November 29, 2012

Why nuts don't make you fat

The message that nuts are a healthy food that can help lower bad LDL cholesterol has been around for years – so why aren't we eating more of them? The surprise finding from a new nut industry report on Australia's nut eating habits is that most of us nibble them once a month or less, often on planes or at parties, with only two per cent of us eating them daily.

What's holding us back is the F word: fat.  We might know that the fat in nuts, like the fat in foods like olive oil and avocado, is healthy fat, but we're still keeping it at arms' length.

"We're clinging to the low fat message that came out of the late 80s and I think this is partly because the number of low fat products available in the supermarket reinforces the idea that all fat is bad," says dietitian Lisa Yates of Nuts for Life, the industry organisation which provides nutrition information about nuts.

The paradox of nuts is that while they're loaded with fat (walnuts have 69 per cent fat, for instance, and pistachios around 51 per cent), studies show that regular nut eaters don't appear to gain weight and that nuts may help with weight loss if they're eaten in an energy-controlled diet. That's why Weight Watchers now recommends a handful (30g) of unsalted nuts as a between meal snack because their fibre and protein content can quell hunger pangs.

But there may be more to nuts' positive effect on weight than filling power alone – other studies show that some of the fat from nuts is excreted, not absorbed, says dietitian Sue Radd of Sydney's Nutrition and Wellbeing Clinic.

"This means the assumed calorie contribution of nuts is actually less than what food composition tables would tell us. Some studies suggest we may not absorb up to 30 per cent of the fat in nuts, depending on the nut and how well it is chewed – chewing nuts less seems to be better from a weight loss point of view."

What makes nuts heart healthy? A number of studies suggest that eating 30g of nuts at least five times a week reduces heart disease risk by 30 to 50 per cent, a result that's probably due to a mix of different effects on the body. One is that nuts naturally contain plant sterols (the same substances added to cholesterol-lowering margarines), as well as antioxidants that help keep arteries healthy.

"Mother Nature has supplied nuts with antioxidants which prevent the fat turning rancid too quickly – and these antioxidants help prevent LDL cholesterol from sticking to the artery walls," Lisa Yates explains. "Nuts also contain an amino acid called arginine that's important for producing nitric oxide  – this helps keep the artery walls relaxed which in turn helps keep blood pressure healthy."

If you're looking for sources of plant protein as an alternative to animal protein, nuts are a good option.  In main meals, larger servings of  nuts can stand in for flesh foods – think stir fried vegetables and noodles with cashews or macadamias, or pasta tossed with crushed hazelnuts, olive oil and chilli. Another bonus of adding nuts to meals? They  help lower  a meal's glycaemic  index (GI)  which may help  keep blood glucose  levels healthy – this could explain why eating nuts is also  linked to a lower risk of  type 2 diabetes, as well as better diabetes control for people who already have the disease.

Where should you store nuts – the fridge or pantry? That depends on how fast you eat them. Yates' advice is to store the nuts you use less frequently in airtight containers in the fridge or freezer, although it's okay to keep everyday snacking nuts in the cupboard, again in airtight containers, if the turnover is quick. Just remember to bring refrigerated nuts to room temperature before eating – or warm them gently – to bring out their flavour.

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