Raw asparagus can be quite stringy and tough, and neither of these qualities is conducive for proper nutrient absorption. However, if you just boil it for a few minutes or braise it on the frying pan for 10-15 minutes with some olive oil, the thick cell walls of the plant start dissolving, releasing a multitude of nutrients.
Cooking makes vitamins A, C, and E, as well as folate and ferulic acid, an anti-aging antioxidant, more bioavailable in asparagus. One study suggested that cooking asparagus boosted its antioxidants by 16-25%. A different study also discovered that cooking increased the quantity of phenolic acid, an antioxidant linked to lowering cancer risks, in asparagus.
2. Pumpkin (and Other Squashes)
Eating pumpkin raw is not very common, but there is no danger in doing so. However, cooking pumpkin in any way your heart desires, be it in pumpkin soup or pumpkin pie, will boost its nutrient content by miles. Just like asparagus, the vitamin A content in pumpkin becomes more easily digestible when it's cooked, so you end up absorbing more of it.
Apart from that, cooking increases the amount of available carotenoid antioxidants in pumpkin, which are known for their immune-boosting effects.
3. Green Beans (and Beans)
When it comes to beans, such as green beans, peas, and kidney beans, just to name a few, cooking them is essential. Sure, not everyone would consider beans vegetables, but peas and green beans are used identically to veggies, so we decided to include them in this list. For one, steamed green beans were found to have greater cholesterol-lowering capabilities than raw ones.
A different study revealed, however, that boiling or pressure cooking green beans may actually lower their nutrient content, so make sure to choose a different method of preparation, e.g. baking, cooking in the microwave, or even frying. As for beans, these need to be cooked because they naturally contain toxic proteins called lectins that get destroyed by cooking. If not cooked, eating beans can upset your stomach.
Related Article: 15 Common ‘Healthy’ Foods That Can Be Toxic to Humans
If cooking certain vegetables only boosts their nutrient content, when it comes to mushrooms, cooking is the only thing that can actually make your body absorb ANY nutrients. Like legumes, mushrooms aren't strictly considered vegetables, but they are used as such and sold in the veggie section of the store, so we'll include them here as well.
Uncooked mushrooms are essentially indigestible and go right through the digestive system, but any kind of heat will help release a multitude of nutrients from mushrooms, such as protein and B vitamins, and antioxidants. The US Department of Agriculture also mentions that cooking can increase the levels of potassium and zinc in mushrooms.
Spinach is actually tricky, as it's healthy both raw and cooked, but each way offers a different set of nutrients, so our best recommendation is to eat it both ways.
To be more specific, nutrients like vitamins B2, B3, C, and potassium seem to be best absorbed from raw spinach, whereas cooking can increase the availability of vitamins A, B1 and E, protein, zinc, calcium, and iron. Levels of folate associated with cancer prevention remain equally available in both steamed and fresh spinach.
6. Bell Peppers
If you cook bell peppers carefully, you'll be able to both preserve the vitamin C they contain and boost the availability of antioxidants, such as ferulic acid and carotenoids. To do so, cook peppers only until they're tender on the outside, but still crisp, just like they're typically served in stir-fry dishes. You can also use other preparation methods, it's just important not to overdo it with the heat.
People typically eat eggplants cooked, and not only because raw aubergines contain a toxin called solanine that could potentially upset your stomach. Still, we find that it's still interesting to learn what kind of preparation will provide more of which nutrients.
When it comes to eggplants, grilling them will retain more chlorogenic acid, a compound that may potentially lower your blood pressure and decrease the risks of developing type 2 diabetes because it slows down the absorption of glucose into the bloodstream. Boiled or steamed eggplants, on the other hand, will contain more antioxidants and cholesterol-lowering compounds.
You've likely heard of beta-carotene - it's a carotenoid antioxidant that is transformed into vitamin A in our body. Vitamin A, in turn, plays a key role in vision, bone growth and immune health. Beta-carotene is also the compound that gives carrots their orange color.
Now, to maximize the amount of carotene from your carrots, there are a few things you can do. First, it's best not to peel the carrots, as studies suggest this helps retain up to 13% more beta-carotene. Also, it's best to cook the carrots with minimal quantities of water, so microwaving and roasting are both excellent options.
9. Broccoli (and Other Cruciferous Vegetables)
Cruciferous vegetables require a bit of fuss, but ultimately, the variety of health benefits they offer far outweigh the time it takes to prepare them. Which foods belong to the cruciferous vegetables? Here's a short list:
All of these veggies contain sugars that may be difficult for you to digest, which is why they can cause bloating when eaten raw. This can be easily reversed by any type of cooking. Raw kale specifically also contains compounds that can prevent the absorption of iodine, which can contribute to thyroid issues, especially if you eat a lot of fresh kale. Once again, cooking destroys this harmful compound.
Apart from destroying potentially harmful compounds, however, heat can also increase the number of available nutrients in cruciferous vegetables. Most notably, cooked cabbage, cauliflower, broccoli, and brussels sprouts contain indole and other cancer-fighting compounds that can kill precancerous cells.
Enjoying tomatoes raw is fine, but if you want to reap their cancer-fighting properties, you might want to eat them cooked instead. This will increase the amount of lycopene available - a powerful antioxidant, a high intake of which has been linked to a lower risk of many diseases, among which are cancer and heart disease. It's best to combine lycopene with plant-based fats, such as olive oil, for example, this will further aid its absorption by your body.
Keep in mind, however, that it's best not to mix lycopene-rich foods, such as tomatoes and red bell peppers with foods high in iron, such as red meat, for example, as this may cancel out its benefits. We explain why that is the case in a previous article titled Tomatoes Have Anticancer Properties, BUT There’s a Catch.