Q I am a 35-year-old man who suffers from seasonal affective disorder (SAD), including depression and sleep disturbance. I have tried remedies such as St John’s wort, melatonin (which did help, but I cannot obtain it in the UK) and antidepressants, but they didn’t agree with me. What do you advise? I travel frequently, so a liquid remedy would be impractical.

Name and address withheld

A SAD symptoms often stem from disrupted body rhythms, triggered by lower light levels in winter. The pineal gland in the brain responds to changing levels of light, regulating body rhythms and producing melatonin, the hormone that prepares the body for sleep. In darkness, it produces more, which is why we can feel depressed and lethargic in winter.

Taken at the right time, melatonin can help to stabilise circadian rhythms, which control sleep and wakefulness, by resetting the brain’s internal clock. If you tend to get to sleep after midnight and wake up tired in the morning, wanting to sleep for longer, a dose of melatonin at about 9pm can help to induce sleep and normalise your cycle. In the UK, melatonin is only available on prescription, but it is found naturally in porridge oats, bananas and peanuts. It can also be found in Asphalia (£11.95 for 30 capsules, from Revital; 0800 252875), a supplement made from fruit, vegetables, leaves and edible grasses. I have found it highly effective at regulating sleep patterns, even when they are disrupted by jet lag. Take one capsule before bedtime. It is not suitable for asthmatics or pregnant women.

Bright-light therapy is also an effective treatment for SAD. A good version for you would be the portable Litebook Elite (£150, from Health Innovations; 01926 645714), which is about the size of a CD box set. Litebook uses white-light emitting diodes with an emission spectrum that is broadly similar to the visible portion of the spectrum of natural sunlight. As little as 15 minutes each morning can make a profound difference.

Dr Julian Kenyon (www.doveclinic.com) uses Filisa (Sutherlandia frutescens) in the treatment of SAD-associated depression (£26.50 for 120 capsules; www.littleherbal-international.com). It contains GABA, an inhibitory neurotransmitter that is in short supply in the body during periods of stress and depression. Take two capsules twice a day, with meals.

— Jennifer Harper-Deacon is a registered naturopathic physician; www.jenniferharper-deacon.com

If you have any questions, write to: What’s the Alternative? Style, The Sunday Times, 1 Pennington Street, London E98 1ST. We can only provide replies to published letters

Before following any recommendation, consult your GP