I can vaguely remember my parents enthusing about a book called Man alive, you’re half dead by Dr Daniel Munro which was supposed to be the ultimate answer to weight loss back in the day.
Nowadays the public often enquire about the so-called "food combining theory", which states that proteins and carbohydrates should not be eaten together, and fruit should be eaten on its own. When I hear these theories about "wrong combinations" of foods causing acidity and weight gain, I must admit that I tend to suffer from déjà vu.
But as humans we do tend revisit theories even ones that apparently do not work. After all if the food combining theory had worked 30 years ago and people had managed to lose masses of weight by only eating carbs at one meal and only eating proteins at another, then we would by now all be applying the principles of food combining and no one would suffer from overweight anymore.
Read: Tim Noakes on carbohydrates
A mix of macronutrients
One of the reasons why it is practically impossible to apply the theory of food combining effectively, is that most foods are a combination of macronutrients (protein, carbs and fats). Notable exceptions to this rule are sugar which is pure carbohydrate, oils and lard which are all fat, and egg white which is more or less 100% protein (and water). Every other food is a mixture of protein, carbohydrate and fat (Pearce, 2011).
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Man - the omnivore
Human beings developed as omnivores. According to the Oxford Dictionary the term “omnivorous” refers to "feeding on many kinds of food, esp. both on plants and flesh". We are equipped physiologically to eat a mixture of plant and flesh foods and our digestive systems are adapted to handling everything from proteins to insoluble dietary fibre. If we were herbivores (plant eaters), we would not be able to digest meat and other protein foods derived from animals. Conversely if we were carnivores, we would struggle to digest plant material.
The supporters of high-protein diets and Dr Munro who announced in 1940, that “We cannot chew our cud” (Peskin, 2012), state that the human digestive tract is more similar to the digestive tract of a lion than of a lamb. But the colon, for example, contains millions of beneficial microorganisms that digest high-fibre carbohydrates and produce short-chain fatty acids, vitamin K and B vitamins, to name but a few essential functions of our gut which are predominantly dependent on us eating plant material.
Conversely anyone who bans all "foods from animals" (milk, dairy products, eggs, meat, fish), needs to explain why the human body requires nutrients such as vitamin B12, iron, zinc and calcium which are found most abundantly in high-protein or flesh-type foods. Yes, you can obtain your daily calcium requirement from broccoli, but you would need to eat 2.6kg per day to ingest the necessary 1200 mg of calcium. Vitamin B12 is even more difficult to obtain from an exclusive plant diet as this nutrient is only found in foods derived from animals. A lack of vitamin B12 can cause pernicious anaemia and may also be linked to heart disease and mental deterioration in old age.
So if we humans are designed to eat proteins, carbs and fats then trying to separate these macronutrients so as not to "combine" them in a given meal does not appear to be logical.
Busy digestive tract
The gastrointestinal tract is always active and capable of digesting any food that comes its way. This means that the body will secrete enzymes to digest foods depending on what combination of macronutrients such foods consist of, not the other way round (Pearce, 2011).
There is also no proof that eating all three macronutrients in the same meal will lead to increased "acidity". Our bodies are well equipped to control their pH or acid-alkaline balance within a tight range. Factors that can affect the body’s pH and upset the acid-alkaline balance are illnesses such as kidney disease and lack of essential electrolytes like potassium due to excessive water intake or loss (e.g. diarrhoea, vomiting, drinking more water than required, etc).
“But my friend applied the principles of food combining and lost lots of weight!” is a statement I hear quite often. In such cases, it is probable that the person in question has lost weight because she gave attention to what she was eating, and not because she tried to eat carbs at one meal and protein at another.
Any change in a person’s basic diet is capable of causing weight loss if it makes that person conscious of what he is eating and/or reduces energy intake.
For example, if you eat only carbs like bread at one meal minus any fats or fatty proteins, then your energy intake for that meal will automatically be lower and over time you will lose weight.
Variety is vital
The first and most important Food-Based Dietary Guideline for South Africans is "Eat a variety of foods". The reason why this guideline was formulated, was to ensure balanced nutrition without undue emphasis of any one food or group of foods. It is literally a practical application of "what you lose on the swings, you make up on the roundabouts". Just think of all the millions of foods that modern man can select for his diet. One food will be rich in iron, but contain a pesticide residue, while another food will be rich in B vitamins to boost your liver function so that you can render the offending pesticide harmless.
There is no real scientific evidence that supports the idea of food combining and applying these principles too strictly may even lead to a lack of nutrients in your diet. Rather eat a variety of foods every day and at every meal to sustain good health. And if you need to lose weight, then reduce your energy intake and increase your energy output while still eating a varied diet.
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(References: Pearce J (2011). Healthy Food. Fact of fiction: Don’t eat protein and carbs together. Mahan LK et al, 2011. Krause’s Food and the Nutrition Care Process. 13th Edition. Elsevier Saunders, USA; Peskin B (2010). They ignored this back in 1940, too! June 9, 2010. http://brianpeskinonline.wordpress.com)