Vitamin D for SAD: Does It Really Help?

Vitamin D for SAD: Does It Really Help?

Experts believe that between 1% and 3% of all people in northern climates experience Seasonal Affective Disorder, with women being particularly at risk. The “seasonality” of SAD has naturally raised questions as to its specific causes, with some research suggesting links with shorter day length or lower sunlight intensity. Both of these, by extension, are likely to result in lower vitamin D levels than during the summer.

The obvious questions then become whether vitamin D itself has any effect on SAD, and whether supplementing with vitamin D during the winter months can improve depressive symptoms. It is these subjects that we’ll look at in this article, searching through published scientific literature together for clues...  

The Relationship Between Vitamin D Status and Depression

The starting point of our journey is whether there is any recorded affiliation between vitamin D and depression in general.

To assess the link, a psychiatric clinic collected blood samples from their patients. The vitamin D concentration was then compared to the general populace. Their results showed that not only were 58% of their psychiatric patients suffering from a vitamin D insufficiency, but furthermore the average vitamin D level in their samples was 29% below the population in general.

A similar study in the Netherlands looked at vitamin D status in retirees. Despite their greater free time (and hence ability to spend time outdoors in the sunshine) a clear pattern was observed between vitamin D levels and depressive disorders. On average, levels were found to be 14% lower in those diagnosed with depression when compared to those without.

Lastly, one of the widest-ranging studies of all looked at the vitamin D status of almost 8,000 Americans. They, too, found strong evidence of a link between vitamin D and depression, stating that the “likelihood of having depression in persons with [a] vitamin D deficiency is significantly higher compared to those with [a] vitamin D sufficiency.”

Broadly speaking, then, we can safely say that studies have repeatedly observed quite startling links. Correlation doesn’t necessarily equal causation, however. Does depression naturally cause lower levels of vitamin D, or do low levels of vitamin D increase the chances of conditions like SAD? Just as importantly, can artificially increasing vitamin D levels lessen depressive symptoms?

Does Supplementary Vitamin D Improve Seasonal Affective Disorder?

A number of studies have sought to better understand the treatment of SAD. One study, for example, compared the impact of vitamin D supplementation with that of light therapy. They found that while vitamin D levels improved in both groups, the group taking vitamin D supplements experienced far greater improvements. The experts concluded that “vitamin D may be an important treatment for SAD”.

Further evidence of this effect comes from a relatively small-scale analysis where SAD sufferers were provided either with vitamin D or a placebo tablet. Notably, this regime was commenced in late winter, when vitamin D levels tend to be at their absolute lowest. The results showed that vitamin D3 “significantly” improved depressive symptoms in volunteers.

Elsewhere, 441 Norweigians took either 20,000ius of vitamin D or a placebo, while undergoing regular assessments for SAD over the course of a year. The findings showed that “supplementation with high doses of vitamin D seems to ameliorate [depressive] symptoms indicating a possible causal relationship.”

Lastly, while most research has involved oral vitamin D supplementation, one analysis from Iran used vitamin D injections as the mode of delivery. 120 patients suffering from both depression and low vitamin D status were provided with an enormous 300,000iu dose of vitamin D. The scientists found that “the correction of vitamin D deficiency improved the depression state”.

While these are all positive results, it should be said that not all scientists are in agreement and not all research shows such overwhelming results. The effect of vitamin D on Seasonal Affective Disorder is still contentious, with one well-researched meta-analysis claiming that “current evidence does not definitively demonstrate that… vitamin D is an effective therapy for depression”.

So what are we to think? While it would be wrong to categorically say that vitamin D supplements help Seasonal Affective Disorder there is evidence to suggest that it can help in some cases.

Other Health Benefits of Vitamin D

Vitamin D has a surprisingly diverse range of positive effects on the body. Alongside the potential to ease the symptoms of SAD, individuals taking a regular vitamin D supplement may therefore find other concomitant benefits. These can make regular supplementation an even more appealing option for health-conscious individuals.

Some of the bigger benefits of maintaining optimal vitamin D can include:

Skeletal Strength

Vitamin D is perhaps best-known for its role in maintaining strong teeth and bones. It does this by facilitating the absorption of calcium from the diet, where it can be used as a key building block of the skeleton. Low vitamin D status therefore has the potential to increase the chance of fractures and breaks. While this is relevant to everyone, it should be a particular concern to individuals with a higher-than-average risk, such as post-menopausal women or older individuals.

Immune Support

Scientists are increasingly finding that vitamin D helps to fight off infections, which is perhaps at least one reason why coughs and colds are more prevalent in the winter months. If you’re prone to getting ill then you’ll want to ensure optimal vitamin D levels at all times.

Heart Function

Scientists have long noted that there is a link between high blood pressure and low vitamin D status. While the direct relationship isn’t yet fully understood, anyone concerned about their heart health would be well-advised to ensure suitable vitamin D levels in the body.

The important message here is that vitamin D can have a multitude of (positive) effects on your health. Even if supplementing with vitamin D doesn’t help your SAD, it could be argued that a vitamin D supplement still has value for the aforementioned reasons.

Vitamin D2 Vs Vitamin D3 for SAD

Vitamin D is a safe, cheap and widely-available supplement. Taking a vitamin D tablet during the darker months of the year has therefore become a way of life for many people. However, before you go out and purchase a vitamin D supplement (whether for SAD or not), it is important to understand the significant difference between the two main types - vitamin D2 and vitamin D3.

While both are forms of vitamin D that can benefit the body, D3 is the variety produced naturally by your skin. It is also far more readily absorbed by the body. One study claimed that “D3 is approximately 87% more potent” than vitamin D2, while another concluded that “vitamin D2 potency is less than one third that of vitamin D3.”

The message here is quite clear; irrespective of why you take a vitamin D supplement, wherever possible you should favour vitamin D3 over D2.

Vitamin D Lagging

Vitamin D is a so-called “fat soluble” vitamin. This means that vitamin D can be stored in the fat cells of the body for a finite period of time. This makes for a natural oscillation in vitamin D levels found within the body.

Vitamin D can be stored after production in the peak of summer, then these resources are slowly exhausted. This means that vitamin D levels in the body don’t always match the seasons exactly; it may time for stores to ramp up in the summer months, while equally supplies in the body may carry you through for some considerable time in the winter. One study, for example, found that this “lag” can be as much as 8 weeks. In this case, the statistics showed that levels of vitamin D were highest in August, with the lowest levels observed in February.

This “delayed reaction” can have a number of important impacts. Firstly, SAD sufferers may not start to experience low vitamin D levels until quite late into the autumn or winter. This can lead some sufferers to feel they’ve “got away with it” initially, only for supplies to fade some weeks or months later. Consequently if you have suffered from SAD in the past, it may be worth continuing treatment even if you feel fine, to ensure you’re not experiencing this lag phase.

Secondly, it can take time for vitamin D stores to be re-established. A few days of bright sunshine or vitamin D supplementation probably isn’t enough to fully “recharge” the body, though improvements in your outlook may become noticeable far sooner. This means that if you choose to supplement with vitamin D then it may take some time to feel the full effect, and that starting earlier than you might think necessary can make sense.

Not Just a Winter Supplement

Traditionally, vitamin D has been seen as a “winter” supplement, to take as the sun’s intensity ebbs away. Increasingly, however, health-conscious individuals are choosing to supplement year-round.

There are several reasons to consider a regular intake of vitamin D. Firstly, many of us spend long periods of time indoors, even in the summer months. Despite the opportunities for natural vitamin D production, therefore, we’re just not exposing our skin enough to benefit.

When we do finally go outside on weekends, we’re careful to cover ourselves in sunblock, which can limit the skin’s ability to generate vitamin D.

Lastly, some people - such as more mature individuals - may not create vitamin D as efficiently as they once did.

While winter is certainly the most important time of the year to consider taking a vitamin D supplement, you may wish to consider taking it as a matter-of-course all year long.

Alternative Treatments for Seasonal Affective Disorder

While vitamin D seems to represent a promising “natural” remedy for SAD, it is far from the only option. Indeed, some experts would likely recommend the following solutions before considering vitamin D supplementation.


Exposure to bright light can be highly effective in many cases of Seasonal Affective Disorder. Studies disagree with the overall success rate, with some suggesting that up to 75% of patients experience remission. Other research suggests that phototherapy is far more effective among those with mild SAD, while the impact on serious cases can be much lower.

In any case, this is one of the most frequently recommended treatments by medical professionals. The results can be surprisingly quick; many patients report improvements in as little as one to two weeks of treatment.

Traditional Antidepressants

Traditional antidepressants can be highly effective in cases of Seasonal Affective Disorder, but of course can also come with some nasty side effects. They should only be taken on the advice of your doctor, who will necessarily monitor you to ensure their suitability.

The Importance of Consulting Your Doctor

SAD is considered a depressive syndrome. Let’s be clear: depression is a serious condition. As a result, it should not be under-estimated. While there are those who will choose to supplement their diet with vitamin D as a natural remedy, it is important to seek medical attention if you suffer from any form of depression.

Your doctor will be able to gauge the seriousness of your condition and to suggest the best course of action for your situation. This may involve any or all of the treatments discussed in this article. It is also important to consult your doctor before taking any supplements if you’re receiving any other medical treatment, to ensure that negative reactions do not occur.


If you suffer from SAD then there is help available. This should always start with a visit to your doctor, who may advise a range of potential treatments.

Assuming it won’t interact with any other medications or medical conditions there is a reasonable amount of research to show that vitamin D may help SAD symptoms, at least in some patients. Bearing in mind the low cost of buying a vitamin D supplement, and all the ancillary benefits that vitamin D can have, supplementation is likely a worthy consideration.

We’ll close with the “official” advice from the Department of Health in the UK which pertains to vitamin D for the British population at large:

During the autumn and winter, you need to get vitamin D from your diet because the sun isn't strong enough for the body to make vitamin D.

But since it's difficult for people to get enough vitamin D from food alone, everyone (including pregnant and breastfeeding women) should consider taking a daily supplement containing 10 micrograms of vitamin D during the autumn and winter.