How to fight depression with vitamin D
And minimize risk of sun damage
Welcome back, warm sun. We missed you. Log fires and binge-worthy box sets are great, for a while, but they have limited appeal. It’s time to go outside, make vitamin D and feel a whole lot better.
And therein lies your dilemma. You’re advised to cover up, or slather yourself in sunscreen at the first hint of a sunbeam. Yet avoiding the sun is counterintuitive: humans have a primeval love of warm weather, and merrily strip off to the bare minimum whenever the opportunity to do so presents itself.
The advice to avoid direct sunlight at all costs is now under question, as understanding of the role of vitamin D as an antidote to depression continues to grow. So too is our understanding of certain plant chemicals — carotenoids — which can help protect against the damaging effects of the sun.
Vitamin D and mental health
You probably associate vitamin D with bone health, but that’s just a fraction of the picture. Vitamin D also plays an important role in brain development — there are receptor sites for this vitamin throughout the brain.
A whole spectrum of neurological disorders have been linked to lack of vitamin D. These include depression, schizophrenia, dementia (including Alzheimer’s disease), and Parkinson’s disease.
Over two-thirds of people in the US and Canada have ‘suboptimal’ vitamin D.
Figures for people living in the UK are similar. A study of 45 year-old British adults revealed that 60% were vitamin D deficient — rising to 90% during spring and winter.
And even in the southern hemisphere, specifically Australia, deficiency affects a third of the population.
No wonder levels of depression continue to skyrocket. According to a major review examining the relationship between depression and vitamin D, published in the British Journal of Psychiatry in 2013,
“Our analyses are consistent with the hypothesis that low vitamin D concentration is associated with depression, and highlight the need for randomised controlled trials of vitamin D for the prevention and treatment of depression to determine whether this association is causal.”
Vitamin D — limited production
Vitamin D is made in the skin in the presence of sunlight. Or more specifically, on exposure to solar ultraviolet B (UVB). You obtain around 90% of your vitamin D supply from sun exposure - so you can see why there’s a problem here with the advice we are given to avoid the sun.
Some vitamin D is stored in the liver, which is just as well, considering. However, we can only make it during the summer months, and we can only store so much. Supplies are probably non-existent by the end of October; after that you need backup.
I am assuming that, like me, you are a resident of the northern hemisphere (with apologies to any southern hemisphere folk.) Wherever you currently reside, and whatever your ethnicity, we all share the same genetic inheritance. We can all trace our roots back to Africa. Equatorial East Africa, to be precise.
Those were the days! We ran about, mostly naked, enjoying wall-to-wall sunshine all year round. Bliss. We didn’t know it, but we had vitamin D on tap. Our dark skins offered protection from the excesses of the sun’s rays.
Then, around 70,000 years ago (the experts are still debating the exact date) we upsticked and set off to explore the big wide world.
Going up north, and down hill
Our ancestors made some baffling choices about where to settle, and ended up in some rather inhospitable places, places that required wearing more than just a strategically positioned fig leaf if they were to survive.
Migrating away from the equator, and wearing animal skins, meant a much-reduced level of exposure to sunlight.
But at least they still lived their lives in the great outdoors. Today, we have less exposure than ever, spending most of our time enclosed within insulated buildings. Couple that with lousy summers and surplus sun screen, and your chances of making adequate vitamin D are toast.
Who’s at risk? (Clue: everyone)
Vitamin D deficiency is a problem for higher latitude dwellers (we northern folk), and for dark-skinned people, who need about five times as long to produce vitamin D as the fair skinned. That’s because of the skin pigment melanin, which blocks absorption of UVB.
It’s also a problem for anyone who doesn’t get out much, for the elderly, for the very young, and for people who cover their entire bodies whenever they do venture out.
If, in addition to any of the above, you’re vegetarian or vegan, I wouldn’t fancy your chances much.
That’s because the few dietary sources of this vitamin are all animal-based. Oily fish is a good source, especially salmon. Even then, it has to be wild. Farmed salmon contains relatively little vitamin D. A smaller amount can be obtained from eggs, meat and dairy.
If, like me, you were forced to chug cod liver oil as a child, get over it. It is an exceptionally rich, albeit unpalatable, source of vitamin D.
A study published in 2011 in Public Health Nutrition investigated the differences in vitamin D blood levels of meat and fish eaters, vegetarians and vegans. The meat and fish eaters had the highest blood concentrations of vitamin D, and the vegans the lowest, even during the summer months.
Before you breathe a sigh of relief, omnivores, remember that diet still contributes only around 10% of your vitamin D intake. That makes us all vulnerable.
D, from A to Z
It’s important to ensure adequate vitamin D from an early age, because:
“Deprivation of vitamin D in early life, including prenatal life, may increase the risk of later developing schizophrenia and psychotic symptoms; conversely adults with high vitamin D status have a lower prevalence of psychotic symptoms”.
Yet children spend less time outdoors than ever before.
A recent UK study found that children spend just half the time playing outside than their parents did, clocking up just over four hours a week. In May 2018, the BBC reported that there had been a “Sharp rise in mentally ill children aged under 11.”
Figures show that 10% of UK children aged 5–16 have been diagnosed with a mental health illness.
In the US, things are not looking any better. In 2017, research found that children spend three times as many hours in front of computers and televisions each week as they do playing outside. According to the 2011–2012 National Survey of Children’s Health, 1 in 7 US children aged 2–8 had a diagnosed mental, behavioral or developmental disorder.
As we age, we become more vulnerable. That’s because our ability to make vitamin D in the skin reduces with age. People over 60 require three to four times more sun exposure than people under 20.
To block, or not to block
So the advice that we should avoid the sun at all costs clearly leaves us with a big vitamin D-shaped dilemma. And it is sound advice, up to a point.
Sunlight has two ultraviolet rays: UVA and UVB. UVB is the one needed to make vitamin D, but it can also cause your skin to burn. UVA is more damaging, as it can penetrate the outer skin and reach the cells that can become cancerous.
Sunscreen blocks the rays that are needed to make vitamin D in the skin. Even factor 15 sunscreen blocks approximately 99% of vitamin D production in the skin.
The American Academy of Dermatology recommends that vitamin D should be obtained exclusively from diet and supplements, rather than sun exposure, because of the risk of developing skin cancer.
However, not everyone agrees with that advice. Here in the UK, Public Health England has changed its policy and now recommends that everyone should have a short daily burst of sun exposure, without the use of sunscreen.
What’s the right sort of daily burst? Good question. Fortunately, researchers in Spain have endeavoured to answer it. They estimated that the duration of daily sun exposure required to obtain the recommended dose of vitamin D (around 1,000iu/day) is 10 to 20 minutes in spring and summer. That’s in Valencia, Spain. Unfortunately figures for other countries are not available, but you get the drift.
What you and tomatoes have in common
Here’s something else you can do, to maximise your protection during those short, sensible bursts. Make like a tomato.
If you have ever lain in bed, staring at the ceiling and wondering how it is that all plant life on Earth does not burn to a crisp, shortly after sunrise, here is your answer: carotenoids.
Carotenoids are plant antioxidants that protect plants from damage from UV light. They are able to absorb the harmful chemicals produced during photosynthesis, the process whereby plants make energy from sunlight.
When we eat foods that contain carotenoids, they kindly pass on this built-in protection mechanism. It is a beautiful example of the circular nature of life, of which we are an integral part.
Carotenoids take the form of an orange/red pigment, so foods that contain them are easily identifiable: sweet potato, carrots, bell peppers, tomatoes, pumpkin, squash, cantaloupe melon, mango and apricots are good examples. Less identifiable are the carotenoid-rich, dark leafy greens whose green pigment camouflages the orange. These include kale, spinach, cabbage and broccoli.
There are many different types of carotenoid, the best known being beta carotene (carrots), lycopene (tomatoes), alpha carotene (pumpkin and carrots), lutein, and zeaxanthin (kale and spinach).
Consuming carotenoid-rich food significantly lowers your risk of sun damage and skin cancer. A diet rich in lycopene in particular has been found to significantly lower the risk of burns to the skin.
Both animal and human studies have consistently shown that eating carotenoid-rich foods protects against damage from ultraviolet irradiation from the sun.
No one is suggesting that you strip off and toil semi-naked under a high sun all day, pausing only to eat carrots and drink tomato juice. We are all adults here, and know that it would be foolhardy to exposure ourselves, without sunscreen, for prolonged periods. But unless medically advised otherwise, brief, daily exposure is a great way to ensure adequate vitamin D synthesis.
And although carotenoid-rich foods provide an extra layer of protection, the odd tomato or carrot is not going to cut it. The carotenoids that you eat from fruit and vegetables are distributed around the body, with higher concentrations found in the skin and the eye. They perform many functions, and you need a regular supply, all year round.
And when the sun don’t shine?
That still leaves the autumn and winter to think about.
Whatever your level of exposure to sunlight, or how much oily fish you eat, unless you are living on the equator you almost certainly need to take supplements during the dark cold months.
Vitamin D supplementation is available in two forms: ergocalciferol (D2) and cholecalciferol (D3). It was once thought that both forms were used by the body, but we know now that D2 is considered inert, and of no value. Vitamin D3 is the form the body can use, and which is made in the skin on exposure to UVB. It is converted to 25-OHD, also known as calcidiol. This is the form of vitamin D that circulates in the blood.
Always choose D3 supplements, and read those labels carefully. You’ll still find D2 used in some supplements, because it’s cheap and convenient (for manufacturers).
Vitamin D supplements are emerging as a potentially effective way to help combat depression.
“Effective detection and treatment of inadequate vitamin D levels in persons with depression and other mental disorders may be an easy and cost-effective therapy which could improve patients’ long-term health outcomes as well as their quality of life.”
We need vitamin D, but the fact is that vitamin D deficiency is highly prevalent — deficiency is now described as a world-wide pandemic.
Just as we humans evolved in the sun, so did plants. We are also designed to eat those plant foods that can help protect from the excesses of the sun’s effects. The problem is that people are just not eating enough of these foods any more.
Only one in ten Americans meet the national recommendations for fruit and vegetable consumption.
So get eating your carotenoids now. And here’s an extra tip. Carotenoids are fat-soluble, so put some butter on those carrots. Importantly, bear in mind that these carotenoids are much more readily absorbed from cooked food, not raw. Cooking breaks down the cellulose in plant foods, making the carotenoids and other nutrients available.
If you’re wondering what to have for dinner tonight, may I suggest some grilled peppers and tomatoes, with a side of steamed spinach, to go with a fillet of wild salmon.
And keep frolicking al fresco — it’s perfectly human. You need to make vitamin D while the sun shines, but always expose yourself responsibly.