What Does Inadequate Intake of Calcium and Vitamin D Cause?

October 26, 2025 •

4 min read

According to the NIH, almost one in four people in the United States have inadequate vitamin D levels. This can lead to serious health issues, as insufficient intake of both calcium and vitamin D causes a cascade of problems, most notably affecting the skeletal system but also impacting overall well-being.

Quick Summary

This guide details the wide-ranging health consequences of insufficient calcium and vitamin D, from bone diseases like rickets and osteoporosis to impaired muscle and nerve function.

Key Points

Osteoporosis Risk: Insufficient calcium and vitamin D lead to weakened, porous bones, increasing the risk of osteoporosis and fractures.
Rickets in Children: Inadequate intake during childhood causes rickets, resulting in skeletal deformities such as bowed legs due to improper bone mineralization.
Osteomalacia in Adults: The adult version of rickets, osteomalacia, causes softened bones, leading to persistent bone pain and muscle weakness.
Neuromuscular Issues: A deficiency can cause fatigue, muscle weakness, cramps, and tingling sensations by impacting nerve and muscle function.
Depression and Mood Changes: Low levels have been linked to an increased risk of mood changes, including depression and irritability.
Weakened Immunity: Vitamin D is essential for a healthy immune system, and inadequate levels can increase susceptibility to infections.
Cardiovascular and Metabolic Links: Emerging research suggests connections between insufficient calcium/vitamin D and cardiovascular disease and metabolic issues.

The Critical Role of Calcium and Vitamin D

Calcium and vitamin D are two nutrients that work in tandem to support bone health and numerous other bodily functions. Calcium is the primary building block for bones and teeth, providing them with structure and density. Our bodies cannot produce calcium, so we must obtain it through our diet. When dietary intake is insufficient, the body is forced to pull calcium from the bones to maintain normal blood levels, which are critical for nerve function, muscle contraction, and heart rhythm.

Vitamin D's essential role is to help the body absorb calcium from the intestines. It is synthesized in the skin from sun exposure and found in a limited number of foods. Without enough vitamin D, the body cannot effectively utilize the calcium consumed, regardless of the amount. This deficiency is a global issue, often resulting from insufficient sun exposure, particularly in northern latitudes, during winter months, or due to darker skin pigmentation.

Serious Bone Diseases Caused by Inadequate Intake

Chronic deficiencies in calcium and vitamin D primarily manifest as bone disorders, which can be particularly severe depending on the age of onset.

Rickets in Children

Rickets is the softening and weakening of bones in children, which can lead to painful, skeletal deformities. Because a child's bones are still growing, the growth plates are especially vulnerable to insufficient mineralization. Symptoms can include bowed legs, thickened wrists and ankles, delayed growth, bone pain, and muscle weakness.

Osteomalacia in Adults

Osteomalacia, the adult equivalent of rickets, causes a softening of the bones after growth plates have fused. This condition can lead to persistent, aching bone pain and muscle weakness, as well as an increased risk of fractures.

Osteoporosis in Adults

Osteoporosis is a condition characterized by reduced bone mass and structural deterioration, leading to increased bone fragility and a higher risk of fractures. It is often called a "silent disease" because bone loss occurs without symptoms until a fracture happens. Long-term deficiency is a significant risk factor for this condition. Advanced osteoporosis symptoms include fractures from minor trauma, loss of height, and a stooped posture.

Impact on Non-Skeletal Systems

The effects of insufficient calcium and vitamin D extend far beyond bone health, influencing several other systems in the body.

Neuromuscular and Psychological Effects

Both nutrients are crucial for proper nerve and muscle function. A severe deficiency can cause low blood calcium levels (hypocalcemia), impacting the nervous system and potentially leading to fatigue, muscle aches, cramps, tingling, and mood changes like depression.

Immune System Dysfunction

Research shows that vitamin D is vital for supporting the immune system, and deficiency is linked to an increased risk of infections.

Cardiovascular and Metabolic Issues

Emerging evidence suggests links between inadequate calcium and vitamin D and cardiovascular risk factors, as well as an increased risk of metabolic syndrome and type 2 diabetes.

Comparison of Deficiency-Related Conditions

To illustrate the differences, here is a comparison of the primary bone conditions resulting from inadequate intake.


Feature	Rickets	Osteomalacia	Osteoporosis
Affected Population	Children	Adults	Adults, particularly older adults
Pathology	Failure of bone to mineralize properly during growth	Softening of existing bone tissue due to demineralization	Loss of overall bone mass and density
Primary Cause	Severe and prolonged vitamin D and/or calcium deficiency	Severe and prolonged vitamin D and/or calcium deficiency	Long-term inadequate calcium/vitamin D, age-related bone loss
Skeletal Impact	Deformities, such as bowed legs, widened joints, and spinal curvature	Bone pain and increased fracture risk, but no deformities in adults	Increased fragility and fracture risk, especially in the hips, spine, and wrists
Key Symptom	Skeletal deformities and poor growth	Widespread bone pain and muscle weakness	Silent until a fracture occurs

Preventing Deficiency: Sources of Calcium and Vitamin D

Ensuring you get enough calcium and vitamin D is vital. A balanced diet is the best starting point.

Dietary Sources of Calcium

Calcium is available in foods like dairy products, fortified foods (cereals, juices, plant-based milks), green leafy vegetables (kale, broccoli), and canned fish with bones.

Sources of Vitamin D

Sources include sunlight exposure, fatty fish (salmon, mackerel, tuna), fortified foods, and egg yolks.

Supplementation and Lifestyle

Supplements may be recommended if diet and sun exposure are insufficient, especially for certain individuals. Magnesium is also important for vitamin D activation. Weight-bearing exercises help maintain bone strength, contributing to a defense against bone diseases.

How the Body Compensates for Insufficient Intake

When calcium and vitamin D are low, the body releases parathyroid hormone (PTH), which signals bones to release calcium into the blood. This bone demineralization helps maintain blood calcium but weakens bones over time, contributing to osteoporosis. Low vitamin D also reduces calcium absorption in the intestines.

Conclusion

Inadequate intake of calcium and vitamin D causes significant health problems, primarily affecting bone density and strength, and leading to conditions like rickets, osteomalacia, and osteoporosis. However, the consequences are not limited to the skeletal system, also impacting neuromuscular, immune, and cardiovascular health. Ensuring sufficient intake through diet, sun exposure, and supplementation is crucial for maintaining overall well-being. Consult a healthcare provider for personalized recommendations. For more detailed health information, the National Institutes of Health provides comprehensive fact sheets.

Frequently Asked Questions

Rickets affects children whose bones are still growing, causing skeletal deformities like bowed legs. Osteomalacia is the adult equivalent, causing existing bones to soften, which leads to bone pain and fractures but not deformities.

While sunlight is a major source of vitamin D, factors like latitude, season, skin pigmentation, and sunscreen use can limit production. Most people, especially in winter or at higher latitudes, cannot rely on sun exposure alone for adequate intake.

Mild calcium deficiency (hypocalcemia) is often asymptomatic, but early signs can include muscle cramps, particularly in the back and legs, dry and scaly skin, and brittle nails.

Vitamin D is crucial because it helps the intestines absorb calcium from the food you eat. Without sufficient vitamin D, your body cannot effectively use dietary calcium, forcing it to pull calcium from your bones.

Good sources of calcium include dairy products, fortified plant-based milks, leafy greens, and canned fish with bones. Vitamin D is found in fatty fish, some mushrooms, and fortified foods like milk and cereals.

Supplements can be effective, but it is important to consult a healthcare provider for the correct dosage. Excessive intake can be harmful, and a provider can determine if supplements are right for your needs.

The duration of treatment depends on the severity of the deficiency, but it can take weeks or months to restore levels. A healthcare provider can recommend a plan involving supplements to correct the imbalance.