Is A Vegan Diet Healthy
Many nutritionists claim that vegan diets can be healthy; the American Dietetic Association (ADA), for example, has argued that ‘appropriately planned … vegan diets … are appropriate for individuals during all stages of the life cycle’. To address this question in detail, however, it is necessary to focus on those dietary components that have frequently been suspected to be deficient in vegan diets. The components that deserve special scrutiny are:
- Vitamin B12,
- Vitamin D,
- Essential fatty acids,
- Iodine, and
Peas, lentils, and beans are good sources of protein that are readily available and relatively easy to grow in many parts of the world. It is important that vegans consume protein foods that contain the full range of essential amino acids overall; although there is no need for the full range of essential amino acids to be part of every meal.
It is clear that we do need all essential amino acids to be healthy, which is why diets that rely on a very limited range of protein sources must be avoided. Although concern has been expressed over some populations that rely heavily on staples with limited quantities of protein, such as taro, cassava, and yams, has argued that ‘cereal-based diets, especially those based on wheat and maize, supply protein levels considerably above the requirement level’.
However, there is no evidence to suggest that those who consume relatively small quantities of cereals are likely to have deficiencies, provided that they consume other foods that contain significant quantities of protein. Overall, there is no evidence to suggest that vegans who eat a good range of plant foods are likely to lack protein.
Fruits and vegetables that contain relatively large amounts of potassium and magnesium decrease bone calcium resorption, whereas diets that include relatively large amounts of nuts and grains increase such resorption by producing a high renal acid load, mainly caused by residues of sulphates and phosphates.
Green leafy vegetables that are low in oxalate, including broccoli, kale, spring greens, and cabbage, tend to be high in calcium, as well as in vitamin K, another important contributor to bone health.
The study of the Oxford-cohort of the European Prospective Investigation into Cancer and Nutrition (the ‘Oxford-EPIC cohort’) found that adult vegans who consume more than 525 mg of calcium per day do not show higher fracture rates than omnivores. There is no evidence that well-planned vegan diets fail to provide sufficient calcium, but there is evidence that diets that include adequate amounts of calcium and vitamin D are protective of bone health.
No plant foods are known to produce vitamin B12 or cobalamin, but those who eat plants inadvertently eat B12 as this vitamin is produced by micro-organisms. Who live in symbiosis with many plants. The presence of vitamin B12 is essential for cell growth, and crucial for a healthy nervous system.
Vitamin B12 deficiency leads to elevated plasma homocysteine (Hcy) concentrations (hyperhomocysteinemia), a risk factor for neurological disorders and cardiovascular problems, including pernicious anemia and hematological disease. Whereas our intestinal bacteria can synthesize B12, it is generally assumed that we should also consume products containing B12
Some studies have found that some vegans had inadequate intakes of B12, where particular concerns have been raised over the B12 status of older people due to their limited absorption capacity and of pregnant women due to their higher demands.
This is not a reason to eat flesh, as B12 binds with the protein in animal foods, impeding absorption, which is precisely why older people are better off with vegan sources of B12. Since the hematological symptoms of vitamin B12 deficiency may go undetected for a long time due to high consumption of foods containing folate (folic acid), of which many vegans consume rather a lot through the consumption of things like oranges, green leafy vegetables, and beans, vegans must be very careful to ensure that their consumption of B12 is sufficient.
Many products, including cereals and yeast extracts, now exist that have been fortified with B12 produced through industrial fermentation of bacteria. In his assessment of the evidence has written that, provided that ‘these foods are consumed regularly, the hazard of vitamin B12 deficiency is easily avoided’.
usefully point out that the human body only absorbs a tiny amount of B12 every time the vitamin is consumed, which is why they recommend the adoption of any one of these strategies for optimal consumption: 1/ two daily servings of fortified foods, providing 1.5 to 2.5 micrograms with each; 2/ one daily supplement of at least 25 micrograms; 3/ one supplement of 1,000 micrograms twice weekly.
Inadequate levels of vitamin D have long been known to contribute to bone problems such as rickets, but more recently have also been found to contribute to a range of other conditions, including fibromyalgia, rheumatoid arthritis, multiple sclerosis, depression, cancer, hypertension, and diabetes. Adequate exposure to sunlight can provide the body with all the vitamin D it needs, but overexposure must be avoided as ultraviolet irradiation is a significant contributor to skin cancer.
Those people who are not regularly exposed to sunlight, as well as those whose bodies are limited in the uptake of vitamin D, such as older and dark-skinned people, must therefore consume products that have been fortified with vitamin D or take supplements Vitamin D3 (cholecalciferol), used as a supplement, is usually derived from lanolin (sheep’s wool) or fish oil, and is also found in some lichen and extracted from them by some companies, but the consumption of vitamin D2 (ergocalciferol)—produced from the ultraviolet irradiation of ergosterol from yeast—has been shown to be as effective in providing the human body with vitamin D
Plasma 25-hydroxyvitamin D concentrations were measured in 2,107 participants of the Oxford-EPIC cohort, showing that vegans had lower concentrations of vitamin D, particularly during the winter months. Whereas most participants in this study had concentrations that were deemed to be adequate, it is nevertheless very important to recognize that many people who live far away from the equator and who do not expose themselves frequently to sunlight (because of spending much time indoors and clothing) fail to meet recommended levels.
This may be why has expressed the view that a daily supplement of 5–10 micrograms of vitamin D would be ‘highly desirable for elderly vegans’; however, some recent studies suggest that a higher dosage may be required to maintain optimal blood levels, which is why to recommend 25 micrograms or 1,000 International Units (IUs) daily for people who do not benefit from adequate sun exposure.
Essential Fatty Acids
Omega-3 (or n-3) and omega-6 (or n-6) fatty acids are widely regarded to be beneficial for human health. The two most important ones of these are two short-chain polyunsaturated fatty acids: α-linolenic acid (ALA), which the body can use to create other fats within the n-3 fatty acid family, and linoleic acid (LA), which the body can use to create other fats within the n-6 fatty acid family.
These two fatty acids are called ‘essential’ because they cannot be synthesized by the human body, but are required for healthy functioning. They must therefore be supplied by our diets. Enzymes in our bodies convert these short-chain fatty acids to long-chain n-3 and n-6 polyunsaturated fatty acids.
ALA is converted (incidentally, not only by humans but also by many other animals, including fish) to eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and docosapentaenoic acid, with stearidonic acid (SDA) as an intermediate in the pathway; LA is converted to arachidonic acid.
The Paleolithic diets that were adopted by hunter-gatherers are estimated to have had an n-6:n-3 ratio of 1:1 to 2:1. Many people who live today, by contrast, overconsume LA. The n-6:n-3 ratio of typical Western diets has been estimated to be around 15:1 to 17:1. This is a serious problem, as overconsumption of LA impairs ALA conversion. Many people also under-consume ALA, which may cause deficiencies in the, particularly important EPA and DHA.
High intakes of trans-fatty acids, alcohol, and caffeine, as well as imbalanced diets and illness in general, may produce the same deficiencies in EPA and DHA. Such deficiencies are believed to cause cardiovascular disease and cancer, as well as exacerbated pain associated with a range of conditions. They may also cause cognitive decline, age-related macular degeneration, and depression.
A clear message emerges from this. Vegans must make sure to consume adequate amounts of ALA, and avoid high consumption of products that inhibit the conversion of ALA, including products that contain relatively large quantities of LA. Accordingly, a recent study recommends that at least one unit of n-3 be consumed for every four units of n-6.
The authors of the study also recommend an ALA intake of 2.6 g/day for men and 1.6 g/day for women, whilst recommending the following daily intakes for infants and children: 0.5 g at 0–6 months; 0.5 g at 7–12 months; 1 g for children aged 1–3; 1.6 g for children aged 4–8; 2 g for boys aged 9–13; 2.4 g for boys aged 14–18; and 1.6 g for girls aged 9. The main reason for the gender differences relates to the fact that males tend to convert ALA less efficiently
Plant foods that are high in omega-3 fatty acids include chia, flax, canola (rapeseed), hemp, walnuts, perilla, and olive oil. Blackcurrant seed oil, derived from the seeds of Ribes nigrum, is rich not only in omega-3 fatty acids, but also in SDA, and the same applies to oil derived from plants belonging to the Echium genus, a collection of species within the Boraginaceae family.
Genetically engineered soybeans that contain SDA have also been recommended (but their inclusion within a diet would depend on their acceptability, a debate that I touched upon briefly in and that I shall not engage with any further here.
To ensure adequate consumption of ALA, recommend that adults consume three to four daily servings from this list: ‘1 teaspoon canola oil, 1/4 teaspoon flaxseed oil, 2/3 teaspoon hemp seed oil, 1 teaspoon walnut oil, 2 teaspoons ground English walnuts or 2 walnut halves, 1 teaspoon ground flaxseeds, 1/2 cup cooked soybeans, 1 cup firm tofu, 1 cup tempeh, 2 tablespoons soynuts’.
People with increased needs (for example pregnant and lactating women) and people with compromised conversion rates (for example people with diabetes or hypertension, and older people) may also benefit from consuming limited amounts of DHA- and—where available—EPA-fortified foods and DHA-supplements derived from microalgae (which can retro-convert to EPA inside the human body), as well as from consuming brown algae (kelp) oils write that vegans over the age of 60 ‘should consider a daily DHA (or a combination of DHA and EPA) supplement of 200 to 300 milligrams, a supplement dose that they are also ‘inclined to recommend’ at a frequency of every two to three days for those who are younger.
Although it may be unlikely to happen, overconsumption of DHA-rich products must be avoided, as this may raise total and low-density lipoprotein (LDL) cholesterol, cause prolonged bleeding, and reduce immunity.
Provided that it is present in the soil, many plant foods contain zinc. Plants that tend to be high in zinc are cereals and legumes. Unrefined whole grains provide higher concentrations than refined grains, as zinc can be found particularly within the outer layer of grains. Various ways to increase zinc uptake have been described, including soaking and sprouting beans, seeds, and grains, as well as leavening bread and consuming foods that contain citric acids.
Zinc absorption can be reduced by phytates (phytic acids), protein, and insoluble fibre, as well as by some minerals, including iron, calcium, and potassium. Whereas whole grains are higher in phytates than refined grains, the relative greater effect of phytates in the former is more than compensated for by the fact that whole grains are higher in zinc.
A study that compared 25 vegans with 20 omnivores found that the inhibitory effect of phytate failed to compromise zinc status as the bodies of people who take in little zinc appear to be able to increase zinc absorption and retention.
As an aside, whereas it is good to be mindful that potassium may inhibit the absorption of zinc, it is nevertheless important to secure a sufficient intake of potassium as well. The following are listed as good sources of potassium by beet greens, spinach, Swiss chard, cooked tomatoes and tomato juice, bananas, sea vegetables, orange juice, and legumes.
Iodine deficiency affects more than two billion people. It is the leading cause of preventable mental retardation worldwide. Fetuses and breastfed children are particularly vulnerable as they depend on maternal iodine intake for thyroid hormone synthesis, which is essential for human neurological development.
Thyroid iodine uptake is inhibited by perchlorate—a ubiquitous environmental contaminant—cigarette smoke, cruciferous vegetables and seaweeds of the genus there is also concern over the inhibitory effects of particular is flavones found in soy and flaxseed.
Both the underconsumption and the overconsumption of iodine can cause goitre (an enlargement of the thyroid gland) and hypothyroidism, but the latter can also cause hyperthyroidism. A small American study found, however, that in spite of the fact that a cohort of Boston-area vegans had relatively low urinary iodine levels, these low levels were not associated with thyroid dysfunction
Provided that they have access to adequate nutrition, vegans should not suffer from iodine deficiencies. Iodine can be provided through plants grown on iodine-rich soil, the consumption of seaweed, and the consumption of iodized salt.
As levels of iodine in seaweed vary considerably and are therefore unreliable, and as the overconsumption of salt must be avoided, recommend the use of supplements as their favourite strategy, where their recommendation for adults is that they take supplements of 75 to 150 micrograms three to four days per week in order to meet a recommended daily allowance of 150 micrograms, whereas lower levels of 90 micrograms daily are recommended for very small children and higher levels of up to 290 micrograms daily for lactating women.
They also recommend one-quarter of a teaspoon of iodized salt per day as an alternative to supplementation. The development of a global strategy to ensure routine, adequate iodization of foods that are commonly used that guard at the same time against excessive intake of iodine, which negatively affects the thyroid gland, would seem to be appropriate in view of the scale of the problem of iodine deficiency. Some localities have already developed guidelines; in the USA, for example, vegan pregnant and lactating women have been recommended to supplement their diets with 150 micrograms of iodine daily
Foods contain iron in two forms: haem iron and non-haem iron. Vegan foods only contain the latter, which is less easily absorbed by the body. Whereas iron deficiency can be a problem for vegans, it is more likely to be a problem for omnivores who consume large quantities of milk than for diet-conscious vegans. Good vegan sources of iron are dried fruit, sea vegetables, leafy green vegetables, and beans.
Vegans who consume a good range of fruit and vegetables in addition to foods that contain relatively large amounts of iron are unlikely to be affected by a deficiency as many fruits and vegetables contain large quantities of vitamin C, as well as other organic acids, which enhance iron absorption.
Retinol, carotenes, and alcohol have also been reported to increase iron absorption, whereas inhibitors include oxalates, phytates, and calcium, as well as the polyphenolics that are present in tea, some herbal ‘teas’, coffee, and cocoa.
It is for these reasons that recommend that people who drink tea and coffee only do so between meals rather than with their meals. As low iron status is moderately common in premenopausal women, these women need to make sure that their diets include good sources of iron, together with vitamin C to aid absorption. At the same time, there is evidence of the human body’s ability to adapt to low iron intake by increasing absorption and decreasing losses
The account presented above shows that vegan diets can fulfil all the nutritional requirements that are needed to support good health. Nutrients that present particular concerns are vitamin B12 and omega-3 fatty acids as few vegan foods that are currently used for human consumption contain these. Accordingly, vegans must make sure that they consume adequate portions of such foods.
A nutrient that I have not mentioned, but that may be a concern, is selenium as the selenium content of soil varies across the world, vegans must ensure that they do not restrict their diets to foods that are grown on soils that have low selenium levels. All in all, vegan diets can be adequate for all human beings, including children.
Although small children with reduced stomach capacities may need to eat regularly and must ensure that they eat foods that are sufficiently high in energy density to provide sufficient calories, that are relatively easy to digest (for example by including cooked rather than raw foods), and that are not excessive in fibre many nutritionists adopt the view that vegan diets can be adequate for all human beings
Vegan diets are growing in popularity. A vegan diet can offer many health benefits, including better heart health, weight loss, and a reduced risk of chronic diseases. Research also suggests that vegan diets are better for the environment. People who wish to adopt a vegan diet will need to plan their meals carefully to ensure that they are getting enough key nutrients to avoid deficiencies.
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