The pros and cons of going vegan
There’s no doubt that vegan diets are increasing in popularity.[1] Such diets, which exclude all animal products including meat, fish, eggs, dairy, and even honey, are often followed for health reasons as well as ethical, religious, and environmental concerns.[2],[3]
Although often framed in terms of lacking, vegan diets have higher amounts of fiber, folic acid, vitamins C and E, potassium, magnesium, phytochemicals, antioxidants, and more unsaturated fat than most non-vegan diets.[4],[5],[6] From weight loss to a healthy decrease in blood pressure, there seem to be many health benefits to ditching meat, dairy, and eggs.[7],[8],[9] Nonetheless, such diets can have suboptimal levels of important macro- and micronutrients.[10],[11] So is a vegan diet something we all should be considering?
Why go vegan?
The beneficial features of a plant-based diet include lower intakes of saturated fat and cholesterol, and higher intakes of dietary fiber.
Numerous studies have shown a significant protective effect of vegan diets against cardiovascular disease and some types of cancer.[12],[13],[14] In overweight individuals, a vegan diet proved to be superior to participants’ typical diets in lowering body weight, fat mass, and insulin resistance markers.[15] In another study, vegans were found to have lower body weight, blood pressure, fasting blood glucose, and low-density lipoprotein (LDL) cholesterol levels compared to non-vegans.[16] The beneficial features of a plant-based diet include lower intakes of saturated fat and cholesterol, and higher intakes of dietary fiber, as discussed below.[14]
Increased dietary fiber is good for your gut
Vegetables and fruits, beans, legumes and whole grains contain different types of plant fibers that support health in several ways.[1] Insoluble fiber such as wheat bran helps improve bowel function and provide relief from constipation,[17] and soluble “prebiotic” plant fibers are fermented by beneficial bacteria to produce short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate.[18],[19] SCFAs support the gut epithelial cell barrier and help prevent leaky gut,[18],[20] a condition that has been linked to various chronic ailments.[21],[22],[23]
Prebiotic fibers, including inulin and natural oligosaccharides (fructooligosaccharides, galactooligosaccharides, and xylooligosaccharides), also promote the growth of beneficial Bifidobacterium in the gut, while beta-glucan (a fiber present in oats) induces the growth of beneficial Prevotella and Roseburia.[19] Such improvements in the microbiota composition help reduce serum triglyceride and cholesterol levels, thus reducing the risk of cardiovascular disease.[17],[24] Increased fiber consumption is also associated with improved glucose metabolism and cholesterol balance.[17],[25]
Despite the benefits of a high-fiber diet, what about the important micronutrients that are missing when meat and dairy products are eliminated from the diet? By consuming a vegan diet, are we setting ourselves up for nutritional deficiencies?
The short answer is that a complete lack of animal foods does pose a risk for critical nutritional deficiencies. Nutrients of concern include vitamin B12, vitamin D, calcium, omega-3 fatty acids, protein, zinc, iodine, selenium, choline, and iron.[6] A team at the Mayo Clinic states, “We found that some of these nutrients, which can have implications in neurologic disorders, anemia, bone strength and other health concerns, can be deficient in poorly planned vegan diets.”[26],[27] The more restrictive the vegan diet is, the greater the nutritional risks. Here is a synopsis of nutrients of concern for vegans:
Vitamin B12
Vegetarians, especially vegans, should give strong consideration to the use of vitamin B12 supplements to ensure adequate vitamin B12 intake.
Because vitamin B12 is only present in animal foods, vegans are susceptible to deficiencies with attendant risks of megaloblastic anemia, cognitive decline, neuropathy, and depression.[1],[5],[28],[29] Vitamin B12 deficiency among vegans leads to an increase in blood levels of homocysteine, which can increase the risk for various diseases, including age-related dementia and cardiovascular disease.[30],[31],[32] Chronic low intake of vitamin B12 can lead to a progressive deficiency that may become clinically evident after years, resulting in permanent neurologic damage.[28],[30],[33] The authors of a recent review state, “Vegetarians, especially vegans, should give strong consideration to the use of vitamin B12 supplements to ensure adequate vitamin B12 intake.”[28]
Omega-3 fatty acids
Curcumin could help compensate for the low consumption of DHA in vegan populations.
The bioactive eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) forms of omega 3 polyunsaturated fatty acids, which are present in fatty fish and eggs, are essential for optimal function of the brain and nervous system.[34] Vegans consistently show plasma EPA or DHA levels that are up to 60% lower than those who consume seafood.[35],[36],[37],[38],[39]
Flaxseed oil contains alpha-linolenic acid (ALA), a precursor to EPA and DHA,[37],[40],[41] but the amount of ALA converted to DHA is very low.[41],[42],[43] Interestingly, curcumin, a component of the spice known as turmeric,increases the conversion of ALA to DHA in human cells.[44] Scientists have speculated that this effect of curcumin could help compensate for the low consumption of DHA in vegan populations.[44] Consuming adequate magnesium and vitamin B6 also helps support this pathway.[45],[46]
Very few plants contain preformed DHA, although sea vegetables and algae contain low levels of EPA.[35],[41],[47] For supplementation purposes, the primary source of DHA is fish oil, but supplemental algae oil is an alternative for those who prefer plant sources.[43],[48]
Vitamin D3 and calcium
Vegetarians and vegans had lower bone mineral densities and higher bone fracture rates compared with omnivores.
Because vegan diets exclude dairy products, vegans often have low vitamin D and/or calcium intakes,[1],[49] which can predispose to osteoporosis. A systematic review of twenty different studies, with over 37,000 participants, showed that vegetarians and vegans had lower bone mineral densities and higher bone fracture rates compared with omnivores.[50]
Especially in the vegan population, vitamin D3 (cholecalciferol) supplements seem to be the best way to ensure adequate vitamin D status.[51],[52] Although some plant foods contain calcium, it can be difficult for vegans to meet recommended daily calcium intakes unless fortified foods or supplements are included in their diet.[53] Thus people who adhere to vegan diets may wish to take daily supplements of vitamin D3 and calcium to support bone health. For those who want to avoid animal-derived cholecalciferol (which is made from lanolin), there are vitamin D3 supplements made from lichen, a plant species with the ability to grow and accumulate vitamin D3.[54] Certain types of mushrooms also provide modest amounts of vitamin D which has been shown to be well absorbed and support healthy vitamin D levels in humans.[55]
Zinc, iron, iodine, selenium
Zinc, which is required for antiviral immunity and other functions,[56] is found at higher levels in animal products. Zinc deficiency is common in vegans and vegetarians because plant phytates interfere with zinc absorption.[57],[58] Vegan food sources of zinc include pumpkin seeds and nuts, but supplementation of this mineral is often recommended.[59]
Iron is also a nutrient of concern for vegans, because the form of iron found in plants (non-heme iron) is less bioavailable than the heme iron found in meat.[37],[60] Vegetarians have a higher risk of iron deficiency anemia compared to non-vegetarians, and this is especially true for premenopausal vegetarian women.[61]
Approximately 80% of vegans may suffer from iodine deficiency, compared to 9% of omnivores.[62],[63] One-half teaspoon of iodized salt provides the daily recommended dose (150 mcg) of iodine for adults.[64] However, if you wish to minimize your intake of salt, an iodine supplement may be warranted.[63] Additional micronutrients that may be inadequate in vegan diets include choline and selenium.[3],[5],[52],[65]
Protein
For vegans who have low or unbalanced amino acid intakes, amino acid supplementation may be of benefit.
It is important for vegans (and all of us) to consume adequate protein, since inadequate dietary protein is a major contributor to age-related muscle atrophy.[66] Higher protein intakes, and in particular animal protein intake, can help preserve muscle mass.[67] Meat is a complete protein source, providing all the essential amino acids (EAAs), while plant foods are often missing one or more EAAs. The Academy of Nutrition and Dietetics states that a vegetarian diet that includes a variety of plant products throughout the day can provide the same protein quality as a diet that includes meat.[1],[68] A recent article notes that immature lima beans can provide high-quality protein, so finding ways to include this in dishes or as a side will support adequate protein consumption.[52] However, other studies found that the intake of 18 dietary amino acids is up to 47% lower in vegans than in meat-eaters,[69] and that taurine, a conditionally essential amino acid,[70] is negligible.[71] For vegans who have low or unbalanced amino acid intakes, amino acid supplementation may be of benefit.
Summing up
Nutritionists often state that vegan diets can provide adequate nutrition throughout all stages of life.[4] On the other hand, adopting a vegan diet requires careful food selection to ensure complete nutrition.[14] Supplementation with the nutrients discussed in this post can fill in many nutrient gaps if you are following a strict vegan diet. And if you’re not vegan but are concerned about heart disease, don’t worry: eliminating animal foods may not be essential for cardiovascular health.[72],[73] In fact, a Mediterranean-type diet may be equally good for your heart.[74] Stay tuned for more details on Mediterranean diets!
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