The Independent Pharmacy

The Seasonal Affective Disorder & Vitamin D Connection

Scott McDougall
Scott McDougallMPharmDirector & Registered Manager

Reviewed on 6 Dec 2022

Seasonal affective disorder (SAD) is something millions of people experience. It strikes during the colder months of the year, causing them to suffer from many of the symptoms associated with depression.

Vitamin D is often called the ‘sunshine vitamin’. This is because it’s produced by your body when you come in contact with natural light. A deficiency in vitamin D can cause a range of medical issues, with some studies noting that it can lead people to suffer from depression.

Sunlight is in shorter supply during the colder seasons and this is why many research papers have made a link between SAD and vitamin D deficiency.

In this guide, we examine seasonal affective disorder and the vitamin D connection.

We explain what seasonal affective disorder is, and highlight the symptoms. and consider if taking vitamin D supplements can help people suffering from SAD.

What is seasonal affective disorder (SAD)?

Seasonal affective disorder (SAD) is a mood disorder that causes people to experience depression at specific times of the year. This leads sufferers to sleep more than they normally would, have lower energy levels and encounter a number of other symptoms.

People who suffer from SAD have a normal mood throughout the year but exhibit symptoms of depression during certain seasons, most commonly in winter. As a result, SAD is often referred to as ‘winter depression'.

SAD affects around 3% of the UK population, meaning that over two million people suffer from the disorder (based on Worldometer figures as of 25 October 2021).

Do I have seasonal affective disorder?

Because seasonal affective disorder (SAD) affects around 3% of people in the UK, you’re potentially close to a person suffering from SAD. This includes friends, family, colleagues and (potentially) yourself.

There are several symptoms associated with SAD, with the NHS noting that they’re similar to those that come from (non-seasonal) depression.

These are the signs the NHS highlights as being indicators that you may have depression (including SAD):

  • No longer experiencing pleasure from everyday activities
  • Loss of interest in partaking in everyday activities
  • Cravings for food containing lots of carbohydrates
  • Feeling sleeping and lethargic during the day
  • Feelings of worthlessness, guilt and despair
  • Less desire to socialise with other people
  • Not as active as you would normally be
  • Sleeping for longer periods than usual
  • Difficulty getting up in the morning
  • Feelings of anxiety and/or stress
  • Low levels of self-esteem
  • Problems concentrating
  • Persistent low mood
  • Increased appetite
  • Reduction in sex drive
  • Tearfulness
  • Irritability

These depressive indicators are also SAD symptoms. They can have a real impact on your everyday life, making it difficult for you to function.

If you think you’re suffering from SAD or depression, you should speak to a GP. They will be able to offer advice about the status of your condition and recommend the appropriate steps to take to manage and relieve it.

Is seasonal affective disorder caused by vitamin D deficiency?

There isn’t a definitive scientific opinion on the cause of seasonal affective disorder (SAD) but low levels of vitamin D have been noted in people who suffer from the condition.

It’s believed SAD is caused by a lack of sunlight, something that happens during shorter days in autumn and winter. Reduced exposure to sunlight is thought to influence the body’s production of melatonin, a hormone that makes people feel sleepy.

People suffering from SAD may produce higher than normal levels of melatonin, causing them to experience depressive symptoms of the disorder.

Our bodies use natural sunlight exposure to create vitamin D — because it’s a fat-soluble vitamin, it also needs “dietary fat in the gut for absorption”.

With there being less sunlight in the colder months, people develop less vitamin D during the autumn and winter seasons. Having lower levels of vitamin D leads to the following health issues:

  • Immune system disorders
  • Certain types of cancer
  • High blood pressure
  • Multiple sclerosis
  • Heart disease
  • Infections

Some studies have also made a connection between depression and a low vitamin D level.

A 2013 meta-analysis summarised that the results of the researchers' work “suggest a relationship between vitamin D and depression, and all but one were close to being statistically significant”.

The analysis also notes that “lower vitamin D levels were found in people with depression”.

With SAD being a depressive disorder and there being assessments conducted that form a connection between low levels of vitamin D and depression, it could be said that a vitamin D insufficiency might trigger SAD.

Is vitamin D good for seasonal affective disorder?

Studies have noted a connection between seasonal affective disorder (SAD) and low levels of vitamin D.

Specific groups have been highlighted in scientific and medical papers as having a connection between depression and a deficiency of vitamin D. A 2011 paper looked at the link between low levels of vitamin D and depression in the elderly. A 2008 study noted that vitamin D might be a valuable nutrient for women’s mental and physical well-being.

However, research on the topic hasn’t conclusively determined whether vitamin D is good for SAD. What can be done is a consideration the benefits of taking vitamin D and review them against the symptoms of SAD.

These are the benefits of taking vitamin D:

  • Supports the brain, immune system and nervous system
  • Helps regulate calcium and phosphate levels
  • Aids cardiovascular health and lung function
  • Regulates the body’s insulin levels
  • Promotes healthy teeth and bones
  • Lowers chances of flu developing
  • Reduces the threat of heart disease
  • Cuts the risk of multiple sclerosis
  • May ward off depression

The final point notes that fighting off depression is one of the benefits of taking vitamin D, meaning it might be good for seasonal affective disorder.

The capacity of vitamin D to help battle depression (and, by association, SAD) is based on research such as this 2008 paper and this 2006 study.

The former looks at the “effects of vitamin D supplementation on symptoms of depression in overweight and obese subjects”. The latter assesses whether “vitamin D deficiency is associated with anxiety and depression in fibromyalgia”.

So, it can’t be conclusively said that vitamin D is good for seasonal affective disorder. Still, it could be argued that it can help people suffering from depressive conditions, such as SAD.

What’s the best vitamin D supplementation for SAD?

Supplements are a great way of ensuring your body has the vitamins, minerals and nutrients it needs to be at its healthiest.

It’s vital to get the balance right when taking supplements, as your body can have both too many and not enough of the things it needs. This is why you should always first refer to the recommended daily allowance when deciding which vitamin supplements are best for you.

The UK government advises that taking up to 100 micrograms (µg) of vitamin D is safe for most people.

There’s also advice from the Department of Health and Social Care regarding people at risk of a vitamin D deficiency. This is is what the Department of Health and Social Care recommends:

  • Babies from birth to the age of one take 8.5µg to 10µg of vitamin D a day
  • Children aged one to four take 10µg of vitamin D a day
  • Adults and children over four take 10µg of vitamin D a day

Forceval capsules are one of the best vitamin D supplements available that provide you with 10µg of vitamin D per day. They contain a blend of 24 essential minerals, trace elements and vitamins that helps ensure your body gets the nutrients it needs to stay healthy.

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Other factors that can help people suffering from SAD

Seasonal affective disorder (SAD) is a depressive condition.

While SAD relates specifically to seasonal occurrences, its traits are characteristic of many of the symptoms people experience when suffering from depression.

There are many factors that can be considered when people are suffering from SAD, or seeking to manage and treat depression. Methods such as light therapy (SAD lamps) are used by many people for SAD, while counselling can help treat a major depressive disorder.

Treating SAD, depression and other mental health disorders isn’t a simple case of there being a single method that will treat everyone. The mental health outcomes differ from person to person, so what works for one individual might not be effective for another.

This is why it’s so important to speak to a GP if you’re struggling with SAD, as they will be able to discuss your symptoms with you and recommend the best treatment for you.

What other medical issues are connected to low vitamin D?

SAD isn’t the only thing that’s been linked to low levels of vitamin D.

A 2016 study made a connection between inflammatory bowel disease and a deficiency of vitamin D. It studied 965 patients and established that 29.9% of them had low levels of vitamin D.

Having low vitamin D could also lead to other serious conditions, such as heart disease and diabetes.

It’s even been connected to some cancers, with a 2009 paper stating that “there is a well-documented association between vitamin D intake and the risk of breast cancer”.

It adds: “low vitamin D intake has also been indicated in colorectal carcinogenesis”.

It also notes: “a vitamin D deficiency has also been documented in patients with prostate cancer, ovarian cancer, as well as multiple myeloma”.

Speak to a doctor or pharmacist to get advice on SAD

Millions of people experience seasonal affective disorder (SAD). It leads people to suffer from depressive symptoms and can have a real impact on their lives.

We’ve highlighted some methods that can help people suffering from SAD, highlighting vitamin D supplements, light therapy and counselling.

But SAD affects different people in different ways and there’s no single solution that will treat all cases of it. This means you may benefit from speaking to a doctor or pharmacist, so they can review your specific symptoms and recommend the best course of treatment.

You can speak to one of our medically qualified experts if you’d like some guidance on which course of treatment is right for your SAD.

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