In regards to how a person eats, it is important to understand that everyone is different, and your diet or lifestyle is likely not right for everyone. Take veganism for example. A plant-based vegan diet will not include anything from an animal.
Like vegetarians, vegans avoid eating meat, but they also do not consume animal by-products like dairy, eggs, or honey.
Some on the vegan diet will struggle with various nutrient deficiencies, including iron, calcium, zinc, omega-3 fatty acids, vitamin D, and vitamin B12.
As a result, vegans may experience osteoporosis, anemia, and mental health disorders. It is important to note that some proponents of veganism will rely heavily on packaged tofu and soy products, which may lead to infertility, impaired thyroid function, malnutrition, digestive issues, and cancer.
On the other hand, certain long-term vegans have experienced a lot of success on the diet. In general, a whole foods approach to eating can help prevent various diseases, such as heart disease, diabetes, arthritis, osteoporosis, and even cancer.
A study published in The Permanente Journal in 2015 suggested that a plant-based diet could protect against atherosclerotic coronary artery disease. It is a condition associated with a high intake of meat and fat, and results from progressive damage to the endothelial cells lining the vascular system like the heart.
The polyphenols from many plant-based foods have protective effects on vascular endothelial cells.
4 Reasons Why Veganism May Not Work for Everyone
It shouldnât be ignored that a vegan diet does have its health benefits. However, some vegans insist that anyone that struggles with veganism must be âdoing it wrong.â On the other hand, sometimes ex-vegans will speak of their rapid health decline on the vegan diet, and may be convinced that others trying veganism will revert to eating meat.
Luckily, scientific research is now helping us discover why people respond differently on diets with no to little animal foods. Studies show that genetics and gut health both play a major factor in whether a vegan diet is best for you.
In other words, no matter how nutritionally adequate a vegan diet may look on paper, metabolic variation can help determine whether someone is successful or not while going meat-free or vegan.
The following are four reasons why some may have success as vegans, while others may not.
1. Vitamin A Conversion
Vitamin A is a very important nutrient. For instance, it supports the immune system, maintains vision, promotes healthy skin, and is essential for reproductive health. Contrary to what many believe, vitamin A (retinol) is not found in plant foods. Instead, they are vitamin A precursors or carotenoids like beta-carotene.
In the liver and intestine, enzyme beta-carotene-15, 15â-monooxygenase (BCMO1) converts beta-carotene and other precursors into vitamin A.
When everything goes well, we can make retinol from plant foods like carrots, spinach, and other plants thought to be high in vitamin A. On the other hand, animal foods donât require BCMO1 conversion because they supply the body with vitamin A in the form of retinoids.
However, the bad news is several gene mutations can interfere with BCMO1 activity, and negatively affect carotenoid conversion. In this case, plant foods become inadequate sources of vitamin A.
For example, research published in the FASEB Journal in 2009 found that frequent polymorphisms in the BCMO1 gene called A379V and R267S can decrease beta-carotene conversion by 69%. A less common mutation called T170M can also lower vitamin A conversion by around 90% in those that carry two copies.
Overall, 45% of the population carries polymorphisms that reduce their effectiveness of converting beta-carotene into vitamin A.
Various non-genetic factors can also reduce carotenoid conversion and absorption, including zinc deficiency, liver disease, alcoholism, low thyroid function, and compromised gut health. The ability to produce retinol from plant foods reduces even further if anyone with the aforementioned health issues also has poor genetic carotenoid conversion abilities.
The reason vitamin A deficiency is not an epidemic is because animal foods provide 70% of a personâs vitamin A intake and carotenoids provide less than 30%. So, meat eaters with the BCMO1 gene can survive just fine on vitamin A from animals, while unaware that they even have a carotenoid conversion problem.
But, for vegans and vegetarians that forgo animal products, the effects of the BCMO1 gene will be detrimental. The personâs carotenoid levels will increase, while vitamin A status decreases. The result is vitamin A deficiency, although there is seemingly an adequate amount in the diet.
Unsurprisingly, problems reported from some vegans and vegetarians mirror the effects of vitamin A deficiency, such as vision issues, thyroid dysfunction, tooth enamel problems, and frequent colds and infections. At the same time, vegans with normal BCMO1 function and consume plant-based carotenoid-rich foods, will indeed produce enough vitamin A to be at optimal health.
2. Amylase and Starch Tolerance
Although not always the case, most meat-free vegan or vegetarian diets are higher in carbohydrates than omnivore diets. In fact, some plant-based diets will include about 80% carbs from mostly legumes, starchy grains, and tubers.
Some of these diets include the Caldwell Esselstynâs diet, the Dean Ornish Program, and the Pritikin Program. Some following these programs have success while others do not. Why?
Genes and saliva may be rooted in why. You see, human saliva contains the enzyme alpha-amylase, which cuts starch molecules into simple sugars through hydrolysis. Depending on how many amylase-coding gene (AMY1) copies we carry, as well as lifestyle factors like circadian rhythms and stress, amylase levels can range from barely there to 50% of our salivaâs total protein.
In general, AMY1 patterns tend to have an association with the traditional diets of our ancestors. This is where people from starch-centric cultures like the Japanese tend to carry more AMY1 copies and have higher salivary amylase levels than populations historically consuming more protein and fat.
The reason this is important is that amylase production strongly influences how starchy foods are metabolized and whether it produces major blood sugar problems. When people with low amylase consume starch, they experience steeper and more frequent blood sugar spikes than those with high amylase levels, according to a study published in The Journal of Nutrition in 2012.
Low amylase producers also have a higher risk of obesity and metabolic syndrome when eating a high-starch diet.
Why does all this matter for vegans and vegetarians? Although the amylase issue can be a problem for anyone, those on a plant-based diet centered around eating high amounts of tubers, grains, and legumes are likely to bring carb intolerances to the forefront.
When low amylase producers radically increase their starch intake, there could be devastating results, such as weight gain, low satiation, and poor blood sugar regulation. On the other hand, in someone with a high metabolism to produce lots of amylase, a high-carb plant-based diet may not be an issue at all.
3. Gut Microbiome and Vitamin K2
A personâs gut microbiome has several important responsibilities that range from fiber fermentation to nutrient synthesis and toxin neutralization. Various studies show that the bacterial population shifts in the gut microbiome in response to a personâs age, environment, and diet.
With that said, many microbes are inherited or established from a young age. For instance, high levels of Bifidobacteria has a link with the gene for lactase persistence, which indicates a genetic association to the microbiome.
Studies show that babies born vaginally obtain their first microbes in the birth canal. As a result, there is a long-term bacterial composition differentiation between C-section babies and those born vaginally. Also, certain bacterial populations may be permanently damaged and have trouble returning to normal after chemotherapy, antibiotic exposure, or particular illnesses.
How are vegans impacted from certain gut microbiome features beyond their control? Some microbiome communities may be more vegan-friendly than others due to how the gut microbiome responds to different foods while synthesizing specific nutrients. In particular, the body requires certain gut bacteria for the synthesis of vitamin K2 (menaquinone).
Vitamin K2 is important for insulin sensitivity, heart health, skeletal health, and protection against liver and prostate cancers. Some bacteria needed for producing vitamin K2 include Escheria coli, Bacteroides species, Klebsiella pneumoniae, and Prevotella species.
Vitamin K1 is found in plant-based foods like parsley, kale, spinach, and other leafy greens. However, vitamin K2 is exclusively found in animal foods, with the exception of a fermented soy product called natto.
Studies have found that full-spectrum antibiotic usage will dramatically reduce vitamin K2 levels in the body through the destruction of the bacteria needed for vitamin K2 synthesis. If someoneâs microbiome is low on vitamin K2-producing bacteria whether the cause is genetic, environmental, or due to antibiotics, vitamin K2 levels will sink even further, especially if there arenât any animal foods in the diet.
As a result of a lack of vitamin K2, vegans and some vegetarians may increase their risk of bone fractures, dental problems, cardiovascular disease, diabetes, and certain cancers. On the other hand, people with a robust vitamin K2-synthesizing microbiome, or those that eat plenty of natto, may be able to get enough vitamin K2 as a vegan.
4. PEMT Activity and Choline
Choline is an essential but sometimes overlooked nutrient that is important for neurotransmitter synthesis, brain health, metabolism, methylation, and lipid transport. Choline deficiency is a growing problem that contributes to fatty liver disease, heart disease, neurological conditions, and developmental problems in children.
Choline-rich foods include animal products, such as liver, eggs, salmon, and cod. Plants foods are thought to contain more modest choline levels. However, choline can also be produced internally in the body with an enzyme called phosphatidylethanolamine-N-methyltransferase (PEMT), which is responsible for the methylation of phosphatidylethanolamine into phosphatidylcholine.
Much of the time, the small amounts of choline in plant foods and the choline synthesized through the PEMT pathway may be enough to meet a personâs choline needs without meat or eggs. However, there are some concerns with veganism and choline. For starters, a personâs individual requirements of choline can vary, and what looks like enough may still produce choline deficiency.
One study published in the American Journal of Clinical Nutrition in 2008 found that 23% of male participants developed choline deficiency symptoms despite consuming an adequate intake of 550 milligrams of choline daily. The study also found that pregnant and breastfeeding women also require more choline due to amounts used for the fetus or breast milk. Also, postmenopausal women need more choline than those still at reproductive age.
Mutations in folate pathways or in the PEMT gene can also make low-choline diets very problematic according to a study published in the Proceedings of the National Academy of Sciences of the United States of America in 2005. The study found that women with the MTHFD1 G1958A mutation were 15 times more susceptible to organ dysfunction on a diet with low choline.
Other research indicates that the rs12325817 polymorphism in the PEMT gene significantly increases choline requirements. The rs12325817 polymorphism is found in about 75% of the population, and so more choline is needed to prevent fatty liver disease, according to a 2010 study published in The American Journal of Clinical Nutrition.
Some research also suggests that the rs12676 polymorphism in the choline dehydrogenase (CHDH) gene increases susceptibility to choline deficiency, and therefore greater amounts of choline are needed.
It is possible for vegans and vegetarians to maintain sufficient amounts of choline for those with normal choline requirements and fortunate genes. However, choline-rich plants may not be enough for men or postmenopausal women with low estrogen, pregnant or nursing women, or those with gene mutations that increase choline requirements. In that case, going vegan may lead to cognitive problems, heart disease, fatty liver disease, and muscle damage.
Final Thoughts on Veganism
Is veganism right for you? The potential problems with veganism go well beyond the common nutrient deficiencies like vitamin B12, zinc, or vitamin D, or health problems like anemia or mental disorders. The right genetic and gut microbiome help vegans meet their nutritional needs.
However, the odds of vegans being able to thrive drop considerably when there are issues with the gut microbiome makeup, vitamin A conversion, choline requirements, or amylase levels.
At the same time, some vegans may have done it wrong, especially when their diet is highly processed and full of potato chips, tofu, and sandwiches with vegetables.
For a vegan diet to be healthy, it should be plant-based and contain lots of vegetables and some fruit along with lentils, beans, other legumes, non-gluten grains like quinoa and brown rice, as well as nut and seed butters and flours. It is also a must for vegans, and even vegetarians to supplement with at least vitamin B12.
Science is also increasingly supportive that individual variation impacts how people respond to certain diets, including the vegan diet. That is why some respond to veganism while others suffer from it. Are you curious whether you possess any of the genetic mutations or tendencies mentioned in this article? Certain genetic testing can help reveal human DNA sequences to discover genetic mutations, anomalies, or differences.
Minger, D., â4 Reasons Why Some People Do Well as Vegan (While Others Fail Miserably),â Authority Nutrition, October 20, 2016; https://authoritynutrition.com/4-reasons-some-do-well-as-vegans/.
Nordqvist, C., âVegan Diet: Health Benefits of Being Vegan,â Medical News Today, December 2, 2015; http://www.medicalnewstoday.com/articles/149636.php.
Tuso, P., et al., âA Plant-Based Diet, Atherogenesis, and Coronary Artery Disease,â Permanente Journal, November 24, 2014; doi: 10.7812/TPP/14-036.
Leung, W. C., et al., âTwo common single nucleotide polymorphisms in the gene encoding beta-carotene 15, 15â-monooxygenase alter beta-carotene metabolism in female volunteers,â FASEB Journal, April 2009; 23(4): 1041-1053; doi: 10.1096/fj.08.121962.
Lindqvist, A., et al., âLoss-of-Function Mutation in Carotenoid 15, 15â-Monooxygenase Identified in a Patient with Hypercarotenemia and Hypovitaminosis A,â The Journal of Nutrition, November 2007; 137(11): 2346-2350. http://jn.nutrition.org/content/137/11/2346.long.
Lietz, G., et al., âSingle nucleotide polymorphisms upstream from the beta-carotene 15, 15â-monooxygenase gene influence provitamin A conversion efficiency in female volunteers,â The Journal of Nutrition, January 2012; 142(1): 161S-165S; doi: 10.3945.111.1407556.
Mandel, A. L., et al., âHigh Endogenous Salivary Amylase Activity Is Associated with Improved Glycemic Homeostasis following Starch Ingestion in Adults,â The Journal of Nutrition, May 2012; 142(5): 853-858; doi: 10.3945/jn.11.156984.
Falchi, M., et al., âLow copy number of the salivary amylase gene predisposes to obesity,â Nature Genetics, May 2014; 46(5): 492-297; doi: 10.1038/ng.2939.
DâArgenio, V., et al., âThe role of the gut microbiome in the healthy adult status,â Clinica Chimica Acta, December 7, 2015; 451(Part A); 97-102; doi: 10.1016/j.cca.2015.01.003.
Goodrich, J. K., et al., âGenetic Determinants of the Gut Microbiome in UK Twins,â Cell Host & Microbe, May 11, 2016; 19(5): 731-743; doi: 10.1016/j.chom.2016.04.017.
Conly, J., et al., âReduction of vitamin K2 concentrations in human liver associated with the use of broad spectrum antimicrobials,â Clinical and Investigative Medicine, December 1994; 17(6): 531-539; https://www.ncbi.nlm.nih.gov/pubmed/7895417.
Fischer, L. M., et al., âSex and menopausal status influence human dietary requirements for the nutrient choline,â American Journal of Clinical Nutrition, June 23, 2008; 85(5): 1275-1285; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2435503/.
Kohlmeier, M., et al., âGenetic variation of folate-mediated one-carbon transfer pathway predicts susceptibility to choline deficiency in humans,â Proceedings of the National Academy of Sciences of the United States of America, November 1, 2005; 102(44): 16025-16030; doi: 10.1073/pnas.0504285102.
Fischer, L. M., et al., âDietary choline requirements of women: effects of estrogen and genetic variation,â The American Journal of Clinical Nutrition, November 2010; 92(5): 1113-1119; doi: 10.3945/ajcn.2010.30064.