Chia seeds are considered a superfood, due to their high nutrient contents and proven (article coming soon) wide range of health benefits.

Chia seeds are generally considered as safe to eat by the majority of the population.  However, as with any other food, there are exceptions. Some individuals may be affected, especially if large quantities are consumed.

Please consider the following cases of documented negative reactions to chia seeds.

Abdominal discomfort from excess fiber

Abdominal discomfort is probably the most common side effect of chia seeds.

Chia seeds are a great source of fiber (1oz/28g/2 tablespoons contain about 35% of RDA).

Although dietary fiber has many health benefits, it may also cause digestive issues, such as abdominal pain and discomfort, bloating, gas, diarrhea and constipation (especially with insufficient water intake).

These symptoms may occur if large amounts of chia seeds are eaten in one sitting, or if one is not accustomed to eating fiber rich foods or taking fiber supplements.

To prevent these symptoms from occurring, start with small amounts and increase gradually, but avoid excessive consumption. (1, 2)

An increase the water intake is necessary, since adequate hydration is required for the fiber to bulk up and move along the intestine.

Consumption of chia seeds may increase the risk of prostate cancer

Results from studies on the association between chia seeds and cancer are conflicting.

Chia seeds contain high amounts of Alpha-linolenic acid (ALAs) – a type of omega 3 fatty acid.

Some studies show that elevated consumption of ALAs increase the risk of prostate cancer. However, other studies show that ALAs may be protective to prostate cancer. (3, 4, 5, 6)

More research is needed.

Allergy to chia seeds is rare but possible

Cases of allergic reactions, including severe anaphylaxis, to plants of to the same family as chia (Lamiaceae) are well-documented.

Common products such as menthol toothpaste, cosmetic products containing Salvia officinalis extracts, ingesting oregano and thyme can cause such a reaction.

However, allergy to chia seeds is very rare.

In fact, the first documented case of an allergic reaction was only registered in 2015.

A 54-year-old man with a previous diagnosis of rhinitis and asthma, sensitive to grass pollen and cats dander, had the following allergic reactions to chia seeds: itchiness in the mouth, hives all over the body on the third day, angioedema (swelling of the lower layer of skin), shortness of breath and dizziness.

Six allergens in chia seeds have been identified: lectin, elongation factor, 11S globulin and another  three, not yet identified. (7)

Chia seeds and blood thinners/blood pressure medications

While two omega 3 fatty acids: EPA and DHA sourced from fish oils are well-known inhibitors of platelet aggregation, there are many studies that don’t detect any changes in platelet aggregation after supplementation with ALA rich oils.

The consumption of chia seeds may be not as effective anticoagulant as previously thought. 

Currently there is no evidence that patients on blood thinners, such as warfarin, need to restrict the consumption of the chia seeds or chia oil.

More studies are needed to reach definite conclusions on dose dependent association between ALA supplementation and coagulation factors. (8, 9, 10, 11)

Chia seeds and blood sugar related conditions

Chia seeds, due to their high fiber contents, can lower blood sugar levels after a meal. 

Patients with hypotension or on insulin management need to take special care, when introducing a high fiber food, such as chia seeds.

To prevent hypoglycemia, adjusting the insulin dosage may be necessary to compensate for the effects of fiber on lowering blood sugar. (12)

Chia seeds and Inflammatory bowel diseases (IBDs)

Although fiber is recommended for IBDs, such as Crohn’s disease or ulcerative colitis, it is recommended that, during moderate or severe activity of disease, fistulas, strictures or after surgery, fiber should be restricted and whole grain products should be avoided.

During periods of no symptoms or mild disease activity, it is recommended to slowly introduce high-fiber foods one at a time to achieve daily adequate intake.

In case of ulcerative proctitis (a mild form of ulcerative colitis), a high fiber diet accompanied  by plenty of water is recommended in case of constipation. (13)

Chia seeds and swallowing problems

People with eosinophilic esophagitis, constricted esophagus or other swallowing problems should take care when consuming chia seeds.

Eosinophilic esophagitis is an inflammatory condition with symptoms, such as swallowing difficulty and food impaction in the esophagus. 

Although rare, the first case of esophageal obstruction has been reported in 2017, in a patient with who ate a tablespoon of dry chia seeds with a glass of water. (14)

This is not a surprising risk, since chia seeds absorb water up to 27 times its size forming a gel-like substance, which can cause obstruction.

For people with swallowing problems, it is recommended to consume chia seeds after they have been fully expanded in liquid, rather than consuming them dry. It usually takes about 10 minutes for the chia seeds to fully absorb water.

Chia seeds may be contaminated

Since chia seeds absorb water so readily, they are prone to mold formation, yeast and salmonella, if not handled properly when harvesting or during sprouting.

Commercial chia producers usually test the crop for such contamination, but it may be unsafe to buy untested chia seed products from home-grown producers. (15, 16)