Vegan Diet: Not A One-Size-Fits-All Approach

why do some people not thrive on a vegan diet

There are many reasons why some people may struggle to thrive on a vegan diet. Firstly, some people may have health conditions that make it difficult to follow a vegan diet. For example, people with certain allergies or intolerances may find it challenging to exclude all animal products from their diet. Additionally, some people may have nutrient deficiencies that are not easily addressed on a vegan diet, such as vitamin B12 or iron deficiencies.

Another factor that can impact a person's ability to thrive on a vegan diet is their gut microbiome. The gut microbiome plays a significant role in how the body responds to different foods and synthesizes specific nutrients. Some microbial communities may be more veg-friendly than others, and a disruption to the gut microbiome (such as from antibiotics) can have long-lasting effects.

Genetics also plays a role in how people respond to different diets. For instance, some people may have gene mutations that affect their ability to convert beta carotene into vitamin A, leading to a deficiency despite consuming plenty of plant-based sources. Similarly, variations in the AMY1 gene can influence how well a person metabolizes starchy foods, with low amylase producers being more likely to experience blood sugar spikes and metabolic issues on a high-starch vegan diet.

Finally, social and practical factors can also impact a person's ability to follow a vegan diet successfully. For example, people living in food deserts or with limited access to healthy vegan options may find it challenging to maintain a balanced vegan diet. Additionally, the social aspect of eating can be a barrier, as it can be difficult to navigate social events and gatherings while adhering to a vegan diet.

Characteristics Values
Health conditions Alzheimer's Disease, Chronic Kidney Disease, Chronic Obstructive Pulmonary Disease (COPD), Multiple Sclerosis (MS), Rheumatoid Arthritis (RA), Ulcerative Colitis, Bipolar Disorder, Type 2 Diabetes, Anxiety, Depression, Crohn's Disease, Psoriasis, Geographic Atrophy, Eczema, Sleep Issues, Thyroid Dysfunction, Vision Issues, Compromised Gut Health, Alcoholism, Liver Disease, Zinc Deficiency, Iron Deficiency, Vitamin B12 Deficiency, Vitamin D Deficiency, etc.
Genetic factors Polymorphisms in the BCMO1 gene, Low thyroid function, Compromised gut health, etc.
Nutritional deficiencies Vitamin A, Vitamin K2, Choline, Protein, Iron, Zinc, Calcium, Vitamin B12, Vitamin D, etc.
Social factors Lack of access to vegan products, Lack of support from friends and family, etc.

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Genetic factors may make it difficult for some people to convert beta carotene into vitamin A

Beta carotene is an ideal provitamin A carotenoid, but it needs to be converted into active vitamin A in the body. This conversion is an important metabolic pathway that is influenced by genetics. Vitamin A is important for good vision, healthy eyes, skin, and fighting infections. It is also used in the treatment of cataracts and age-related macular degeneration.

Genetic variants in the BCMO1 gene are associated with the conversion of beta carotene into retinol. Several gene mutations can reduce BCMO1 activity and hinder carotenoid conversion, making plant foods inadequate sources of vitamin A. For example, two common polymorphisms in the BCMO1 gene (R267S and A379V) can collectively reduce beta carotene conversion by 69%. A less common mutation (T170M) can reduce conversion by about 90% in people who carry two copies. In total, about 45% of the population carries polymorphisms that make them "low responders" to beta carotene.

A study by researchers from Newcastle University showed that individuals carrying the T allele of rs7501331 had a 32% reduction in enzyme activity, while those carrying the T allele for both rs7501331 and rs12934922 had a 69% reduction. Other variants that influence enzyme activity include rs11645428, rs6420424, and rs6564851.

The efficiency of beta carotene conversion to vitamin A can vary depending on the dietary dose. A study by Brubacher and Weiser (1985) found that the vitamin A equivalence of beta carotene decreased with increasing doses in rats. Another study by Tang et al. (2000) reported similar results in a human participant, with a higher dose resulting in a lower retinol equivalence.

The bioavailability and vitamin A equivalency of beta carotene can also be affected by various food- and diet-related factors, such as the food matrix, food processing techniques, the size of the beta carotene dose, and the amounts of dietary fat, fiber, vitamin A, and other carotenoids in the diet.

Therefore, genetic factors can indeed make it difficult for some people to convert beta carotene into vitamin A, potentially impacting their ability to thrive on a vegan diet.

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Some people may have a gut microbiome that makes it difficult to synthesise vitamin K2

The gut microbiome plays a significant role in how we respond to different foods and synthesise specific nutrients. Some people may have a gut microbiome that makes it difficult to synthesise vitamin K2, a nutrient with unique benefits for skeletal health, insulin sensitivity, and cardiovascular health.

Vitamin K2 (menaquinone) is a nutrient with multiple health benefits. It is produced by specific bacteria species in the human gut and during bacterial fermentation of certain food products. It can also be supplied to the body through dietary supplements or fermented food such as yellow cheese and fermented soybeans (natto).

The main K2-producing bacteria include certain Bacteroides species, Prevotella species, Escherichia coli, and Klebsiella pneumoniae. The gut microbiome's ability to synthesise vitamin K2 can be affected by factors such as genetic factors, environment, and antibiotic usage.

Studies have shown that full-spectrum antibiotic usage can dramatically lower levels of vitamin K2 in the body by destroying the bacteria responsible for its synthesis. Additionally, a high plant, low meat diet can also influence vitamin K2 levels, with the main determinant being the proportion of Prevotella, Bacteroides, and Escherichia/Shigella species in the gut.

If someone's microbiome is lacking in vitamin K2-producing bacteria and they do not consume animal foods, their vitamin K2 levels can decrease significantly. This could potentially lead to dental problems, an increased risk of bone fractures, and a reduced ability to fight against diabetes, cardiovascular disease, and certain cancers.

On the other hand, people with a robust, K2-synthesising microbiome or those who consume natto may be able to obtain sufficient amounts of this vitamin on a vegan diet.

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Some people may have low levels of the enzyme alpha-amylase, which can lead to poor blood sugar regulation and weight gain on a high-starch vegan diet

Human saliva contains the enzyme alpha-amylase, which is encoded by the AMY1 gene. This enzyme breaks down starch molecules into simple sugars. The number of copies of the AMY1 gene that a person has can vary, and this influences their amylase levels. Amylase levels can range from barely detectable to 50% of total salivary protein.

People from starch-centric cultures tend to have more copies of the AMY1 gene and higher salivary amylase levels than populations that have historically relied more on fat and protein. This suggests that AMY1 patterns are linked to the traditional diets of a person's ancestors.

Amylase production strongly influences how the body metabolises starchy foods and whether these foods cause blood sugar spikes. People with low amylase levels who consume a lot of starch experience steeper and more prolonged blood sugar spikes compared to those with high amylase levels. Low amylase producers also have a higher risk of metabolic syndrome and obesity when eating a high-starch diet.

Therefore, a vegan diet high in starch, grains, legumes and tubers may not be suitable for people with low amylase levels. Increasing starch intake in this way could lead to poor blood sugar regulation, weight gain and low satiation. However, for someone with high amylase levels, a high-carb, plant-based diet may not be an issue.

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Variations in PEMT activity and individual choline requirements can determine whether someone can get enough choline on a vegan diet

Choline is an essential nutrient involved in brain function, fat metabolism, and the health of cell membranes. While humans produce small amounts of choline in their liver, it is not sufficient to meet their needs, and most choline comes from the diet.

Choline is found in a variety of animal and plant foods, with animal products like egg yolks and liver containing the highest amounts. Plant foods, on the other hand, contain much lower levels of choline. However, the choline requirements for individuals vary significantly, and what appears to be an adequate choline intake on paper may still result in a deficiency.

The body can also produce choline internally through the PEMT pathway, which involves the enzyme phosphatidylethanolamine-N-methyltransferase (PEMT) converting a molecule of phosphatidylethanolamine (PE) into phosphatidylcholine (PC). However, not everyone's bodies are equally efficient at producing choline through this pathway.

For instance, postmenopausal women have lower estrogen levels, which hinder choline synthesis, and thus require a higher dietary intake of choline compared to premenopausal women. Additionally, common mutations in the PEMT gene or folate pathways can further increase choline requirements, making low-choline diets hazardous.

Therefore, variations in PEMT activity and individual choline requirements play a crucial role in determining whether an individual can obtain sufficient choline on a vegan diet. While some people may be able to meet their choline needs through a combination of plant-based sources and internal synthesis, others with higher requirements or inefficient PEMT activity may need to include animal products or consider supplementation to avoid choline deficiency.

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Some people may have a diet that is too restrictive and/or they are not taking appropriate supplements

It is important to note that a vegan diet is not inherently restrictive. However, some people may interpret it as such and restrict their diet too much, leading to nutritional deficiencies. For example, some people may cut out entire food groups, such as grains or legumes, or restrict their calorie intake too much, which can lead to malnutrition and health issues.

It is crucial for vegans to ensure they are getting all the necessary nutrients from their diet. This may involve taking supplements, especially for nutrients that are more difficult to obtain from plant-based sources, such as vitamin B12, vitamin D, iodine, selenium, calcium, and iron.

A well-planned vegan diet can be nutritionally adequate and provide numerous health benefits. However, it is important to be mindful of potential restrictions and ensure a varied and balanced diet to meet all nutritional needs.

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