Salutaris

The way we cook, chop, soak, or ferment wholefoods can significantly affect the bioavailability of nutrients — in other words, how easily our bodies can absorb and use them. Some preparation methods can enhance nutrient absorption, while others may lead to nutrient losses. Understanding these effects allows us to get the most out of the food we eat.

Heat and Cooking: Destroying or Unlocking Nutrients

Cooking is the most obvious way preparation alters nutrient availability. Heat can destroy certain heat-sensitive vitamins, but it can also make other nutrients more accessible.

• Vitamin C: Found in citrus, capsicum, and leafy greens, this water-soluble vitamin is easily destroyed by prolonged boiling or high heat. Light steaming or stir-frying helps preserve it better than boiling. For instance, steamed broccoli retains much more vitamin C compared to boiled broccoli.
• Carotenoids: These fat-soluble antioxidants (such as beta-carotene in carrots and lycopene in tomatoes) become more bioavailable with cooking. The heat breaks down plant cell walls and releases these compounds. Tomato sauce, for example, provides more absorbable lycopene than raw tomatoes, especially when cooked with a little oil.
• Cruciferous vegetables (broccoli, kale, Brussels sprouts): Overcooking may destroy the enzyme myrosinase, which helps release cancer-protective compounds called isothiocyanates. To maximise benefits, lightly steam or sauté rather than boiling for long periods.

Chopping and Crushing: Enzyme Activation

How we cut and prepare food before cooking can also influence nutrient activity.

• Garlic: Crushing or chopping garlic activates the enzyme alliinase, which converts alliin into allicin, a compound with antimicrobial and heart-protective properties. However, heat quickly destroys allicin. To retain these benefits, crush garlic and let it sit for about 10 minutes before cooking, or add it near the end of cooking.
• Onions: Similar to garlic, chopping onions releases sulphur compounds that may support cardiovascular health. Gentle cooking preserves some of these compounds, but prolonged high heat reduces them.
• Carrots and spinach: Cutting or pureeing can increase carotenoid bioavailability by breaking down plant matrices, making nutrients easier to absorb once eaten with fat (e.g., olive oil or avocado).

Soaking and Sprouting: Reducing Anti-Nutrients

Many plant-based foods contain compounds that can reduce nutrient absorption, often called “anti-nutrients.” While not inherently harmful, they can bind minerals like iron, zinc, and calcium. Traditional preparation techniques such as soaking, sprouting, and fermenting reduce these compounds.

• Legumes (beans, lentils, chickpeas): They contain phytic acid and lectins, which can reduce mineral absorption and cause digestive discomfort. Soaking legumes overnight and then cooking them thoroughly reduces these compounds, improving digestibility and mineral availability.
• Nuts and seeds: Soaking or lightly roasting can reduce phytic acid, making magnesium, zinc, and iron more accessible. Sprouting seeds (like alfalfa or mung beans) also boosts vitamin C levels.
• Whole grains: Soaking and fermenting grains (as in traditional sourdough bread making) breaks down phytic acid and enhances mineral absorption. This is why sourdough bread is often more digestible than regular bread.

Pairing with Fats and Acids: Boosting Uptake

Sometimes the secret to nutrient absorption isn’t just in the cooking but in what foods we pair together.

• Fat-soluble vitamins (A, D, E, K) and carotenoids: These require dietary fat for absorption. For example, adding avocado to a spinach salad, or cooking carrots in olive oil, increases the absorption of beta-carotene.
• Iron: Plant-based (non-heme) iron found in beans and spinach is less easily absorbed than animal-based (heme) iron. Pairing these foods with vitamin C-rich ingredients (like lemon juice or capsicum) enhances iron uptake. For example, lentil salad with lemon dressing is a nutrient-smart combination.

Fermentation: Enhancing Digestibility and Nutrient Content

Fermentation is one of the most powerful preparation methods for improving nutrient bioavailability.

• Soy products: Fermentation reduces anti-nutrients and increases bioactive compounds. Tempeh and miso provide more accessible protein and minerals compared to unfermented soybeans.
• Cabbage (sauerkraut, kimchi): Fermentation not only enhances vitamin C and B vitamins but also introduces probiotics that benefit gut health, further supporting nutrient absorption.
• Dairy (yoghurt, kefir): Fermentation breaks down lactose, making it easier to digest, while also enhancing levels of certain B vitamins.

Practical Tips for Maximising Nutrient Benefits

1. Use gentle heat: Steam or sauté vegetables to preserve heat-sensitive vitamins.
2. Cut smartly: Chop or crush garlic and onions to activate beneficial enzymes before cooking.
3. Soak or sprout: Reduce anti-nutrients in legumes, nuts, seeds, and grains for better mineral absorption.
4. Pair foods wisely: Combine fats with fat-soluble nutrients and vitamin C with plant-based iron.
5. Embrace fermentation: Include foods like sauerkraut, tempeh, or kefir for enhanced digestibility and nutrient value.

Final Thoughts

Wholefoods naturally offer a wealth of nutrients, but preparation can make the difference between simply eating nutrients and absorbing them. A balance of raw and cooked foods, smart food pairings, and traditional preparation techniques like soaking and fermenting all work together to unlock the full nutritional potential of your meals. By paying attention not just to what you eat, but also to how you prepare it, you can make your diet far more nourishing.

Nutrient Bioavailability Quick Guide

Cooking

• Steam > Boil: Preserves vitamin C & B vitamins.
• Cook tomatoes & carrots: Heat boosts lycopene & beta-carotene.
• Light steam crucifers: Avoid overcooking to keep isothiocyanates.

Cutting & Crushing

• Garlic: Crush, wait 10 mins → activate allicin. Add at end of cooking.
• Onions: Chop to release sulphur compounds.
• Puree spinach/carrots: Breaks down cell walls → more carotenoids.

Soaking & Sprouting

• Legumes: Soak overnight → reduces phytic acid & lectins.
• Nuts & seeds: Soak/roast → more available magnesium & zinc.
• Whole grains: Ferment (sourdough) → improved iron absorption.

Pairing Foods

• Fat-soluble nutrients (A, D, E, K + carotenoids) → eat with healthy fats (avocado, olive oil).
• Plant iron (beans, spinach) → pair with vitamin C (lemon, capsicum).

Fermentation

• Soy (tempeh, miso): More digestible protein & minerals.
• Cabbage (sauerkraut, kimchi): Extra vitamin C + probiotics.
• Dairy (yoghurt, kefir): Easier digestion + B vitamins.

Here’s a quick and easy recipe to include some fermented food into your diet.

Homemade Fermented Cabbage (Sauerkraut)

Ingredients

• 1 medium green or red cabbage (about 1–1.5 kg)
• 1–1.5 tablespoons sea salt or Himalayan salt (non-iodised)
• Optional: caraway seeds, juniper berries, garlic, or chilli for flavour

Equipment

• Large mixing bowl
• Sharp knife or mandoline slicer
• Clean glass jar (1–2 L capacity) with lid (a fermentation weight or small jar of water helps)

Method

1. Prepare the cabbage
   • Remove the outer leaves and set one aside.
   • Slice the cabbage finely (shredded strips).
2. Massage with salt
   • Place shredded cabbage in a large bowl.
   • Sprinkle salt evenly over it.
   • Massage and squeeze the cabbage for 5–10 minutes until it softens and releases liquid (this becomes the brine).
3. Pack into jar
   • Transfer cabbage and liquid into the jar, pressing it down firmly with your fist or a spoon to remove air pockets.
   • The cabbage should be fully submerged under its brine.
4. Add weight
   • Place the reserved cabbage leaf on top and add a fermentation weight (or a small clean jar filled with water) to keep the cabbage submerged.
5. Cover & ferment
   • Loosely close the jar lid (or use a fermentation airlock if available).
   • Place the jar at room temperature (18–22°C is ideal) away from direct sunlight.
6. Fermentation time
   • Let it ferment for 5–7 days for a mild flavour, or up to 3–4 weeks for a stronger, tangier kraut.
   • Check daily: press cabbage down if it rises above the liquid, and taste for your preferred sourness.
7. Store
   • Once ready, seal the jar tightly and refrigerate. Sauerkraut keeps for several months in the fridge.

Tips for Success

• Submersion is key: Keep cabbage under brine to prevent mould.
• Scum or bubbles: Harmless; skim off if needed.
• Flavour options: Add grated carrot, beetroot, ginger, or spices during step 2.

Image by Freepik