Vegans do not consume food and food products from animals for ideological, religious, ecological or nutritional reasons, as well as animal welfare considerations – no meat and products made from it, no fish and no animal fats, no milk and dairy products, no eggs and also no honey. In addition, the food is taken as natural as possible. Vegans feed exclusively on plant foods and are thus to be distinguished from vegetarians.
Epidemiology
In the 2008 “National Nutrition Survey II,” 1.6% of participants reported being vegetarian. Meanwhile (as of January 2015), the German Vegetarian Union (VEBU) estimates that there are approximately 7.8 million vegetarians and approximately 900,000 vegans (in Germany).
Positive effects
A vegan diet has virtually no cholesterol and only a low proportion of saturated fatty acids and a high proportion of monounsaturated and polyunsaturated fatty acids. These are probably the main reasons why vegans have better laboratory values for total cholesterol, LDL cholesterol, HDL cholesterol, triglycerides and uric acid, a lower body weight and a significantly lower risk of many chronic diseases such as nephropathies (kidney diseases), myocardial infarctions (heart attacks) and diabetes mellitus (diabetes) compared to a control group eating a standard mixed diet. An American study of overweight patients with type 2 diabetes mellitus showed that weight loss and HbA1c reduction were greater on a vegan diet than on a diet recommended by the American Diabetes Association. Under a vegan food sank in studies the average blood pressure values (around 7 mmHg systolisch (upper value) and around 5 mmHg diastolisch (lower value)). Due to the high fiber intake, vegans rarely suffer from diverticulosis (protrusions of the intestinal wall) and gallstones. Furthermore, cancer incidence (rate of new cancer cases) is 18% lower on a vegan diet.
Negative effects
For vegans, adequate supply of essential amino acids is problematic because they do not consume animal protein (egg white). Protein from plant foods – grains, vegetables, legumes, nuts – has a lower biological value than animal protein. Plant proteins lack one or more amino acids. Animal protein, on the other hand, has all nine essential amino acids, including histidine, leucine and threonine, in sufficiently large quantities, with milk and eggs containing the best quality protein in the ratio most suitable for the body. The important amino acids lysine in cereals, nuts and seeds and methionine in legumes and vegetables, for example, are found only in low concentrations in the corresponding foods. Protein undersupply can only be avoided by a very careful broad selection and combination of vegetable protein sources with sufficient dietary energy intake. For example, the biological value can be increased by combining corn and beans. Also recommended are any legumes, soy products (tempeh, tofu, soy milk/yogurt), seitan and lupin products. Vegans should eat three to four servings of these foods daily. Similarly, due to the lack of fish consumption, the intake of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) is critical. In vegans who consume abundant alpha-linolenic acid (ALA) via flax oil, lentils, green leafy vegetables such as spinach, and nuts such as walnuts, lower but stable concentrations of omega-3 fatty acids are found in plasma. This is due to the fact that while the intake of omega-6 fatty acids, especially linoleic acid, is reduced, there is adequate synthesis of ALA into EPA and DHA. Linoleic acid is found in large amounts in sunflower and corn oil. Because vitamin B12 is not found in plant foods, vegans do not meet their vitamin B12 requirements and often have low plasma concentrations of vitamin B12. One possible consequence of vitamin B12 deficiency is hyperhomocysteinemia (pathological (abnormal) increase in the amino acid homocysteine), which is present in half of vegans. Other symptoms of vitamin B12 deficiency are mainly pallor, weakness, rapid fatigability and dizziness. Vegans should therefore have their vitamin B12 levels determined regularly.Even though the body can store vitamin B12, the vitamin B12 level should be determined after the first year on a vegan diet. As a rule, vitamin B12 supplementation is advisable and necessary. Above all, there is a risk of calcium deficiency, because calcium is absorbed to more than 50% through the consumption of milk and milk products. Symptoms of deficiency include abdominal pain, diarrhea (diarrhea), and cramps. Suitable vegan sources of calcium include fortified soy products, dark green vegetables such as kale, spinach and broccoli, nuts such as almonds and hazelnuts, and calcium-rich mineral waters (calcium content > 150 mg/l). Care should be taken to ensure that vegetables are low in oxalate. Oxalic acid reduces the bioavailability of calcium because it forms insoluble complexes with calcium (calcium oxalates). Particularly high levels of oxalate are found in chard, spinach, rhubarb, beet, cocoa powder and chocolate. The consumption of mineral water containing calcium is also recommended. There is often an undersupply of the trace element iodine because people avoid fish, which is a very good source of iodine. Iodine is also contained in algae and seaweed products, but sometimes in very high amounts. The Federal Institute for Risk Assessment (BfR) therefore advises against algae products to prevent iodine oversupply. In any case, vegans should use iodized table salt. If iodine as an essential trace element for the formation of thyroid hormones is missing in our body, it can lead to listlessness. At-risk groups, including people with a family history of iodine-deficiency goiter, are recommended to take iodine tablets.Covering iron requirements is also problematic because the most important sources of iron – veal, pork, beef and liver – are not consumed. Cereals, whole grain and soy products, corn, rice, nuts and other plant products are poorer sources of iron, despite their high iron content, because the utilization of this trace element is reduced by the high phytic acid content in them. Phytic acid or phytates form a non-absorbable complex with iron and consequently inhibit iron absorption. Typical deficiency symptoms are fatigue, pallor and headache. Simultaneous intake of vitamin C or vitamin C-rich foods increases enteric iron absorption (uptake of iron in the intestine) by ascorbic acid attenuating the effect of phytates. The simultaneous supply of ascorbic acid can significantly increase the bioavailability of non-heme plant iron in particular. By reducing Fe3+ (trivalent iron) to Fe2+ (divalent iron), ascorbic acid improves the absorption (uptake) of non-heme iron by a factor of 3-4 and stimulates its incorporation into the iron storage protein ferritin. In order to be able to recognize a deficiency situation at an early stage, vegans should have the corresponding laboratory parameters (serum iron, hemoglobin, serum ferritin) determined once a year.The utilization of zinc in whole grain products is also hindered by the high phytin content. An insufficient supply is manifested, among other things, by immune deficiency, loss of appetite, and delayed wound healing. To increase zinc intake, the same measures as described above for iron are useful. Since the new intake recommendation for vitamin D of 20 µg per day is not reached by anyone in the German population through the normal diet, a sufficient intake of vitamin D is even more critical for vegans – according to the National Nutrition Survey II (NVS II, 2008), more than 40% of the daily vitamin D amount is supplied through fish and fish dishes. There are not many plant foods that contain vitamin D. Mushrooms such as porcini, chanterelles and mushrooms contain appreciable amounts of vitamin D. In children, vitamin D deficiency can lead to rickets (a disease of bone metabolism), especially when the conversion of vitamin D precursors is impaired due to lack of sunlight exposure or due to heavy pigmentation of the skin. Symptoms of deficiency include increased susceptibility to infection, bone and muscle pain, and increased fracture rates. Vegans should therefore improve their supply of vitamin D by spending frequent time outdoors and by eating foods enriched with vitamin D, such as margarine or soy milk.If vegans consume most of their food without prior heat treatment, they have an increased risk of allergies. This is because heat destroys the antigenic potency of the food.This is especially true for stone and pome fruits, vegetables such as carrots or celery, and nuts.
Conclusion
If vegans make their diet one-sided, the risk of malnutrition is high. The more diverse the selection of plant foods, the more legumes, especially soybeans, and many different nuts and seeds are consumed, the better vegans are supplied with macro- and micronutrients. Supplementation with vitamin B12, iodine, and a DHA-rich algae oil is advisable (converting DHA to EPA may also restore EPA levels). Vegans must have appropriate knowledge regarding food selection, preparation, and the appropriate use of supplements. A purely plant-based diet is strongly discouraged due to the inadequate supply of macro- and micronutrients (nutrients and vital substances) in infants, young children, adolescents, the chronically ill, pregnant women, nursing mothers, and seniors.
