Can you eat an eggshell? (3 Things to know)

In this brief guide, we will answer the question, Can you eat an eggshell? We will discuss whether it is safe for a person to eat an eggshell as a calcium source and the right way to make eggshells a source of calcium. 

Can you eat an eggshell?

You can eat an eggshell. Consuming eggshells is considered safe if taken in controlled amounts and can help greatly in calcium deficiencies. The calcium carbonate in eggshells reacts with hydrochloric acid in the stomach to make calcium and carbon dioxide. Eggshells can be a natural and cheaper substitute for calcium supplements. Apart from being calcium-rich, eggshells also contain several minerals like strontium, fluoride, magnesium, and selenium which all help to maintain good bone health (1,3).

According to National Health and Nutrition Examination Survey (NHANES) data, dietary supplements are widely used, with approximately half of U.S. adults and one-third of children reported using them. Furthermore, 12% of adults who used dietary supplements reported taking at least five different products (2).

What is the eggshell made of?

An eggshell is the hard outer covering of an egg made up of mainly Calcium Carbonate (CaCO3), proteins, and some other minerals. A thin layer on the eggshell is called bloom or cuticle, while there is another layer or membrane that keeps the contents inside safe. The bloom keeps bacteria and dust away from the eggshell. The cuticle of the shell is considered to be important in the waterproofing of the avian egg. Chemical analysis indicates that the cuticle contains 85-90% protein most of which is insoluble in water or potassium chloride solution, 4-5% carbohydrate, 1.5-3.5% lipid and 3-3.5% ash  (4).

The eggshell has a bumpy and grainy surface because of pores that run across it. It is estimated that there are between 100 and 300 pores/cm2 of shell surface. It is estimated that there are between 100 and 300 pores/cm2 of shell surface. The eggshell has over 17000 pores. Despite its seemingly tough surface, the eggshell is semi-permeable; it allows the exchange of air and moisture to and from the environment (4). 

How to use eggshells?

For anyone looking to increase the intake of calcium in their diet will go towards calcium supplements. Instead, half an eggshell can help with calcium deficiencies as studies show that naturally occurring calcium carbonate is more effective. It can improve joint health and even illnesses like osteoporosis due to its high calcium content. A 2.7 g of eggshell powder can provide about 100% of the recommended dietary intake of calcium for adults. Some other microelements like boron, copper, iron, molybdenum, sulfur, silicon and zinc are also present in eggshells (1).

Other than making your bones strong, eggshells are also proven to remineralize the enamel of teeth.

To provide absorbable calcium, eggshells must be powdered. There are two methods to reduce the size of the eggshell particles (1):

• mechanical processing of dry eggshell using a mixer mill,

• converting dry eggshells into powdered by using rolling pin and sieve.

What are the risks involved when eating an eggshell?

Firstly, you shouldn’t be eating large chunks of eggshells as their sharp edges might hurt your throat. The correct way would be to make it into a fine powder and consume it according to your requirement.

Secondly, raw eggs can give you Salmonella so the eggshell used must be from a boiled egg or if shells from raw eggs are used then they should be thoroughly washed and heat-treated at 250 degrees Fahrenheit. Other potential pathogens like Avian Influenza virus, Campylobacter, Staphylococcus aureus, and Enterobacteriaceae would not remain a risk after boiling (3).

Thirdly, eggshells contain toxic metals like lead, aluminum, cadmium, and mercury. Although chicken eggs have the least amount of these toxic metals and so it is safe for consumption. However, eggshells contain comparatively lesser amounts of toxic substances than oyster shell’s calcium, which is found in some calcium supplements such as Cipcal-500 (1,3).

Lastly, you should be consuming the right amount of calcium because too much of this mineral may cause kidney damage and other health issues. Use a kitchen scale to measure how many grams are needed for your diet (5). 

Can you eat eggshell membrane?

Apart from having large amounts of calcium, the eggshell also has a thin membrane that is visible when you boil an egg. This membrane is mainly composed of the protein collagen and regular intake of it may improve joint health. When preparing eggshell powder you can leave its membrane in. It also contains carbohydrates like glucose, galactose, and mannose (4).

The membrane of an eggshell has anti-inflammatory properties and can help in joint connective tissue disorders like arthritis and lupus. Medications for these illnesses have side effects like gastrointestinal problems and cardiac risks (6).

How to consume eggshells?

  • Take the eggshell of a boiled egg and dry it before making it into a fine powder using a pestle and mortar or a blender.
  •  Sieve the powder to get rid of any chunks. 
  • An adult requires about 2.5 grams of calcium which is half an eggshell, in a day you can measure the grams needed using a kitchen scale. 
  • The powder can be added to juices, yogurt, bread, or even pizza and you will not be able to taste it.
  • Although, you should control your intake of calcium supplements even in the form of an eggshell and talk to your physician before taking it.

Do you need calcium supplements?

Some individuals are more prone to being calcium deficient. For the best advice, you should consult a health practitioner.  Postmenopausal women, people who take corticosteroids, and those who have a vegan diet are at risk of being calcium deficit. 

Other individuals who have osteoporosis, high blood pressure, high body fat, colorectal cancer Crohn’s disease, or bowel inflammatory disease may also need calcium supplements in their diet (1). 

You need to watch the intake of calcium in your body, an excess dose can bring more harm than good. The body needs 1000-1200 mg of calcium in a day. 

If your body gets excessive amounts of calcium it can cause the body to have constipation, hypercalcemia, calcium build up in the tissue, and as well hinder the absorbance of other minerals including iron (7).and zinc.

Conclusion

In this brief guide, we answered the question, Can you eat an eggshell? We discussed whether it is safe for a person to eat an eggshell as a calcium source and the right way to make eggshells a source of calcium. 

Citations

  1. Waheed, Marium, et al. Eggshell calcium: A cheap alternative to expensive supplements. Trend Food Sci Technol, 2019, 91, 219-230.
  2. Bailey, Regan L. Current regulatory guidelines and resources to support research of dietary supplements in the United States. Crit rev food sci nutr, 2020, 60, 298.
  3. Chakraborty, Sagarika, and Santa Datta De. Eggshell: an alternative, cheap, bioavailable source of calcium in human diet. Res. Rev. J. Dairy Sci. Technol, 2019, 8, 25-33.
  4. Hamilton, R. M. G. The microstructure of the hen’s egg shell-a short review. Food Structure, 1986, 5, 13.
  5. Bargagli, Matteo, et al. Calcium and Vitamin D Supplementation and Their Association with Kidney Stone Disease: A Narrative Review. Nutrients, 2021, 13, 4363.
  6. Ruff, Kevin J., et al. Eggshell membrane: a possible new natural therapeutic for joint and connective tissue disorders. Results from two open-label human clinical studies. Clin Interv Aging, 2009, 4, 235.
  7. Lonnerdal, Bo. Effects of milk and milk components on calcium, magnesium, and trace element absorption during infancy. Physiol Rev, 1997, 77, 643-669.