Roasted vs Raw Nuts
Roasted vs Raw Nuts
Guest contributor: Lisa Yates, Program Manager & Dietitian (Adv. APD) Nuts for Life

The most common question we get asked – which is better raw or roasted nuts?
 
It’s been over 10 years since I started working for Nuts for Life and the Australian Tree Nut Industry. At the time I couldn’t get over the fact that many people thought nuts were unhealthy. I remember thinking how could anyone think something that grows on a tree could be unhealthy?!
 
Well fast forward 10 years and eating nuts is now a daily “must do” which is fantastic but we still get asked the odd question and the one which is popular is “I love the tasted of roasted nuts over raw but does roasting nuts doing something to the nutrients or health benefits?”
 
Let’s take a look at what happens when nuts are roasted.
 
Roasting nuts

Nuts are commerically roasted in different ways. Oil roasted usually means nuts are submerged in hot oil. Dry roasting can occur either as a single layer of nuts on a conveyer belt through an oven or rolling around in a mini rotating drum like a cement mixer over flame.

Roasting nuts in general modifies some of the nutrients. For instance, B group vitamins are not heat stable so levels are reduced during roasting.However since we get most of our B group vitamins from breads and cereal products this is not usually a problem. Roasting also reduces the water content so concentrates minerals such as potassium, magnesium, manganese and copper.

Surprisingly there are only small differences in the amount and type of fats. Nuts are so dense they can’t absorb a lot of extra oil even if submerged in oil unlike potato for instance when making chips. Industry members tell me nuts absorb about 2 to 5% of the oil they are roasted in.

Some polyunsaturated fats can be converted to saturated fats when heated but in nuts the change is only about 10%. Is this clinically relevant since saturated fats can increase blood cholesterol? Probably not – two clinical trials have reviewed this. The cholesterol lowering effects of roasted almonds versus raw almonds were studied by researchers in the US and they found roasted almonds reduced total and LDL blood cholesterol similarly to raw almonds (1). Another study with roasted peanuts found similar results (2).

One major difference with oil roasted nuts is that they are usually then also salted.
 

Nuts and blood pressure

Health authorities recommend reducing the salt/sodium content of diets to help reduce the risk of cardiovascular disease and high blood pressure. So do salted nuts have a positive or negative effect on health?

A meta analysis of many nut studies (3) and a specific pistachio clinical trial (4,5) (where half the pistachios given were salted about 15g a day but as part of a lower sodium diet overall) indicate that nuts (and specifically pistachios) appear to have a good effect on blood pressure. Nuts appear to help keep blood vessels elastic and reduce inflammation which may explain this (6). Nuts are also sources of potassium and contain an amino acid called arginine which is involved in blood vessel health.
 
The large population studies that found a link between regular nut consumption and a reduced risk of heart disease were done in 1990s-2000s. At a time when a large portion of nuts sold and eaten were salted nuts. Researchers of these studies didn’t ask participants if they ate raw or salted nuts just “nuts”. And in general eating “nuts” at least five times a week resulted in a 30-50% reduced risk of heart disease (7-11). 
 

Flavour benefits of roasted nuts

Many people tell us they enjoy the flavour of roasted nuts more and studies have analysed and identified the flavour compounds of roasted nuts that makes them ...well...nuttier (12-15).
 
So if someone has an overall healthy diet does it matter if they enjoy salted nuts on occasion? I don’t think so as the effect of the salt may be offset by the other heart health nutrients that nuts contain such as: healthy fats, fibre, vitamin E, folate, potassium, selenium, manganese, copper, plant sterols and arginine.

For the most part roasted nuts have a flavour profile people enjoy and if this means they eat a handful of nuts more regularly then that’s good for their health overall.
 
For more information and recipes using nuts visit www.nutsforlife.com.au, follow @nutsforlife or like www.facebook.com/nuts4life



References

1.      Spiller GA et al Effects of plant-based diets high in raw or roasted almonds, or roasted almond butter on serum lipoproteins in humans. J Am Coll Nutr. 2003 Jun;22(3):195-200.
2.      McKiernan F et al Effects of peanut processing on body weight and fasting plasma lipids. Br J Nutr. 2010 Aug;104(3):418-26.
3.      Mohammadifard N et al The effect of tree nut, peanut, and soy nut consumption on blood pressure: a systematic review and meta-analysis of randomized controlled clinical trials. Am J Clin Nutr. 2015 May;101(5):966-82.
4.      Sauder KA et al Pistachio nut consumption modifies systemic hemodynamics, increases heart rate variability, and reduces ambulatory blood pressure in well-controlled type 2 diabetes: a randomized trial. J Am Heart Assoc. 2014 Jun 30;3(4).
5.      West SG et al Diets containing pistachios reduce systolic blood pressure and peripheral vascular responses to stress in adults with dyslipidemia. Hypertension. 2012 Jul;60(1):58-63
6.      Barbour JA et al. Nut consumption for vascular health and cognitive function. Nutr Res Rev.2014 Jun;27(1):131-58.
7.     Fraser GE, Sabate J, Beeson WL, Strahan TM. A possible protective effect of nut consumption on risk of coronary heart disease. The Adventist Health Study. Archives of Internal Medicine 1992;152(7):1416-24.
8.     Hu FB, Stampfer MJ, Manson JE, Rimm EB, Colditz GA, Rosner BA, et al. Frequent nut consumption and risk of coronary heart disease in women: prospective cohort study. British Medical Journal 1998;317(7169):1341-5.
9.     Albert C.M. et al. Nut consumption and decreased risk of sudden cardiac death in the Physicians Health Study. Arch Intern Med 2002;162(12):1382-7.
10.   Ellsworth JL, Kushi LH, Folsom AR. Frequent nut intake and risk of death from coronary heart disease and all causes in postmenopausal women: the Iowa Women's Health Study. Nutrition Metabolism and Cardiovascular Disease 2001;11(6):372-7.
11.   Blomhoff R et al. Health benefits of nuts: potential role of antioxidants. Brit J Nutr 2007;96(SupplS2):S52-S60.
12.   Agila A, Barringer S. Effect of roasting conditions on color and volatile profile including HMF level in sweet almonds (Prunus dulcis). J Food Sci. 2012 Apr;77(4):C461-8.
13.   Burdack-Freitag A1, Schieberle P. Changes in the key odorants of Italian Hazelnuts ( Coryllus avellana L. Var. Tonda Romana) induced by roasting. J Agric Food Chem. 2010 May 26;58(10):6351-9.
14.   Aceña L et al Determination of roasted pistachio (Pistacia vera L.) key odorants by headspace solid-phase microextraction and gas chromatography-olfactometry. J Agric Food Chem. 2011 Mar 23;59(6):2518-23.
15.   Tey SL et al The dose of hazelnuts influences acceptance and diet quality but not inflammatory markers and body composition in overweight and obese individuals. J Nutr.2013 Aug;143(8):1254-62.




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