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The epidemic of degenerative diseases that plague people in Western countries is caused by a diet lacking in protective plant foods. In other words, it's not so much what we eat at the moment, but what we're not eating that's important to our health.

Natural compounds called phytoestrogens have been identified as a key deficiency in the Western diet and, consequently, they've become one of the hottest topics in medical research.

Phyto means plant, and estrogen is a hormone vital to both men and women. So phytoestrogens are oestrogen-like substances that come from plants. But note, they're not identical to oestrogen. They are natural plant protectants that have a range of positive effects on the body and are probably one of the most important reasons why a plant-rich-diet offers such protection against many diseases.

In the 20 years since their importance was first recognised, a mountain of research has shown the potential health benefits of a phytoestrogen-rich diet, including reducing the risk of:

There are bold claims, but they are supported by thousands of research papers in scientific and medical journals. They're not just anecdotal tales promoting yet another fad diet and ignoring the importance of other lifestyle factors such as exercise, stress and smoking.

In October 1999 the US Food and Drug Administration (FDA) approved a health claim allowing food labels to proclaim that soy protein reduces the risk of heart disease by lowering blood cholesterol. Health claims are generally prohibited in Australia and New Zealand, the exception being that the Australia New Zealand Food Authority (ANZFA) has granted a temporary provision for folate reducing the risk of certain child defects.

Soy protein is one of our richest sources of phytoestrogens. A pivotal study of patients with high cholesterol at Wake Forest University School of Medicine in the US showed that the more phytoestrogens present in the soy protein, the greater the cholesterol reduction.

In 1999, more than 300 new soy foods were launched on the US market, many of which display this health claim and quote the phytoestrogen level. Purified phytoestrogens are also available as over-the-counter pills and supplements, and large food companies worldwide such as General Mills, Goodman Fielder, Heinz, Kellogg's and Sanitarium now see phytoestrogens as a marketing buzz word. The interest is so high that even major dairy companies in Australia, such as National Foods Limited and Paul's Parmalat, are investing in this area of nutrition.

There is overwhelming evidence from population-based studies that people who consume the highest levels of phytoestrogens enjoy better health and live longer. Asians and vegetarians are two groups who are often studied, as are people who consume a traditional Mediterranean diet.

Japanese people have much lower rates of cancer and heart disease, the killer diseases of Western countries. This is largely because the traditional Japanese diet offers 30-100 times more phytoestrogens than the modern Western diet.

You might wonder whether the Japanese advantage comes from being lucky enough to have healthier genes. While genes are important, this cannot be the explanation, because Japanese people who migrate to the US tend to acquire similar rates of disease as Americans within a few generations as they adopt the local diet.

Disease rates in Asia are dramatically rising as traditional phytoestrogen-rich foods such as tofu are being replaced with Western-style fast-food diets. Statistics from Japan's Ministry of Agriculture, Forestry and Fisheries show that from 1955 to 1990, the average intake of meat increased ninefold from 5 kg to 29 kg per year while an intake of cereal grains fell from 118 kg to 104 kg. Despite this alarming trend, people in Asia still have much lower rates of the major diseases that kill Australians and New Zealanders.

The benefits of phytoestrogens go beyond just the major killers. Middle-aged women in Asia report fewer symptoms of the menopause. Only 5 per cent of Japanese women complain of hot flushes, compared with 85 per cent for North American women. Asian women also have fewer hip fractures, and phytoestrogens have been implicated because they help prevent bone loss.

The darling of all diets - probably because of its rich flavours - the traditional Mediterranean diet, also produces lower rates of heart disease and certain cancers. This diet is rich in plant foods such as vegetables, fruits, legumes, nuts, grains and olive oil. All of these foods are sources of phytoestrogens. Wine is usually drunk at meals and in moderation, while dairy products and red meat are limited.

Yet the modern Italian restaurant - except for the wine - doesn't follow this diet. Portion sizes are large, and meat and cheese will feature prominently, while legumes and the large quantity of vegetables and salads typically consumed in the Mediterranean are usually lacking. Again, the Western influence has meant the inclusion of more animal products at the expense of plant foods with all their protective elements.

Vegetarians have amazing health statistics - such as 25 per cent lower risk of dying from heart disease - according to a review of five large international studies from the US, England and Germany. They also have a lower risk of many types of cancers, based on numerous studies of Seventh-day Adventists, about half of whom are vegetarians.

One important finding from Loma Linda University in the US was a 70 per cent reduction in prostate cancer risk among Californian Seventh-day Adventist men who drank soy milk more than once a day. Soy milk is rich in phytoestrogens.

Most people know that the typical Western diet contains too many calories and excessive amounts of animal fat and foods such as red meat, which are all linked to an increased risk of heart disease and cancer. What makes the Western diet a recipe for disaster, though, is that it lacks many protective elements especially phytoestrogens.

Estimates of the American and British diets put phytoestrogen intakes at less than 1 mg/day. Intakes by Australians and New Zealanders are also generally low. This is because most Western diets lack plant foods that provide phytoestrogens and other important plant protectants, called phytoprotectants.

These foods include wholegrains, nuts, vegetables and legumes such as Soya beans, kidney beans, lentils and chick-peas. If you regularly eat a typical Western diet, you're missing out on the foods that prevent degenerative diseases.

The common thread in all the protective diets, be they Asian, Mediterranean or Vegetarian, is that they are rich in the plant foods that provide us with a large array of protectants, of which phytoestrogens are one of the most important families. There is more evidence supporting the health benefits of phytoestrogens than for any other family of plant constituents.

Traditional societies have long recognised the value of plants, not just as healthful foods, but also for medicinal purposes. They may not have understood the science, but many have eaten phytoestrogens naturally and safely for millennia - so the recent research can actually be regarded as a rediscovery of ancient knowledge. Many Westerns are unaware of the benefits of a phytoestrogen-rich diet, which is understandable because a diet deficient in these phytoestrogens does not cause obvious symptoms immediately.

Phytoestrogens are widely available in plant foods, but not in animal products, such as meat or dairy. The highest amounts of phytoestrogens are found in linseed and Soya beans and products made from them. Legumes also contain high levels. Other valuable sources include wholegrains, nuts, seeds, vegetables and fruits. The best way to get a regular dose is to choose cuisines based around these foods. Realistically, you're more likely to consume regular doses of phytoestrogens if the come in a variety of great tastes.

Phytoestrogen supplements may be helpful for some conditions, but aren't likely to have the full range of effects of phytoestrogen-rich whole foods.

* Sue Radd, is a leading nutritionist and health communicator with Sanitarium Nutrition Education Service, Locked Bag 7, Central Mail Centre, NSW 2252 Australia.