Why Shorter Days Mess With Our Mood

You know the feeling: alarm goes off, it’s still pitch black, and somehow you’re meant to summon the motivation to tackle the day. Autumn and winter in the UK mean long stretches of darkness, commutes in the rain, and barely a glimpse of sunshine between September and early March.

We romanticise the cosy season — blankets, candles, hot drinks. But alongside that cosy glow, many of us feel a little flat. Shorter days throw your circadian rhythm out of sync, leaving your body unsure when to wake up or wind down. Less light exposure affects energy, mood, and even the small rituals that usually keep stress in check.

Ever notice how winter stress feels stickier — like small things hit harder, and your energy just doesn’t bounce back? Low vitamin D might be part of the picture. Without enough of it, your body loses one of its best tools for staying resilient.

Cheat Sheet

• The hype: Vitamin D is marketed as the “sunshine vitamin” — a cure-all for winter blues.
• The science: Your main source is vitamin D from sunlight, but between late September and early March the sun isn’t strong enough. That’s why vitamin D deficiency is so common in the UK.
• The benefits: Supports healthy bones, muscle health, energy regulation, and immunity. Research suggests it may also help regulate cortisol, giving you a steadier stress baseline.
• The caveats: Supplements aren’t a miracle cure. High doses can cause too much calcium in the body, so stick to around 10 micrograms daily unless advised otherwise.
• The alternatives: Oily fish, red meat, fortified foods (breakfast cereals, fat spreads, formula milk), plus outdoor daylight for circadian rhythm. But in winter, a supplement containing 10 micrograms is the most reliable option.

For a deeper dive — keep reading…

Vitamin D, Stress and Mood: What’s the Link?

Your skin naturally produces vitamin D from sunlight. But in the UK’s autumn and winter months, sunshine isn’t strong enough to provide enough vitamin D — even if you’re outside daily.

Inside the body, vitamin D regulates calcium and phosphate, keeping bones and muscles healthy. It also supports immunity and recovery. And here’s where stress comes in:

• Cortisol regulation: Vitamin D helps balance cortisol, the body’s main stress hormone. A steady baseline means you’re less reactive under pressure.
• Circadian rhythm: Sunlight regulates your body clock. Without enough vitamin D, you’re more likely to feel fatigued, foggy, and less resilient.

Why? Deficiency doesn’t cause stress, but it strips away resilience.
How? A daily vitamin D supplement helps steady your system, so stress feels easier to manage.

Low Vitamin D Levels in UK Adults: Why a Daily Supplement Is Essential

Government advice is clear: during autumn and winter, most adults in the UK should take vitamin D supplements. Here’s why deficiency is so common:

• Diet isn’t enough. Oily fish, red meat, fortified breakfast cereals, fat spreads, or infant formula all contribute, but are not enough to prevent deficiency.
• Sunlight isn’t reliable. It's no surprise that between September and early March, the UK sun isn't powerful enough to produce vitamin D in our skin.
• Symptoms are subtle. Bone pain, muscle weakness, fatigue, and low mood often overlap with stress — so deficiency can go unnoticed.

Who’s Most at Risk of Vitamin D Deficiency?

Certain groups face a higher risk of deficiency in the UK:

• People with higher melanin (darker complexions) — higher melanin reduces vitamin D production.
• Pregnant and breastfeeding women — they need more to support themselves and their baby.
• Babies and children — breastfed babies often need vitamin drops. Formula-fed babies usually get vitamin D through fortified milk.
• Older adults or those who spend long periods indoors.

For these groups, the government recommends supplements year-round. Some families can even access free vitamin D supplements through the NHS Healthy Start scheme.

Supplements vs Lifestyle: Do You Need Both?

Supplements: Consistency Through Winter

A daily vitamin D supplement containing 10 micrograms is simple, safe, and effective. Capsules, sprays, drops, or fortified drinks all work — consistency is what matters.

Lifestyle: Helpful, But Not Enough

Oily fish (salmon, sardines, mackerel), red meat, fortified foods, and daylight walks support energy and circadian rhythm. But lifestyle habits can’t fully prevent deficiency.

Why? Lifestyle helps, but can’t guarantee enough vitamin D.
How? Combine both — supplements for reliability, lifestyle for overall well-being.

How Much Vitamin D Is Enough?

• Adults: 10 micrograms daily (400 IU).
• Pregnant and breastfeeding women: supplements recommended year-round.
• Babies and young children: usually need vitamin drops.
• Adults with darker skin often benefit from supplements all year, not just winter.

High doses over long periods can cause risk of vitamin problems such as too much calcium. Stick to the standard daily supplement unless advised by a healthcare professional.

Do Vitamin D Supplements Really Work?

Evidence shows they do:

• Energy & resilience: Support muscle health and bones, creating the baseline for coping with stress.
• Immunity: Reduce the risk of acute respiratory tract infections.
• Mood: Deficiency is linked with low mood and fatigue — topping up helps remove that barrier.

Supplements won’t erase stress or symptoms. But they take deficiency off the table, giving your body steadier ground to handle pressure.

Practical Ways to Stay Steady This Autumn and Winter

• Take a daily vitamin D supplement — around 10 micrograms.
• Blend diet and daylight — oily fish, red meat, fortified foods.
• Move regularly — keeps muscles healthy and supports energy.
• Get outside — daylight helps regulate circadian rhythm.
• Stay consistent — supplements are easier than relying on food alone.

Where Chill.com Comes In

At CHILL, we curate products that actually help — so your winter toolkit feels supportive, not cluttered. Here are three simple ways to top up your vitamin D, depending on how you like to take it:

• Punchy Blueberry Hydration Drink
  Multipacks x 330ml cans by Punchy Drinks
  Hydration is an underrated stress tool. This refreshing drink delivers electrolytes (magnesium, potassium, zinc) plus vitamins C and D — supporting immunity, muscle function, and daily energy. All natural, low calorie, caffeine-free, and flavoured with real fruit.
• SuppStore Vitamin D3 + K2 Capsules
  90 vegetarian capsules | 90 day supply
  A high-strength formula designed for steady, reliable support. Each capsule combines vitamin D3 (3000 IU) with vitamin K2, helping calcium reach your bones where it’s needed most. Supports bone density, muscle strength, and immune function — ideal if you’re spending more time indoors through autumn and winter.
• Nutriburst Vitamin D3 + K2 Gummies
  60 sugar-free gummies | 30 day supply
  A plant-based option sourced from mushrooms, these gummies pair vitamin D3 with vitamin K2 to support bones, muscles, mood, and energy. Easy, tasty, and sugar-free — perfect if you want your daily supplement to feel more like a treat than a chore.

Three formats — drink, capsule, or gummy — so you can choose what fits best into your daily rhythm.

A Smarter Winter Reset

Dark mornings will always be part of UK life. But dragging yourself through them doesn’t have to be. With enough vitamin D, a steady rhythm, and small stress rituals, winter can feel more manageable.

Winter might limit the light — but you don’t have to limit your energy. Build your toolkit, find what works for you, and remember:

Stress Less. Live More.

FAQs About Vitamin D and Stress

Do pregnant women need vitamin D supplements all year round?
Yes. Government advice recommends that pregnant women and breastfeeding women take vitamin D supplements daily, as they have a higher risk of deficiency.

Can I get enough vitamin D from sunlight in autumn and winter?
No. In the UK, sunlight isn’t strong enough between September and early March. A daily vitamin D supplement is the most reliable option.

Who qualifies for free vitamin D supplements?
Some families, including those with young children, pregnant women, and those on certain benefits, can access free vitamin D supplements through the NHS Healthy Start scheme.

What happens if you take too much vitamin D?
High doses over time can lead to too much calcium in the body, increasing the risk of vitamin problems like kidney issues or bone weakness. Stick to about 10 micrograms daily unless advised otherwise.