Frequently Asked Questions

Nutritionists typically recommend cooking methods that preserve nutrients and minimise the addition of unhealthy fats. The most beneficial methods include steaming, which retains water-soluble vitamins and minerals; grilling and baking, which require minimal added oils; boiling with minimal water to reduce nutrient loss; and poaching, which is ideal for proteins. Microwaving is also considered excellent as it cooks food quickly and retains more nutrients compared to traditional boiling. Stir-frying with small amounts of healthy oils can be nutritious when done properly.

Each method has specific applications depending on the ingredient and desired outcome. For example, steaming works best for vegetables and fish, whilst baking suits root vegetables and lean meats. Understanding when to use each technique helps create meals that are both delicious and nutritionally dense.

Steaming is superior to boiling because food doesn't come into contact with water, preventing the leaching of water-soluble vitamins like vitamin C and B vitamins into the cooking liquid. When you boil vegetables, many nutrients dissolve into the water and are discarded, resulting in significant nutrient loss—sometimes up to 40-50% depending on the vegetable and boiling duration.

During steaming, vegetables are heated by steam vapour above the water level. This gentle heat cooks food evenly whilst keeping nutrients intact within the food cells. Additionally, steaming typically requires shorter cooking times than boiling, which further reduces nutrient degradation from heat exposure.

For optimal nutrition, steam vegetables until they are just tender-crisp rather than completely soft. This maintains both nutrients and the food's natural flavour. Use a bamboo steamer, metal steaming basket, or dedicated electric steamer for best results.

Deep-fat frying is generally not recommended by nutritionists because it adds significant amounts of calories and often uses oils that become unstable at high temperatures, creating harmful compounds. However, shallow frying or stir-frying with minimal amounts of healthy oils—such as extra virgin olive oil, coconut oil, or avocado oil—can be acceptable when done properly.

The key is using the right oil for the right temperature. Extra virgin olive oil has a lower smoke point (around 160°C) and is best for lower-heat cooking or finishing dishes. Avocado oil and refined coconut oil have higher smoke points (around 200°C+) and are better suited for stir-frying. Keep frying sessions brief and use minimal oil.

Air frying is an excellent modern alternative that uses circulating hot air to cook food with little to no oil, providing a crispy texture whilst significantly reducing calorie and fat content. Many nutritionists view air frying as a practical compromise for those who enjoy fried foods.

For proteins like fish, poultry, and lean meats, the best cooking methods are gentle and involve moderate temperatures. Poaching—simmering in broth or water—keeps proteins moist and preserves amino acids whilst preventing the formation of harmful compounds that can occur with high-heat cooking. Steaming fish is particularly excellent as it retains omega-3 fatty acids and B vitamins.

Baking at moderate temperatures (around 180-200°C) is also nutritionally sound and allows for even cooking without excessive surface browning. Grilling can be healthy too, but avoid charring the protein excessively, as this creates potentially harmful compounds. Keep grilling times reasonable and use moderate heat.

For eggs, gentle cooking methods like poaching, soft-boiling, or scrambling at low temperatures preserve heat-sensitive nutrients and cholesterol structure. Avoid overcooking eggs, as extended heat exposure can diminish the bioavailability of certain proteins. The key principle is cooking proteins thoroughly enough for food safety whilst using moderate temperatures to preserve nutritional value.

Contrary to common myths, microwaving is actually one of the most nutritionally beneficial cooking methods available. Microwave radiation heats water molecules within food, cooking it quickly from the inside out. This rapid cooking minimises nutrient degradation because exposure to heat is brief. Studies show that microwaved vegetables often retain more vitamin C and other heat-sensitive nutrients than vegetables cooked on a stovetop.

The microwave is particularly effective for vegetables because it requires minimal added water, preventing nutrient loss through leaching. For example, microwaved broccoli retains significantly more vitamin C than boiled broccoli. The key is using minimal water and avoiding overcooking—monitor cooking times carefully and stop as soon as food reaches desired doneness.

One consideration is to use microwave-safe containers rather than certain plastics that might leach chemicals. Glass and ceramic containers are ideal. For maximum nutrition, microwave vegetables in covered containers with just a tablespoon or two of water, which creates steam that cooks food evenly whilst retaining nutrients.

Raw food preparation involves consuming foods without heat treatment, maintaining all heat-sensitive vitamins and enzymes. This approach is excellent for preserving vitamin C, certain B vitamins, and raw enzymes that may aid digestion. Raw vegetables, fruits, nuts, and seeds prepared by chopping, blending, or juicing offer maximum nutrient density in their uncooked state.

However, raw food preparation is not universally superior for all foods. Some nutrients actually become more bioavailable—meaning our bodies can absorb them more effectively—when food is lightly cooked. For example, lycopene in tomatoes and beta-carotene in carrots increase in availability after gentle cooking. Cooking can also break down plant cell walls, making nutrients more accessible to our digestive system.

A balanced approach combines raw and cooked foods. Nutritionists often recommend including a variety of raw vegetables and fruits in salads and as snacks, whilst also incorporating lightly cooked vegetables to optimise nutrient absorption from different food types. The goal is dietary diversity rather than adhering strictly to either raw or cooked eating.

Grains and legumes contain compounds called phytates and tannins that can inhibit mineral absorption. To optimise nutrition, nutritionists recommend soaking these foods before cooking. Soaking legumes like beans and lentils for 8-12 hours (or overnight) reduces cooking time and decreases phytate levels, allowing better absorption of minerals like iron, zinc, and calcium.

For grains like rice, oats, and quinoa, a shorter soak of 30 minutes to 2 hours can be beneficial. Sprouting—allowing grains and legumes to begin germination—further reduces anti-nutrients and increases vitamin content, particularly B vitamins. After soaking, drain the soaking water and rinse thoroughly before cooking with fresh water.

When cooking grains and legumes, use minimal water to prevent nutrient leaching. The cooking liquid should be mostly absorbed rather than drained away. Cooking methods like steaming (after initial boiling) or pressure cooking (which uses less liquid and shorter times) help preserve nutrients. Brown rice and whole grain varieties retain more fibre and micronutrients compared to refined white varieties, making them nutritionally superior choices.

Temperature and duration are critical factors in nutrient preservation. Lower temperatures and shorter cooking times generally preserve more heat-sensitive vitamins like vitamin C and folate. Most vegetables benefit from cooking at temperatures between 60-90°C (steaming) rather than boiling at 100°C. Even a few degrees difference can significantly impact nutrient retention.

The concept of "tender-crisp" cooking—stopping just as vegetables become soft enough to eat—is nutritionally ideal. This typically takes 4-6 minutes for most steamed vegetables. Overcooking vegetables (beyond 10-15 minutes of boiling) can result in nutrient loss of 30-50% or more. For leafy greens like spinach, cooking times should be minimal—often just 1-2 minutes.

Pressure cooking is worth noting as it cooks food quickly under higher temperatures, which paradoxically preserves some nutrients because the short duration limits exposure time. High-temperature, short-duration cooking (like stir-frying) follows the same principle. The key is finding the balance between cooking food thoroughly for food safety and digestibility whilst minimising nutrient loss through excessive heating.

Slow cooking involves heating food at low temperatures for extended periods, typically 4-8 hours or more. Whilst this method breaks down connective tissues in tougher cuts of meat and increases collagen conversion to digestible gelatin, the prolonged heat exposure does result in some nutrient loss. Water-soluble vitamins like B vitamins and vitamin C can degrade during extended cooking times.

However, slow cooking offers nutritional advantages in other ways. The low temperature minimises the formation of harmful compounds that form at very high heat, such as advanced glycation end products (AGEs). Additionally, for mineral-rich foods, the cooking liquid becomes nutrient-dense and is typically consumed as part of the stew, retaining minerals that would be discarded in other cooking methods. The gelatin from slow-cooked meat bones provides collagen and amino acids beneficial for joint and gut health.

To optimise slow cooking nutrition, add vegetables near the end of cooking (in the final 1-2 hours) to minimise their nutrient loss. Use bone broth or vegetable broth as the cooking liquid to enhance mineral content. Consider slow cooking as best reserved for proteins and root vegetables, whilst adding more delicate vegetables separately to preserve their nutrients.

Leafy greens like spinach, kale, and lettuce contain highly heat-sensitive nutrients, particularly water-soluble vitamins. For maximum nutrition, consuming them raw in salads is ideal—this preserves all vitamins, minerals, and enzymes. Raw greens should be washed thoroughly but not soaked for extended periods, as water immersion can leach some water-soluble nutrients.

However, light cooking of certain greens like kale and chard can increase the bioavailability of minerals such as iron and calcium by reducing oxalic acid content, which inhibits mineral absorption. Brief steaming for 1-2 minutes or wilting in a pan with minimal oil provides an excellent balance. This light cooking makes minerals more accessible to absorption whilst minimising vitamin loss.

For leafy green smoothies and juices, use a high-powered blender to break down cell walls and improve nutrient extraction. Mix raw greens with fruits containing vitamin C (like oranges or berries) to enhance iron absorption. The ideal approach is consuming leafy greens in multiple forms: raw in salads, lightly cooked as a side dish, and blended in smoothies, ensuring you capture different beneficial nutrients and maintain dietary variety.

Choosing the right oil and using it correctly is fundamental to nutritionist-approved cooking. Each oil has a smoke point—the temperature at which it begins to break down and produce harmful compounds. Extra virgin olive oil has a smoke point around 160°C and is best for low-heat cooking, finishing dishes, and drizzling over finished foods. Heating it beyond its smoke point destroys beneficial polyphenols and creates trans fats.

For higher-heat cooking like stir-frying or sautéing, use refined oils with higher smoke points: avocado oil (around 200°C), refined coconut oil (around 200°C), or light olive oil (around 200°C). These maintain stability at cooking temperatures whilst providing beneficial fats. Coconut oil contains medium-chain triglycerides that are metabolised differently than other fats. Avoid vegetable oils and seed oils high in omega-6 polyunsaturated fats, which can create inflammation when heated repeatedly.

Use oils in moderation—a light coating rather than pooling oil in the pan. For weight-conscious cooking, use oil spray or cooking spray to distribute minimal amounts evenly. Never reuse cooking oil; dispose of it after cooking. Store oils in cool, dark places to prevent oxidation. Remember that even healthy oils are calorie-dense (approximately 120 calories per tablespoon), so mindful portions are important regardless of the oil type.

Several cooking techniques should be minimised or avoided for nutritional reasons. Deep-fat frying at extremely high temperatures (180°C+) for extended periods creates trans fats, oxidised lipids, and other harmful compounds whilst adding excessive calories. Prolonged boiling of vegetables, particularly for longer than 15 minutes, results in significant nutrient loss through leaching—potentially losing 40-50% of water-soluble vitamins and minerals.

Charring or heavily blackening food through high-heat grilling or barbecuing creates heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs), compounds that may contribute to cellular stress. While occasional consumption is not typically problematic, regularly eating heavily charred foods should be avoided. Similarly, overcooking food at very high temperatures can damage proteins and create advanced glycation end products (AGEs).

Microwaving in certain plastic containers that leach BPA and other chemicals should be avoided; use glass or ceramic instead. Reusing cooking oil multiple times creates oxidised fats and should not be done. Deep-frying processed foods (like commercial frozen chips or fried snacks) combines two problematic factors: high-heat cooking and processed food ingredients. Instead, prioritise the cooking methods highlighted in previous answers—steaming, gentle grilling, baking, poaching, and light stir-frying with minimal healthy oils.