Is Nutrition Lost When Nuts Are Roasted?

Close-up of cashews roasting in a pan.
Image Credit: MeePoohyaphoto/iStock/Getty Images

Since 2005, researchers from Harvard University have shown that men, both healthy and those who have suffered a heart attack, reduced their cardiovascular risk by eating nuts regularly. By replacing less healthy snacks with nuts rich in mono- and polyunsaturated fats and fiber lowers cholesterol. Omega-3 fats in nuts prevent irregular heart rhythms and those rich in arginine may improve the function of your blood vessels. Vitamin E, a powerful antioxidant, is found in nuts to fight off free radicals. The question is, do the same benefits apply if you buy roasted nuts compared to those not roasted?

Roasting and Heat Treating of Certain Nuts

Roasted nuts may be more appetizing than the unroasted ones, but you may want to consider buying some specific types in their raw forms instead on your next trip to the market. Chemical analysis of raw and processed pistachios, almonds, peanuts and tahina or sesame seed paste are published in the "Journal of Agricultural and Food Chemistry" in 2008. Results from the study reveals an increase of lipid oxidation indicators in the roasted and heat treated nuts compared to the raw ones. Also, results from the heat treated nuts show an increase of trans fats, a type of fat that the American Heart Association recommends to be eliminated from your diet due to its adverse health effects.

Roasting Cashews Increases Their Antioxidant Activity

Some nuts, such as cashews, you want to buy roasted. The "Journal of Agricultural and Food Chemistry" published a study by the Memorial University of Newfoundland, Canada, on the antioxidant activity of roasting cashews in May of 2011. The results shows an increase in the absorbency and scavenging capabilities of the antioxidants in cashews, leading to an increase in the power of reducing oxygen radicals in these nuts. Also, there is a higher yield in the phenolic compounds and flavonoids, both powerful antioxidants in those cashews roasted at 130 degrees Celsius for 33 minutes and less.

Heat Treated Peanuts Are Better Than Raw

Although thermal processing alters the antioxidants composition in peanuts, roasted or boiled peanuts may still be a better choice for you as their antioxidant activities are preserved and, in some cases, enhanced after processing. In September 2010 "Plant Foods For Human Nutrition" displays results from a study where scientists from the University of Georgia finds that the antioxidant activity increases the most by oil roasting peanuts compared to dry roasting them and that raw peanuts had the lowest amount of antioxidants. From another study in 2007 from the "Journal of Agricultural and Food Chemistry" shows that boiling peanuts compared to dry or oil roasting them, had significantly the highest total flavonoid and polyphenol content, suggesting that heat-treated peanuts are better than the raw variety.

Almonds Are Better Raw

On the other hand, you may want to choose raw almonds. In March 2011, the "Journal of Food Science" reveals that almonds roasted over 140 degrees Celsius can damage their cellular structures and degrade their quality, making them more susceptible of releasing oil during storage. Roasting almonds above 130 degrees Celsius encourages acrylamide formation, a product with links to causing cancer. In another study from the "Journal of Food Science" in 2007, the amount of acrylamide formed increases as the color of the almonds gets darker as they roast. Depending on where the almonds are grown, an article from the "Journal of Agricultural and Food Chemistry" in 2005 states that varieties from Europe have less acrylamide formation potential than those from the US because the asparagine levels in European almonds are much lower.

Warning With Nut Comsumption

Nut allergy is one of the most common food sensitivity today. Just like starting any new regimen, consult your physician first to clarify any possibilities of nut allergy before proceeding with eating nuts on a regular basis. Nuts are not only a source of protein and fiber, but is also a source of fat, so depending on your body and medical history, ask your dietitian for advice for how much you should be consuming in a day. The American Heart Association suggests no more than 7 percent of your daily fat intake to come from saturated fats, which is also present in nuts along with unsaturated fats.

references & resources