Can low levels of vitamin D cause depression? Doctors not yet sure, but research shows a connection

It’s a vital vitamin that helps build strong bones, promotes calcium absorption, reduces inflammation, and modulates cell growth, neuromuscular and immune function. Now, new research adds to vitamin D’s myriad benefits: a healthy mind.

Dr Mari Nerhus, of Norment Research Centre at the University of Oslo’s Institute of Clinical Medicine, and colleagues have found low vitamin D levels associated with increased disease severity in psychotic disorders, and increased negative and depressive symptoms. The researchers were also able to show an association between vitamin D deficiency and cognitive impairments in processing speed and verbal fluency . Nerhus and her team are currently running studies investigating potential associations between vitamin D levels and brain structures as measured by magnetic resonance imaging (MRI).

According to Dr Tommy Chan, registered clinical psychologist at Matilda International Hospital and Matilda Medical Centre in Hong Kong, most studies show mild to moderate correlation between depression and vitamin D levels, but not a clear-cut and not a causal relationship.

“For example, individuals with low vitamin D may be due to a lack of sun exposure from outdoor activities. An active outdoor lifestyle and sport activity themselves may actually lead to less depression, not because of sun exposure and a high level of vitamin D,” Chan says. “In other words, being outdoors a lot such as playing sport could act as a confounding variable leading to less depression, instead of due to increased vitamin D from sun exposure.”

Depression is one of the biggest mental health problems among young people in Hong Kong. The number and severity of cases is on the rise, as is the number seeking help for the condition.The causes of their depression vary: work stress – high academic demands, long working hours and a fast-paced lifestyle; family discord – generational and cultural gaps – and breakdown of traditional family values; lack of transparency and intimacy in social relations; lack of physical space, privacy and time in nature; environmental pollution such as air, noise and light; and alcohol and drug abuse.

Vitamin D is a hot topic in research right now and linked to many mental and degenerative diseases such as Parkinson’s, Alzheimer’s, mood disorders and depression. It is unclear whether a low vitamin D level is causing these diseases/disorders or if the condition is causing people with these diseases to have lower vitamin D. There is no medical consensus on whether low vitamin D causes or is a symptom of these conditions.

However, it does seem that increasing vitamin D levels in the body helps with depression. One theory is that vitamin D affects the amount of monoamine neurotransmitters such as serotonin and its effect on the brain. Since antidepressant medications work by increasing the amount of monoamines in the brain, some researchers suggest that vitamin D works in a similar fashion by increasing the amount of monoamines, which in turn may help curb depression.

It is important to know that we don’t get this so-called “sunshine vitamin” from the sun. We have an inactive form near the surface of our skin, and ultraviolet B radiation in sunlight triggers the conversion and synthesis of pro-vitamin D to feasible vitamin D in skin that is then adapted in the body.

Enjoying outdoor activities for between five to 10 minutes at least twice a week can help maintain vitamin D levels.

Experts recommend between five to 10 minutes of exposure to sunlight, preferably between 10am and 3pm, at least twice a week to the face, arms, legs, or back without sunscreen.

In cities like Hong Kong, air pollution is a major concern, due to which most people tend to stay mostly indoors. “However, we have seen in our clinic that even people with healthy tans are coming in vitamin D deficient,” says Denise Fair, an accredited dietitian at Central Health Medical Practice. “It is something we are looking at more and more and finding an increasing number of people with low vitamin D levels.”

Vitamin D deficiency can be diagnosed through a 25-hydroxy vitamin D blood test. The normal range is between 30 to 74 nanograms per millilitre.

There is some indication that vitamin D deficiency might be one of the factors in seasonal affective disorder (SAD) during winter, and new evidence correlates lower levels of this nutrient with heightened risk of chronic disease including cancer and cardiovascular disease. Since vitamin D deficiency predisposes the body to high blood pressure, diabetes, metabolic syndrome, inflammation and overactivity of the parathyroid gland, these can be potential risk factors for cardiovascular disease.

Vitamin D supplements.

Apart from sunlight, another source of this fat-soluble vitamin is diet. Karen Chong, registered dietitian at Matilda International Hospital, says not many foods contain vitamin D naturally, especially vegetables. However, fish such as salmon, swordfish, and mackerel, and cod liver, can provide a healthy amount of this vitamin. Fatty fish such as tuna and sardines, egg yolk, or other fortified foods, usually cereal and milk, contain smaller amounts of it.

Apart from its role in calcium absorption, vitamin D regulates the body’s homeostasis (hormonal and immune function) and bone health. Some evidence also indicates a beneficial effect on chronic conditions such as heart disease, colon cancer, breast cancer, prostate cancer and dementia. However, its effect is uncertain and more scientifically proven studies are needed to ascertain this.

What is known for sure is that vitamin D deficiency in adults can lead to osteomalacia (softening of the bones) and bone fracture. In children, rickets and skeletal problems might be found in some cases. At-risk groups include breastfed infants, older adults, and people with limited sun exposure.

Other than sunlight and certain foods, supplements are another viable source of the vitamin. The current recommended dietary allowance set by the US Food and Nutrition Board at the Institute of Medicine of The National Academies for the population aged one to 70 is 600 IU (international units) per day.

Various studies support much higher intakes for the prevention and management of a number of diseases. The Integrated Medicine Institute recommends adults increase their intake of vitamin D to 5,000 IU per day most of the year, except when in sunny locations, to prevent major types of cancer, several other serious illnesses, and fractures.

A study conducted at Caritas Medical Centre found vitamin D deficiency to be common in Hong Kong Chinese cancer patients receiving palliative care. Moderate or severe vitamin D deficiency was associated with a higher HADS (Hospital Anxiety and Depression Scale) depression score.

But too much of a good thing could be detrimental. Since vitamin D is fat-soluble, our body has a hard time getting rid of an overdose (more than 40,000 IU per day) of it, causing the liver to produce too much of the 25(OH)D chemical. This in turn could cause hypercalcemia (high levels of calcium in the blood).

Overall, with the increasing evidence linking higher vitamin D levels with improved health outcomes, getting sufficient amounts of vitamin D appears to be a good bet to optimising our health.

Foods containing vitamin D include mushrooms, egg yolks, salmon and sardines.

Five things to eat to raise your vitamin D intake

1. Oily fish such as salmon, especially smoked salmon, swordfish, trout, white fish, mackerel, tuna, halibut, herring, sardine, rockfish, tilapia, sole and flounder.

2. A teaspoon of cod liver oil contains 440 IU of vitamin D.

3. Mushrooms, especially portobello mushrooms exposed to sunlight when growing, or before eating, provide more vitamin D.

4. Eggs yolks are a great way to get your intake of vitamin D and are quite convenient to incorporate into any meal, be it breakfast, lunch or dinner.

5. Dairy products such as fortified whole milk, buttermilk, fortified low-fat fruit yogurt, fortified goat’s milk, fortified semi-skim milk and fortified skim milk. Some dairy alternatives high in Vitamin D are soy milk, almond milk, chocolate almond milk, non-soy imitation milk, and rice drink.

(SCMP)