Cooking methods
Now that you have your ingredients chosen and your portion sizes worked out, let’s think about the cooking method you want to use. Below is a simple guide to the nutritional pros and cons of the most common cooking methods.
Boiling
If vegetables and fruits are boiled for a long time then many of the vitamins will be lost (the most affected is vitamin C). So when it comes to boiling veg it’s best to keep it short and leave them with some crunch.
Boiling whole dishes for a long time (e.g. bone broths, stews, etc.) will have a higher amount of histamines which can cause allergic style symptoms to some people but on the whole are a good, healthy method of cooking. Boiling/poaching fish is a better way than frying to preserve omega3. When you cook tubers (potatoes/yams/pumpkins/squash), you will always increase the Glycaemic Index (GI) of that food i.e. the amount of sugar that enters the blood stream. However, boiling tubers is the best method for minimising that GI increase.
How often can I use this method?
Every day - just don’t boil the life out of your veg.
Steaming
When it comes to veg, steaming preserves more vitamins than boiling, but it has to be gently steamed or pressured cooked and the veg has to still be "crunchy" . Vitamin C is the most "delicate" one as it decays very rapidly with heat.
How often can I use this method?
Every day - just don’t steam the life out of your veg.
Grilling
Chargrilled part of foods can have toxic compounds, so should be consumed in moderation. When grilling, you want to get colour on your food for that delicious taste but it’s best to avoid charring things too much. Grilling can also affect vitamin B - in meat around 40% of it gets lost during grilling/broiling.
How often can I use this method?
Weekly
Shallow frying
/sautéing/stir frying
Despite what you might think, this is a healthy cooking method as the temperature is not too high (not as many vitamins and antioxidants are lost as in boiling) and the cooking the time isn’t too long which also helps preserve nutrients. The use of fats such as olive oil or butter can increase the bio-availability of fat based vitamins and antioxidants, such as lycopene.
How often can I use this method?
Every day
Pressure cooking
Preserves more vitamins than boiling, comparable to steaming (for example broccoli keeps 92% of vitamin C content). Legumes which are pressure cooked have a slightly higher GI than boiled ones, but can be more digestible.
How often can I use this method?
Every day
Deep frying
The high temperature of deep frying can destroy many vitamins, and frying increases the Kcal of foods. When oil is heated to a high temperature for a long period of time, toxic substances called aldehydes are formed. Aldehydes have been linked to an increased risk of cancer and other diseases. Good oils to fry with have a high smoking point, for example avocado oil (smoking point 270c).
How often can I use this method?
As a treat, 1 or 2 x month
Raw foods
Maximum amount of vitamins and antioxidants in fruits and vegetables. Obviously there’s a risk of pathogenic contamination for fish and meat so
on the whole avoid eating these raw.
How often can I use this method?
Every day
Microwaving
Can significantly increase the GI (glycaemic index) of starchy foods such as potatoes and reheated pasta.
How often can I use this method?
Try to limit and instead reheat food in a pan
Roasting/
Baking
This is a good cooking method, like with grilling, just make sure food doesn't chargrill as "black" bits can have toxic compounds, so should be consumed in moderation. Roasting temperatures can also exceed oils smoking points, altering their nutritional value (see below).
How often can I use this method?
2/3 times per week
A guide to which oils to use
Olive oil
Very high in monounsaturated fats (good for cardiovascular system). Even when heated to a high temperature for a long time, extra virgin olive oil releases a lower amount of unhealthy compounds compared with canola and vegetable oils. This is because the high levels of monounsaturated fats are more stable in high heat. Ideal for roasting, stir frying as it won't loose nutritional value.
Smoking point - 210 c
Avocado oil
Like olive oil, avocado oil is rich in the monounsaturated fat oleic acid, so is heart-healthy. In comparison to olive oil it has less omega 3, but has more vitamin E. Ideal for roasting and stir frying as it won't loose nutritional value. Can be also be used for frying as it has a very high smoking point.
Smoking point 271 c
Coconut oil
Very high in saturated fats (too many saturated fats can have a negative impact on the cardiovascular system). Can be used to sauté but only occasionally as is high in saturated fats.
Smoking point - 171 c
Sesame oil
Sesame oil is a combo of mono- and polyunsaturated fats (PUFAs) but because the PUFAs (good for cardio vascular health) are slightly higher, it's usually considered a polyunsaturated fat/oil. Can be used to sauté in Asian dishes.
Smoking point 210 c
Butter
Butter is a source of butyrate (a short chain fatty acids, essential for metabolism regulation) but is also high in saturated fats. Use to sauté occasionally as it is high in saturated fats and has a low smoking point.
Smoking point 150 c
N.B. preserve all kind of oils in a dark bottle and at room temperature to avoid fat oxidation (a process which creates toxic by-products and contributes to the food going off).