Celiac disease is a chronic autoimmune condition triggered by the consumption of gluten, a protein found in wheat, barley, and rye. When a person with celiac disease ingests gluten, their immune system mistakenly launches an attack on the lining of the small intestine. This sustained immune response causes damage that significantly impairs the body’s ability to absorb nutrients from food. The resulting malabsorption makes nutritional deficiencies a common concern for individuals with untreated celiac disease.
Understanding Intestinal Damage and Malabsorption
The small intestine is lined with millions of tiny, finger-like projections called villi, which dramatically increase the surface area available for nutrient absorption. These villi are covered with even smaller microvilli, forming what is known as the brush border. In celiac disease, the immune reaction to gluten causes chronic inflammation, leading to the flattening and eventual atrophy of these villi structures.
This destruction of the small intestine’s lining drastically reduces the absorptive surface area. When the villi flatten, the intestine can no longer efficiently take in micronutrients, including vitamins and minerals, from digested food. This physical damage to the intestinal wall is the fundamental reason why patients with undiagnosed or untreated celiac disease frequently develop nutritional deficiencies.
Common Deficiencies of Water-Soluble Vitamins and Minerals
One of the most common consequences of malabsorption is iron deficiency, which can affect nearly half of all newly diagnosed adult patients. Iron is absorbed primarily in the duodenum, the first part of the small intestine, which is often the most severely damaged area in celiac disease. This deficiency frequently leads to iron-deficiency anemia, causing symptoms like persistent fatigue and weakness.
Deficiencies in B vitamins are also highly prevalent, particularly Folate (Vitamin B9) and Vitamin B12. Folate is absorbed in the upper small intestine, making it readily affected by villous atrophy. Low Folate levels can contribute to anemia and elevate a substance in the blood called homocysteine.
Although Vitamin B12 is absorbed lower down in the small intestine, its deficiency is still common, sometimes affecting up to 41% of untreated patients. A lack of B12 can lead to megaloblastic anemia and may cause neurological issues, including tingling, numbness, and difficulty with balance. Additionally, minerals such as Zinc and Magnesium are frequently found at low levels in celiac patients. Zinc deficiency can impair immune function and wound healing, while low magnesium can cause muscle cramps and weakness.
Deficiencies of Fat-Soluble Vitamins and Bone Health
The absorption of fat-soluble vitamins is compromised because they require dietary fat to be properly absorbed through the intestinal wall. Celiac damage often interferes with the body’s ability to process and absorb fats, leading to deficiencies in all four fat-soluble vitamins: A, D, E, and K.
Vitamin D deficiency is especially common, found in over half of newly diagnosed adults, because its absorption is directly tied to fat intake. Vitamin D helps the body absorb Calcium, and a lack of Vitamin D results in poor Calcium uptake. This dual deficiency significantly increases the risk for reduced bone mineral density, leading to osteopenia and osteoporosis in many untreated celiac patients.
Vitamin K is necessary for proper blood clotting function and bone metabolism. Deficiencies in Vitamin A can affect vision and immune function, though severe cases are less common in developed countries. Vitamin E, an antioxidant, is also absorbed poorly.
Testing, Supplementation, and the Role of the Gluten-Free Diet
Once a diagnosis of celiac disease is confirmed, identifying the extent of nutritional deficiencies is the next step. Healthcare providers typically use blood tests to check levels of Iron, Folate, Vitamin B12, Vitamin D, and minerals like Zinc. For adults, a bone mineral density scan (DEXA scan) is often performed to assess bone health and screen for osteopenia or osteoporosis.
Management of deficiencies involves a dual approach: initial high-dose supplementation and a lifelong commitment to a strict gluten-free diet (GFD). High-dose supplements are often prescribed to quickly correct low levels and prevent long-term complications, such as a large therapeutic dose of Vitamin D. The GFD is the primary and only treatment for celiac disease, allowing the small intestine’s villi to heal over time and gradually restore normal nutrient absorption.
While the GFD is necessary for intestinal healing, it can sometimes introduce new nutritional challenges. Many commercially available gluten-free products are not fortified with B vitamins and Iron to the same degree as their wheat-based counterparts. Individuals on a GFD must remain vigilant about their nutrient intake, often requiring continued, monitored supplementation and dietary planning to ensure levels of Iron, Folate, and B vitamins remain adequate.