We all take cooking for granted. Whether we love to do it or prefer to eat what someone else has cooked; where food is involved, cooking in some form or other is a given.
However, somewhere way back in evolution, maybe about 1.8 million years ago, humans harnessed the power of fire, began to use that fire to cook food and everything changed.
Before cooking, we ate raw plants - berries, fruit, seeds, leaves, nuts and tubers. It required a lot of chewing and a lot of time to get through some of the more fibrous and denser ones I imagine. Even the mechanical chewing and enzymic breakdown of those plants in the body would still have left a lot of undigestible fibre over. That fibre passed to the large colon and did not provide energy to the body, but did provide excellent food for the bacteria and other microbes in the then large and diverse gut microbiome to 'feed' on.
Of course there would have been some meat or fish too, but that depended on hunting prowess and would also have required a whole lot of chewing to get down. Archaeological evidence seems to point to the large majority of the diet being made up of plants.
So what happened when we started to cook our food?
Food became easier to chew
Digestibility improved (think a cooked wheat grain versus a raw one)
Humans had easier access to more calories since food was now 'giving up' more of its carbohydrates
Potentially toxic microbes were killed off by cooking. eg salmonella in raw meat or eggs and aflatoxin in red kidney beans.
Food could be kept for longer periods once cooked, improving food security.
But here are the two most important outcomes of this new skill:
Due to increase in available energy, our brains grew bigger and started to develop.
And, the microbiome, now with less fibre/undigested carbohydrate to 'feed' on, reduced in diversity and shrank in size.
Despite representing about 2% of body mass in the average adult, our brains use up to 25% of the energy that we derive from food. Given the hard work involved in accessing and eating food in pre-cooking times, no wonder the brain wasn't able to grow any bigger or to develop! With the world of improved energy efficiency that opened up once humans could barbecue, stew and flambe to their hearts' content, our brains had the necessary fuel to get going, and that is a unique difference between humans and other animals.
The microbiome changes however, were a loss. As societies have developed and changed over thousands of years we have honed our Masterchef skills to such an extent that food has become so processed and refined and easy to eat that now in countries where a Western diet is the norm, we see the predominance of lifestyle related disease as the cause of ill health and death.
A Western style diet is characterised by high saturated fats, a lot of animal proteins, high salt and sugar- whether that is in the form of sweet sucrose or quickly digested carbohydrates such as white bread, white rice and white flour. Conversely, it is low in fresh fruits and vegetables and plant foods generally, making it low on fibre- the substrate which gut microbes love to 'eat'.
Is it all bad news?
Of course not. The benefits and the pleasures of cooking are many.
Cooking develops flavours which are delicious- caramelization, barbecuing etc.
Cooking makes more foods edible- eg potato.
Pathogens are killed by the cooking process eg Botulinum and salmonella sp.
Food preservation has been enhanced.
Foods once cooked are easier to chew.
We would never have developed modern brain power without cooking.
So what should we learn from this?
Few people would want to return to a raw food diet. In fact to do so could be dangerous or could create nutrient deficiencies. You can read more about this in my blog post about raw diets. Instead, armed with the knowledge that your bigger better brain has now obtained, you can take steps to improve your gut microbiota by increasing sources of fibre in your diet.
You could:
Eat a wide variety of fruits, vegetables and whole grains
Include legumes regularly- chickpeas, beans and lentils
Eat the rainbow - strongly coloured vegetables and fruits contain polyphenols which are important 'foods' for the gut microbes
Avoid junk food and processed foods
Cook from scratch using fresh, unrefined ingredients
Grow a garden, or just some herbs in pots!
Use a wide variety of herbs and spices in your cooking
Early life
Before a baby is born the mother's diet is important because her microbiota will be passed to the baby upon birth (in a vaginal delivery). Once born, the baby's diet and exposure to microbes (eg having a pet, going outside, getting dirty...) is quite malleable for the first two to three years. So, here is a big opportunity to influence their gut microbiome in a positive way.
In adulthood changes are possible but to a lesser degree. Start as you mean to go on and set your child up for good health and good dietary habits throughout life. Don't go mad though- babies and toddlers have a limited stomach size and so a diet of all raw fibrous plant foods is not adequate to nourish them for growth and development- remember, we've got big brains now!
Strike a balance but do avoid processed foods and include a wide variety of vegetables in particular to your child. You'll be doing them a lifelong favour.
Cooking has opened up an amazing world of variety and flavour in food to us and it has enabled us to grow bigger brains! Let's use those brains to recognise how we can eat better to create a healthy gut microbiome which will in turn have a positive influence on our health.