Raw vs Cooked
Palatability, digestibility and sustainability

The idea of eating a diet of pure, unprocessed, uncooked foods holds allure for many, so how does it weigh up nutrition-wise, asks dietitian Amy Giannotti – and is it sustainable?

More and more of us are now very aware that the food we eat plays a significant role in our health, performance, mood and body composition. Many are less conscious, though, of how our behaviours and attitudes around food also impact these outcomes.

We are continually bombarded with information on how we should and shouldn’t eat, so it’s not surprising that many of us – and especially our clients – are confused, stressed and anxious about food.

Here are some very sobering facts about dieting:

  • 90% of females and 68% of males aged 12 to 17 years old have been on a diet of some kind (Eating Disorders Victoria, 2016)
  • Dieting is the number one risk factor for eating disorders, a serious mental illness with the highest mortality rate of any psychiatric illness (Eating Disorders Victoria, 2016)
  • Weight loss following lifestyle intervention is maximal at 6-12 months. Regardless of the degree of initial weight loss, most weight is regained within a 2-year period and by 5 years the majority of people are back at their pre-intervention body weight (National Health and Medical Research Council, 2013).
  • Those that yoyo diet, resulting in ‘weight cycling’, have poorer health biomarkers (hypertension, insulin resistance and dyslipidemia), increased morbidity and greater mortality risk than those that have never dieted (Bacon & Aphramor, 2011).
  • Adults with eating disorders experience significantly higher levels of anxiety disorders, cardiovascular disease, chronic fatigue, depressive disorders, neurological symptoms and suicide attempts (Eating Disorders Victoria, 2016).

So what is a ‘healthy’ diet?

As a dietitian I have worked with countless individuals, and have arrived at my own definition of what constitutes a healthy diet – both in terms of physical and social wellbeing:

1. You are intuitive to your hunger and fullness cues.

You can recognise when you are getting hungry and you feel free to eat. No food rules dictate when you should and should not eat, you listen to your body. You can also recognise when you are satisfied and can stop if you choose to. You may find yourself ‘starving’, ‘hangry’ or ‘overfull’, but this is only occasional and not problematic because you can recognise these symptoms and how they came about. Being attuned to your hunger and fullness cues, and acting upon them, will help you arrive at your most healthy weight.

2. Your eating behaviours are flexible.

You are able to travel the world, try new foods and cuisines and eat out with friends and family. Your diet or food rules do not dictate your social life and social health.

3. Your food intake provides your body with all of its essential nutrients.

You eat from all five food groups (fruit, vegetables, grains/pseudo grains and cereals, lean meat/alternatives and dairy/alternatives). Gender, body size, age and activity levels are all factors that affect the amount of energy and certain nutrients we need. The Australian Guide to Healthy Eating and the Recommended Food Groups is a great ‘guide’ to help tick these boxes.

We don’t need to look far to find a diet promising weight loss and a better life. Before jumping on the next diet, however, it is wise to consider my definition of a healthy diet and ask yourself whether it will support your health and your core values – and whether it’s sustainable. If not, you’re most likely setting yourself up for feelings of failure, regret, frustration and poor health outcomes.

In the raw

The raw food diet is on trend, likely recently assisted by celebrities such as Demi Moore and Venus Williams claiming to have followed the ‘raw movement’ at some point. Weight loss, improved health, enhanced energy and sporting performance have all been claimed effects of adhering to this approach to nutrition.

What we know about dieting and weight loss

At this juncture it is prescient to consider a few certain truths about dieting and weight loss, and how these might relate to a raw food diet.

  • An energy deficit is an absolute requirement for weight loss.
  • An energy deficit can be created in many ways.
  • A healthy weight loss occurs when the dieter is still able to meet their nutrition requirements of over 35 essential nutrients (the body’s key tools).
  • When someone loses weight they need to consume fewer calories to maintain their weight loss.
  • A healthy and sustainable weight loss is when someone loses weight gradually over a period of time (e.g. 0.5-1.0kg per week), is still able to meet their nutrition requirements (not malnourished) and changes their lifestyle habits to maintain weight loss.

Where did the raw food diet come from?

The raw food movement probably began way back in 1850 with Sylvester Graham, a Presbyterian minister who started the American Vegetarian Society. A later significant player in the raw food movement was Chicago medical doctor, Edward Howell, who wrote a book called The Status of Food Enzymes in Digestion and Metabolism. Howell claimed that the food we eat contains natural enzymes to digest our food and that the heat of cooking destroyed these enzymes, therefore making the food harder for the body to digest.

Raw food enthusiasts also claim that cooking strips fruit and vegetables of their vital nutrients, and makes them harder for our bodies to metabolise, so that cooked foods are supposedly less healthy than raw foods.

Recent food and nutrition science tells a different story. We now know that the body contains these enzymes, although digestive ability varies between individuals.

Will eating raw make you feel better?

Simple question, not quite so simple answer. Eating raw might make you feel better, but not necessarily because you’re eating raw – rather because the restrictive nature of the raw food diet may have reduced or eliminated a food that your body was struggling to digest – regardless of whether or not it’s cooked.

Irritable bowel syndrome (IBS), with symptoms including bloating, pain, gas, diarrhoea and constipation, is common in Australia, with 1 in 5 suffering. These symptoms are commonly blamed on gluten or lactose, but many people who think they are intolerant actually aren’t. The culprit in many cases might actually be FODMAPs (Fermentable Oligo-, Di- and Mono-saccharides and Polyols), a group of carbohydrates. They are food for the bacteria in our gut, so when they are fermented in the intestines they increase the volume of liquids and gas in the intestines causing cramping, gas, bloating, diarrhoea or constipation.

Most people don’t have any trouble digesting the level of FODMAPs found in a standard diet, but others can struggle to absorb FODMAPs. FODMAP foods also have a cumulative effect, meaning you might not get symptoms every time you eat a particular food because it can depend on the types and accumulation of foods. This is where self-diagnosis often goes wrong, eliminating unnecessary food groups.

It is true that some people have food intolerances that may cause them to have trouble metabolising certain foods, but whether they are cooked or not makes little difference.

Impact of cooking on nutrient composition, digestibility, taste, safety and health

Nutrients are the body’s key tools, and they can be broken down into macro and micronutrients. Macro are our energy yielding nutrients (carbohydrate, protein and fat) and our micronutrients include all our vitamins (e.g. vitamin C) and minerals (e.g. iron and calcium).

Vitamins are further broken down into fat soluble (Vitamin A, D, E and K) and water soluble vitamins (the rest, e.g. Vitamin C).

So what does cooking do to these nutrients?

High intake of char-grilled, burnt and barbecued food has been linked to an increased risk of cancer, due to the formation of carcinogenic substances called polycyclic aromatic hydrocarbons (PAHs) (Phillips, 1999).

Evidence exists that eating extreme amounts of browned or roasted food, which contain high levels of compounds called advanced glycation end-products (AGEs), could contribute to an increased risk of developing age-related diseases such as cataracts, Alzheimer’s disease, heart disease and stroke (Uribarri, et al., 2010). But, to reiterate, these correlations relate to cases of very high consumption, so your mum’s Sunday roast isn’t off the menu.

Vitamins have the greatest instability in food. The losses vary widely according to cooking method and type of food. Vitamin degradation depends on specific parameters during the culinary process, e.g. temperature, oxygen, light, moisture, pH, and, obviously, length of exposure. The most unstable vitamins during cooking processes are retinol (vegetable boiling, 33% retention), vitamin C (the most damaging factors are cooking and oxidation), folate (leaching into the cooking water, 40% retention), and thiamin (cooking, retention 20-80%). Niacin, biotin, and pantothenic acid are quite stable (Lešková, et al., 2009).

Vitamin C is abundant in fruit, especially citrus fruit, and vegetables, and, of course, fruit is most often eaten raw. Retinol (vitamin A) is found in some fish, milk, cheese and liver. Folate is found in asparagus, cooked spinach, romaine lettuce, Brussels sprouts, beets, broccoli, corn, green peas, oranges, bread, enriched pasta, wheat germ, liver, dried beans, soybeans, chickpeas, lentils, sunflower seeds and flaxseeds. Thiamin (Vitamin B1) is found in whole grains, enriched grains, liver, pork, dried beans, nuts and seeds.

Heating most foods improves their digestibility. Heat breaks down the physical barriers in the food, for example, husk and thick skins, and bursts open the cells so that the contents are more accessible while also breaking down toxins or chemicals.

Although some losses are found in cooking, these nutrients are often easy to attain when eating a ‘balanced diet’ that includes the recommended amounts of food from each of the five food groups (National Health and Medical Research Council, 2015).

And despite nutrient losses through cooking, most vegetables still retain substantial concentrations of their vitamins and minerals, particularly if you use cooking techniques that don’t require extreme temperatures and long cooking times. Steaming, blanching, simmering and stir frying are preferable to boiling them in big pots of water (Nutrient Data Laboratory et al. 2007). Aim to retain the vegetables' vibrant colours rather than overcooking them until they are brown!

Another aspect, of course, is how appealing the food is to eat. The more tempting something is, the more of it we are likely to consume. Palatability is often improved with cooking, making meeting our recommended serves from the food groups, and hence all of our essential nutrients, more achievable. The latest Australian Health Survey showed that only 6.8% of adults meet their recommended daily five serves of vegetables!

Food safety and hygiene is also a consideration, as cooking kills most of the bacteria responsible for food poisoning.

Eating from each of the five food groups can be difficult when following a raw diet, increasing your risk of nutrient deficiencies. A raw food diet will struggle to provide adequate calcium, iron, zinc and omega 3, impacting immunity, cardiovascular health and bones, as well as the health of skin, hair and nails.

Considerations

When thinking about a change of diet, it’s important to consider your core values, health and goals. There is no one-size-fits-all way to eat. We all have different lifestyles, goals, likes/dislikes, access to food, cooking skills, financial situations and circumstances. While the idea of eating in a ‘clean and natural’ manner may be appealing, a raw food diet may not cure what ails you.

If you have, or suspect you may have, any diagnosed medical conditions, allergies or intolerances, have a specific training or body composition goal, or feel you are suffering from an unhealthy relationship with food, talk to an expert. Click HERE for a list of Accredited Practicing Dietitians.


References

Bacon, L. & Aphramor, L., 2011. Weight Science: Evaluating the Evidence for a Paradigm Shift. Nutrition Journal, 10(9), pp. 1-13.
Eating Disorders Victoria, 2016. Eating Disorders Victoria. [Online]
Available at: https://www.eatingdisorders.org.au/key-research-a-statistics
[Accessed 14 November 2017].
Lešková, E. et al., 2009. Vitamin losses: Retention during heat treatment and continual changes expressed by mathematical models. Food Composition and Analysis, 19(4), pp. 252-276.
National Health and Medical Research Council, 2013. Clinical practice guidelines for the management of overweight and obesity in adults, adolescents and children in Australia, Melbourne: National Health and Medical Research Counci.
National Health and Medical Research Council, 2015. Food Essentials. [Online]
Available at: https://www.eatforhealth.gov.au/food-essentials/how-much-do-we-need-each-day/what-serve
[Accessed 16 November 2017].
N. D. L., B. H. N. R. C., A. R. S. & U. D. o. A., 2007. USDA Table of Nutrient Retention Factors. [Online]
Available at: https://www.ars.usda.gov/ARSUserFiles/80400525/Data/retn/retn06.pdf
[Accessed 16 November 2017].
Phillips, D., 1999. Polycyclic aromatic hydrocarbons in the diet. Mutation Research, 443(1-2), pp. 139-147.
Uribarri, J. et al., 2010. Advanced Glycation End Products in Foods and a Practical Guide to Their Reduction in the Diet. Journal of the Academy of Nutrition and Dietetics, 110(6), pp. 911-916.


Amy Giannotti is a dietitian, sports dietitian, strength coach, running coach and yoga instructor. The owner of Eating Fit, she is available for individual and group face-to-face and online nutrition consultations and education workshops. eatingfit.com.au