Thirty years ago, nutrition science looked very different. Today we exult healthy fats like avocado and olive oil, but in the 1980s, the war on dietary fat resulted in the proliferation of low-fat products on supermarket shelves. By the end of the 1990s, low-carb diets were in vogue as carbohydrates fell out of favour.
Clare Collins, a professor in nutrition and dietetics at the University of Newcastle, has had a long career in nutrition science. She says the average Australian diet has changed markedly since she graduated from university in 1982. Back then, fast food was a luxury and supermarkets stocked far fewer products.
Today, she says, "people eat a lot more crap." Highly processed food is ubiquitous, and portion sizes have increased. You need never cook again, yet we're not more healthy," says Collins. "We can find too many kilojoules too quickly."
Despite the easy access to unhealthy food, if you want to eat well in 2020, there's a vast amount of information out there about what constitutes a good diet. In the recently revised and updated edition of Nutrition for Life (Hardie Grant, $34.99), a pioneering book about nutrition and diet first published in 1986, dietitian Catherine Saxelby examines the new trends to emerge in nutrition science over the last three decades, from ancient grains to raw foods.
So, what have been the significant changes in nutrition science over this time?
Probiotics and the microbiome
One of the most exciting frontiers of nutrition science is the microbiome – the collective term for the colonies of bacteria that populate our digestive system – and pro- and prebiotics, or the foods we eat to keep it healthy.
A healthy microbiome is associated with overall good health. It fends off unwelcome pathogens, reduces inflammation, enhances the body's immune response, aids digestions, reduces symptoms of irritable bowel syndrome and bowel disease, keeps the bowel healthy and reduces the likelihood of developing colorectal cancer.
Our gut health is also closely associated with our mental wellbeing. More than 100 million neurons in the gut form the enteric system, explains Saxelby in Nutrition for Life. "These neurons 'communicate' with the microbiome, which can then affect your behaviour and feelings, including eating habits, cravings and moods." There is also evidence, she adds, that making a positive change to the microbiome may reduce anxiety and depression.
We can nourish our microbiome by consuming probiotics (live bacteria found in food and drinks such as yoghurt, fermented vegetables including sauerkraut and kimchi, and kombucha) and prebiotics (non-digestible components of food such as resistant starch, found in cold potatoes, that feed friendly bacteria in the gut).
The shift from single nutrients to a whole diet approach
According to Collins, one of the biggest changes in nutrition science in recent decades is the shift from focusing on individual macro- and micronutrients towards looking at overall dietary patterns. We have a greater understanding of the way food and its component elements work as a bundle, she says.
An important part of the picture is phytonutrients, the chemicals found in food – once referred to as antioxidants – that protect against cancer and heart disease. As Saxelby explains in Nutrition for Life, we now know these substances do more than prevent oxidation. Beta-carotene inhibits the early stages of tumour development, Vitamin C reduces cancers of the digestive tract, and selenium enhances the body's immune response.
Not all phytochemicals have a positive effect on the body. Some are anti-nutrients, such as lectin, a phytochemical found in tomatoes, beans and lentils that can inhibit the absorption of other nutrients when eaten raw.
The best way to boost your phytochemical intake is to eat a colourful array of fruit and vegetables, use herbs and spices such as rosemary, turmeric and ginger liberally, and drink red wine instead of white and tea instead of coffee.
The rise of omega-3 fatty acids
In Nutrition for Life, Saxelby explains why she is "a big fan" of omega-3 fatty acids: they keep your heart and blood healthy, assist in maintaining brain power and healthy eyesight, help manage mental health and diabetes, and decrease inflammation.
Omega-3s play a particularly vital role in neural development. "Babies need omega-3s for their brain to grow properly…so pregnant and breastfeeding mums must get a steady supply of omega-3s for the sake of their baby's health," Saxelby writes.
"Babies need omega-3s for their brain to grow properly."
We should all eat around 500 milligrams a day of long-chain omega-3s found in oily fish such as salmon and mackerel and 1000 milligrams of plant-sourced omega-3s found in chia seeds, linseed, pecans and walnuts.
The information age
Increased access to information has revolutionised nutrition science, says Collins. "Thirty years ago, I still had to go to the library and get a CD-ROM to look up old journal articles or look in paper-based journals. Now, I can do that at my desk."
Digitisation means that "we now synthesise and critique information in much more powerful ways than we ever could before” through systematic reviews and meta-analyses", she says. "As a health professional, I can get better information, which means I'm better able to advise people."
However, there is a downside to the explosion of information found online: the rise of the "self-styled guru". A large part of Collins's job today is to "connect people to the best available information and interpret it for them," she says. "It's why I'm more passionate about science communication than ever. I've written 90-plus articles for The Conversation, and I draw heavily on information from systematic reviews or good studies."
In an age of misinformation, it's vital to draw information from reputable sources like trusted news organisations and credentialled experts, says Collins, rather than celebrities who follow the latest fad diet.
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