Should it be raw or cooked? Roasted or sprouted? What about lectins, oxalates, goitrogens, and more?
Simple questions, complex responses. To begin, there are various factors to consider in the raw vs cooked question – digestive tolerance, quantity, and the potential role of anti-nutrients. Some of you may find that you simply tolerate cooked, or slightly cooked foods more easily than raw foods. Generally speaking, the cooking process helps break down the cellular walls of plant foods that allows for easier digestibility. In regards to quantity, think spinach. If you place 20 cups of spinach in a pot and wilt it briefly, it shrinks down to the tiniest amount of spinach. So, cooked spinach will be much higher in nutrients and phytochemicals than raw simply based on volume density.
Raw vegetables have been shown to have a statistically significant inverse relationship with several types of cancers, particularly oral, pharyngeal, laryngeal, esophageal, and gastric cancers. While cooking can alter the availability of some nutrients, destroy digestive enzymes, and change the structure and digestibility of food, this effect can go both ways.
Which vegetables/compounds are nutritionally best raw?
Garlic/Onions - The garlic and onion family contain sulfur compounds and cancer-preventive substances that may be lost or altered when cooked. Allicin, a beneficial sulfur compound that enhances both the flavor and health benefits of garlic and onions, is destroyed during cooking, particularly high heat cooking – frying garlic and/or onions leads to a greater loss of allicin than microwaving (not that I microwave garlic/onions, just what the research has shown). For garlic, implement the "10-minute garlic rule" - allow chopped or crushed garlic to sit for about 10 minutes before cooking or consuming it. This practice maximizes the formation of allicin. To release its most potent flavor, crush or mince garlic very finely. Note that acid, such as that present in vinegar or lemon juice, also denatures allinase, preventing allicin being made. So when making a garlic vinaigrette, utilize the 10-minute garlic rule before adding to the vinaigrette.
Anthocyanins are plant pigments that offer protective antioxidant properties. Some common dietary sources of anthocyanins indicated by their blue-purple color include blueberries, blackberries, pomegranate, purple cabbage, eggplant, and purple sweet potatoes. Cooking can significantly impact the anthocyanin pigments in vegetables. Anthocyanins are significantly degraded by moist-heat cooking methods such as pressure boiling and pressure steaming. Pressure steaming may reduce the anthocyanin content to 1% of their original concentration. Dry-heat methods, on the other hand, like microwaving and baking, can increase anthocyanin levels, with microwaving increasing them to 351% and baking to 295% of their original levels.
Leafy Greens - The consumption of raw leafy greens can help preserve vitamins A, C, and K, and B vitamins like folate, making them a nutrient powerhouse. That said, remember volume density. Cooked greens are loaded with protective phytochemicals.
Cruciferous Vegetables (benefits of raw & cooked) – This family could be included in the best raw and best cooked category depending on the variable assessed. Cooking can significantly reduce the goitrogenic properties of food, particularly in cruciferous vegetables like cabbage, broccoli, and Brussels sprouts. Due to the goitrogens, eating a lot of raw cruciferous vegetables can keep your body from using iodine properly to make the thyroid hormone and stifle your thyroid's natural function. Additionally, cooked cruciferous vegetables have been shown to significantly reduce DNA damage induced by aflatoxin B1, compared to raw cruciferous vegetables. Furthermore, cooked cruciferous vegetables have been associated with increased telomerase activity in CD8+ T cells.
Conversely, myrosinase, is a key enzyme needed to convert glucosinolates into cancer-fighting and heart healthy compounds such as sulforaphane. And raw cruciferous vegetables have a much greater myrosinase content than cooked. Fortunately, steaming or quickly stir-frying these vegetables preserves both the vitamin C and myrosinase to some extent. And sprouting cruciferous vegetables is an excellent option to concentrate sulforaphane. Note that myrosinase is activated when cruciferous vegetables are crushed or chewed. Chopping broccoli and letting it sit for a minimum of 40 minutes before cooking also allows myrosinase to activate.
Which vegetables are nutritionally best cooked?
Carotenoid-rich vegetables – Among others, these include carrots, rich in beta carotene, tomatoes, rich in lycopene, and spinach, rich in lutein.
Carotenoids are fat-soluble compounds in which the heat breaks down the cellular walls, releasing more carotenoids for absorption. However, some cooking methods can also reduce carotenoid content. For example, high-heat frying and microwaving can degrade carotenoids. Stewing foods rich in carotenoids increases their carotenoid content. Microwaving results in a reduction to 79% of the original carotenoid levels, while frying reduces the content to 59%. Conversely, stewing can increase carotenoid levels to 133% of their original concentration. While both raw and cooked carrots offer benefits, cooked carrots are generally considered more nutritious, particularly for beta-carotene absorption. Raw carrots retain more fiber and vitamin C, but less beta-carotene compared to their cooked counterparts.
Tomatoes are rich in vitamins A, C, and B6, and the most potent source of lycopene. They can be eaten raw or cooked, depending on preference. The vitamin C content will be greater in raw tomatoes, however, the lycopene present in tomatoes, which enhances immunity, is better absorbed when they are cooked. Although cooking tomatoes reduces their vitamin C content by 29%, their lycopene content increases by more than 50% within 30 minutes of cooking.
Anti-Nutrients
Lectins are proteins that bind to carbohydrates. They’re considered to be anti-nutrients as they can interfere with nutrient absorption. Active lectins are found in raw plants. When foods that contain lectins are boiled, baked, soaked, and/or pressure-cooked, the lectins are deactivated. Fermentation, sprouting and removing peels and seeds can also reduce the amount of active lectin in plant foods. Beans, legumes, and grains are known to be the richest sources of lectins and since we don’t consume those raw, I don’t find lectins to be problematic for most people.
Another common antinutrient are phytates or phytic acid. Phytic acid can bind to minerals like iron, zinc, calcium, and magnesium, potentially reducing their absorption. However, this effect is often negligible when eating a variety of foods and may be more significant in populations with unbalanced diets, particularly those relying heavily on a single source of grain or those with inadequate iron and zinc intake. Soaking, sprouting, fermenting, and cooking helps to reduce the phytic acid content in grains and legumes.
Oxalates are water-soluble compounds found in many plant foods. Oxalates can bind with calcium and other minerals and have the potential to form oxalate crystals that can lead to kidney stones. Similar to other antinutrients, oxalates can be reduced by various methods, including soaking, sprouting, boiling, and steaming. For example, sprouting kidney beans can significantly reduce the total oxalate content by up to 80%. Note that 1 cup cooked spinach contains more oxalates than 1 cup raw spinach; this is not because raw has more than cooked, but due to the volume density of how much more spinach is in 1 cup cooked spinach. For most individuals, avoiding oxalates is not necessary. If you have a concern of oxalate kidney stones, it would be wise to avoid the richest dietary sources of oxalates – spinach, chard, and rhubarb.
Nuts – Raw vs Roasted vs Sprouted
Raw nuts are often considered beneficial due to their high phenolic content and antioxidant activity, which can be altered by processing methods like roasting. At the same time, roasting almonds and walnuts can enhance the bioavailbility of certain phenolic compounds. Both raw and roasted nuts contain significant polyphenols, which contribute to their antioxidant properties. Roasting has little effect on the total polyphenol content in most nuts. Phytic acid and lectins, two types of anti-nutrients, are reduced or neutralized when nuts are roasted, improving mineral absorption and digestion. Conversely, raw pistachio nuts have slightly higher amino acid digestibility compared to roasted ones, although both forms are considered good protein sources. Both raw and roasted nuts can improve cardiovascular health markers. For instance, roasted hazelnuts maintain similar cardioprotective properties as raw ones.
Sprouted nuts are an excellent option. The sprouting process activates enzymes and helps to break down antinutrients, improving digestibility, enhanced nutrient absorption, and potentially reduced inflammation. Sprouted nuts exhibit a reduction in oxidative damage due to increased activity of antioxidant enzymes like superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase. This helps in balancing reactive oxygen species and reducing membrane lipid peroxidation.
Making your Own Sprouted Nuts/Seeds
Place raw almonds in a bowl covered with a few inches of water. Cover with a paper or cloth towel and let them soak for 8–12 hours.
Drain, rinse, and replace the water a few times during this period — once every 3 hours.
Using a colander, drain the water from the soaked almonds and transfer them to a shallow bowl with a breathable lid to allow for air exposure.
Add 1–2 tablespoons of water to help keep them moist.
Allow the almonds to sprout for 3 days.
Transfer them to a breathable container in the refrigerator, where they will keep for 7 days. Alternatively, you can store them in the freezer or dehydrate them to make crispy sprouted almonds.
If you’re seeking easier to digest nuts and seeds, but not quite up to sprouting your own or paying premium for sprouted nuts/seeds, consider soaking and dehydrating nuts as noted below.
Easier to Digest Nuts
Almonds: soak for 6–12 hours, dehydrate for 15 hours
Brazil nuts: soak for 12 hours, dehydrate for 18 hours
Cashews: soak for 3–4 hours, dehydrate for 15 hours
Hazelnuts: soak for 8 hours, dehydrate for 12 hours
Macadamia nuts: soak for 4 hours, dehydrate for 12 hours
Pecans: soak for 4–6 hours, dehydrate for 8–10 hours
Pine nut: soak for 3–4 hours, dehydrate for 6–8 hours
Walnuts: soak for 6–12 hours, dehydrate for 12 hours
Summary
Hopefully, I have not thoroughly confused you on this topic. Bottom line – some nutrients and phytochemicals are higher in raw foods and others in cooked foods. If your digestion allows, aim for a balanced diet that includes both raw and cooked foods.
Learning the ins and outs of our foods is helpful and also confusing. If feeling overwhelmed, focus on using your food to nourish you. Do your best to not get bogged down with the details.
In Health,
Natalie