Why It's Important to Eat Leafy Greens Especially for Vegans

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What are Leafy Greens: A List of Leafy Green Vegetables

Leafy green vegetables are any plant leaves that humans eat as a vegetable. There are dozens, if not hundreds, of edible plant leaves. When most people think about leafy greens, only a few examples readily come to mind.

The term dark leafy green is also common. To my knowledge, there's no rule about the distinction between a dark leafy green and one that isn’t. Just look at the produce you buy to see if your greens are dark or not. If you seek the most nutrition value possible, aim for darker and more pigmented leaves.

The other question that comes up when defining leafy green vegetables is how to classify red or purple pigmented leaves. I include them in the leafy green category because I use them in the same way. However, due to their pigment, red or purple leaves have unique antioxidant profiles. Aim for a variety of colors in your produce selections; try some purple kale or radicchio!

Here’s a list of leafy green vegetables you can start adding to your dishes:

*Broccoli is technically a flower, however it's easy to categorize with leafy greens because of similar nutrient composition.

Nutrient Content of Leafy Green Vegetables

Leafy green vegetables are nutrient powerhouses. They’re also good sources of fiber, vitamin C, vitamin K, folate, beta carotene, B-vitamins, magnesium, potassium, iron, and calcium. They are low in calories and therefore don’t provide much carbohydrates, fat or protein.

Each leafy green provides a unique combination of nutrients. This is one reason why variety is key!

Leafy green vegetables are also an excellent source of antioxidants including carotenoids and polyphenols. Antioxidant compounds are very beneficial to human health and increased intake is commonly associated with lower risk of some types of cancer, cardiovascular disease including stroke ^{1, 2, 3}, depression ⁴, macular degeneration ⁵, and diabetes ⁶ in addition to improvements in asthma symptoms ⁷, sleep quality ⁸, and lung function in COPD ⁹.

Anti-nutrient Content of Leafy Green Vegetables: Impact of Oxalates on Nutrient Absorption from Leafy Greens

Oxalates are often touted as an “anti-nutrient” or something that doesn’t have nutritional value and may inhibit absorption of other nutrients. Oxalates are found in many plant foods, and are also produced by the body as an end-product of some metabolic pathways. The human body cannot breakdown oxalate, therefore it must be excreted through urine.

Oxalates bind to calcium in the digestive tract. This binding prevents both the oxalate and calcium from being absorbed. This is good because absorbing too much oxalate increases the risk of kidney stones and possibly other conditions (although research is limited) ¹⁰.

At the same time, oxalates are a main factor limiting calcium absorption. If a diet is high enough in calcium, there shouldn’t be an issue with consuming foods with oxalate since enough calcium will get absorbed. The recommended amount of calcium to consume daily is based on a 25% absorption rate.

Leafy greens are an important source of calcium in vegan diets. However, due to the high content of oxalates in some leafy greens, calcium absorption can decrease to almost zero. This is an issue if you rely on leafy greens to provide a source of calcium, and if you only eat leafy greens high in oxalate.

Low-oxalate Leafy Greens and High-oxalate Leafy Greens ¹¹

There’s debate over the accuracy of methods used to determine the oxalate content of foods. Kale and turnip greens sometimes land on the high-oxalate list, but absorption of calcium should be adequate from these two greens ¹⁰. Leafy greens that are low in oxalate include:

• Bok choy
• Kale
• Mustard greens
• Turnip greens
• Watercress
• Broccoli
• Romaine lettuce
• Brussels sprouts
• Collard greens

It’s also helpful to know what leafy greens are high in oxalates. This doesn’t mean these foods aren’t healthy, just that they are not a reliable source of calcium because absorption is quite low. If you want to limit the oxalate content in these leafy greens, boil them and discard the water. Leafy greens that are high in oxalate are:

• Spinach
• Beet greens
• Swiss chard
• Endive

There are other foods high and low in oxalate content, but I’m keeping the focus of this list to only leafy greens.

Health Benefits of Leafy Greens

There are many research studies linking vegetables, green vegetables, leafy vegetables, and the individual nutrients found in abundance in green leafy vegetables with positive health outcomes.

The two main benefits of increased vegetable intake are decreased risk of cardiovascular disease ^{18, 19} and cancer ^{21, 22, 23}, thought to be largely due to the vegetables’ antioxidant content ²⁰.

Green leafy vegetables are also a source of dietary nitrate, which may help lower blood pressure, a major risk factor for cardiovascular disease ¹⁶. Nitrate from vegetables is shown to decrease the thickness of the common carotid artery ¹⁷. Carotid artery thickness is an indicator of heart disease risk, where a thicker carotid artery is a sign of atherosclerosis and increased risk of heart disease.

Research also suggests consuming leafy, fibrous vegetables lowers risk of metabolic syndrome ¹², decreases type 2 diabetes risk ¹⁵, and lowers risk of eye disease, including macular degeneration ¹³. Furthermore, polyphenols, which are found in leafy green vegetables, are thought to help with brain health ¹⁴.

Don’t forget, you'll also benefit from the vitamin C, beta carotene (vitamin A precursor), vitamin K, fiber, folate, other B-vitamins, magnesium, potassium, iron and calcium.

Why Eating Leafy Greens is Especially Important for Vegans

As you can see, there are many health benefits associated with adding more leafy greens into your diet. Leafy greens are a great source of nutrition for omnivores and vegans alike. But the purpose of this article was to raise the point that leafy greens might be especially important for vegans.

My reasoning for this is largely the calcium content of leafy greens. Vegan diets can provide adequate amounts of calcium, especially if someone consumes fortified non-dairy beverages (almond milk, soy milk etc.). However, not all vegans consume plant-based milks or make non-dairy milks at home, which means they might not receive calcium fortification.

If a vegan doesn’t consume fortified beverages, it becomes more difficult to meet daily calcium requirements. Leafy greens can be a huge help to fill that gap as long as you select low-oxalate leafy greens. Leafy greens can provide a huge calcium boost and be a great addition to a healthy vegan diet which is why they're my recommended source of calcium for vegans. Even if you consume calcium-fortified beverages, you'll need calcium from other sources, and leafy greens are my first choice.

Calcium is an often overlooked nutrient since the effects of low intake occur over years or even decades. It’s still very important to meet calcium needs, even if you won’t see a direct benefit for the health of your bones until later in life.

“Junk-food Vegans”: Can you be Vegan without Fruits and Vegetables?

Another reason I think it’s important for vegans consume leafy greens is for all the other nutrients and health benefits they can provide beyond just calcium. With the rise in processed vegan foods, there's now a category of vegans who call themselves "junk-food vegans".

I don't like to label food as "junk" because all foods can fit into a balanced eating pattern. However, relying solely on processed vegan foods is not a health-promoting approach. All vegan foods are great for animals (which is the point) but strictly from a nutrition standpoint, many of these foods do not deserve the health halo they have received.

So, if you're a “junk-food vegan” and are looking to boost your nutrient intake, leafy greens are my first suggestion. If you’re not a “junk-food vegan” and looking to boost your intake of antioxidants, vitamins and minerals, you can add in leafy green vegetables. And lastly, if you are an omnivore looking for these same nutrients and health outcomes, add some leafy greens.

One last point I'd like to make is that there’s nothing wrong with consuming processed or “junk” foods. They can make a vegan diet fun, tasty, nostalgic and are a source of some nutrition.

How to Cook with Leafy Green Vegetables

There’s debate over the benefits of raw vs. cooked vegetables, including leafy greens. There's a sub-group of vegans who promote a raw-food vegan diet (although it seems this group is getting smaller). Eating raw foods is great if that’s the way you enjoy food. However, there is no harm in consuming cooked foods, including vegetables and leafy greens.

Research seems to agree that some nutrient content might be lost from freezing or cooking, but much of the nutritional value is preserved. Some nutrients might even become more active or better absorbed after they have been cooked.

As noted above, if high-oxalate leafy greens are boiled and you discard the cooking water, it can lower the oxalate content of the food, which can be a benefit of cooking high-oxalate leafy greens.

Since leafy greens are so healthy, I think it’s best to get them into your diet in whatever way works for you. However you can work leafy greens into your eating routine is fine. Cooked, raw, blended or hidden in something else…. Go for it!

How to Maximize Nutrient Absorption from Leafy Green Vegetables

Some of the beneficial compounds in leafy greens are fat-soluble. This means that they require fat to absorb and transport around your body. Since the fat content of leafy greens alone is very low, research suggests adding a small portion of fat to leafy greens (and other vegetables) can help boost absorption of important nutrients.

If you make a salad, the dressing likely contains some fat which is great. Otherwise, add a source of fat to the dish you're eating your greens with. If you make a smoothie, why not add some avocado or hemp seeds. If you cook leafy greens, add nuts or seeds or top the dish with avocado. If you cook with oil, it's likely enough fat to maximize absorption.

Getting Enough Leafy Greens: My Best Tips

II admit it, it can be hard to eat enough leafy greens sometimes. My struggle seems to stem from forgetting that I can cook with greens; I often only think about greens in terms of making a salad.

The best method I’ve found is to purchase frozen kale or a frozen leafy greens mix (typically a blend of kale, collard greens and spinach). The greens are chopped, won’t go bad for months, and are easy to toss into whatever I’m cooking. These greens aren’t going to work for raw preparation, but are perfect to use in hot dishes. Add them at the end of the cooking time because frozen vegetables are almost always blanched and this is often all the cooking leafy greens need to be tender.

My second tip is to buy pre-cut or ready-to-go greens that are already washed. My favorites are spring mix or baby kale (I choose kale over spinach when I can because of the high oxalate content of spinach). My local grocery store also sells “kale slaw” which is a blend of shredded broccoli stems, Brussels sprouts, kale, and a very small amount of purple cabbage and carrot. This slaw mix is amazing because you can toss it fresh onto anything or make a quick salad. The best part is, if it starts to go bad, it’s great to cook with. I wouldn’t typically want to cook spring mix, but this slaw is great in hot dishes too.

I don’t know about you, but having to remove stems or wash individual leaves seems tedious. Even though I fully appreciate the health benefit of leafy green vegetables, my motivation to prep them sometimes lacks. That’s why prepared greens are amazing. If you struggle with leafy greens spoiling, try to buy smaller amounts more frequently or try frozen options.

I’ve made it a personal goal to increase my intake of leafy greens so using them becomes part of my routine. Do you have any nutrition goals right now? If so, please share them in the comment section below!

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References cited:

Please note that this is a curated list of references for the topics above and is not intended to be comprehensive.

1. Total Antioxidant Capacity of Diet and Risk of Stroke A Population-Based Prospective Cohort of Women
2. Greater Total Antioxidant Capacity from Diet and Supplements Is Associated with a Less Atherogenic Blood Profile in U.S. Adults
3. Food selection based on high total antioxidant capacity improves endothelial function in a low cardiovascular risk population
4. Antioxidant status and its association with elevated depressive symptoms among US adults: National Health and Nutrition Examination Surveys 2005-6
5. Lutein and Zeaxanthin-Food Sources, Bioavailability and Dietary Variety in Age-Related Macular  Degeneration Protection
6. The Protective Effect of Antioxidants Consumption on Diabetes and Vascular Complications
7. Manipulating antioxidant intake in asthma: a randomized controlled trial
8. Inflammation, Oxidative Stress, and Antioxidants Contribute to Selected Sleep Quality and Cardiometabolic Health Relationships: A Cross-Sectional Study
9. Impact of dietary shift to higher-antioxidant foods in COPD: a randomised trial
10. Oxalate
11. Calcium Part 3–Calcium and Oxalate Content of Foods
12. Key Elements of Plant-Based Diets Associated with Reduced Risk of Metabolic Syndrome
13. Carotenoids in Green Vegetables and Health Aspects
14. Natural mood foods: The actions of polyphenols against psychiatric and cognitive disorders
15. Higher intake of fruits, vegetables or their fiber reduces the risk of type 2 diabetes: A meta-analysis
16. High-nitrate vegetable diet increases plasma nitrate and nitrite concentrations and reduces blood pressure in healthy women
17. Association of Vegetable Nitrate Intake With Carotid Atherosclerosis and Ischemic Cerebrovascular Disease in Older Women
18. Quantity and variety in fruit and vegetable intake and risk of coronary heart disease
19. Raw and Processed Fruit and Vegetable Consumption and 10-Year Coronary Heart Disease Incidence in aPopulation-Based Cohort Study in the Netherlands
20. Effect of fruit and vegetable antioxidants on total antioxidant capacity of blood plasma
21. Cancer chemoprevention by dietary phytochemicals: Epidemiological evidence
22. Associations of dietary dark-green and deep-yellow vegetables and fruits with cervical intraepithelial neoplasia: modification by smoking
23. Fruit, Vegetable, and Animal Food Intake and Breast Cancer Risk by Hormone Receptor Status

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