Supplements That May Be Needed When Following a Gluten-Free Diet

Answer:

Although a gluten-free diet can resolve nutrient deficiencies in many people with celiac disease — a condition that results in damage to the lining of the small bowel that can lead to malabsorption — research has found that certain nutrient inadequacies may still persist among people with celiac disease, as well as those with gluten sensitivity, even after a gluten-free diet is initiated. The nutrient inadequacies are thought to be due to low nutrient intake rather than disease activity (Jivraj, Nutrition 2022).

Lower nutrient intake associated with a gluten-free diet may occur because processed and packaged gluten-free foods — particularly gluten-free flour alternatives — are not required to be fortified with folic acid, iron, thiamin, riboflavin and niacin, which is otherwise mandatory in the U.S. and Canada for wheat flour. Consequently, packaged and processed gluten-free products tend to be less nutritious than gluten-containing equivalents: For example, a study in Canada found that, on average, gluten-free grain/cereal-based foods contained 55% less iron and 44% less folate than similar gluten-containing foods. Gluten-free pasta contained 63% less fiber than gluten-containing pasta (Jamieson, PeerJ 2018). Consequently, it is important to ensure that a gluten-free diet contains sufficient amounts of nutrients. Supplementation may be necessary for people following a gluten-free diet that relies heavily on processed and packaged foods.

B vitamins

Following a gluten-free diet has been linked with inadequate blood levels of thiamin (vitamin B-1), niacin (vitamin B-3), folate (vitamin B-9), and vitamin B-12 (cyanocobalamin) (Demirkesen, Crit Rev Food Sci Nutr 2022; Caruso, Ann Med 2013; Shepherd J Hum Nutr Diet 2013). This likely results, at least in part, from the fact that gluten-free cereals/flours are not required to be fortified with B vitamins such as folate, thiamin, niacin, or riboflavin, unlike wheat flour, and people following a gluten-free diet that is also vegetarian or vegan may not get enough vitamin B-12 (Jamieson, PeerJ 2018).

Folate

Folate deficiency among people following a gluten-free diet may result from lower folate levels in some gluten-free grains as well as a lack of folate fortification/enrichment of gluten-free products (Lee, J Hum Nutr Diet 2009). Unlike cereal grains and wheat flour-based products, which are required by the FDA to be enriched with folic acid, gluten-free grains such as amaranth, buckwheat, quinoa, rice flour, potato flour, and teff are not required to be folate-fortified (Mitchell, Curr Dev Nutr 2019). Therefore, people following a gluten-free diet based heavily on these grains may not get adequate folate. (See our Top Picks among folate supplements.)

Fortunate, folate is found naturally in high amounts in a number of gluten-free foods including lentils, chickpeas, spinach, and peas (see our list of foods high in folate).

Vitamin B-12

Vitamin B-12 deficiency is common among people with celiac disease. Although long-term adherence to a gluten-free diet can resolve vitamin B-12 deficiency in many individuals, research suggests that vitamin B-12 blood levels may remain inadequate in 3% to 41% of people following a gluten-free diet (Jivraj, Nutrition 2022; Rondanelli, Medicina (Kaunas) 2019).

For this reason, it is important to ensure that a gluten-free diet includes adequate amounts of foods that are high in vitamin B-12, such as meats, poultry and fish (see our list of foods high in vitamin B-12). In some cases, people following a gluten-free diet may require a supplement (Theethira, Expert Rev Gastroenterol Hepatol 2014). This may be particularly true for those following a gluten-free diet who are vegetarian or vegan, as unfortified plant-based foods are not good sources of vitamin B-12. (See our Top Picks among vitamin B-12 supplements.)

Niacin and Thiamin

Following a gluten-free diet has been linked with inadequate intake of niacin and thiamin (Demirkesen, Crit Rev Food Sci Nutr 2022; Caruso, Ann Med 2013; Shepherd J Hum Nutr Diet 2013), although these nutrients are naturally found in many gluten-free foods as well as gluten-free products, so supplementation may not be needed provided the diet is well-balanced.

See our list of foods high in niacin and thiamin.

Fiber

Following a gluten-free diet can lead to inadequate fiber intake, as the diet involves avoiding many fiber-rich foods, and many gluten-free products are made with starches or flours with low fiber content. To avoid this risk, it may be prudent for people following gluten-free to consider consuming minor or pseudocereals such as amaranth, buckwheat, quinoa, sorghum, or teff, which contain higher amounts of fiber than grains such as rice (Saturni, Nutrients 2010; Kupper, Gastroenterology 2005). Also, consuming limited quantities oats can improve the nutrient content of gluten-free diet, although caution should be used when introducing oats into the diet as commercial oats may be contaminated with gluten from other grains (Rubio-Tapia, Am J Gastroenterol 2013) — our tests of oats and oat products showed that some products labeled "gluten-free" met the FDA standard (no more than 20 ppm of gluten) still had some gluten (at levels above 5 ppm).

Iron

Celiac disease is often associated with iron-deficiency anemia and many gluten-free foods are not fortified with iron, thus iron supplementation might be necessary (Lebovits, Pract Gastro 2023; Demirkesen, Crit Rev Food Sci Nutr 2022). See the fifth column of the Results table in our Iron Supplements Review to find out which iron supplements tested by ConsumerLab are gluten-free. Also see our Top Picks among iron supplements.

Keep in mind that it is possible to obtain necessary dietary intake of iron from a gluten-free diet alone if certain gluten-free grains are included in the diet. For example, replacing gluten-free grains with low iron content (such as rice and potato) with grains such as oats or quinoa with higher amounts of iron can boost iron intake from about 1.4 mg to 18.4 mg/day (Lee, J Hum Nutr Diet 2009).

Vitamin D

Celiac disease has been linked with lower blood levels of vitamin D, which generally results from fat malabsorption and possibly avoidance of milk products due to lactose intolerance (which is common among people with both celiac disease, as well as those with gluten sensitivity). Although strict adherence to a gluten-free diet has been shown to normalize blood levels vitamin D and improve bone mineral density among many people with celiac disease (Verma, J Family Med Prim Care 2022), some research has found that postmenopausal women with celiac disease following gluten-free diet may still have persistently low bone mineral density (Caruso, Ann Med 2013).

For this reason, it is important that people following a gluten-free diet make sure to get adequate vitamin D from their diet, particularly during winter months when sun exposure is limited. See the Getting Vitamin D from Foods section of our Vitamin D Supplements Review for details about good dietary sources of vitamin D. If vitamin D levels remain low, supplementation may be necessary although experts caution that thyroid function should be evaluated, as certain thyroid disorders have been linked to low vitamin D levels (Dura-Trave, Int J Mol Sci 2024; Di Stefano, Metabolites 2023). (See our Top Picks among vitamin D supplements.)

Other Concerns with Gluten-Free Diets

Because gluten-free foods often contain higher amounts of saturated fat and sugar than their gluten-containing counterparts, maintaining a gluten-free diet can lead to obesity and insulin resistance. A gluten-free diet can also increase exposure to heavy metals (such as arsenic in rice) (Reilly, J Pediatr 2016), although the higher amount may not represent a safety concern and may not be due specifically to intake of gluten-free foods.

If you are considering a gluten-free diet due to physical symptoms, consult your healthcare provider first, as removing gluten from your diet can make celiac disease more difficult to diagnose (NIDDK, October 2020).

How To Tell If a Drug or Supplement Is Gluten-Free?

Unlike common allergens such as peanuts or soy, which must be declared on food labels (FDA, Food Allergies 4/12/2024), supplements and drug products (including prescription and OTC medications) do not need to disclose the presence of all gluten-containing ingredients in the product (FDA, 6/30/2022; FDA, 12/12/2017).

Drugs

Fortunately, the FDA states that most drug products available in the U.S. contain no gluten or virtually no gluten. Furthermore, based on formulation information available for drug products, products that do contain wheat starch or other wheat-derived ingredients are estimated by the FDA to contain less than 0.5 mg per dose, which is slightly less than amounts allowable in 30-gram (about 1 ounce) servings of food labeled as "gluten-free." Drug products that do not list wheat gluten or wheat flour in the inactive ingredients list should not contain gluten in appreciable amounts (i.e., likely to affect a person with celiac disease). Nevertheless, the FDA encourages drug manufacturers to have updated information available about the source of their ingredients to respond to patient questions about gluten content of drug products (FDA, 12/12/2017).

Supplements

Supplements do not need to list all sources of gluten on a label, so it is advisable that people following a gluten-free diet look for supplement products listed as being "gluten-free," since this indicates the supplement should contain less than 20 ppm (i.e., 20 mg/kg) of gluten, which is considered safe for people with celiac disease. Products that include the claims "free of gluten," "without gluten," or "no gluten" are also required to meet the gluten-free claim. Be aware that products with claims such as "made with no gluten-containing ingredients" or "not made with gluten-containing ingredients" should not be assumed to be gluten-free unless the product also includes a "gluten-free" claim (FDA, 6/30/2022).

Are Hypoallergenic Supplements Always Gluten Free?

Not necessarily. Although many supplements claiming to be hypoallergenic do not contain gluten, it is important to look for products labeled as "gluten-free" and to check ingredients lists to be sure the supplement is free of gluten. See our article about gluten-free supplements for details about ConsumerLab.com's limit for gluten when testing supplements or foods labeled as being "gluten-free."

Finding Gluten-Free Supplements on ConsumerLab.com

To help people with gluten-sensitivity know whether or not products are gluten-free, ConsumerLab.com has tested for gluten in products claiming to be "gluten-free" for select, popular categories of our Product Reviews to see if the products meet their claim. For product categories in which we have tested for gluten "How can I find supplements that are gluten-free on ConsumerLab.com?"