Feel sluggish and demotivated at this time of year?

If the answer's 'yes', and you find yourself reaching for caffeine or sugar for a quick boost, you're in good company.

More than 54 per cent of British workers admit they do less work in the winter time, according to a new survey by Industry body British Summer Fruits (www.britishsummerfruits.co.uk).

Two-thirds (66 per cent) of the 2,000 workers quizzed believe they're less productive, while 69 per cent reported lower morale, and over half admit they find colleagues more difficult to work with during winter - plus, as a result, the majority (66 per cent) confessed to reaching for unhealthy snacks as a pick-me-up.

The trouble is, while reaching for a sugary quick-fix is tempting - and might provide a short-term boost - what we eat and drink can dramatically impact our moods and energy levels.

"Relying on high sugar foods, biscuits and crisps to keep us going can leave us riding the blood sugar roller coaster. We feel buzzed for a spell but soon our energy, concentration and mood can plummet," says leading food psychologist Dr Christy Fergusson, from Channel 4's Secret Eaters.

So what should we be eating to keep those moods supported? Experts share some suggestions...

:: Turkey

"During winter, we don't get as much exposure to sunlight; this can lead to a dip in your feel-good brain chemical serotonin," says Dr Fergusson. "One of the best foods for supporting your serotonin production is turkey. It's high in the amino acid tryptophan, the building block to creating serotonin."

:: Broccoli

"A lack of B vitamins can impact production of serotonin," notes Dr Fergusson. "Leafy green vegetables are packed with vital B vitamins such as folate, vitamins B3, B6 and B12. Eating your greens is a tasty way to help keep depression at bay."

:: Berries

"These nutrient-rich gems are packed with antioxidants essential for supporting the proper functioning of the brain," says Dr Fergusson. "Berries are loaded with anthocyanidins, known to help boost brain function and support the nervous system. As well as being nutrient dense, one of the best things about berries is that despite being sweet, they're low in sugar. This means you can snack away without spiking your blood sugar levels."

:: Beetroot

"Bright purple foods and berries may help clear our minds, and they certainly help me think straight," writes Rachel Kelly in new book The Happy Kitchen: Good Mood Food (Short Books, £14.99), who joined forces with nutritional therapist Alice Mackintosh to produce a collection of recipes designed to 'harness the power of food to boost mental health'. "Their pigment indicates the antioxidants they contain. These help the body produce nitric oxide, a compound that, by relaxing blood vessels, may help blood flow as well as helping in other ways."

:: Oats

Sleep is essential for balanced moods and energy. Kelly writes: "When I am not sleeping well, I like to start the day with porridge and almond milk. Oats have been associated with calming us for centuries."

:: Herbal teas

"Herbs have been used for centuries to help relax the body and induce sleep," Kelly notes in her book. Camomile is famed for its calming qualities, and "lemon balm is a member of the mint family and thought to improve mood and reduce anxiety and restlessness."

:: Oily Fish

"Oily fish, such as salmon, is high in essential omega-3 fatty acids. The modern-day diet is often deficient in omega-3, leaving people susceptible to low moods. A large percentage of our brain tissue consists of these fatty acids. We therefore need to ensure we provide our body with a good supply, so our brain messengers can work well," says Dr Fergusson.

:: Green tea

"[Green tea] contains some caffeine, which gives you a bit of a lift, but also contains the amino acid theanine, which can have a relaxing effect and may help relieve anxiety and mental stress, potentially by increasing levels of serotonin, dopamine (responsible for reward and pleasure), and gamma-aminobutyric acid (GABA, which has a relaxant effect)," explains Shona Wilkinson, nutritionist at SuperfoodUK.com.

:: Avocado

Trendy, versatile avos could help balance stress, notes Wilkinson: "Add avocado to your diet. These are a good source of magnesium, which helps with efficient energy production, while also helping to calm the nervous system."

:: Dark chocolate

"Chocolate contains several substances that may improve mood, including phenylethylamine, which can act as a brain neurotransmitter and affect mood and pleasure. Also magnesium, one of the nutrients needed for the production of serotonin. Eating any food you enjoy also stimulates endorphin release, which makes you feel good," says Wilkinson.

:: Whole-grain carbs

"Whole-grain carbs, such as rye crisp breads, help regulate levels of serotonin, the 'feel-good' neurotransmitter that helps us remain calm," notes Wilkinson.

:: Eggs

"Like nuts or seeds, Wilkinson says "eggs are a great source of protein which, when broken down in the body, will make amino acids, and these are then used to make neurotransmitters to help keep our mood balanced".