Can you eat sunflower seed shells?

In this article, we will answer the question “Can you eat sunflower seed shells?” and discuss what is its health risk?

Can you eat sunflower seed shells?

Yes, you can eventually eat sunflower seed shells, although you should not. Although sunflower seed shells are a source of antioxidants, (1) they are considered a by-product from the sunflower seed.

Due to its composition, a form of lignocellulose of high molecular weight, sunflower seed shells cannot be fully digested by the human body in its native form. Lignocellulosic biomass is a non-edible plant material which consist of the polysaccharides cellulose and hemicellulose (4).

What are the risks of eating sunflower seed shells?

The risks of eating sunflower seed shells experience a gastric bezoar, leading to intestinal perforation, possible gastric obstruction and other complications. 

The shells of sunflower seeds are not possible to be completely digested by the human digestive system and should not be consumed, as the ingestion of a high quantity of the indigestible material can lead to the formation of bezoars. 

Bezoars are retained aggregates of indigestible material that accumulate and conglomerate in the gastrointestinal tract. Based on their components, they are classified into four main types: phytobezoar (fruit and vegetable fibers), trichobezoar (hair), lactobezoar (undigested milk concretions) and pharmacobezoar (medications). Seed bezoars are a distinct subtype of phytobezoars, caused by undigested vegetable seeds or fruit pits (3).

Fibers contained in fruits and vegetables (cellulose, lignin, tannins) polymerise and agglutinate in the acidic environment of the stomach, and form a glue-like coagulum which affixes to other material and only rarely overcomes the pyloric sphincter (3). 

Case reports have documented that ingestion of unshelled sunflower seeds can cause obstructive or partially obstructive colonic or rectal bezoar. Sunflower seeds can reach the most distal colon or rectum or even the anal verge before they coalesce to form a bezoar. 

In this circumstance the patient presents with severe pain at the anal verge along with symptoms of overflow incontinence and constipation (2).

What are the benefits of eating sunflower seed shells?

The benefits of eating sunflower seed shells are the ingestion of dietary fibers. The sunflower shells contain a high amount of dietary fibers. When pulverized into very fine particles, the shell powder can be used as a fiber supplement (6).

Fiber the edible parts of the plants or analogous carbohydrates that are resistant to digestion and absorption in the human small intestine with complete or partial fermentation in the large intestine and functional fiber. 

Several studies have related consumption of dietary fiber with reduction in chronic ailments like high serum cholesterol, cardiovascular disease, certain forms of cancer, and constipation (5). 

Shells are considered a waste of the sunflower industry. However, it is possible to, through mechanical, thermal and chemical processes, such as pulverization, roasting and alkalinization or enzymatic treatment, enhance their sensory properties and improve the absorption of their nutrients.

What is the composition of sunflower seed shells?

Sunflower seed shells are composed mainly of cellulose. It contains no fat and no proteins. The chemical composition of 100 g of sunflower seed shells is as follows (7):

  • 35 g cellulose
  • 9 g hemicellulose
  • 14 g lignin
  • 1.43 g ash (minerals)

Cellulose is a natural polymer present in plants as the main component. Hemicellulose and lignin make part of the plant tissue, in a fest connection with cellulose, resulting in a very tight material, which resists digestion. Cellulose, hemicellulose and lignin are insoluble fibers.

Once ingested, this plant material is partially digested in the stomach and is fermented in the large intestine by the gut microbiota. Insoluble fibers help in treating constipation and reduce the risk of colon cancer and diverticular disease (5).

In addition to fibers, sunflower seed shells contain phenolic compounds, which are antioxidants. The natural antioxidants in foods neutralizes free radicals in the body and prevents cellular aging, development of cancer and degenerative diseases (1).

Conclusion

In this article, we answered the question “Can you eat sunflower seed shells?” and we discussed why you should not eat sunflower seed shells.

Reference

  1. Adeleke, Bartholomew Saanu, and Olubukola Oluranti Babalola. Oilseed crop sunflower (Helianthus annuus) as a source of food: Nutritional and health benefits. Food Sci Nutr, 2020, 8, 4666-4684. 
  2. Lowry, Matthew H., and Ashok N. Shah. Sunflower seed rectal bezoar in an adult. Gastroint endoscopy, 2001, 53, 388-389.
  3. Manatakis, Dimitrios K., et al. Gastrointestinal seed bezoars: a systematic review of case reports and case series. Cureus, 2019, 11, 5.
  4. Fadeyi, Adewale Elijah, et al. Compositional analysis and characterization of lignocellulosic biomass from selected agricultural wastes. J Sci Math Lett, 2020, 8, 48-56.
  5. Gajula, H., et al. Precooked bran‐enriched wheat flour using extrusion: Dietary fiber profile and sensory characteristics. J food sci, 2008, 73, S173-S179.
  6. Panak Balentić, Jelena, et al. Cocoa shell: A by-product with great potential for wide application. Molecules, 2018, 23, 1404.
  7. Silva, Mariana P., et al. Pyrolytic biochars from sunflower seed shells, peanut shells and Spirulina algae: their potential as soil amendment and natural growth regulators. SN Appl Sci, 2020, 2, 1-15.

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