How can I find out what this list means? How natural or safe is it? I am worried about my osteoporosis, which is getting worse. - AT, Wilberfoss, York

A Many of the scary-sounding contents listed are used in the cream carrying the ‘active ingredients’ - in this case, the female hormones progesterone and oestrogen. First: are they ‘natural’? Second: do they work in the form of a cream?

‘Natural’ is a much misused and misunderstood word in alternative medicine. The only truly natural female hormones are the ones produced by the body itself. But, although the hormones used in conventional HRT drugs are either synthetic chemicals or animal-derived hormones, manufacturers of alternatives to HRT often use chemicals derived from plants such as wild yam or red clover. So they sound natural. However, as the molecules in the plants are only relatives of the hormones in women, they have to be processed in the laboratory - and thus end up being essentially the same chemicals as the ones used in conventional synthesised HRT.

Why put these so-called natural hormones in a cream rather than a pill? According to their proponents, a cream is a better delivery route than oral HRT. The theory is that, by allowing the hormones to enter the body via the skin, they bypass the liver and so bind directly with proteins in the bloodstream.

But skin creams also side-step the official drug regulatory process. As cosmetics and as long as no medicinal claims are made, ingredients need only be shown to be non-toxic rather than efficacious.

So, are they effective?

There have been two separate clinical tests of skin-based hormones in the last five years. In 1998, doctors at the Menopause Clinic in Kings College Hospital gave 20 women a hormone cream to rub on twice a day and analysed how much of the hormone entered the bloodstream. Despite the dose being four times higher than is recommended, the amount absorbed was barely detectable - and far too small to have any clinical effect (Lancet, 1998; 351: 1255-6).

In the second study, doctors in Sydney tested a skin patch containing oestrogen and progesterone on 27 postmenopausal women. To see how much of the hormones had entered the body, the researchers analysed samples of both blood and womb tissue. Again, any increases in hormone levels were negligible (Lancet, 1999; 354: 1447-8).

If you’re looking for natural treatments for osteoporosis, there are a number of other things you can try. First, supplements - of which calcium is the most important. Studies show that 1400 mg of calcium a day helps keep osteoporosis at bay after the menopause. Given that women of that age already consume about 500-600 mg of calcium in their diet, this suggests that a daily supplement of 800 mg is the minimum (J Int Med Res, 1999; 27: 1-14). You can halve that dose if you also take 3 mg (120 IU) of vitamin D, as this vitamin will double calcium uptake and use in the body. For maximum effect on osteoporosis, you can raise the daily dose to 1200 mg calcium plus 800 IU of vitamin D (Osteoporos Int, 2002; 13: 257-64).