Over the last couple of years, certain seeds have come to be seen as superfoods. Chia and flax seeds are two well-known examples.

Both are incredibly rich in nutrients, and both have been linked to health benefits such as a healthier heart, lower blood sugar levels, and protection against certain types of cancers (1, 2).

But many people wonder which of the two seeds is actually the healthiest. This article looks at the science-based evidence behind each to answer this question.

Chia seeds are little oval-shaped seeds originating from the Salvia hispanica plant, more commonly known as the chia plant. They are sometimes called salba seeds, are usually bought whole, and come in black and white varieties.

Chia seeds are native to Mexico and Guatemala and were likely used as a staple food in ancient Aztec and Mayan diets (2).

In comparison, flax seeds are flatter and slightly bigger than chia seeds. Also known as linseeds, they are generally brown or golden, can be bought whole or ground, and are thought to originate from the Middle East.

Chia seeds taste pretty bland, whereas flax seeds have a slightly nuttier flavor. However, both types of seeds are easy to incorporate into a variety of dishes.

Summary

Chia and flax are types of seeds. Chia seeds are smaller and blander-tasting, whereas flax seeds are larger and nuttier in flavor.

Both chia and flax seeds are rich in a variety of nutrients.

This table compares the two, listing the amounts of major nutrients per 1-ounce (28-gram) portion, or around 4 tablespoons (3, 4, 5).

Flax seedsChia seeds
Calories150138
Carbs8 grams12 grams
Fiber8 grams10 grams
Protein5 grams5 grams
Fat12 grams9 grams
Thiamine38% of the DV15% of the DV
Magnesium26% of the DV23% of the DV
Phosphorus5% of the DV5% of the DV
Copper38% of the DV29% of the DV
Selenium13% of the DV28% of the DV
Iron9% of the DV12% of the DV
Zinc11% of the DV12% of the DV
Calcium6% of the DV14% of the DV
Potassium5% of the DV2% of the DV

Both seeds contain a good amount of protein and omega-3 fats. An ounce of flax contains 6,388 mg of omega-3s, while the same amount of chia seeds contains 4,915 mg (6, 7).

Flax seeds also have significantly more copper and potassium.

Chia seeds have slightly fewer calories and more fiber. They also have 2.5 times more of the bone-strengthening mineral calcium, as well as slightly more iron and phosphorus.

Summary

Both seeds are very nutritious. If you’re looking for more omega-3s, pick flax seeds. If you’re seeking higher amounts of fiber and bone-strengthening minerals, opt for chia seeds.

Both chia and flax seeds contain good amounts of alpha-linolenic acid (ALA), a type of plant-based omega-3 fat.

ALA is considered essential because it’s a type of fat your body cannot produce. This means you can only get it through your diet.

Interestingly, several studies have linked ALA to a lower risk of heart disease (8).

Several studies have also looked at the benefits of flax or chia seeds on blood pressure and cholesterol levels, two risk factors for heart disease.

Eating about 1 ounce (35 grams) of chia seeds or chia flour per day may lower blood pressure by 3–6 mm Hg in people with diabetes and by up to 11 mm Hg in those with high blood pressure (9).

Similarly, a study in 2013 found that eating about 1 ounce (about 30 grams) of flax seeds per day may help reduce blood pressure by 7–10 mm Hg in the general population and by as much as 15 mm Hg in those with high blood pressure (10).

Other older studies have shown that flax seed-enriched diets reduced levels of LDL (bad) cholesterol by up to 18% and triglyceride levels by up to 11% (11, 12).

Only a handful of studies have examined the effect of chia seeds on blood cholesterol levels, and most have failed to report any cholesterol-lowering benefits (13, 14).

That said, chia seeds contain just slightly less ALA than flax seeds, so it’s possible that they have similar heart-protective effects. More studies may simply be needed to confirm this effect.

It’s worth noting that, because of their high omega-3 content, both flax and chia may reduce blood clotting and thin the blood. People who take blood thinners should consult a healthcare professional before adding large amounts of these seeds to their diets (2, 11, 15, 16).

Summary

Both chia and flax seem to have benefits for reducing blood pressure. They may also have similar cholesterol-lowering properties, although more studies on chia seeds are needed.

Both flax and chia seeds contain good amounts of fiber, which has been linked to a lower risk of developing type 2 diabetes (17).

Fiber helps guard against type 2 diabetes by slowing down the digestion of carbs and the absorption of sugar into the blood. This leads to a more gradual rise in blood sugar levels after a meal (17).

In other words, fiber helps prevent blood sugar spikes. This stabilizes blood sugar levels and offers some protection against type 2 diabetes. In fact, several studies have linked regular consumption of flax and chia seeds to this protective effect.

For instance, studies in 2011 of people with type 2 diabetes found that taking 1–2 tablespoons of flax seed powder per day may reduce fasting blood sugar by 8–20%. These effects were seen after as little as 1–2 months (18, 19).

Similarly, older animal studies show that chia seeds may help stabilize blood sugar levels and reduce insulin resistance, both of which may help reduce the risk of developing type 2 diabetes (20, 21, 22).

Human studies from 2010 and 2013 also found that eating bread made with chia seeds may lead to smaller spikes in blood sugar than eating more traditional breads (23, 24).

Summary

Eating either flax or chia seeds each day appears to help lower blood sugar levels.

Both chia and flax seeds may help protect you against cancer in several ways.

For starters, they’re both rich in fiber, a nutrient generally linked to a lower risk of certain types of cancer (25).

Insoluble fiber, the predominant type in both chia and flax seeds, may be linked to a lower likelihood of developing colon or breast cancer (26, 27).

Both seeds also contain antioxidants, which help your body reduce its levels of free radicals. Free radicals are cell-damaging molecules that can contribute to aging and diseases such as cancer (1, 28).

However, when it comes to antioxidant levels, flax seeds may have the upper hand. That’s because they contain up to 15 times higher levels of lignans, a specific type of cancer-fighting antioxidant, than chia seeds (29).

For this reason, flax seeds may be slightly more effective than chia seeds at preventing cancers from developing.

Several observational studies support the notion that eating flax seeds on a regular basis can lower the risk of developing certain cancers.

For instance, one review noted a link between the antioxidants found in flax seeds and a lower risk of breast cancer, especially in postmenopausal women (30).

Furthermore, one 2013 study in more than 6,000 women reported that eating flax seeds regularly appeared to reduce the risk of developing breast cancer by up to 18% (31).

In a recent study, the lignans in flax seeds showed promise in slowing the growth of acute myeloid leukemia (32).

Few studies have looked at the effects of chia seeds on the risk of cancer. Because of their lower antioxidant levels, chia seeds may be slightly less effective than flax at guarding against cancer.

However, more studies are needed before strong conclusions can be made.

Summary

Both chia and flax seeds are good sources of fiber, which may reduce the risk of certain cancers. However, flax seeds contain significantly higher levels of cancer-fighting antioxidants, which give them a slight upper hand.

Chia seeds and flax seeds are both great sources of fiber, which can help reduce hunger and cravings (33).

However, they contain different levels of soluble fiber, a type particularly effective at reducing hunger and controlling appetite.

Soluble fiber tends to become sticky when mixed with water, slowing down digestion and increasing feelings of fullness.

This type of fiber is also known to trigger hormones involved in controlling hunger, which may further reduce appetite (34).

About 33% of the fiber from flax is soluble. In contrast, only 7–15% of the total fiber in chia is soluble. For this reason, flax seeds may be slightly more effective at reducing hunger and appetite than chia seeds (1, 35).

In one study, participants given a drink containing the amount of soluble fiber found in approximately 1 ounce (28 grams) of flax seeds reported lower feelings of hunger and overall appetite than those given a control drink (36).

In another, men who consumed a flax seed-containing meal reported feeling fuller and less hungry than those who ate no flax seeds (33).

Only one study could be found on the fullness effects of chia seeds.

Researchers gave participants bread containing different amounts of chia seeds. The breads with the most chia seeds reduced appetite 1.5–2 times faster than those with the least (23).

Overall, both flax seeds and chia seeds seem to reduce hunger and appetite. However, because of their higher soluble fiber content, flax seeds may be slightly more effective at doing so.

However, more studies directly comparing the two are needed.

Summary

Flax seeds contain more soluble fiber than chia seeds, which may make them slightly more effective at reducing hunger and appetite. However, more studies are needed.

Digestion is a critical function your body performs every day, helping you break down the foods you eat and absorb their nutrients.

Poor digestion can make it more difficult for your body to get all the nutrients it needs and can produce some unpleasant side effects.

Constipation and diarrhea are two of the most common side effects of poor digestion, affecting as many as 27% of people (37, 38).

Thanks to their high fiber content, flax and chia seeds may help relieve both constipation and diarrhea (39).

As mentioned earlier, there are two types of fiber: soluble and insoluble.

Soluble fiber dissolves in water, forming a gel in your gut. It can slow down the passage of food, promoting feelings of fullness (40).

Insoluble fiber does not dissolve in water and passes through your gut without changing much. This type of fiber adds bulk to your stool and may speed up the passage of food through your gut (41).

Found in both chia and flax seeds, insoluble fiber acts as a laxative, reducing constipation (42).

On the other hand, the gel-forming properties of soluble fiber, which is found mostly in flax seeds, can help digestive waste bind together, reducing diarrhea (43).

Summary

Both flax and chia seeds contain insoluble fiber, which helps relieve constipation. Flax seeds contain more soluble fiber, which may help reduce diarrhea.

Both flax and chia seeds are incredibly versatile and very easy to add to your diet. Both taste relatively bland, so you can add them to almost anything.

You can sprinkle them on top of yogurts or incorporate them into smoothies, oatmeal, or baked goods. Both can also be used to thicken sauces or as egg substitutes in many recipes.

Regarding how much to eat, most of the benefits listed above were seen with 1–2 tablespoons (10–20 grams) of seeds per day.

While both types can be consumed whole, there are advantages to consuming them ground.

Whole flax seeds can go through your gut without being absorbed, because their outer shells are hard for your intestines to break down. Eating them ground can help increase the absorption of the nutrients they contain.

Chia seeds are often consumed whole. However, studies have shown that the nutrients they contain may also be better absorbed when the seeds are ground (44).

Because of their high fat content, you should ideally store both types of seeds in the refrigerator or freezer to prevent them from going rancid. For this same reason, make sure to consume them promptly.

Summary

Both chia and flax seeds are incredibly versatile and easy to add to many dishes. Both should be consumed ground for the most health benefits.

Chia and flax seeds are both very nutritious. Both also offer similar benefits for heart health, blood sugar levels, and digestion.

However, flax seeds appear to have a slight advantage, especially when it comes to reducing hunger and appetite and lowering the risk of certain cancers. Plus, they’re often less expensive.

Ultimately, the differences between the two seeds remain small. Either flax seeds or chia seeds would be a great addition to your diet.