Do you know your onions?

Did you know that you can vastly improve the nutrient density of your fruit and vegetables by how you prepare, store and serve them? Harvard Medical School trained Dr. Akil Palanisamy teaches us how.

We all know that on the level of soul and taste, there is a world of difference between freshly pulled broccoli or a head of lettuce from your garden and ones that have been transported for miles in plastic or stored on a supermarket shelf for days. Unsurprisingly, there is also a world of difference in their nutrient density.

“Vegetables are alive. After harvest they continue to consume oxygen and produce carbon dioxide. They are breathing,” explains Dr. Palanisamy. “Start thinking about your vegetables as living things – because in fact they are, and this will remind you to pay attention to how they are stored.”

Leafy green vegetables have what is known as a ‘rapid respiratory rate’ and lose their nutrients quickly. If you pull a lettuce from your garden, you know you have to use it immediately – even within a couple of hours it will start to look a bit sorry for itself. The leaves still need to breathe but, with too much oxygen they will respire quickly and this is the important point, use up all their anti-oxidants in the process.

You can double the amount of anti-oxidants in your leafy greens by ‘wounding’ them or tearing them up into smaller pieces before you put them in the fridge. “The plant responds like it is being attacked by an insect and produces a burst of phytonutrients to fend off its intruder. It’s like eating four servings instead of two.” reveals Dr. Palanisamy. “This process hastens their decay, so you will need to eat them within two days.”


Eat all greens with good fats, especially extra virgin olive oil as this makes the nutrients in them more bio-available. Soybean oil (check this is not in your salad dressings) is seven times less effective in transporting the nutrients.

Vegetables with a High Respiratory Rate

(which need to be consumed quickly and should not be bought too far in advance)

Broccoli – has high levels of cancer-fighting compounds called sulphorophanes. Raw broccoli has 25 times more than the cooked version. Therefore, lightly steam or flash fry. Do not boil it.

Brussels sprouts – have suffered from appalling cooking and are delicious when properly prepared. What is more, they kill more human cancer cells in the lab than any other crucifer. Amanda’s tip – trim the outer layers and steam the sprouts for 6-7 minutes. Be sure to time this and don’t guess. The sprouts should be firm and crisp and not soft and mushy. Toss the sprouts in homemade lemon, garlic and hazelnut butter.

Kale – “Kale has the highest density of phytonutrients per gram than any other vegetable,” says Dr. Palanisamy

Medium Respiratory Rate 

Cauliflower – is high in the cancer fighting compounds glucosinolates. Eat within one week.

Low Respiratory Rate

Cabbage – red cabbage has six times the antioxidants of white cabbage. It will keep for up to a couple of weeks. All root vegetables have a low respiratory rate and store well without loss of nutrients. Did you know that you can lower the glycaemic load of potatoes? Dr. Palanisamy recommends cooking the potatoes and chilling them for 24 hours before re-heating them. “This transforms the starch into ‘resistant starch’ which is digested and absorbed more slowly and also benefits your microbiome.”

Sweet potatoes – have a lower glycaemic load and more anti-oxidants than white potatoes. “The skin is more nutritious than the flesh, so eat them whole,” advises Dr. Palanisamy.

Carrots – “Carrots are better for you when cooked and eaten with oil,” explains Dr. Palanisamy. “Heat breaks down tough cell walls and makes nutrients more bio available. Beta-carotene is a fat soluble nutrient that needs to be eaten with fat for maximum absorption.”

“Once a carrot is cut it begins losing nutrients,” he continues. “Cooking a carrot whole and then cutting it into pieces preserves 30% more nutrients. Cooked uncut carrots with olive oil give you eight times the amount of beta-carotene than raw baby carrots.”

Beetroot Greens – the tops of beetroots have fifty times the anti-oxidant activity of carrots. “They are the richest source of betaine, a phytochemical that supports the liver and protects cells from environmental stress.”

Garlic – did you know that you need to wait ten minutes after crushing garlic before eating it or cooking with it to get the maximum health benefits? Those tiny cloves pack a huge anti-bacterial, antiviral and anti-cancerous punch. “Allicin, the main sulphur-based active ingredient, is made in garlic when two substances in garlic that are stored in separate compartments within the clove are mixed together. However, it takes about ten minutes for this process to occur.”

Onions – spring onions have 140 times more phytonutrients in them than a white onion! Shallots have six times the nutrients. Cooking onions increases both the level and bio-availability of the antioxidants they contain.

Tomatoes – tomatoes are rich in lycopene which is hypothesised to reduce the risk of some cancers and heart disease. Cherry tomatoes having up to twelve times more lycopene than larger varieties. Tomatoes cooked in olive oil for thirty minutes can have double the lycopene level as cooking breaks down the cell wall and makes the lycopene more bio-available.

Palm Beach ChicFor a wealth of further information and great dietary advice to burn fat, increase energy and reverse disease consult The Paleovedic Diet by Dr Akil Palanisamy, £16.99, Published by Skyhorse Publishing New York. Buy here