Plants Provide: How a Vegan Diet Supports Complete Nutrition
Introduction
Plant-based diets have become increasingly popular in recent years, with more and more people adopting vegetarian, vegan, or flexitarian eating patterns for health, ethical, environmental, or other reasons. But can diets devoid of all or most animal products really provide the full range of nutrients our bodies require?
Research shows that well-planned plant-based diets can in fact meet nutritional needs at all stages of life.
This article will provide an overview of how key vitamins, minerals, protein, and other dietary components can be obtained on plant-based diets that minimize or exclude animal foods.
Defining Plant-Based Diets
To understand how plant-based eating can be nutritionally adequate, we first need to define what constitutes a plant-based diet. There is a range of plant-based eating patterns:
- Vegetarian diets exclude meat, poultry, and fish but allow eggs and dairy. Lacto-ovo vegetarian is the most common type.
- Pescatarian diets exclude meat and poultry but allow fish and seafood along with plant foods.
- Vegan diets exclude all animal products including meat, fish, dairy, eggs, and honey.
- Flexitarian diets are predominantly plant foods but occasionally include modest amounts of meat, dairy, eggs or fish on occasion.
Any diet that focuses on plants while limiting or avoiding animal foods can be considered plant-based. Well-planned versions of these diets can fully meet nutritional needs.
Plant-Based Dietary Patterns
Well-planned plant-based diets generally emphasize whole, minimally processed foods over refined products. For example, brown rice would be chosen over white rice for its higher fiber and nutrient content. Whole grain bread or pasta would be preferred to white varieties. And while the occasional sweet treat is fine, desserts and snacks high in added sugar are minimized.
Including a wide variety of produce, whole grains, proteins, oils, and spices ensures a diversity of nutrients. Eating patterns on plant-based diets can vary significantly based on individual preferences. Some choose to follow a structured meal plan, eating set combinations of foods or recipes to simplify nutrition. Others may take a more flexible approach. As long as core food groups are included throughout the day or week, plant-based diets can meet nutrient needs in different ways.
Key Nutrients to Focus On
When adopting a plant-based diet, there are some key nutrients that require a little extra attention to ensure needs are met. These include:
- Protein
- Omega-3 fatty acids
- Iron
- Calcium
- Vitamin B12
- Vitamin D
- Zinc
- Iodine
With some guidance on the best plant sources of these nutrients, a plant-based diet can easily provide adequate amounts without supplementation. We will look at each in more detail.
Protein
Protein is essential for building and repairing tissues and muscle, making hormones and enzymes, transporting nutrients, and providing energy. While animal products contain complete protein with all nine essential amino acids, plant proteins can also adequately meet needs when a variety of sources are consumed throughout the day.
Legumes including beans, lentils, peas, and peanuts are excellent sources of plant-based protein. One cup of cooked beans or lentils provides 15-18 grams of protein. Nuts, seeds, whole grains, vegetables, and soy products also contribute smaller amounts that add up. As long as complementary plant proteins from various sources are eaten during the same day, all essential amino acids can be utilized by the body.
Those following plant-based diets do need to consume slightly more total protein than meat-eaters to account for differences in digestibility and amino acid composition. Active individuals may require more protein as well. But needs can easily be met by including a serving of legumes, soy, or nuts/seeds with each meal and snack throughout the day. Spacing protein intake out over 4-5 meals rather than concentrating it at dinner helps optimize use of amino acids as well.
Omega-3 Fatty Acids
Omega-3 fats provide anti-inflammatory effects and heart health benefits. The best source is fatty fish, but plant foods can also provide alpha-linolenic acid (ALA) that the body can convert to active forms of omega-3s. Chia seeds, hemp seeds, flaxseeds, walnuts, and their oils are particularly high in ALA. ALA can also be found in lower amounts in soybeans, navy beans, kidney beans, Brussels sprouts, kale and other leafy greens.
While the conversion process of ALA to active omega-3s is not very efficient, consuming plenty of ALA along with reducing omega-6 fats from oils can help increase levels sufficiently on plant-based diets. Those with heart disease risk may want to supplement with algae-derived EPA/DHA as well. Aim for at least 2-3 servings of high ALA foods or DHA/EPA supplements daily.
Iron
Iron carries oxygen in the blood to cells throughout the body. While iron is plentiful in meat, plant foods can also provide adequate amounts. Legumes, whole grains, nuts, seeds, dried fruits, and leafy greens all supply iron. Vitamin C from fruits, veggies, and citrus juice boosts iron absorption from plant sources.
Since the type of iron in plants is non-heme iron that is not absorbed as well, vegetarians need about 1.8 times as much iron while vegans require 2.1 times the recommended daily amount. Eating a varied diet with iron-rich choices at each meal can enable plant-based eaters to meet needs. Those prone to iron deficiency may benefit from occasional supplementation as well.
Some iron-rich plant-based food choices include lentils, spinach, white beans, tofu, cashews, pumpkin seeds, tomato sauce, Swiss chard, edamame, and fortified breakfast cereals. Including a few of these in meals and snacks each day helps provide the 25-30 mg of iron recommended for plant-based diets.
Calcium
Calcium builds bones and teeth while supporting muscle and nerve function. Milk and other dairy products are good sources of calcium, but vegetables can also supply this mineral. Kale, broccoli, Chinese cabbage, okra, and other greens contain highly absorbable calcium. Tofu prepared with calcium sulfate and fortified plant milks provide large amounts as well. Beans, almonds, figs, blackstrap molasses, and calcium-set tofu offer additional amounts.
The amount of calcium absorbed depends on the total consumed from all dietary sources. Those eating plant-based diets simply need to include plenty of calcium-rich vegetables, tofu, and/or fortified foods to meet daily requirements. Aim for 5-6 servings daily of foods providing at least 10% DV per serving. Consuming calcium sources throughout the day optimal absorption as well.
Vitamin B12
Vitamin B12 aids in producing blood cells, DNA synthesis, and supporting neuron function. Since B12 is mainly found in animal foods, those adhering to vegetarian or vegan diets require supplementation or fortified foods. Common sources are fortified plant milks, nutritional yeast, breakfast cereals, and B12 supplements, often in the form of a daily chewable or sublingual tablet.
As we age, vitamin B12 absorption decreases, so adults over 50 should aim for B12 from supplements or fortified foods providing at least 100% DV to ensure adequate intake. Deficiency symptoms like fatigue, weakness, and neurological issues can otherwise occur on plant-based diets over time.
For those following vegan or near-vegan diets, a simple daily B12 supplement or serving of fortified food provides assurance this nutrient is covered. Check the label for B12 amounts of fortified foods, as levels can vary widely.
Vitamin D
Vitamin D promotes calcium absorption for bone health and modulates cell growth. While found in cod liver oil and oily fish, the majority of vitamin D is obtained from sun exposure rather than foods. Just 15-20 minutes outdoors exposing forearms and face to direct sunlight several times weekly can enable sufficient vitamin D production. For those with limited sun exposure, supplementation is often needed regardless of diet type. Vitamin D is easy to obtain in standalone capsules or multivitamins.
Since vitamin D needs do not differ for plant-based diets, simply ensure adequate sun exposure, check blood levels periodically, and supplement as needed to maintain optimal status. Those living in northern climates or who cover skin for cultural reasons may require more supplementation.
Zinc
Zinc supports immune function, wound healing, growth, reproduction, taste and smell. It is abundant in beef, lamb, and oysters. Whole grains, soy foods, legumes, nuts and wheat germ can also supply zinc on plant-based diets. As with iron, the zinc in plants has lower bioavailability so total intake should be increased by about 50% recommended amounts.
Eating beans, lentils, tofu, cashews, chia seeds, fortified cereals, and pumpkin seeds regularly helps provide the RDA of 11mg per day. Soaking, sprouting, and leavening can help reduce phytate compounds that inhibit mineral absorption as well. Those prone to deficiency may benefit from zinc supplementation.
Iodine
Iodine is required for production of thyroid hormones. While iodized salt and seafood provide iodine, plants grown in iodine-rich soil also contain this mineral. Iodized salt, sea vegetables like kelp and dulse, potatoes, navy beans, strawberries, cranberries, yogurt, and milk are common sources on plant-based diets. Most multivitamins also provide iodine. Vegans who avoid salt, sea vegetables and processed foods may struggle to meet needs and require monitoring.
A guide for plant-based iodine intake is to include 1/4 teaspoon iodized salt daily, 1-2 servings of sea vegetables per week, and/or a multivitamin containing 150 mcg iodine. Those with thyroid issues should speak to their doctor about proper iodine intake.
Phytochemicals and Fiber
In addition to vitamins and minerals, plant foods provide a wide range of protective phytochemicals, compounds that provide antioxidant and anti-inflammatory benefits. Produce, in particular, supplies phytochemicals that promote health and reduce disease risk. Whole plant foods also provide fiber to support digestive and heart health. While any balanced diet should provide a range of vitamins and minerals, the phytochemical and fiber content of plant-based diets give them an added advantage for disease protection.
Sample Meal Plan
To illustrate how key nutrients can be obtained from plants, here is a sample day on a balanced vegetarian diet:
Breakfast:
Oatmeal made with fortified almond milk, topped with banana, walnuts, and flaxseed
Lunch:
Lentil vegetable soup, mixed green salad with tomatoes, kidney beans, and avocado
Snacks:
Edamame, apple with almond butter
Dinner:
Tofu veggie stir fry over brown rice with cashews and sesame seeds
Dessert:
Fresh berries with dark chocolate
This provides a balanced distribution of proteins, healthy fats,produce, whole grains, and key nutrients like calcium, iron, zinc and B12 throughout the day from plant sources. Variations could include hummus wraps, bean chili and sweet potatoes, pasta primavera, tempeh bowls and more.
Conclusion
Well-planned plant-based diets can provide adequate nutrition for all stages life when a variety of whole foods are consumed and attention is paid to key nutrients like protein, omega-3s, vitamin B12, iron, calcium, vitamin D and zinc. A diet rich in vegetables, fruits, whole grains, legumes, nuts, seeds, and healthy plant oils can meet human nutritional needs and promote long-term health. With sound nutrition knowledge, those adopting vegetarian, vegan, or flexitarian eating patterns can easily meet their needs from plant foods.
