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California Walnuts | Essential Food for Health

What's in a walnut?

California walnuts are an amazing food. Inside that hard outer shell you’ll find a wide variety of substances that nourish and promote good health. But before we look inside, let’s examine the protective outer shell, which comprises 55% of the walnut’s weight.

Some shelled and unshelled walnuts

Walnut shells are composed of two halves. The space between the two halves is called the shell seal. Shell seal strength varies by variety, but most are very tightly sealed to protect the nut from moisture and pests. A tight shell seal does a good job of protecting the nut, but it makes getting to the walnut meat a bit challenging.

If you pick a walnut off a tree, you’ll discover that the shell can easily be cracked open by hand; however, after washing and drying the shell becomes very hard and must be broken open using a nutcracker, hammer or other tool. Some people are able to crack the shell by placing two walnuts in one hand and squeezing, but most folks need some help.

Once you break open a walnut you’ll discover a hard fibrous membrane lining the inside of the shell and running between the two halves of the nut.  You need to remove this before eating. You’ll also notice that the walnut itself is covered by a thin skin called the pellicle. The pellicle is edible, but if you prefer your walnuts “naked”, you can blanch them in rapidly boiling water for 30 to 60 seconds and rinse under cold water. The pellicle should then slip off quite easily.

Walnut close up

The pellicle contains tannins, the same compounds found in red wine that are associated with promoting heart health. The darker the pellicle, the more tannins it contains.

Now let’s look at the walnut and all of the substances it contains. The following list represents 60 known compounds in walnuts, but there may be thousands more phytochemicals waiting to be discovered.

What’s in a walnut?

Water (4% of total shelled nut weight)

Macronutrients (94% of total shelled nut weight)

  • Fat (composed of seven different fatty acids including the essential fatty acids, linoleic acid (LA) and alpha-linolenic acid (ALA), an omega-3 fatty acid)
  • Protein (composed of 18 different amino acids)
  • Carbohydrate (composed of three different types of sugar)
  • Dietary Fiber

Micronutrients – Minerals (1% of total shelled nut weight)

  • Calcium
  • Iron
  • Magnesium
  • Phosphorus
  • Potassium
  • Sodium
  • Zinc
  • Copper
  • Manganese
  • Selenium

Micronutrients – Vitamins (0.3% of total shelled nut weight)

  • Vitamin C
  • Thiamin
  • Riboflavin
  • Niacin
  • Pantothenic Acid
  • Vitamin B6
  • Folic Acid
  • Vitamin A
  • Vitamin E (alpha-tocopherol)
  • Vitamin E (delta-tocopherol)
  • Vitamin E (gamma-tocopherol)
  • Vitamin K

Plant Sterols (0.6% of total shelled nut weight)

  • Stigmasterol
  • Campesterol
  • Beta-sitosterol

Other Substances (0.1% of total shelled nut weight)

  • Melatonin
  • Beta-carotene
  • Lutein
  • Zeaxanthin
  • Ellagic Acid
  • Gallic Acid