Are Acorns Safe to Eat?

Medically Reviewed by Dan Brennan, MD on December 09, 2022
4 min read

Acorn trees are found in many parts of the world, yet few people eat them these days. You might wonder if acorns are edible. Yes, they are, but you can’t just eat them off the tree. It takes some preparation to make them edible for humans. 

Acorns are the fruit of oak trees. There are hundreds of species of oak trees around the world, with about 90 oak trees native to the US.

Acorns are easy to harvest. They store well and are relatively simple to process. Most species of acorn don’t have much flavor, similar to wheat and corn. This allows them to be used in a variety of ways. These factors are likely to have made them a major food source for millennia. They were regularly eaten by ancient peoples such as the Assyrians and Greeks, and more recently by the Chinese and Native Americans. 

You can easily harvest acorns from oak trees, but there are some important things to know about them. 

Tannins. Acorns have tannins, which taste bitter. They're toxic if consumed in large amounts and can block your body’s ability to absorb nutrients. This means tannin is actually an anti-nutrient. Consuming too many tannin-rich foods and drinks has been associated with cancers and liver damage. 

The different species of acorns have varying tannin levels. For instance, red oaks have more tannins and more bitter acorns than white oaks. This is because they germinate at different times of the year.

But tannins can be removed from acorns. When boiling or soaking the acorns, the water will turn brown from the tannic acid. This brown water should be thrown out and replaced, and then the acorns must be boiled or soaked again. This process should be repeated until the water no longer turns brown.

Another method to remove tannins is by blending the acorns with water (3 parts water to 1 part acorns). Place this mixture in large jars and put it in the fridge. The acorn meal will settle at the bottom. Pour the brown water out once per day and replace it.

Acorn pests. Acorn weevils will lay eggs in developing acorns. Their larvae feed on the nutmeat and then chew a hole to crawl out. So it’s important to check to make sure your acorns don’t have holes. 

A 1-ounce (28-gram) serving of raw acorns provides you with:

  • 110 calories
  • 1.74 grams of protein
  • 6.8 grams of fat
  • 0 grams of cholesterol
  • 11.5 grams of carbohydrates
  • 11.62 milligrams of calcium
  • 0.22 milligrams of iron
  • 17.58 milligrams of magnesium
  • 22.40 milligrams of phosphorus
  • 152.81 milligrams of potassium

Acorns also provide six vitamins, 18 amino acids, and eight minerals.

Acorns are lower in fat than many other nuts. For instance, raw almonds have 50 grams of fats in a 100-gram portion. Acorns only have half that amount. 

Peanuts are another example of this. Raw peanuts have 49 grams of fat per 100-gram serving. Again, acorns only have half that amount.

Omega-3 fatty acids. Like many nuts, acorn oil is a good source of essential fatty acids. Your body can’t make essential fatty acids so you have to get them from foods and drinks. They're important parts of the membranes that surround your cells. They also have many important functions such as storing energy.

Heart health. Researchers found that acorn oil has more phytosterols than almonds, soybeans, and olive oil.

Phytosterols or plant sterols are plant compounds that may help to lower your total and LDL or “bad” cholesterol.

Antioxidants. Acorns contain more than 60 different phenolics. These are plant compounds that act as antioxidants in your system. 

Antioxidants may help prevent some types of cell damage. Experts recommend consuming foods that are rich in antioxidants instead of taking supplements. High doses of such supplements can be harmful to you.

Acorns can be used in a variety of ways. They can be eaten whole, ground up into acorn meal or flour, or made into mush to have their oil extracted.

Once you’ve safely leached the tannins from your raw acorns, you can roast them for 15 to 20 minutes and sprinkle them with salt for a snack. You can also use roasted acorns to make acorn brittle, which is similar to peanut brittle.

Acorn coffee is a caffeine-free substitute for regular coffee. You can make it by slowly roasting acorns over low heat for about 2 hours, moving them around regularly. Remove them from the heat, let them cool, and then grind them.

If you don't want to go through the process of removing the tannins from raw acorns, you can purchase acorn flour from some specialty stores and Korean supermarkets. You can use this in bread recipes. Substitute 25% to 50% of the wheat flour in the recipe with acorn flour.  

You can make many different recipes with acorn flour, including:

  • Acorn pancakes
  • Acorn bread
  • Acorn pasta
  • Acorn dumplings
  • Acorn muffins

Ground acorns can be used in place of nuts in recipes such as cookies and brownies. You can also use it in place of cornmeal in many recipes.  

Acorn meal and flour can be kept in a sealed container in a refrigerator for a few weeks. If you store it in a freezer, it should keep for a few months. Ground acorn meal contains oil, so it’ll turn rancid if you leave it in a warm place. 

If you want to store whole acorns, dry them in their shells in direct sunlight for 2 to 5 days or in a 175-degree oven for 20 minutes. Keep the oven door slightly open so that moisture can escape. Dried acorns will remain safe to eat for several years.