Myth one: Organic farming is good for the environment

The study of Life Cycle Assessments (LCAs) for the UK, sponsored by the Department for Environment, Food and Rural Affairs, should concern anyone who buys organic. It shows that milk and dairy production is a major source of greenhouse gas emissions (GHGs). A litre of organic milk requires 80 per cent more land than conventional milk to produce, has 20 per cent greater global warming potential, releases 60 per cent more nutrients to water sources, and contributes 70 per cent more to acid rain.

Also, organically reared cows burp twice as much methane as conventionally reared cattle – and methane is 20 times more powerful a greenhouse gas than CO2. Meat and poultry are the largest agricultural contributors to GHG emissions. LCA assessment counts the energy used to manufacture pesticide for growing cattle feed, but still shows that a kilo of organic beef releases 12 per cent more GHGs, causes twice as much nutrient pollution and more acid rain.

Download the new Independent Premium app Sharing the full story, not just the headlines

Life Cycle Assessment (LCA) relates food production to: energy required to manufacture artificial fertilisers and pesticides; fossil fuel burnt by farm equipment; nutrient pollution caused by nitrate and phosphate run-off into water courses; release of gases that cause acid rain; and the area of land farmed. A similar review by the University of Hohenheim, Germany, in 2000 reached the same conclusions (Hohenheim is a proponent of organic farming and quoted by the Soil Association).

Myth two: Organic farming is more sustainable

Organic potatoes use less energy in terms of fertiliser production, but need more fossil fuel for ploughing. A hectare of conventionally farmed land produces 2.5 times more potatoes than an organic one.

Heated greenhouse tomatoes in Britain use up to 100 times more energy than those grown in fields in Africa. Organic yield is 75 per cent of conventional tomato crops but takes twice the energy – so the climate consequences of home-grown organic tomatoes exceed those of Kenyan imports.

Defra estimates organic tomato production in the UK releases almost three times the nutrient pollution and uses 25 per cent more water per kg of fruit than normal production. However, a kilogram of wheat takes 1,700 joules (J) of energy to produce, against 2,500J for the same amount of conventional wheat, although nutrient pollution is three times higher for organic.

Myth three: Organic farming doesn't use pesticides

Food scares are always good news for the organic food industry. The Soil Association and other organic farming trade groups say conventional food must be unhealthy because farmers use pesticides. Actually, organic farmers also use pesticides. The difference is that "organic" pesticides are so dangerous that they have been "grandfathered" with current regulations and do not have to pass stringent modern safety tests.

For example, organic farmers can treat fungal diseases with copper solutions. Unlike modern, biodegradable, pesticides copper stays toxic in the soil for ever. The organic insecticide rotenone (in derris) is highly neurotoxic to humans – exposure can cause Parkinson's disease. But none of these "natural" chemicals is a reason not to buy organic food; nor are the man-made chemicals used in conventional farming.

Myth four: Pesticide levels in conventional food are dangerous

The proponents of organic food – particularly celebrities, such as Gwyneth Paltrow, who have jumped on the organic bandwagon – say there is a "cocktail effect" of pesticides. Some point to an "epidemic of cancer". In fact, there is no epidemic of cancer. When age-standardised, cancer rates are falling dramatically and have been doing so for 50 years.

If there is a "cocktail effect" it would first show up in farmers, but they have among the lowest cancer rates of any group. Carcinogenic effects of pesticides could show up as stomach cancer, but stomach cancer rates have fallen faster than any other. Sixty years ago, all Britain's food was organic; we lived only until our early sixties, malnutrition and food poisoning were rife. Now, modern agriculture (including the careful use of well-tested chemicals) makes food cheap and safe and we live into our eighties.

Myth five: Organic food is healthier

To quote Hohenheim University: "No clear conclusions about the quality of organic food can be reached using the results of present literature and research results." What research there is does not support the claims made for organic food.

Large studies in Holland, Denmark and Austria found the food-poisoning bacterium Campylobacter in 100 per cent of organic chicken flocks but only a third of conventional flocks; equal rates of contamination with Salmonella (despite many organic flocks being vaccinated against it); and 72 per cent of organic chickens infected with parasites.

This high level of infection among organic chickens could cross-contaminate non-organic chickens processed on the same production lines. Organic farmers boast that their animals are not routinely treated with antibiotics or (for example) worming medicines. But, as a result, organic animals suffer more diseases. In 2006 an Austrian and Dutch study found that a quarter of organic pigs had pneumonia against 4 per cent of conventionally raised pigs; their piglets died twice as often.

Disease is the major reason why organic animals are only half the weight of conventionally reared animals – so organic farming is not necessarily a boon to animal welfare.

Myth six: Organic food contains more nutrients

The Soil Association points to a few small studies that demonstrate slightly higher concentrations of some nutrients in organic produce – flavonoids in organic tomatoes and omega-3 fatty acids in organic milk, for example.

The easiest way to increase the concentration of nutrients in food is to leave it in an airing cupboard for a few days. Dehydrated foods contain much higher concentrations of carbohydrates and nutrients than whole foods. But, just as in humans, dehydration is often a sign of disease.

The study that found higher flavonoid levels in organic tomatoes revealed them to be the result of stress from lack of nitrogen – the plants stopped making flesh and made defensive chemicals (such as flavonoids) instead.

Myth seven: The demand for organic food is booming

Less than 1 per cent of the food sold in Britain is organic, but you would never guess it from the media. The Soil Association positions itself as a charity that promotes good farming practices. Modestly, on its website, it claims: "... in many ways the Soil Association can claim to be the first organisation to promote and practice sustainable development." But the Soil Association is also, in effect, a trade group – and very successful lobbying organisation.

Every year, news outlets report the Soil Association's annual claim of a big increase in the size of the organic market. For 2006 (the latest available figures) it boasted sales of £1.937bn.

Mintel (a retail consultantcy hired by the Soil Association) estimated only £1.5bn in organic food sales for 2006. The more reliable TNS Worldpanel, (tracking actual purchases) found just £1bn of organics sold – from a total food sector of £104bn. Sixty years ago all our food was organic so demand has actually gone down by 99 per cent. Despite the "boom" in organics, the amount of land being farmed organically has been decreasing since its height in 2003. Although the area of land being converted to organic usage is scheduled to rise, more farmers are going back to conventional farming.

The Soil Association invariably claims that anyone who questions the value of organic farming works for chemical manufacturers and agribusiness or is in league with some shady right-wing US free-market lobby group. Which is ironic, considering that a number of British fascists were involved in the founding of the Soil Association and its journal was edited by one of Oswald Mosley's blackshirts until the late 1960s.

All Britain's food is safer than ever before, In a serious age, we should talk about the future seriously and not use food scares and misinformation as a tactic to increase sales.

Rob Johnston is a doctor and science writer