How your menstrual cycle affects you might become more noticeable as you get older.

Dr Clare Morrison, GP at online doctor and pharmacy MedExpress.co.uk, says:

"Premenstrual syndrome is the name given to the range of symptoms which occur for several days before the period starts each month. The main features are low mood, irritability, fatigue, bloating, breast tenderness, oily skin and increased appetite.

"The cause of these symptoms is the hormone progesterone, which is secreted by the ovary from mid-cycle (ovulation) until the period starts. The effect of progesterone is in contrast to the other female hormone, oestrogen, which is produced both before and after ovulation. In general, the two hormones have opposite effects on mood, with progesterone decreasing the 'feel-good' chemical serotonin, and oestrogen boosting its effect.

"It isn't entirely clear why PMS gets worse with age. It may be because the ovaries need more stimulation to produce a fertile egg, as the quality of each individual egg declines once a woman reaches her 30s. To compensate for the poorer quality, the pituitary gland stimulates the ovaries a bit more, so that the egg is produced earlier in the cycle, and there's a greater chance that more than one egg will be released each month. This is why older women are more likely to have non-identical twins. All this causes more progesterone to be made by the ovaries, and it starts being produced earlier in the cycle.

"This problem can become worse as the menopause approaches - the 'peri-menopause' - because not only is there lots of stimulation of the ovaries (the quality of eggs becoming much worse in a woman's 40s), but oestrogen production declines as well. The decline in oestrogen leads to hot flushes, sweats, vaginal dryness and reduced libido. There is also the tendency for heavier periods, anxieties relating to ageing, and more stress, perhaps caused by ageing parents or teenage children.

"In addition, ageing may associated with a sedentary lifestyle, less exercise, nutritional deficiencies and obesity, all of which increase the likelihood of PMS. In fact, studies show that obesity increases the risk of PMS threefold.

"Deficiency of magnesium is a much understated cause of health problems, of which PMS is one. Weight gain, alcohol, processed food, and excessive refined carbohydrate, all cause magnesium to be leached from the body. Because magnesium is a natural 'relaxer' of muscles and the nervous system, a lack of this essential mineral can cause both physical and mental tension.

"This not only results in cramps, but also PMS, anxiety and insomnia. If affected, I would suggest a supplement of magnesium citrate 100-200mg at night, or try bathing with epsom salts (which consist of magnesium sulphate) dissolved in the bath water. A lack of vitamin B6 (pyridoxine) can also increase the risk of PMS, so it may help to take a supplement.

"Progesterone is the 'pregnancy hormone'. It prepares the body for a possible pregnancy each month, and so it stimulates the appetite, which can lead to weight gain. Rather than fighting the instinctive desire to eat more (which could make the mood swings worse), I would suggest eating small regular meals, and more healthy food. Eat a diet high in lean protein, complex carbohydrates, healthy fats (such as olive oil or oily fish) and plenty of salads and vegetables - i.e. a Mediterranean diet.

"It also helps to get regular exercise, avoid alcohol and excess caffeine. Try to get some early nights and avoid stress if you can. If these strategies fail to solve the problem, see your GP. They may be able to help with hormone treatment, such as the contraceptive pill, or even antidepressants."