Can vitamin D be used as a treatment for depression?
• Vitamin D supplementation can be beneficial to reduce the risk of developing depressive symptoms in people with low levels of vitamin D.
*There is not enough evidence to recommend the use of vitamin D as a general treatment for depression.
• Vitamin D may also reduce depressive symptoms in people who are deficient in vitamin D.
What is the best source of vitamin D?
• Vitamin D is naturally present in some foods such as oily fish (e.g. salmon, trout and sardines), egg yolk, liver and red meat. Whilst these foods can promote the maintenance of vitamin D levels; vitamin D deficiency cannot be corrected by diet alone.
• During the summer months, most people obtain enough vitamin D from sun-exposure.
• During winter in the UK, or people who already are deficient in vitamin D; oral supplements of vitamin D should be taken.
What type of vitamin D and dose should I take?
25 mcg of vitamin D3 a day.
Is taking Vitamin D alone enough?
Vitamin D is best absorbed when supported by a diet containing magnesium and probiotics; and taken with fat-containing meals – opt for healthy sources of fat like olive-oil, nuts, and avocado.
(1)(2) Vitamin D deficiency should be considered in people with the following symptoms:
• Bone pain and tenderness
• Muscle weakness
• Fatigue
• Tiredness
If you have various of these symptoms, consider talking to your GP or health professional to get your levels of vitamin D checked.
You may be at higher risk of vitamin D deficiency if you pertain to one of the following groups:
• Pregnant and breastfeeding women
• Over the age of 65
• People with darker skin – as their bodies produce less vitamin D
• Live in a region with low sun exposure or at a high latitude
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Vitamin D as a treatment for Depressive Symptoms: exploring the double D link
Vitamin D is becoming one of the most recognized vitamins in medical history (Maxmen, 2012); with its deficiency being related to the development of cardiovascular diseases (Grandi, Breitling & Brenner, 2010), coronary heart disease, and stroke (Anderson et al., 2010). Likewise, the psychological importance of vitamin D is starting to emerge. A link between vitamin D and depression followed when noticing that depressive symptoms became more common during winter, possibly because there is less opportunity to obtain vitamin D from sun exposure (Li et al., 2013). Vitamin D deficiency presents a serious health concern, with around 20% of the British population being vitamin D deficient (serum levels below 25 nmol/L) (Wise, 2014). Depression currently affects 3.3% of the British population (McManus, Bebbington, Jenkins & Brugha, 2016). The use of vitamin D as a preventative method or treatment for depression would present considerable benefits as it is much safer than antidepressants and more economical (Young, 2016). The present review will consider the scientific evidence behind: (1) whether vitamin D can be used as a treatment for depression; (2) what the best sources of vitamin D are; (3) what type and dose of vitamin D is recommended; (4) how to improve absorbance of vitamin D; and (5) who may be at higher risk of deficiency.
The double D link: Vitamin D and Depression
A large cross-sectional (level-3) study of 1,786 people aged 19 to 69 was carried out in Japan; revealing a greater likelihood of experiencing depressive symptoms for those deficient in vitamin D even after controlling alcohol consumption, sleep duration and physical activity (Mizoue et al., 2014). Similar results were found in a cross-sectional study of 52,228 Korean participants (Shin, Jung, Kim, Kim & Lim, 2016); a British study (level-3) of 5,607 older adults (de Oliveira, Hirani & Biddulph, 2018); and a cross-sectional of 7,358 patients suffering from cardiovascular disease – revealing people with low levels of vitamin D to be three times as likely to develop depression than those with normal levels, and even more likely during winter (May et al., 2010). Several meta-analyses (level-1) have associated vitamin D and depression. A systematic review and subsequent meta-analysis of 14 studies found a gradient effect between vitamin D and depression, with individuals who were deficient in vitamin D being twice as likely to develop depression (Anglin, Samaan, Walter & McDonald, 2013). Another meta-analyses found a significant inverse association in 7/16 studies (Ju, Lee & Jeong, 2012). Despite the clear association between vitamin D and depression; there is a need for randomized control trials to establish causation.
Mechanisms behind the double D link
The biological underpinnings linking vitamin D and depression are unclear. A possible explanation is an interaction between vitamin D and the Amygdala, the Amygdala contains receptors specific for Vitamin D and enzymes involved in activating vitamin D (Walbert, Jirikowski & Prüfer, 2001). The amygdala regulates emotions and hyperactivity of the amygdala has been repeatedly found to be present in individuals with depression (Yang et al., 2010).
Vitamin D as a treatment for depression in people with low levels of vitamin D
Spedding carried out a rigorous systematic review (level-1) and meta-analysis of 15 randomized control trials. All studies demonstrated statistically significant improvements of depression with Vitamin D supplements (≥200 mcg daily) with an effect size comparable to that of antidepressants. Congruent results were achieved from a longitudinal study (level-2) of 441 overweight males. After one year, subjects who took vitamin D every week showed a significant improvement in depressive scores (measured with Beck-Depression-Inventory) compared to those taking a placebo. Improvements were greatest in subjects with high depressive scores at baseline, regardless of age and body mass index. However, not all evidence is consistent, a randomized control trial (level-2) found vitamin D supplementation to be no different from placebos at reducing symptoms of depression (Kjaergaard, 2018). Such inconsistencies may result from using different measures of depression, dose of vitamin D, sample-population differences, and study duration (Cannell, 2018). Due to the inconsistency of evidence, vitamin D cannot be recommended as a treatment for depression. However, vitamin D should be taken to prevent depressive symptoms in people with low levels of vitamin D; and people with depression should ensure they maintain appropriate levels of vitamin D.
Sources of vitamin D: oral supplementation during winter
Vitamin D is mostly synthesized from upon skin exposure to sunlight (Nair., & Maseeh., 2012). During the summer months, sun-exposure is sufficient to maintain healthy levels of vitamin D ("Vitamin D", 2018). When sunlight is not available such as in winter (Jamall et al., 2016) or in locations at high latitude, vitamin D should be supplemented (Bertone-Johnson, 2009). Vitamin D requirements are also greater during pregnancy due to fetal needs of vitamin D (Althaus, 2011). A study in rural India (level-3) found that 74% of pregnant women were vitamin D deficient despite having good sun exposure (Sahu et al., 2009). Likewise, old age reduces synthesis and gut absorption of vitamin D (Boucher, 2012); and so does melatonin pigmentation in people with dark skin (Nair., & Maseeh., 2012). Vitamin D is not naturally rich in many foods aside from fatty fish. Thus, supplementation of vitamin D and light therapy have been considered as possible alternatives. For the treatment of seasonal affective disorder, a study revealed improvements in depressive scores were obtained in those subjects taking vitamin D but not light-therapy (level-2) (Alam, & Hollis,.1999).
Recommended dose and type of vitamin D
Research suggests 25 mcg of vitamin D per day is enough to increase levels 25-hydroxyvitamin D and combat vitamin D deficiency (Wolpowitz, 2016). Levels of 25-hydroxyvitamin D can be targeted either with vitamin D2 or D3; however, vitamin D3 is found to have a stronger effect (Armas, 2004).
The magnesium, fat, and, probiotics support the absorption of vitamin D
Magnesium: Magnesium activates the enzymes necessary to metabolize vitamin D (Rude et al., 1985). An analysis of two national datasets (level-3) revealed a significant association between a high intake of magnesium and reduced risks of vitamin D deficiency. They also found a significant association between vitamin D level and mortality, which was mediated by magnesium intake (Deng et al., 2013).
Fat: A systematic review and meta-analysis (level-1) of 46 studies were carried out, revealing Vitamin D is absorbed better when consumed with fat-containing meals (Silva & Furlanetto, 2017). The rationale being that fatty acids aid the absorption of vitamin D through the intestinal cell membrane (Goncalves et al., 2013).
Probiotics: Probiotics are important for maintaining gut health (Pagninia et al., 2018). A randomized controlled trial (level-2) was carried out in 127 healthy hypercholesterolemic individuals. Subjects were assigned to take either a probiotic or placebo capsule over a 9-week period, revealing that Probiotic Lactobacillus increases the circulating levels of vitamin D by facilitating the absorption of fat-soluble vitamins (Jones, Martoni & Prakash, 2013).
Conclusion
The evidence for vitamin D as a treatment for depression is unclear, with insufficient randomized controlled trial evidence supporting clinical improvement. However, unlike depression, vitamin D supplementation is relatively safe. Thus, a dose of 25 mcg vitamin D3 daily is recommended to people with vitamin D deficiency to diminish the risk of developing depressive symptoms. Moreover, people with depression should maintain adequate levels of vitamin D.