Vitamin D: Deficiency Symptoms, Health Benefits, Optimal Sources, And Side Effects

Vitamin D, or the “sunshine vitamin,” is considered both a fat-soluble vitamin and a hormone because it can be obtained nutritionally, and our skin can synthesise it through sunlight exposure. It is integral to various bodily functions.

Primarily recognised for enhancing calcium absorption, vitamin D plays a role in maintaining bone and dental health, supporting the immune system, regulating cell growth, influencing mood, and preventing conditions such as multiple sclerosis.

What Are the Signs and Symptoms of Vitamin D Deficiency?

Vitamin D deficiency is the most prevalent nutritional deficiency, affecting people of all ages globally. In the United States, nearly one-quarter of individuals have insufficient or deficient vitamin D blood levels, which can impact bone and overall health. Approximately 50 percent of children between ages 1 and 5 and 70 percent aged 6 to 11 experience vitamin D deficiency.

Vitamin D deficiency often arises due to insufficient sunlight exposure, inadequate dietary intake, and the skin’s inability to produce it. Also, natural foods typically do not provide enough vitamin D to prevent deficiency, making sunlight exposure a crucial factor.

Most people with vitamin D deficiency experience no symptoms. For others, common symptoms may include:

• Fatigue: Vitamin D deficiency has been linked to fatigue in uncontrolled trials, and treatment with the vitamin has been shown to improve the condition in blinded, randomised, placebo-controlled trials. Individuals with persistent and severe vitamin D deficiency may encounter symptoms linked to secondary hyperparathyroidism, including fatigue. Secondary hyperparathyroidism is when the parathyroid excretes too much hormone due to low calcium levels.
• Bone and muscle pain: A mild but prolonged vitamin D deficiency can result in chronic hypocalcemia (low calcium) and hyperparathyroidism, with symptoms such as bone pain and muscle aches.
• Muscle weakness and cramps (spasms): Increased levels of vitamin D in the bloodstream have been linked to enhanced muscle strength, physical activity, and the capability to ascend stairs, while lower concentrations are associated with a higher risk of falls among older people. Muscle spasms, particularly in infants, can be an early indication of rickets due to low blood calcium levels resulting from severe vitamin D deficiency.
• Mood changes: According to a systematic review, about a third of the studies indicated inadequate vitamin D levels were associated with depression. Others suggested supplementing with it was helpful if combined with exercise or along with other nutritional supplements.
• Bone loss: Vitamin D deficiency can cause bone loss as it impairs calcium absorption, leading to decreased calcium levels in the blood. Specifically, insufficient vitamin D limits the body’s ability to absorb only 10 percent to 15 percent of dietary calcium, whereas with normal vitamin reserves, absorption typically ranges from 30 percent to 40 percent.

Other symptoms and signs of deficiency may include:

• Heightened pain sensitivity
• A tingling sensation in the hands or feet
• A waddling gait from weakened hip or leg muscles
• Bone fractures
• Bowed legs (severe deficiency)
• Knock-knees
• Poor sleep
• Hair loss
• Increased susceptibility to illness

 Complications

The complications of vitamin D deficiency are:

• Rickets: Rickets affect children’s bones, causing them to become soft and weak, potentially leading to deformities. Symptoms and signs include bone pain, reluctance to walk, skeletal deformities such as bowed legs, thickening of joints, dental issues, delayed growth, and fragile bones prone to fractures in severe cases.
• Osteoporosis: Vitamin D deficiency can result in secondary hyperparathyroidism, leading to bone loss, osteoporosis, fractures, mineralization defects, and long-term risks of osteomalacia. Osteoporosis may cause intense back discomfort, diminished stature, or deformities in the spine, such as a bent or hunched posture.
• Osteomalacia: This is similar to rickets but can happen at any age. Characterized by bone softening, osteomalacia is primarily linked to vitamin D issues negatively affecting calcium absorption. Its symptoms and signs include bone fractures, muscle weakness, and widespread bone pain, particularly in the hips.

What Are the Health Benefits of Vitamin D?

When you eat food or supplements containing vitamin D, your body undergoes two processes to activate it. First, in the liver, vitamin D is converted to calcidiol (25-hydroxyvitamin D). After that, the kidneys further transform it into calcitriol (1,25-dihydroxyvitamin D).

Calcitriol encourages the absorption of calcium and phosphorus in the small intestine. It also works with parathyroid hormone to enhance calcium transport, which is essential for maintaining proper calcium and phosphorus levels.

Vitamin D plays a crucial role in calcium absorption, essential for strong bones and teeth. It also supports muscle and nerve function, facilitating movement and communication within the body. In addition, vitamin D is vital for the immune system, as it helps defend against infections.

• Bone health: Vitamin D helps with the absorption of calcium and phosphorus, promoting bone mineralization and bone mineral density. A meta-analysis of 12 studies involving over 42,000 individuals aged 65 and above discovered that the prevention of nonvertebral fractures with vitamin D is dependent on the dosage. A higher dose of about 500 to 800 international units (IU) resulted in a reduction of hip fractures by 18 percent and nonvertebral fractures by 20 percent for people aged 65 years or older. However, in another study involving over 25,000 generally healthy midlife and older adults, supplementing with vitamin D3 did not lead to a significantly lower risk of fractures compared to a placebo. Of note, though, patients in this study had no controlled calcium supplementation.
• Muscle and nerve function: Vitamin D may contribute to increased muscle strength by preserving muscle fibers, potentially reducing the risk of falls, a prevalent issue associated with significant disability and mortality in older individuals. Research also suggests that vitamin D plays a vital role in essential neurological functions such as cell growth, development, nerve support, protection, signal transmission, and adaptability.
• Immune system support: Vitamin D contributes to a healthy immune system. The vitamin D receptor is present in immune cells, allowing vitamin D to act locally in the immune system. The vitamin can influence both the innate and adaptive immune responses and its deficiency is linked to higher autoimmunity risk and increased vulnerability to infections. Moreover, vitamin D exhibits strong anti-inflammatory effects.

Other health benefits of vitamin D include:

• Pregnancy support: Vitamin D supplementation during pregnancy has also been associated with a reduction in the risks of small-for-gestational-age babies, preeclampsia, preterm birth, and gestational diabetes.
• Mood regulation
• Insulin level regulation: Vitamin D has been shown to lower blood glucose levels and enhance insulin sensitivity in people with diabetes.
• Weight loss: Vitamin D plays a role in preventing the formation of fat cells by influencing specific molecules, such as vitamin D receptors.
• Dental health: Research highlights a link between alveolar bone density, osteoporosis, tooth loss, and periodontal disease risk. Several reports suggest a significant connection between periodontal health and vitamin D intake.

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