Monday, 14 May 2012

Why You Don't Need Five a Day

I eat certain vegetables and fruits for their nutritional qualities and because I like the taste and texture.  However, I never weigh or measure out servings unless I'm writing a recipe and I don't ever worry if I only eat a couple of servings in a given day.  In another blog post, I'll have a rant about the government and food advertisers teaming up to back the  '5 A DAY ' campaign.  In this one, I just want to demonstrate that there is no evidence to back up the claim that we should be eating  five portions of fruit and vegetables every day.

Human Diets in Cold Climates

If we look at history, it's obvious that human beings do not require five servings of fruit and vegetables a day.  Homo Sapiens has been around for 200,000 years.  Agriculture developed around 10,000 years ago and spread to the British Isles between 4000 and 2000 BC.  In  pre-agricultural Northern Europe, fruits and vegetables would have only been available at certain times of the year.  Even after the development of farming, lack of modern methods of preservation would mean that the supply of vegetables, and especially fruits, would be scarce during winter and spring.  Nevertheless, people managed to survive and thrive.

Up until the 20th century, the Inuit tribes living near the arctic circle had very limited access to fruits or vegetables.  On land, they hunted reindeer, moose, ptarmigan and waterfowl.  They also ate seal, whale and plenty of oily fish.  During the height of summer, they gathered berries, roots and greens.  For most of the year they were carnivores.  These tribes were incredibly healthy until many began to adopt a modern Western diet, at which point the incidence of heart disease and diabetes skyrocketed.

 Human beings can get all the vitamins and minerals they need from animal sources - as long as they aren't picky about which bits they eat.  Fish oil and eggs are both  good source of vitamins A and D.  Organ meats like liver and brains contain vitamin C. 


Scientific Studies

The largest studies ever conducted to look into the effects of fruit and vegetable consumption on disease prevention have not found any conclusive evidence to support the 5 A DAY recommendations.

The Women’s Health Initiative Dietary Modification Trial (WHIDMT) followed 48,835 postmenopausal women over eight years from 1993 - 1998.  Approximately 20,000 of them were assigned to a dietary modification intervention group.  The intervention goal was to reduce total fat intake and to increase consumption of vegetables, fruits and grains.  Comparing the two groups, researchers found that the dietary intervention did not significantly reduce the incidence of breast cancer, colorectal cancer, ovarian cancer, endometrial cancer, heart disease or stroke.  The dietary intervention also had no effect on the women's weight.

An article published in the April 2010 Journal of the National Cancer Institute reviewed data from the European Prospective Investigation into Cancer study,  This study looked into the diets of 142,605 men and 335,873 women from ten European countries between 1992 - 2000.  The authors concluded that 'the observed association of cancer risk overall with vegetable and fruit intake was very weak.'  And 'given the small magnitude of the observed associations, caution should be applied in interpretation of the results.'  They note that 'a higher intake of fruits and vegetables was also associated with other lifestyle variables, such as lower intake of alcohol, never-smoking, short duration of tobacco smoking, and higher level of physical activity, which may have contributed to a lower cancer risk.'

Fruit and vegetables can be a healthy substitute for junk food and processed foods, but the benefits depend on making informed choices.  Simply getting five portions every day without considering the rest of your diet is unlikely to lower your risk of disease or help you to lose weight.

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