Wednesday, July 30, 2008

Fats In Nuts

Shaun asked me a question about nuts. So, I dredged up this chart from 2005. I made it while discussing why nuts go rancid, and why some nuts go rancid sooner than others. (Nuts with a higher percentage of polyunsaturated fat go rancid sooner.)

Click for larger.

Different nuts have different amounts of different fats. This study suggested that consumption of monounsaturated fat "provides cardiovascular benefits," and "is thought to improve insulin sensitivity."

The chart above is misleading in that it suggests that all nuts have the same amount of fat/serving, which they do not. Although as a group, they're similar:

Total fat in 1 ounce (about the size of 14 walnut halves, 23 almonds, 49 pistachios):
  • Walnuts, 18.3g fat
  • Brazil nuts, 18.6g fat
  • Pecans, 20.2g fat
  • Almonds, 13.8g fat
  • Filberts (Hazelnuts), 17.2g fat
One that's not on the chart:
  • Pistachios, 12.4 g fat (12.1% SFA, 52.4% MUFA, 30.6% PUFA) 1
For comparison, the total fat in:
  • 1 oz. olive oil (2 tablespoons), 28.0 g fat, (13.9% SFA, 72.8% MUFA, 10.4% PUFA)
  • 1 oz. flax seeds (4 tablespoons), 11.8 g fat (8.5% SFA, 17.8% MUFA, 67.8% PUFA)
  • 1 oz. dry oatmeal (1/3 cup), 1.8 g fat (16.7% SFA, 33.3% MUFA, 33.3% PUFA)
  • 1 oz. whole wheat bread (1 slice), 0.9 g fat (22% SFA, 49% MUFA, 22% PUFA)
  • 1 medium banana, 0.4 g fat (25% SFA, <1% MUFA, 25% PUFA)
Rancid nuts produce free radicals. Outside of the body, rancid nuts smell like old socks and paint thinner. Inside the body, rancid nuts' radicals, peroxides, etc., can damage cells -- or not, depending on how effectively our body quenches (reduces) those oxidized fats, and how effectively our body repairs tissue.

Dietary omega-3 fatty acids, precursors to anti-inflammatory compounds in our body, are polyunsaturated fats. Can you tell, just by looking at the chart above, which nut contains the most omega-3? 2 Flax seeds are also high in omega-3; note their higher PUFA content above. Although, if it's an improvement in the omega-3/omega-6 ratio you're after, reducing the amount of the more abundant omega-6 in the diet is a more effective solution. (Omega-6 fatty acids are also polyunsaturated fatty acids.)

In my opinion, some nuts are better than no nuts. But there's such a thing as too many nuts.
1 SFA: Saturated fatty acid, MUFA: Monounsaturated fatty acid, PUFA: Polyunsaturated fatty acid
2 Walnuts
Graph: Homegrown

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