Eating nuts as part of a healthy diet is good for your heart. They’re also a super nutritious snack for any time of the day. But, what about all that fat? Be fearful not of fat as not only is the type of fat found in nuts considered healthy, but a major systematic review finds little impact of eating nuts on body weight. And that’s what I’ll cover in today’s episode.
Nuts can be a healthy addition to any diet. And even though nuts are high in fat, most of this is the healthy monounsaturated and polyunsaturated types. That’s probably one of the reasons, along with their fibre and vitamin E content, why there is such a positive link between regular nut eating and a lower risk of cardiovascular disease.
And here, nuts could be helping to lower LDL-cholesterol and triglyceride levels, which play a major role in the build-up of deposits of plaques in the arteries. Nuts can also help lower levels of inflammation linked to heart disease as well as reduce the risk of developing blood clots, which can lead to a heart attack and death.
All nuts appear to be generally healthy, though some may have more heart-healthy nutrients than others. For example, walnuts contain high amounts of omega-3 fatty acids. Almonds, macadamias, hazelnuts and pecans also appear to be quite heart healthy. But really, there is a good case to promote a variety of nuts in your diet.
So nuts are good for your heart. But what about your weight? Well, I’m one person who is glad we’ve left the well-meaning era of ‘low fat’ advice behind. Because such advice on its own ignores the nutritional merits of a food. And here, nuts really do shine with the research building for some years that they aren’t a factor to worry much about when it comes to weight gain. In fact, the opposite could be true.
And that was the topic of a recent systematic review and meta-analysis looking at nuts and body weight across both observational studies and randomised-controlled trials. And I’ll link to this review in the show notes. https://onlinelibrary.wiley.com/doi/full/10.1111/obr.13330
And there was an astounding amount of research that could be examined. There were 6 observational studies and 86 randomised controlled trials included. You heard correctly – 86 randomised controlled trials where nut consumption was the key difference between two random groups of people. And some of those RCTs ran for up to two years. Almonds, walnuts and pistachios were the most common nuts eaten, but you could also find studies that used a bunch of other popular nuts as well as mixed nuts.
And here is all you need to know about the results: eating nuts was linked with a lower risk of weight gain if you just used the observational research and the evidence rating for it was considered ‘moderate’. Moving to the more powerful RCTs of which there were heaps, there was no impact of eating nuts on body weight and the evidence rating for this was considered ‘high’.
And pleasing to see, as the amount of nuts eaten went up, it was more likely that weight and body fat was lost.
So the big question: why is it so? There are three very plausible mechanisms to explain why nuts, even though being a high-fat food, don’t contribute to weight gain.
The first is their unsaturated fatty acid content which is suggested to be more readily oxidised and have a greater thermogenic effect. The second is an effect on hunger and fullness – nuts help to suppress hunger meaning you’re more likely to eat less. This effect is due to the protein, fat and fibre content of nuts.
And the final one is certainly one that gets my attention. It is to do with the physical structure of the nuts which affects the bioavailability of nutrients – in particular fat. Thanks to the complex cellular structure, the fat in nuts may not be completely digested and absorbed by the body. When less fat is absorbed it means that less energy from nuts is absorbed too.
And there has been some interesting research showing that when whole nuts are eaten and not fully chewed, less of the fat is absorbed. It also likely explains why in previous research, the benefits of nuts on weight regulation may not transfer to homogenised spreads like peanut butter. This could be because of the more processed nature of this food and the breaking down of the cellular structure, meaning more of the fat is available for digestion and absorption compared to whole nuts where some of that fat can pass through the intestinal tract undigested.
So, let’s wrap all this up. Snacking on nuts, especially in place of less healthy convenience snack foods, is a simple and healthy way to prevent the slow insidious weight gain that can happen with ageing. The Australian Dietary Guidelines recommend 30 grams of nuts on most days of the week. A single handful of nuts will get you to that 30-gram serving.
So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.
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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.