As part of the Dr. P Heart Nuts Project, the skeptical cardiologist has been trying to determine what constitutes the best and most cardioprotective almonds.
Cardioprotective Almonds: Best Raw or Roasted?
There are two issues with roasting: are we destroying good nutrients and are we creating bad chemicals?
Effects of Roasting on Good Nutrients
The cardioprotective component of nuts and almonds is presumed related to phytochemicals, especially phenolics and flavonoids which may act as antioxidants. But truly we don’t know with any certainty which of the many potentially beneficial components-minerals, vitamins, fatty acids, proteins are helpful. And we have little understanding of how roasting, steaming, soaking, fermenting, germinating, or fumigating affects the cardioprotective components.
In terms of measurable important macronutrients, vitamins and minerals there is no significant difference between roasted and raw nuts.
One study compared consuming roasted versus raw hazelnuts on various cardiovascular parameters. Compared with baseline, consuming both forms of hazelnuts significantly improved HDL-cholesterol and apolipoprotein A1 concentrations, total-C/HDL-C ratio, and systolic blood pressure. These changes would be expected to result in improved cardiovascular outomes.
One argument I hear frequently from patients worried about weight gain is that nuts are very energy dense and therefore will contribute to weight gain if added to the diet or consumed as a snack.
In the roasted versus raw hazelnut study:
However, no evidence for weight gain was observed with the consumption of either raw or dry roasted, lightly salted hazelnuts in the present study, and in fact, small reductions in weight were observed. Results of the present study further add to previous research, which suggests that regular nut consumption results in either no weight gain or less weight gain than predicted This may be explained by dietary compensation, inefficient energy absorption, and an increase in metabolic rate.
Thus, neither roasted nor raw nuts contribute to weight gain.
I particular like one line from the conclusions of this study:
both forms of nuts are resistant to monotony
Really! That is tremendously reassuring because I have always worried about my nuts getting bored.
Bottom line: Probably little change in the good components of nuts and almonds with roasting.
Effects of Roasting Almonds on Increasing Bad Chemicals
About a third of almonds and nuts are consumed in roasted form because a majority of people prefer the taste created by the Maillard reaction during roasting. Almonds can be roasted at home and the typical recommendation is an oven temperature of 350 degrees which corresponds to 177 degrees Celsius.
An analysis from the Winnipeg Health Authority found that roasting at temperatures higher than 140 degrees Celsius has some potentially worrisome consequences:
-High heat used during the processing of nuts has the potential to develop lipid oxidation products, which include trans fatty acids. Trans fatty acids, while not present in raw nuts, were found to be significantly higher in roasted pistachios, peanuts, and almonds (0.5-0.9g/100g).
-Trans fat is known to increase LDL cholesterol and decrease HDL cholesterol, leading to increased cardiovascular disease risk.
-While roasting temperature was found to substantially increase lipid oxidation, roasting time had less of an effect on lipid oxidation. It is therefore recommended to roast nuts at a moderate temperature (130-150°C), for a longer period of time, rather than roasting at high heat for a shorter period of time (reference here)
-Acrylamide has been identified as a probable carcinogen to humans. The amount of free aspargine in almonds makes them more susceptible to the Maillard reaction, which results in acrylamide formation. Time and temperature are known determinants of acrylamide formation in foods. Hence, darkly roasted almonds were found to have a much higher amount of acrylamide than lightly roasted almonds. The amount of acrylamide that is initially formed after processing was found to decrease over time. Acrylamide content of almonds therefore differs widely depending on roasting time and temperature, as well as length of time after processing.
-It was observed that almonds processed under roasting temperatures of 140-180°C led to the accelerated production of acrylamide. It is therefore recommended to roast almonds below 140°C
The acrylamide study authors noted that:
Almonds of European origin contained significantly less free asparagine and formed significantly less acrylamide during roasting as compared to the almonds from the U.S. Roasted hazelnuts contained very little acrylamide because of the low content of free asparagine in the raw nut.).
Bottom Line: Roasting almonds has the potential for creating some bad chemicals which might negate their beneficial effects.
I asked Whole Foods (my typical almond source) about the roasting process for their roasted almonds and they responded thusly:
“PPO and chemical methods of pasteurization are against our Quality Standards. Our almonds are pasteurized with steam. Our almonds are roasted with canola oil at 148 degrees (celsius).”
Yikes! Canola oil! 148 degrees! (When I asked Whole Foods did they really mean 148 degrees Celsius, the response was , no, I meant 148 degrees Fahrenheit. The skeptical cardiologist wonders.)
It appears even Whole Foods roasted almonds have the potential for containing harmful acrylamides and trans-fats therefore when the skeptical cardiologist starts handing out packets of his cardioprotective nuts the almonds will be raw and they will be from Spain just like the almonds consumed in the landmark PREDIMED study that established their heart benefits.
Happy Thanksgiving!I hope you are able to stay resistant to monotony during this festive season.
Speaking of resisting monotony, did you know this about thermobaric weapons?
“The [blast] kill mechanism against living targets is unique–and unpleasant…. What kills is the pressure wave, and more importantly, the subsequent rarefaction [vacuum], which ruptures the lungs…. If the fuel deflagrates but does not detonate, victims will be severely burned and will probably also inhale the burning fuel. Since the most common FAE fuels, ethylene oxide and propylene oxide, are highly toxic, undetonated FAE should prove as lethal to personnel caught within the cloud as most chemical agents.”