When we begin to practice a vegan diet, we are constantly concerned about whether we are achieving a correct nutrition, there are many myths and false beliefs about vegetarian eating that tend to give a false perception of this eating practice.
In the healthy nutrition article (see here) I talk about the elements of a healthy diet these are: proteins, carbohydrates, fats, vitamins and minerals, these are the same for both an omnivorous diet (based on foods of plant and animal origin) and for a vegetarian or vegan diet.
It´s not a secret to anyone that any diet, whether omnivorous or vegan, if it´s unhealthy it can lead to nutritional deficiencies, as a vegetarian diet is more restrictive with foods that came from animals than an omnivorous diet, nutritional deficiencies happen easier.
However, as long as a vegetarian diet is healthy and balanced, it provides an adequate intake of nutrients in all stages of life. On the contrary, when it´s restrictive and unhealthy (poorly planned) it can lead to nutritional deficiencies of vitamin B12, iron, calcium, protein, omega 3 fatty acids and even vitamin D (in certain countries).
Types of vegetarian diets
There are different dietary practices within the vegetarian diet, these are classified according to the foods of animal origin that are excluded in the diet.
Table 1 Types of vegetarian diets
|
Types of vegetarian diets (all exclude animal meats) |
|
|
Ovo-Lacto-vegetarian |
Includes eggs and dairy products |
|
Lacto-vegetarian |
Includes dairy
products, but not eggs |
|
Ovo-vegetarian |
Includes eggs and derivatives, but not dairy
products |
|
Vegan |
Excludes eggs, dairy products and may exclude honey |
Source: (Academy of Nutrition and Dietetics, 2016, p. 1971).
Vitamin B12 in vegetarian diets
Vitamin B12 is found naturally only in foods that came from animals, which is why vegetables, fruits, cereals and legumes lack of it, unless they are contaminated with bacteria that produce B12 or have been fortified. For this reason, its deficiency can be quite common among vegetarians.
Deficiencies
A deficiency of vitamin B12 can lead to anemia and neuronal problems, since this vitamin together with folic acid is necessary for red blood cells to divide properly, it also has an important role in neuronal health, its deficiency leads to an alteration in the transmission of the nerve impulse.
Symptoms of B12 deficiency are unusual fatigue, tingling in fingers or toes, poor cognition, poor digestion and poor growth in young children. A prolonged deficiency of B12 can lead to cardiovascular disease, dementia and bone weakness.
Vitamin B12 in our diet.
Vitamin B12 requirements vary between 2.4 - 2.8 μg/day (micrograms) depending to gender, age and physiological status. For vegetarians it is necessary to eat fortified foods with B12 (such as some vegan milks & some soy products) and take B12 supplements to avoid deficiencies.
Controversy with vitamin B12 from plant sources
Fermented plant foods such as tempeh, nori, spirulina, chlorella algae, and unfortified nutritional yeast were formerly thought to be plant sources of B12 in vegetarian diets.
However, scientific studies currently indicate that these foods cannot be considered reliable sources of B12, because provide inactive vitamin B12 analogs. Molecules that appear to be B12, but they are not and can even hinder true B12 absorption.
Recommendations to avoid B12 deficiencies
- Eat fortified foods with vitamin B12 two or three times a day.
- Take vitamin B12 supplements: you can take one vitamin B12 supplement daily that contains at least 280µg (micrograms) or one B12 supplement each week that contains at least 2000µg.
Vitamin B12 absorption mechanism is complex in our body, the less frequent is vitamin B12 intake a greater amount needs to be taken, since it´s absorbed in small amounts (in large doses, only 1% approximately is absorbed),
It doesn't hurt to combine recommendations. For example, taking a B12 supplement and then drinking a glass of fortified milk, it can be done and will not do any harm.
Tips
- If you only choose to eat fortified foods with B12, you should read the label to make sure you are getting enough B12. For example, if a vegan milk contains 1 microgram of B12 per serving, then you should drink three servings a day to get enough vitamin B12.
- Most vegetarians should eat reliable sources of vitamin B12 in their diet since 1 cup of cow's milk and one egg per day only provides about two-thirds of vitamin B12 requirements.
- On the other hand, B12 supplementation in multivitamins (of several vitamins) can be counterproductive, since vitamin B12 is degraded in the presence of vitamin C and copper (common in multivitamins) giving rise to inactive products, so is recommended a supplement containing only vitamin B12.
Iron in vegetarian diets
Iron is a mineral necessary for energy production, cellular breathing process, immunity, DNA synthesis, and many other reactions in our body. Symptoms of iron deficiency are fatigue, rapid heartbeat, pale skin, brittle nails, weakness, loss of appetite, fissures at the corners of the lips, and many others.
Iron in our diet
Iron requirements vary according to gender, age and physiological status in adult men they are 8 mg/day and in adult women 14 mg/day (milligrams). Vegetarians with a healthy diet generally eat the same or even more iron than omnivores, so they shouldn't worry about iron if they eat a healthy and varied vegetarian diet.
Differences between iron from animal source and plant source
Iron from plant-based foods is harder to absorb so is less available for the body than iron from animal-based foods. This happen because plant-based iron is in non-heme form. The absorption of non-heme iron by the body depends on the physiological needs of each person and is regulated by iron reserve levels of the body, the absorption of non-heme iron can be up to 10 times higher when the individual has an iron deficiency.
Bioavailability of iron from plant sources
Bioavailability of iron from plant sources is influenced by several components in our diet that can enhance or inhibit non-heme iron absorption.
The main inhibitor of non-heme iron absorption are phytates, which are normally found in legumes, nuts, whole grains and unprocessed bran. Industrial processing removes much of the phytate content, but it also removes other beneficial nutrients such as iron and zinc.
Polyphenols also inhibit plant-based iron absorption, these are found in a lot of foods such as tea, infusions, coffee, cocoa and red wine.
How to reduce phytates in our foods?
Hydrating and sprouting legumes, grains and seeds reduces phytate levels, as using yeast in breads.
How to improve plant-based iron absorption?
The greatest enhancer of iron absorption is vitamin C, which counteracts iron inhibitors and can increase iron absorption by 6 times in people with low iron stores.
Vitamin C helps to convert iron to the eases form for our body to absorb, of ferric iron (Fe + 3) to ferrous iron (Fe + 2). Other organic acids such as citric acid, malic acid and lactic acid, as well as vitamin A and L-lysine amino acid improve non-heminic iron absorption.
- Foods rich in vitamin C: fresh fruits and vegetables such as: milky, orange, guava, lemon, tomatoes, bananas, melon, strawberry, broccoli, potatoes and others.
- Foods rich in citric acid: citric fruits and vegetables such as lemons, limes, pineapple, grapefruit, tangerines, orange, blackberry, tomato, carrot, paprika, broccoli, among others.
- Foods rich in malic acid: acid or sour fruits and vegetables such as: grapes, cherries, apples, blueberries, peaches, apricots, pears, plums, tomatoes, pineapple, raspberries and other berries, among others.
- Foods rich in lactic acid dairy such as: yogurt, milk cream, cheeses, cottage cheese and dairy ferments,
- Foods rich in vitamin A yellow, green, and red vegetables, such as carrot, sweet potato, broccoli, spinach, artichoke, cabbage, beet, among others
- Foods rich in L-lysine amino acid such as: peanuts, beans, lentils, peas, quinoa among others.
Tips to increase iron stores
Iron absorption can be increased by following these tips:
- Adding a source of vitamin C to our meals.
- Avoiding tea, coffee, chocolate and red wine with meals.
- Eating more legumes like peanuts, beans, lentils, peas among others.
Calcium in vegetarian diets
Calcium is a mineral that fulfills many functions in our body, it maintains healthy bones and teeth, it´s necessary for blood clotting, for nerve impulse transmission, muscle contraction, hormonal secretion and many chemical reactions since it activates enzymes and collaborates in cell permeability allowing the exchange of substances with the environment such as oxygen and nutrients.
Calcium deficiency produces weak bones and leads to diseases such as osteopenia and osteoporosis.
Calcium in our diet.
The recommended daily intake of calcium in adults varies between 800-1100 mg/day, this may be higher according to gender, age and physiological state (pregnancy, lactation, illness, among others).
Ovo-lacto-vegetarians normally achieve and even exceed calcium recommended intake, while vegan diets need calcium-fortified foods or calcium supplements to achieve calcium recommended intake.
Calcium bioavailability from plant sources.
Calcium bioavailability from plant sources is related to oxalate content in foods, and to a lesser extent to phytate and fiber. Calcium absorption from vegetables with high oxalate content is only 5%, so these are not considered good sources of calcium despite their high calcium content, compared to vegetables low in oxalate calcium absorption is 50%.
Vegetables low in oxalate and rich in absorbable calcium
Low oxalate vegetables rich in calcium are broccoli, cauliflower, cabbage, brucella sprouts, kale, Chinese cabbage, watercress, artichoke, asparagus, turnip greens, mustard greens. These provide calcium with high bioavailability, in addition to calcium they also contain vitamin K, potassium and magnesium, which also contribute to bone health.
Calcium absorption from tofu made with calcium salt and most fortified non-dairy milks is similar to cow's milk by 30%. Other plant foods such as white beans, almonds, tahini, figs and oranges, provide moderate amounts of calcium with a slightly lower bioavailability 20%.
Vegetables rich in oxalate and low in absorbable calcium
Among those vegetables with large amounts of oxalate and low in absorbable calcium are spinach, beet, chard, rhubarb, parsley, leeks, wheat germ and wheat bran whose calcium is not well absorbed due to its high content of oxalates. Oxalate bind itself to calcium and prevent calcium absorption in the digestive tract, which causes the loss of a third of the calcium available in food.
How to improve calcium absorption from plant sources?
The factors that improve calcium absorption are an adequate supply of vitamin D, vitamin B12 and protein in our diet. Physical activity also increases calcium absorption and fixation by our bones, that’s why weight lifting is so good for woman as it helps to prevent osteoporosis.
Recommendations for calcium intake in a vegan diet
Only a few green leafy vegetables are rich in absorbable calcium, if you do not eat at least 3 servings of these foods per day (one serving is 1/2 cup cooked), then you need to eat calcium-fortified foods (vegetable milks, tofu, and others) or take a calcium supplement to ensure an adequate supply of calcium and avoid problems in the future.
Tips for calcium intake
- There are many plant milks fortified with calcium, vitamin D and vitamin B12.
- Calcium fortified beverages should be shaken well to make sure calcium has not settled to the bottom of the carton.
- Calcium supplements should be taken with meals, especially for those prone to kidney stones.
- Calcium supplements can inhibit iron absorption if is taken at the same time, so you should take that into account if you have a deficiency.
Proteins in vegetarian diets
Proteins perform many functions in our body: they have structural functions, allow muscle contraction, transport substances in body fluids and between cells, play the role of chemical messengers in biological reactions, act as regulators in our immune system and in several processes of growth, development and cell differentiation.
Vegetable proteins sources in vegetarian diets:
- Legumes such as: beans (like black beans, white beans, red beans) chickpeas, lentils, peas, soy, tofu, etc.
- Oilseeds such as peanuts, walnuts, hazelnuts, cashew, pistachio, sesame seeds, sunflower seeds, pumping seeds, and others.
Vegetable proteins of low biological value
There are proteins of high and low biological value depending on their composition of essential amino acids. Proteins are built of amino acids; we could say that a protein is a house and amino acids are the blocks which the house is built with.
Vegetable proteins do not possess all the essential amino acids in one food, so they are proteins of low biological value. Unlike animal proteins which are of high biological value since they have all the essential amino acids in one food.
How to make a vegetable protein of high biological value?
We can make a high biological value protein by combining two types of foods like cereals with legumes or legumes with oilseeds in our diet. Thanks to this, people with vegan diets get all the essential amino acids without the need to eat any animal products.
Can vegetable proteins cover all our needs?
Vegetable proteins can cover all our needs as effectively as animal protein, it only takes to eat a variety of foods that must be eaten during the course of a day, and this way they can provide all the essential amino acids.
Bioavailability of vegetable proteins
Protein intake in vegetarian diets must to be higher than an omnivorous diet since vegetable proteins are more difficult to digest due fiber and anti-nutrients found in plant-based foods. This can be done naturally by practicing a healthy vegetarian diet with enough variety of food.
Omega 3 fatty acids in vegetarian diets
Omega 3 fatty acids are essential for our body because we cannot synthesize them by ourselves. They are necessary for brain, retina and cell membranes development and maintenance. In addition, they have an important impact on pregnancy development and are important to reduce the risk cardiovascular diseases and other chronic diseases.
There are 3 essential omega-3 fatty acids:
1. Α-linolenic acid (ALA): found in soybeans, nuts and seeds such as flaxseeds, chia seeds, hemp, and their oils such as soybean oil, canola oil, linseed oil, hemp oil among others.
2. Eicosapentaenoic acid (EPA): found in fatty fish (in large amounts), in eggs (in small amounts), and seaweed (in very small amounts).
It’s quite important for our health because some EPA change into other molecules that can reduce blood clotting, inflammation, blood pressure and cholesterol. Therefore, they help to reduce the risk of chronic diseases.
3. Docosahexaenoic acid (DHA): like EPA, it is found in fatty fish (in large amounts), in eggs (in small amounts), and seaweed (in very small amounts).
Its importance for our body is because it´s a main component of the gray matter of the brain, and it is also found in the retina, testes, sperm, and cell membranes. It´s of great importance in growth periods and during pregnancy.
EPA and DHA in vegetarian diets
Since EPA and DHA are mainly found in fish and shellfish, their consumption in vegetarians is practically nil and therefore they tend to have low levels of EPA and DHA.
Transformation of ALA into EPA and DHA
Our body is capable of transforming ALA into EPA efficiently, but it may require large amounts of ALA to produce optimal amounts of DHA, in addition, this process is affected by gender, diet composition, state of health and age. A high consumption of omega 6 fatty acids (linoleic acid or LA) also inhibits this transformation, so this process can sometimes be inefficient.
Recommendations of (ALA) omega 3
Recommended consumption of ALA is 1.6 g/day for men and 1.1 g/day for women, however, vegetarians benefit from a higher supply of ALA due to the aforementioned.
Tips for raising EPA and DHA levels
We need to make sure we are covering the daily requirements of ALA by eating good sources this nutrient so we can promote a correct transformation of ALA to EPA in our body.
It´s also advisable to take a DHA supplement as ALA transformation to DHA requires large amount of ALA and is not always an effective process. This is especially important in pregnant and lactating women, children, older adults and people with disease where this transformation is even more deficient.
Excess of omega-3 fatty acids
Too much omega-3 can cause bleeding and bruising. If you have any reason to believe you have problems with easy bruising or bleeding, consult your doctor before increasing your intake of omega-3 fatty acids.
Vitamin D in vegetarian diets
Vitamin D helps to control calcium exchange between bones, blood and vice versa, it also has an important role in our immune system. recently vitamin D deficiency has been linked to many diseases. The lack of this vitamin in adults causes a softening of the bones called osteomalacia and in children it causes bone deformation known as rickets.
Sources of vitamin D
There are 2 sources of vitamin D:
- Endogenous: it is synthesized in the skin when we are exposed to the sun, by the action of UV rays on the skin's sterols.
- Exogenous: in foods such as fatty fish and their oils, fortified dairy products and eggs.
Sun the main source of vitamin D
The most important source of vitamin D, for both omnivores and vegetarians, comes from the action of ultraviolet rays on our skin's sterols. Vitamin D state by the body depends on exposure and intensity of sunlight and our food intake or supplements with this vitamin.
Production of vitamin D after exposure to sunlight is variable and depends on certain factors, including time of day, season, latitude, air pollution, skin pigmentation, use of sunscreen, amount of clothing covering our skin and age.
If you live in a country where there is sunlight at all times of the year and there is exposure during times of the day where it is possible to tan, then you should not need any supplements.
The approximate periods of exposure time for an adequate synthesis of vitamin D in the skin are:
- Fair skin: 10 to 15 minutes.
- Dark skin: 20 minutes.
- Seniors: 30 minutes.
Due to skin cancer concerns, some dermatologists recommend getting all our vitamin D from food or supplements rather than from the sun.
The amounts of sun mentioned for light and dark skin, should be safe, but no study has been seen on how much amount of sun is safe for the elderly, it is recommended to speak with your doctor about how to get vitamin D if you think that you are at risk of skin cancer.
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