In reply to: A vegan diet is not for everyone; it made me sick
This is the approved revision of this page, as well as being the most recent.
- 1 Context
- 2 Talking Points
- 2.1 Keep in mind that we know of no nutrients that must come from animal products.
- 2.2 Realize that your malady may be caused by something other than your diet in general or your vegan diet in particular.
- 2.3 Bio-individuality does not confer a need for animal products.
- 2.4 Your body may need more time to acclimate.
- 2.5 You may be eating too much vegan junk food.
- 2.6 You may not be getting enough calories.
- 2.7 You may have introduced a food that causes a mild allergic reaction.
- 2.8 Your body might need a different mix of macronutrients.
- 2.9 You may be deficient in vitamin B12.
- 2.10 You may be one of the few people who need to supplement with more than vitamin B12.
- 2.11 You may be using the vegan diet as an excuse, subconsciously or not.
- 2.12 Some do well on the second attempt.
- 3 See Also
- 4 Footnotes
- 5 Meta
Occasionally we hear of someone who says they got sick, didn't feel well, or lacked energy on a vegan diet. While this is the opposite of what most new vegans experience, it's heard enough to warrant a response.
More often than not, these kinds of assertions are made without a professional diagnosis. And without a diagnosis, it's hard to say the cause of this for any one individual.
Nevertheless, we examine some possibilities and try to shed a little light on the topic, offering the following points gleaned from firsthand reports, personal experience, and those qualified to weigh in.
Keep in mind that we know of no nutrients that must come from animal products.
When the Academy of Nutrition and Dietetics, Mayo Clinic, Harvard Public Health, Cleveland Clinic, and others say that plant-based diets are adequate and even advantageous, they do not say "except that certain people must have meat, dairy, or eggs." Nor do they qualify their statements by pointing out nutrients that are difficult to obtain unless you eat animal products.
Science knows of no nutrient that cannot be obtained—and obtained in sufficient quantities for good health—outside the animal kingdom.
Realize that your malady may be caused by something other than your diet in general or your vegan diet in particular.
When you combine the fact that people get sick or feel bad for a multitude of reasons with the fact that self-diagnosis is often wrong, it seems at least possible that your troubles may not be caused by a vegan diet—or even by any diet at all. People get sick all the time and attribute that to various reasons, often without adequate justification.
Bio-individuality does not confer a need for animal products.
Sometimes the claim is made that because we are all different a vegan diet is not for everyone. It's true that bio-individuality may justifiably cause you to restrict or supplement your diet, but such restrictions have no connection to a vegan diet.
For example, if you have an allergy, you should avoid foods that trigger that allergy. If you are prone to kidney stones, you may decide to restrict oxalates and sodium. If you have absorption problems with any particular nutrient, you may want to supplement for that nutrient. People with diabetes will want to minimize fatty foods and added sugars.
But there is no scientific basis for saying that any given individual should not eat vegan because that individual is unique. The color of our hair and eyes, our height, and our body proportions, for instance, do not dictate which foods to eat. Some attempts to link physical or physiological traits to an optimum diet (attempts such as the blood-type diet), are regarded by the scientific community as lacking credibility.
Your body may need more time to acclimate.
Your body may need more time to adjust to the new way of eating. Some feel sickly and weak when they first start on a vegan diet. Then, as their body adjusts, these feelings go away and the nutritional advantages of a plant-based diet start to be realized.
You may be eating too much vegan junk food.
The science is clear that leaving animal products off the plate reduces your risks for chronic disease, but that alone does not guarantee a healthy diet. You might not be getting enough nutrients because you are consuming too much vegan junk food, such as Oreos, potato chips, and cola.
You may not be getting enough calories.
Animal products and vegetable oils are calorie dense, while fruits and vegetables are nutrient dense.
It takes about 500 calories to fill a stomach with fruits and vegetables but about 1,000 calories to fill a stomach with meat.
So if you are eating the same volume of plant foods as you previously ate of animal foods, it's possible you are not getting enough calories.
You may have introduced a food that causes a mild allergic reaction.
When you adopt a vegan, plant-based diet, it's likely you will be eating a number of foods you didn't previously consume. It's possible that one of those foods will contain an allergen.
Your body might need a different mix of macronutrients.
If your metabolism is high or you are an endurance athlete, you might benefit from a higher percentage of complex carbs.
If you are a bodybuilder or you have a job that constantly rips muscle tissue that needs to be rebuilt, you may need more protein. But before you go wild with the protein, please read our answer to the objection that vegans struggle with that nutrient.
You may be deficient in vitamin B12.
All vegans should take care to ensure that they are getting adequate B12. Known symptoms of B12 deficiency include fatigue and weakness, but a deficiency can also lead to more serious disorders.
If you started a vegan diet recently, your chance of being deficient in B12 is probably small unless you started with a deficiency. This is because your body normally stores enough to last well over a year.
We cover this more fully in "In reply to: B12 is a problem for vegans, so a vegan diet is not natural" which includes recommendations for supplementation. Virtually all professionals familiar with the topic recommend that vegans supplement for B12.
You may be one of the few people who need to supplement with more than vitamin B12.
Dr. Michael Klaper believes that it's possible some people may not be able to adjust to a vegan diet without supplementation beyond B12.
He provides a discussion of the physiological process that may be at work in these cases and suggests a regiment of supplementation that might address the problems. He also offers suggestions on what to do if, after 12 months of supplementation, your situation has not improved.   
It's a good idea to get a professional diagnosis for any suspected nutrient or mineral deficiency, as some supplements can be harmful.
You may be using the vegan diet as an excuse, subconsciously or not.
It's true that a small number of people have health-related issues that are triggered by the transition to a vegan diet. But it's also likely that in some cases, such issues are used as an excuse to give up on their vegan diet. And for some, this could be on a subconscious level.
Humans are experts at rationalization, as Ben Franklin realized when he said, "So convenient a thing is it to be a reasonable creature, since it enables one to find or make a reason for everything one has a mind to do."
Some do well on the second attempt.
Some have reported that on the second attempt at eating vegan, they did not experience any problems and instead felt better, as most of us have experienced.
Given the benefits of veganism to the animals, the planet, the starving and impoverished, and your own health, please consider trying again, taking into consideration the information presented above.
- Citations for each of the organizations mentioned are provided here.
- “Kidney Stones | Health Topics | NutritionFacts.Org.” Accessed August 9, 2018. https://nutritionfacts.org/topics/kidney-stones/
- Barnard, Neal. “Does Sugar Cause Diabetes?” Text. The Physicians Committee, August 7, 2017. https://www.pcrm.org/nbBlog/does-sugar-cause-diabetes
- “The Blood Type Diet: An Evidence-Based Review.” Healthline, June 4, 2017. https://www.healthline.com/nutrition/the-blood-type-diet-review
- Citations for several prominent health organizations are provided here
- Novick, MS, RD, Jeff. “Calorie Density Approach to Nutrition & Weight Management.” Forks Over Knives (blog), June 19, 2012. https://www.forksoverknives.com/the-calorie-density-approach-to-nutrition-and-lifelong-weight-management/
- In reply to: Protein is a problem for vegans
- “Don’t Vegetarians Have Trouble Getting Enough Vitamin B12?” The Physicians Committee, October 13, 2010.href="https://www.pcrm.org/health/diets/vegdiets/dont-vegetarians-have-trouble-getting-enough">https://www.pcrm.org/health/diets/vegdiets/dont-vegetarians-have-trouble-getting-enough
- Folate, Institute of Medicine (US) Standing Committee on the Scientific Evaluation of Dietary Reference Intakes and its Panel on. Estimation of the Period Covered by Vitamin B12 Stores. National Academies Press (US), 1998. https://www.ncbi.nlm.nih.gov/books/NBK114329
- Klaper, M.D., Michael, and John Allen Mollenhaur. “The Failure to Thrive–Speculations on the Nutritional Adequacy of 100% Plant-Based Diets.” Nutrient Rich Superfoods (blog), November 11, 2012. https://nutrientrich.com/premium/the-failure-to-thrive-speculations-on-the-nutritional-adequacy-of-100-plant-based-diets-by-michael-klaper-m-d.html
- Klaper, Michael. “Vegan Health Study.” Vegan Health Study by Michael Klaper, M.D., January 4, 2017.(https://veganhealthstudy.org/
- Plant Based Science London. Why Giving Up Meat Makes You Feel Ill-Carnitine! Dr Michael Klaper, 2016. https://www.youtube.com/watch?v=ps4RN9RezEQ
- Klaper, M.D., Michael. “Thriving on a Plant-Based Diet.” Michael Klaper, M.D., Nutrition-Based Medicine, November 2015. https://doctorklaper.com/webinars/thriving-on-a-plant-based-diet/
- Novick, MS, RD, LD, LN, Jeff. “Q & A’s.” JEFF NOVICK. Accessed August 9, 2018. https://jeffnovick.com/RD/Q_&_As/Entries/2012/10/18_Supplements.html
- Franklin, Benjamin. The Autobiography of Benjamin Franklin. AmazonClassics, 2017. 48-49
- Introduction to Veganism
This article was originally authored by Greg Fuller and copyedited by Isaac Nickerson, with Deborah Pageau B.Sc. contributing to the research. The contents may have been edited since that time by others.