Home / G. Health and nutrition / Part IND
"My body can't adapt."
the complaints of people who tried a vegan diet are real, but they're rarely investigated. Gas, tiredness and hunger usually come from abrupt changes, eating too little or lack of planning, and tend to pass with adjustments. The blood type diet, often cited as proof that some bodies require meat, was tested and refuted in 2014.
Short answer
The symptoms you felt are real, but they usually have simple causes: an abrupt change, a lot more fiber at once, eating too little or too little variety. With adjustments and time, most of them pass. The blood type diet was tested in 2014, and the results didn't depend on people's blood type. Everybody is different, but no study has identified people who need meat by nature.
For children
When we suddenly change what we eat, the body sometimes finds it strange: it can cause gas or hunger. It's like getting up early on the first day of school, which is hard, but then the body gets used to it. Changing little by little and eating plenty helps the body adapt.
"Did you look into the cause, with blood tests and a dietitian, or did you stop before that?"
Como pode aparecer
"I tried and felt sick."
"My blood type needs meat."
"Everybody is different."
"My body craves meat, and I listen to it."
"Genetic variability calls for individualized diets."
"I know someone who got sick being vegan." (which is G10)
The strongest version
"I tried and felt sick. My blood type needs meat. Everybody is different."
Strongest version (steelman):
- P1People vary in metabolism, digestion and preferences.
- P2Some people report symptoms when trying a vegan diet.
- P3If the body reacts badly, it's a sign the diet doesn't suit it.
- CSo the vegan diet doesn't suit everyone, and those who feel unwell should eat meat.
P1 and P2 are true. The problem lies in P3: symptoms of adapting to a dietary change don't indicate a permanent incompatibility, and they're almost never investigated.
The argument is valid. Its soundness fails at P3.
Full answer
- a
Reconstruction and diagnosis
The most reported symptoms have known causes:
Symptom Likely cause Solution Gas and bloating A sudden increase in fiber and legumes Increase gradually; soak and cook well Tiredness Eating too little: plant foods have fewer calories per volume Eat more, include nuts, seeds and grains Frequent hunger Too little protein or fat in meals Include legumes, tofu, nuts Weakness after months Possible lack of B12 or iron Blood tests and supplementation - b
Where the argument breaks
1. Adaptation symptoms aren't incompatibility.
The gut usually adapts to more fiber within a few weeks. Gradual changes reduce symptoms.
2. The blood type diet was refuted.
In 2014, researchers at the University of Toronto tested the hypothesis with about 1,400 people. Associations between the diets and health markers existed, but didn't depend on each person's blood type.
3. Complaints are rarely investigated.
Those who quit almost never get blood tests or see a dietitian. Without investigation, there's no way to know the cause.
4. Individual variation calls for adjustments, not meat.
People with specific conditions, such as bowel diseases, may need adaptations, which a professional can guide.
5. "My body craves it" is often habit.
The craving for meat is largely learned (C11).
- c
Data and sources
Source What it says Note Wang and colleagues, 2014, *PLoS ONE* The associations of "blood type diets" with health markers didn't depend on people's blood type The authors concluded the hypothesis is false Faunalytics, study of current and former vegetarians and vegans 34% of those who quit kept the diet for three months or less Shows that many people quit during the adaptation period - d
The strongest counter-reply: some people have real conditions
The most serious version grants that most complaints are about adaptation, but points out that some people have real conditions, such as bowel diseases or multiple allergies, that make a vegan diet very hard.
- e
Why the counter-reply doesn't reach the conclusion
These conditions justify exceptions.
Veganism already allows for what is "possible and practicable" (D3).
They aren't the rule.
Most people who use the argument don't have these conditions.
Even in these cases, reducing is possible.
A partial limitation doesn't require abandoning the effort.
- f
Back to the moral question
If adaptation symptoms pass and the blood type diet has no basis, most people's bodies adapt. For those with a real condition, exceptions apply. For everyone else, the question remains: does the discomfort of a transition justify the animals' deaths?
Reasoning errors
Logical
Is the form valid?
Post hoc
Epistemological
Does the evidence support it?
Pseudoscience
Lack of investigation
Biases
Motivated reasoning
A passing discomfort becomes a definitive reason
General literature on motivated cognition
Nocebo effect
Expecting to feel unwell increases symptoms
General literature on the nocebo effect
Extrapolations
The principle being tested is: "if the body finds a change strange, it doesn't suit me".
If it applied to…Starting to runTap to see
Whoever felt sore muscles shouldn't run
No one concludes this
If it applied to…Eating more fiberTap to see
No one should eat more fiber
It's a health recommendation
If it applied to…Quitting smokingTap to see
Withdrawal symptoms would show one shouldn't quit
Absurd
Contradictions
Such as schedules, travel and new foods.
Such as when starting to exercise.
Uses it only in this argument.
What the argument gets right
What is true
The experiences of people who tried and felt unwell are real and should be heard with respect. People vary, and some have health conditions that require special care. Animal advocates should offer support and information, not dismissal.
But
But most complaints are about adaptation, and can be resolved with time and adjustments. The human body is flexible, and that very flexibility is what makes it possible to live well without eating animals.
Connections
Usually comes before
Usually comes after