Hate the taste of Brussels sprouts? Do you find coriander disgusting or perceive honey as too sweet? Your genes may be to blame.
Everybody’s food preferences vary and are shaped by their unique combination of three interacting factors: the environment (your health, diet and cultural influences); prior experience; and genes, which alter your sensory perception of foods.
The food we eat is sensed by specialised receptors located in the tongue and nose. The receptors work like a lock and are highly specific in the nutrients or aromas (the keys) they detect. Sweet receptors, for instance, detect only sweet molecules and will not detect bitterness.
When you eat, your brain combines the signals from these specialised taste (in the mouth) and olfactory (aroma in the nose) receptors to form a flavour. Flavour is further influenced by other perceived qualities, such as the burn of chilli, the cooling of mint, or the thickness of yogurt.
Our unique sensory worlds
Humans have about 35 receptors to detect sweet, salty, bitter, sour, umami and fat tastes. They have around 400 receptors to detect aroma. The receptor proteins are produced from instructions encoded in our DNA and there is significant variation in the DNA code between individuals.
In 2004, American researchers identified that olfactory receptors were located in mutational hotspots. These regions have higher than normal genetic variation. Any of these genetic variants may change the shape of the receptor (the lock) and result in a difference in perception of taste or aroma between people.
Another American study shows that any two individuals will have genetic differences that translate to differences in 30% to 40% of their aroma receptors. This suggests we all vary in our flavour perception for foods and that we all live in our own unique sensory world.
How much sugar do you add to your tea?
Our ability to perceive sweetness varies a lot and is partly controlled by our genes. A recent twin study found genetics accounts for about a third of the variation in sweet taste perception of sugar and low-calorie sweeteners. Researchers have identified specific gene variants in the receptors that detect sweetness: TAS1R2 and TAS1R3.
There is also high variation in the detection of bitterness. However, the story is more complicated than sweet taste, as we have 25 receptors that detect different bitter molecules. Bitter receptors evolved to detect and stop us from eating harmful toxins. That’s why bitterness is not widely liked.
One of these bitter taste receptors (TAS2R38) controls the ability to detect a bitter compound called PROP (propylthiouracil). Based on the ability to detect PROP, people can be split into two groups: “tasters” or “non-tasters”. Tasters often dislike bitter green vegetables, such as broccoli and Brussels sprouts.
PROP status has also been used as a marker of food preferences, with non-tasters shown to eat more fat and better tolerate chilli.
Genetics has also been linked to whole foods, such as coriander preference, coffee liking and many others. But genes have only a small influence on preference for these foods due to their sensory complexity and also the contribution of your environment and prior experiences.
Understanding the influence of genes on taste perception offers a way to personalise products tailored specifically to your needs. This could mean tailoring a diet to a person’s genetics to help them lose weight. Indeed, genetic testing companies already offer dietary advice based on your individual genes.
Personalised food products to suit your own genetic dietary preferences are another example. Food products based on personal tastes are already in supermarkets. Salsa can be bought in mild, medium and hot. What if you could purchase food products specifically formulated for your own genetically determined sensory preferences?
Personalisation can also apply at the population level. Food manufacturers could tailor their food products to different populations based on an understanding of how common a genetic variant is in each population.
We are just beginning to understand how genes alter our sense of taste and smell, and how this may affect food preferences. Further research is needed to understand how multiple genes may combine to influence sensory perception and dietary intake. This is no easy feat, as it will require studies with extremely large numbers of people.
Another important research area will be to understand if our taste genes can be modified. Imagine if you could alter your food preferences to consume healthier foods.
It’s World Food Day, and this year’s focus is on the role smallholder farmers play in feeding the world.
Food production is at record levels, yet 842 million people are estimated to be suffering from chronic hunger and under-nourishment. Many of these are themselves small family farmers.
We’re trying to do our bit to help subsistence farmers grow more productive crops, combat plant diseases, farm seafood sustainably, develop climate change adaption strategies and grow coffee more sustainably.
On a broader scale, we’ve also cracked a problem with a globally-significant crop: wheat. With colleagues from the Sydney and Adelaide Universities, we’ve identified a gene that confers resistance to wheat rust – probably the biggest enemy of wheat crop yields worldwide.
Seafood is a major source of protein in both the developed and developing worlds, and we’ve found a way to farm the most delectable kind of all – prawns – more sustainably. Our Novacq™ fishless prawn food is now licenced for use in several South-East Asian countries. It makes use of the marine microbes at the base of the food chain to produce a prawn food that has the added benefit of increasing their growth rate by around 30 per cent.
Climate change is a pressing problem for us all, but some of the people most at risk are farming communities in countries in southern and south-eastern Asia. We’re collaborating with farmers in parts of Cambodia, Laos, Bangladesh and India to identify, select and test climate change adaptation options that are both viable and suitable for local communities. One of the things we’re aiming to do is develop and test new crop and water management practices for rice-based cropping systems that will outperform existing farming practices and can accommodate future climate variability and climate change.
After all that work, we might be tempted to celebrate with a good cup of coffee. Maybe a PNG blend. There are more than 400 000 households involved in coffee production in PNG, and it’s that country’s most important export cash crop.
With our Australian and international partners, we’re developing new ways for farmers and researchers to learn from each other and identify ways to improve the sustainability of PNG’s coffee industry. We hope to identify the points in the coffee-food farming system that can be targeted for the best possible result in retaining and reusing scarce nutrient resources.
By David Cox, Group Leader, Sensory and Behavioural Sciences
So little Harry won’t eat his vegetables? Well, he’s not alone. Poor Harry is just protecting himself from the danger of alkaloid toxins – although he doesn’t actually know this.
At the tender age of four, Harry is neophobic (fearful of new things) and facing “the omnivore’s dilemma”. The dilemma is that humans need to eat a variety of foods to grow healthy and strong but there are lots of foods out there that our sense of taste tells us might be poisonous.
There are good reasons for this because some bitter plants, for instance, contain alkaloid toxins. But some bitter components of foods, particularly in vegetables, are good for us.
So avoidance of bitterness is innate because it’s associated with toxins – and it results in children rejecting vegetables.
Widening Harry’s palate
Children only have an innate preference for sweet foods because of their association with dietary energy, and only learn to like salt early in life (at about four months of age).
But they need to learn to like bitter and sour foods too. In Brassica vegetables such as broccoli, cauliflower and kale, for instance, compounds such as glucosinolates and phenolics that contribute to the tastes bitterness and sourness are the same as those that contribute to their “healthy characteristics – the inhibition of carcinogenesis.
Luckily, for Harry, he has his family around him. Mum is a trusted source of information about what’s right and what’s wrong, and the gatekeeper of the food supply.
The trouble, of course, is that mum can’t face another temper tantrum over a Brussels sprout. So what to do?
The study I was involved in included a group of four- to six-year-old neophobic children. We found exposing kids to vegetables about eight or nine times over two weeks and offering them a non-food reward for tasting them resulted in a significant increase in liking vegetables, compared to just exposing them to the food.
For example, every time a child tasted a vegetable, she got a sticker to put on a chart. This kind of reward provides positive reinforcement, and the display and self-monitoring of achievement. All this is stuff is known to reinforce behaviours.
The UK research echoed and supported these findings.
Models of behaviour
Parental role modelling is important too and more work is needed to provide parents with the skills to deal with refusals. This includes improving parents’ belief in their ability to prevail in certain situations. This belief plays a major role in how people approach goals and tasks.
But does it even matter? Won’t Harry just grow out of it?
It’s true that, at four years of age, Harry has hit his neophobic peak and things might get better through gradual exposure and learning what’s safe.
Things will also change as eating vegetables becomes associated with pleasant outcomes, such as having a nice meal with friends and family. The conviviality associated with the consumption of a formal meal is thought to unconsciously increase the liking for the foods eaten.
But it’s tough because there aren’t too many immediate benefits from eating vegetables and it’s a waste of time telling him they’re healthy.
We know that taste perception rather than health information has the biggest influence on liking brassica vegetables among adults. So learning to like his vegetables early on is important because it’s going to influence what Harry eats for the rest of his life.
The importance of persistence
Loving eating vegetables at an early age could set Harry up for a life of low energy dense, high micronutrient rich diets that are going to help his weight and may protect him against chronic diseases.
So don’t give up. Exposure to a wide range of tastes in a pleasant eating environment, and watching his mum and dad eat vegetables will all help.
And when Harry’s younger sibling is still in the womb, it will probably help a lot if mum eats her vegetables because research shows flavours travel through the amniotic fluid to the growing foetus and influence food acceptance soon after birth.
So investing in their own healthy eating helps mothers save dinner table battles months or years later. Fathers, who are likely to be worse at protecting their health, should also take heed and become the right kind of role model for their children by eating vegetables too.
By Ingrid Appelqvist, Research Scientist, Animal, Food and Health Sciences
How do you like your veggies? Are you a boiler, a roaster, a steamer or maybe even a stir-fryer?
There’s no denying the goodness of vegetables. They provide essential nutrients for our everyday health and wellbeing.
But can the way we prepare them alter how much nutrition we get out of them? The short answer is yes – and it’s all to do with their structure.
For generations, many Aussies soaked their veggies in water, boiling them till they were soft and straining off the water they were cooked in. But this method leaches most of the vitamins and nutrients out of the plant and doesn’t leave much goodness other than fibre.
Vitamin C, for instance, is a delicate food micro-nutrient that’s essential for growth and development. But given that it’s water-soluble, it can be easily damaged by overcooking.
So is it better to eat our veggies raw? Snacking on a carrot when the nibbles hit during the day is more nutritious than eating over-cooked veg, but it’s not always the best way to make the most of the vitamins veggies have to offer.
Fruit and vegetables are built from millions of plant cells that lock up their vitamins in what’s called a ‘cell wall’ structure. For instance, when a carrot is fresh and raw, the cell walls are firmly attached to each other. This is partly what gives carrot its crunch.
Based on this work, we’re helping create a healthier Australian food supply by incorporating more positive nutrients – like vitamins and fibre from vegetables – into our everyday processed foods such as bakery products and yoghurts.
But in the mean time, how can we make the most of our veggies?
Gentle steaming with a very small amount of water, or even grating a fresh veggie like carrot, breaks the plants cell walls and makes the inherent nutrients more ‘bio-available’ – that is, available for absorption by the body as we digest it. Adding the water your veg is cooked in to your meal will help maximise the vitamins available for digestion.
The same goes for fruit. Fruit blitzed into smoothies, pureed and used in sauces and desserts breaks the cell walls and increases the bio-availability of many nutrients – but make sure you eat the pulp as well, as it contains valuable nutrients and fibre.
In many cases, veggies or fruit such as tomatoes can provide better nutrition processed than raw – as is the case for tinned tomatoes and pasta and passata sauces.
Of course, some vegetables like potatoes have to be cooked to be able to eat them at all. But a mixture of raw and gently cooked vegetables and fruit in our diet is key to maximising their nutritional value.
Learn more about how we’re keeping you healthy with our interactive graphic.
About the author
Dr Ingrid Appelqvist is a research scientist with expertise in food materials science. She specialises in developing healthier foods with higher nutritional value.
We’ve all heard the age-old saying, “you are what you eat”. But is there really any evidence behind this?
It turns out there is.
Dr Nathan O’Callaghan and his team of nutritional experts from our Food, Health and Life Sciences group is helping to reduce our risk of developing chronic diseases like diabetes and obesity through the food we eat.
After studying genetics at the University of Adelaide and the Australian National University, Nathan joined us as a post-doctoral fellow in nutritional genomics. Today he leads our team of obesity and metabolic health experts, helping Aussies manage and avoid obesity and its related health effects.
In particular, Nathan is looking at how food and food components interact with our cells, tissues and organs to impact our health.
“The information we can collect is quite amazing – from exquisite details of molecules sitting on top of our DNA, to what the entire Australian population is eating! The challenge is to use what we know to help people optimise their health,” says Nathan.
He is measuring the amounts of particular molecules in people’s bodies to create a ‘picture’ of the way they are functioning. This can help experts determine how certain foods, diets and lifestyle programs might influence our wellbeing. They can do this through a blood test, saliva sample, urine sample and now even a breath test.
The data he collects can also tell us which types of nutrients can help improve our health. In fact, research shows that changing your eating patterns can affect your DNA or genome in just two weeks.
So this raises the question, how can we eat our way to healthier DNA?
Nathan suggests eating a diet high in fibre, fruits and vegetables, with some fish and vitamins can improve our genome and cellular health. Oily fish like salmon and tuna contain high levels of omega 3 fats which can help prevent heart disease.
On the other hand, eating too much processed meat and drinking too much alcohol can actually damage your DNA, age your cells and increase your risk of serious diseases like bowel cancer.
But it’s not all genes and cells for Nathan. Back in 2011 he was a contestant in the very first series of I’m a scientist, get me out of here – an online Australian Idol-style science contest where students vote for the scientists they find the most interesting. Nathan proved to be one of Australia’s most popular scientists, with the highest-ranking overall score for South Australia.
“It was great to be part of the program. I want to inspire the next generation of scientists and give students who are studying science the opportunity to see what we do and how we do it.”
He’s also a devoted family man and loves to travel with his two kids, Tilly (age 7) and Alfie (age 3). He even took them on a recent work trip to Canada where he was investigating how nutrition during pregnancy affects health trajectory in babies. Now that’s multitasking.
Nathan tweets as @nath_oc.
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By Li Day, Research Group Leader, CSIRO Animal, Food and Health Sciences
It’s a food’s structure that gives a carrot its crunch and a loaf of bread its fluffiness, and researchers increasingly believe that many of a food’s key properties relate to its structure.
Nature is able to assemble sophisticated structures and food is no exception, even right down to the microscopic scale. Food components such as protein, carbohydrate, fat and minor ingredients, when mixed, organise into a range of structures, and its becoming clear that many properties key to a food’s processability, nutritional and sensory qualities, and safety are related to its structure.
Plants are structured like honeycomb, called ‘cell wall’ structure. The video below clearly shows the defined cell walls in raw carrot – that’s why it’s crunchy!
A scanning laser confocal microscope video in 3D showing the defined cell wall structure of raw carrot (Video: Sofia Oeseth)
Most foods have a ‘fluffy’ foam structure that forms when air bubbles are incorporated into a liquid, like bread, ice cream and meringue. The microscopic image below shows dough with air bubbles (black), gluten (yellow), starch granules (green) and protein (red).
Then there are suspensions, which are a bit like oceans, with a sea of solid particles (the ingredients) suspended within a major component that is a liquid (quite often water). Think tomato paste, fruit juices and some sauces and soups.
The next microscopic image shows a suspension in 3D of cooked pumpkin in water. Notice how round the pumpkin cells are – that’s why pumpkin soup feels so smooth and creamy when we’re eating it.
Colloids, which have microscopic particles dispersed through another substance, are another type of structure. Milk is an emulsified colloid of liquid butterfat dispersed in a water-based solution. The third microscopic image is of milk, and the red dots are drops of fat dispersed throughout the liquid whey (black).
There are other structure types as well – solutions, emulsions and gels, which all behave differently to each other.
The structure of a food affects the way we chew it, how it breaks down in our mouths and our perception of its texture and flavour. And because each structure also breaks down differently in our digestive system, the release and bioavailability of small molecules such as minerals, vitamins and polyphenols is also different.
Because of all these factors, food structures are increasingly being recognised as important in technology innovation for the development of healthier foods.
And as there is increasing awareness that structure has a significant effect on the bio-availability of nutrients, the focus of developing nutritional guidelines is shifting away from the traditional approach of simply assessing the nutrient composition of foods.
CSIRO is hosting the Food Structures, Digestion and Health Conference on 21 – 24 October, which will discuss the role of structure in designing foods for nutrition and wellbeing.
Over the years, we’ve received lots of feedback on our Total Wellbeing Diet (TWD). This nutritionally balanced eating plan has become a popular way to help people stay healthy and lose weight.
In fact, when the first TWD book was released back in 2005, it went straight to the top of the Australian best sellers list, even outselling Harry Potter!
People from all walks of life have told us how they love the food, have lost weight and feel more energetic on the TWD. However, we also know that the diet can be a bit expensive.
So to solve this problem, we’ve published ‘TWD recipes on a budget’. The book includes over 100 new budget-friendly recipes along with handy tips on how to stock your kitchen, grow your own herbs, use inexpensive cuts of meat for slow cooking and transfer leftovers into delicious meals. It’s the perfect how-to guide for preparing healthy, economic meals that don’t compromise on taste or nutrition.
We now have three different recipe books that are designed to help people incorporate the TWD into their daily lives. These include the TWD recipe book (2010), TWD fast and fresh recipes (2012) and TWD recipes on a budget (2013).
If you’re keen to expand your culinary repertoire, here are some recipes to get you started: