Dr Carrie Ruxton likes to practice what she preaches. The Scottish dietitian, who has carried out extensive research into the health benefits of eggs, believes they're such a potent superfood she eats two to three a day.
"I have an omelette every day for lunch, and I've been doing that for the last four to five years," she says. "That's because eggs are basically nature's multi-vitamin."
Ruxton is an award winning dietitian, health writer and television nutritionist and has worked with a wide range of organisations including the National Health Service in Britain, the Food Standards Agency and the European Commission.
She says the beauty of eggs is that they pack so many nutrients into one small portion. "If you wanted to get the same nutrients you find in an egg elsewhere, you would need to eat a lot of different foods."
Ruxton has reviewed 71 studies into the nutritional composition of eggs and confirms they are an excellent source of high quality protein containing a rich mix of essential amino acids, which are required for proper growth and repair of the body.
They also contain vital nutrients like selenium, iodine, zinc, iron, phosphorus, choline, biotin, folate and riboflavin, along with vitamins A, B12, D and E.
The fact they're a source of B12 is important for vegetarians and people who eat very little meat: "Your body doesn't make B12, you can only get it from animal foods. So if you don't eat meat you can still get B12 if you include eggs in your diet," she says.
Eggs are also a good source of vitamin D. The best source is sunshine, but because many people don't spend much time in the sun – or cover up with sunscreen when they do to protect against skin cancer – vitamin D levels in western countries tend to be low.
"Eggs are one of the few natural food sources of vitamin D, after oily fish, so they're a good way of getting this vitamin, which we need for our bones and also muscle and immune function."
Eggs not only pack a nutritional punch, they are low in fat and calories – and because they contain high-quality protein, they are helpful for weight loss and management.
"Protein helps you to feel fuller for longer," says Ruxton. "There have been studies into breakfast foods, with one comparing bagels with eggs.
"They had similar calories but people lost more weight when they ate the eggs as our bodies process bagels much faster than eggs, so you feel hungry again sooner.
"Eggs don't contain carbohydrates so they have a low impact on your blood sugar. If you mix protein foods with carbohydrates – for example, having eggs on toast – the protein will slow down the absorption of the carbohydrates from the bread so an eggs on toast for breakfast has a lower impact on blood sugar than just eating a couple of slices of toast."
Everyone can benefit from eating eggs, says Ruxton but they're particularly good for children and babies – scrambled eggs and omelettes can be offered to youngsters over six months old – and elderly people.
"Sarcopenia (muscle loss) is a problem for a lot of older people as this increases their risk of frailness and falling.
"Research has found that if you give elderly people high-quality protein, such as eggs, and get them to do a bit of resistance exercise – like using therabands – it can make them a lot stronger, so they don't fall as much," she says. "Vitamin D in eggs also helps to reduce the risk of falls."
Eggs can also support brain and cognitive functioning. In one study of nearly 2,500 dementia-free middle-aged men, egg intake was associated with better performance in neuropsychological tests – thought to be due to the choline in eggs.
A vitamin-like compound that plays a crucial role in brain activity, choline is used in drugs to treat cognitive disturbances in elderly people, and one study found that people with early stage dementia had improved cognitive function after taking choline supplements.
Many people have missed out on the health benefits eggs can provide over the years because of health advice in the 1970s that recommended limiting the number you ate, says Ruxton.
"People believed that food like eggs and prawns, which are high in dietary cholesterol, could change the cholesterol in your blood, and increase the risk of cardiovascular problems. Yet studies have shown these foods weren't having any impact on blood cholesterol; rather it is fats – in particular saturated fats – that will do this.
"Eggs are low in saturated fats and haven't been shown to put up your blood cholesterol."
# They are a healthy, natural whole food that the New Zealand Ministry of Health Eating and Activity Guidelines state can be enjoyed by most people every day of the week.
To find out more head to eggseveryday.org.nz