Five powerhouse foods

Are you really watching what you eat? Here are five of the best powerhouse foods to get into your diet.

Our favourite fruit and vegetables aren't necessarily giving us the greatest benefits. So what should you be eating? If you eat the recommended five serves of vegetables and two of fruit a day, you're already a giant step ahead of the 90 per cent of Australians who don't. But new research suggests that many people might not be eating the best types of vegetables to give them vital phytonutrients, the naturally occurring plant compounds that help protect against chronic disease and even some cancers.

The most commonly eaten sources of these beneficial nutrients, such as carrots and oranges, aren't necessarily going to do the most to improve your health. Instead, the American researchers who recently presented their findings to the 2010 Experimental Biology conference in Anaheim, California, recommend replacing the most commonly consumed fruits and vegetables with "powerhouse" alternatives such as sweet potato, papaya, raspberries and the less common kale and watercress.

Phytonutrient power

The scientists found that for 10 of the 14 phytonutrients studied, a single food type accounted for two-thirds or more of a person's consumption. Whether the individual was a high or low consumer of fruit and vegetables appeared to make no difference. The most popular food sources for five key phytonutrients were carrots (beta-carotene), oranges or orange juice (beta-cryptoxanthin), spinach (lutein and zeaxanthin), strawberries (ellagic acid) and mustard (isothiocyanates).

However, for each of these phytonutrients, there was a better food source available: sweet potatoes (nearly double the beta-carotene of carrots); papaya (15 times more beta-cryptoxanthin than oranges); kale (three times more lutein and zeaxanthin than spinach); raspberries (three times more ellagic acid than strawberries); and watercress (one cup contains as much isothiocyanate as four teaspoons of mustard).

Studies here have found that only one in 10 Australians meets the recommended intake of five serves of vegetables a day, and half meet the suggested two serves of fruit. That means many Australians are missing out on vital nutrients; not just power-packed phytonutrients, but essential vitamins and minerals.

Colour is key

But before rewriting your shopping list, nutritionists say that the best way to ensure an adequate supply and variety of phytonutrients is to eat from a colourful plate. "I think it's probably a bit rich to nut it down to saying these five foods are powerhouse foods," says Kellie Hogan, a nutritionist and dietitian with Nutrition Australia.

"They're very useful and we know that the brightly coloured fruits and vegetables and the highly flavoured do tend to be richer sources of antioxidants and phytonutrients, which certainly have their health benefits. "But in isolation, without a much wider diet underpinning these foods, they are not going to be the reason someone is healthy or not healthy."

Julie Gilbert, a Brisbane-based dietitian and a spokeswoman for the Dietitians Association of Australia, says that rather than replacing carrot with sweet potato, eat both, as phytonutrients play a key role in good health. "They basically mop up the chemicals that can lead to cell destruction and that's what helps to prevent things like cancer," she says. Berries are a fantastic source of phytonutrients and purple plant foods are emerging as the new superfoods.

Eggplant, cabbage, purple-skinned sweet potato, plums and the not-yet-widely- available-in-Australia purple carrot are jam-packed with nutrients, Gilbert says. But she cautions: "If we just focus on trying to achieve high levels of phytonutrients through the five foods identified in the study, we'll miss out on the benefits of other foods. We should just add them more regularly into our diet."

Associate Professor Manny Noakes, nutrition researcher with the CSIRO and author of The CSIRO's Total Wellbeing Diet (Penguin), agrees that fruits and vegies are not only great sources of vitamins and minerals, but also much-hyped phytonutrients. She says some foods are quintessential powerhouse foods, such as liver, and adds that different plants are high in one phytonutrient or another, making it important to treat our palate to a variety.

"Eating a selection of those is a simple shortcut to good nutrition," she says. Phytonutrients can have very beneficial effects on health, and colour and flavour are usually good indicators of their presence in fruits and vegetables, she says. "There's no doubt we could be improving our health and wellbeing enormously by improving our diet," Noakes says. "Very few Australians eat the recommended amount, let alone the variety, of fruits and vegetables that they should."

Three-quarters of a dinner plate should comprise vegetables and, while cooking them in a little olive oil can enhance the absorption of some phytonutrients, peeling can destroy them. While you might be tempted to peel fruits and vegetables to eliminate any pesticide residue, you're better off washing them instead. For example, the skin of a red apple is rich in polyphenols, a type of phytonutrient, but the benefits are lost once the apple is peeled. On the other hand, lycopene, the phytonutrient found in tomato, is absorbed better with the assistance of oil.

Mixing it up

Kathy Chapman, the Cancer Council's nutrition program manager, says Australians are lucky to have such a variety of fruits and vegetables available, and now it's time to get motivated to eat them. She says people perceive fruit and vegetables as expensive, unexciting or sometimes difficult to prepare. Instead of steaming carrots or beans as a side dish, she suggests making a stir-fry with less meat and lots of colourful vegetables.

While research is ongoing into the protective nature of fruits and vegetables, Chapman says it's hard to pinpoint one type as the hero. "In terms of cancer, being a healthy weight is a really important protective factor," she says. "Those who do eat more fruit and vegetables are more likely to be a healthier weight."

The key message is variety, Chapman says, because you don't want to only eat sweet potato, papaya, kale, raspberries and watercress at the expense of other nutritional benefits. "They all have good properties, but if you only eat, say, purple cabbage, you'll miss out on other nutrients. All will be doing slightly different things, so you want to be maximising the benefits from a variety of foods."

The US study, funded by the supplement company Nutrilite Health Institute, found that if people ate more concentrated sources of phytonutrients, they could significantly improve their intake. "This data highlights the importance of not only the quantity but also the significant impact the quality and variety of the fruits and vegetables you eat can have on your health," says study leader Dr Keith Randolph.

While research shows the health benefits of eating fruit and vegetables, Noakes says the evidence is strongest when it comes to preventing cardiovascular diseases such as heart attacks and strokes. "It may not necessarily be all due to phytonutrients," she says. "If you eat a lot of fruits and vegetables, that helps with weight control, which helps with cancer, cardiovascular disease and diabetes."

Hogan says despite the hype and the known benefits, phytonutrients are just one part of a healthy diet. "What you might be gaining in the concentration of phytonutrients by eating certain foods, you might be losing in other nutrients. We recommend eating brightly coloured fruits and vegetables and a mixture of these."

source