We derived protein intake from processed red meat by summing the products between intake frequency (serving/day) and the protein content (g/serving) for various processed red meats (i.e., bacon; beef or pork hot dogs; salami, bologna or other processed meat sandwiches; other processed meats [e.g., sausage, kielbasa, etc.])." It seems the article lumped all plant protein together, but separated animal protein into supposed healthy sources such as fish and unhealthy sources such as processed red meat. It didn't appear to separate whole grains vs refined bread and other processed carbohydrates. But again, it is hard to look at everything in a single study. While inconclusive, the study overall appears to support that, to a degree, plant-based sources of protein tend to be healthier, at least those with some unhealthy lifestyle. It does also site other sources that come to a similar conclusion about benefits of replacing some animal protein sources with plant sources. I encourage you to read the entire article yourself rather than take my word, and also read multiple sources. Of course, look for conflicts of interest. Perhaps the meat industry can fund a study that denies any causal relationship between animal foods and mortality. However, the grain industry may fund other studies showing a stronger relationship between animal foods and mortality, as less Calories from meat may lead to more Calories from grains. So read multiple sources, and be vigilant in looking for funding. Be open to reading articles that disagree with your view rather than only reading articles the reconfirm your beliefs. As a vegan, I also have to be careful to look at my own biases.