What Vitamin Might a Person Who Lacks Lactase Be Deficient In?

December 4, 2025 •

3 min read

According to the National Institutes of Health, approximately 65% of the world's adult population has a reduced ability to digest lactose after infancy. When individuals with lactose intolerance avoid dairy, they often cut out primary sources of specific essential nutrients from their diet, which can lead to deficiencies.

Quick Summary

Individuals who lack lactase and avoid dairy products are at a heightened risk for vitamin D and calcium deficiencies. Since dairy is a major source of these nutrients, those with lactose intolerance must seek alternative food sources or supplements to maintain optimal bone health and overall nutrition.

Key Points

Primary Deficiency: Individuals lacking lactase who avoid dairy are at high risk of vitamin D deficiency.
Secondary Deficiency: Insufficient vitamin D leads to poor calcium absorption, which can cause calcium deficiency.
Importance: Both nutrients are crucial for bone health and preventing conditions like osteoporosis.
Management: Nutritional needs can be met through alternative dietary sources, fortified foods, and supplements.
Seeking Advice: A healthcare provider can help create a balanced diet plan to manage deficiencies effectively.

The Link Between Lactose Intolerance and Vitamin D

Lactose intolerance is the inability to fully digest lactose, the sugar found in milk and milk products. This condition stems from a shortage of the enzyme lactase in the small intestine, which is responsible for breaking down lactose. For many people, symptoms like bloating, gas, and diarrhea become so uncomfortable that they choose to eliminate dairy products from their diet. While this resolves the immediate digestive issues, it can inadvertently create a nutritional problem: a potential deficiency in vitamin D.

Milk and other dairy products are major dietary sources of vitamin D, as they are often fortified with this nutrient. When dairy is removed from the diet, so is this important source. Vitamin D is a fat-soluble vitamin that plays a critical role in the body's absorption of calcium, which is also a concern for those avoiding dairy. Without adequate vitamin D, the body cannot effectively utilize the calcium it consumes, putting bone health at risk. Research has even suggested that people with the genetic predisposition for lactose intolerance may be shorter than the general population due to insufficient vitamin D intake affecting bone growth.

Managing Vitamin D and Calcium Needs

Fortunately, there are many strategies for managing nutritional needs without relying on dairy products. The goal is to find alternative, reliable sources of vitamin D and calcium to prevent long-term health complications like osteoporosis. A varied diet incorporating fortified foods and naturally rich sources is key. In some cases, supplementation may be a necessary and effective option after consulting with a healthcare professional.

Non-Dairy and Fortified Food Sources

Fatty Fish: Excellent natural sources of vitamin D include salmon, trout, and sardines. These fish also provide other beneficial nutrients.
Fortified Plant-Based Milks: Many milk alternatives like soy, almond, and oat milk are fortified with both calcium and vitamin D. Look for labels indicating fortification to ensure you are getting these nutrients.
Fortified Juices and Cereals: A number of cereals and orange juices have added calcium and vitamin D, providing another simple way to increase intake.
Leafy Greens: Calcium-rich vegetables such as kale, collard greens, and bok choy are great dietary additions. However, some greens like spinach contain oxalates that can inhibit calcium absorption, so focusing on a variety is best.
Other Food Sources: Tofu, nuts (especially almonds), and beans can contribute significantly to calcium intake.

Comparison of Dairy vs. Non-Dairy Sources


Feature	Dairy Products (e.g., Milk)	Non-Dairy Alternatives (e.g., Fortified Soy Milk)
Lactase Content	High	None
Vitamin D	Often fortified	Usually fortified
Calcium	Naturally high source	Often fortified to similar levels
Symptom Management	Causes discomfort for lactose intolerant individuals	Does not cause lactose intolerance symptoms
Gut Health	Some fermented dairy (yogurt) contains beneficial probiotics	Some products contain probiotics; often require fortification for key nutrients

The Role of Sunlight and Supplementation

Sun exposure is a primary way for the body to synthesize its own vitamin D. However, factors like geographic location, skin pigmentation, and sun protection habits can affect how much vitamin D the body produces. For those concerned about skin cancer or living in northern latitudes with limited sun, relying on sunlight alone may not be sufficient.

In such cases, dietary supplementation can be an effective way to address potential deficiencies. High-quality vitamin D3 supplements are readily available. Many healthcare providers recommend a combined calcium and vitamin D supplement to support bone health comprehensively. A doctor or registered dietitian can help determine the appropriate dosage to ensure adequate intake without exceeding the tolerable upper limit.

Conclusion

A person who lacks lactase is most likely to be deficient in vitamin D, a consequence of avoiding fortified dairy products to manage symptoms. This nutritional shortfall can also lead to inadequate calcium absorption, jeopardizing bone health. By being mindful of nutrient sources, individuals can proactively manage their health. A diet rich in non-dairy sources of vitamin D and calcium, along with judicious use of fortified products and, if necessary, supplements, can prevent deficiencies and maintain long-term well-being. Consulting a healthcare provider or a registered dietitian is always recommended to create a personalized nutritional plan. For more detailed information on nutrient needs, visit the National Institutes of Health Office of Dietary Supplements website.

Frequently Asked Questions

Lactose intolerance itself does not directly cause vitamin D deficiency. The deficiency results from avoiding fortified dairy products, which are a common dietary source of this vitamin.

Vitamin D is essential for the body to absorb calcium. For lactose intolerant individuals, low intake of fortified milk can lead to a deficiency in both vitamin D and calcium, negatively impacting bone health.

Yes, many non-dairy foods are rich in calcium, including leafy green vegetables like kale, fortified cereals, tofu (made with calcium sulfate), and some nuts and seeds like almonds and sesame seeds.

Some people with lactose intolerance can tolerate yogurt better than milk because the live, active bacterial cultures help break down the lactose. Hard, aged cheeses also have less lactose and are often well-tolerated.

A doctor can order a blood test to check your vitamin D levels. They will then advise you on whether you need to increase your intake through diet, sunlight, or supplementation.

If your diet is consistently low in dairy, you may need a supplement to ensure adequate vitamin D and calcium intake. It is important to consult with a healthcare provider to determine the right supplement and dosage for your needs.

Symptoms can be subtle and include bone or joint pain, muscle weakness, and fatigue. Long-term deficiency can lead to more serious conditions like osteoporosis.