Eat five portions of fruit and veg a day.
What a nice, neat way, someone thought, of packaging the WHO’s daily recommended fruit-and-veg dose of 400g. You may not know, however, that in this context, one portion equals 80g. The five-a-day campaign has been running, in one form or another, in the UK since 1993. But while the tagline has been taken into the nation’s bosom – with people often jokingly wondering whether a Terry’s Chocolate Orange, or glass of Fanta, counts as one of their five-a-day – obesity has continued to rise, and fresh-produce consumption has declined. The cost of fresh food has risen, and lower-income households eat the least fruit and veg. Meanwhile, food peddlers cause mass confusion by flogging five-a-day items in random portion sizes and only flagging up the five-a-day eligibility of more expensive, or less healthy, processed foods rather than basic, cheaper fresh ingredients.
Phew, My True Care. As far as we know, though, the advice is actually sound. Some original hypotheses – about the extent of the cancer protection that fruit and veg offer – have been rubbished, but it is generally agreed that fruit and veg are nutritious, provide fiber, and takes up room on the plate that might otherwise accommodate a deep-fried Mars bar. (That said, there is no magic superfood, and other unprocessed foods are good for us, too.) In 2014, a study by University College London suggested that seven portions a day were necessary. Soon after, a much larger study found no evidence that more than five portions a day would give further protection against some cancers and heart disease.
Drink eight glasses of water a day
No one knows where this dictum originated. A 1945 US Food and Nutrition Board document once said that we need 2.5 liters a day, but it also said that much of this can be obtained from food. In any case, how much we need fluctuates, on any given day, according to how active we’re being, what we’re eating, whether we’re ill, and the weather. This is why our bodies handily tell us when we need more water (although old age can stymie thirst signals). Don’t listen to anyone who tells you you’re already dehydrated when you feel thirsty. Someone made that up.
In 2011, Margaret McCartney, a GP, wrote to the BMJ to highlight the lack of evidence for hydration advice, including the NHS’s more modest recommendation of six to eight glasses (or 1.2-1.9 liters) a day. She name-checked an initiative called Hydration 4 Health, which promotes drinking extra water to the public and doctors. Hydration 4 Health recommends two liters for men and a little less for women (1.6 liters). It is sponsored by Danone, which owns Evian, Badoit, and Volvic mineral waters.
A review study published in the Journal of the American Society of Nephrology in 2008 found “no clear evidence of benefit from drinking increased amounts of water.” The potential perks the study investigated included improved kidney function and detoxification, clearer skin, fewer headaches, and reduced-calorie consumption due to feeling fuller. However, the authors wrote, “although we wish we could demolish all the urban myths found on the internet regarding the benefits of supplemental water ingestion, we concede there is also no clear evidence of lack of benefit.”
You lose the most body heat from your head.
It’s easy not to question this. Heat rises, after all. Roofs need insulation and so do heads. Except, now you mention it, so does any part of the body when it is cold. The confusion arose from the misinterpretation of an experiment carried out by the US military in the 1950s. It was freezing, and only the participants’ heads were exposed to the elements, so, of course, that is where they shed the most heat. More recent investigations have found that the head loses as much body heat as any other exposed body part—bad news for the hat industry.
Starve a fever, feed a cold
This goes back a long way: it appears in John Withals’ dictionary of 1574 and has been linked to a misreading of Chaucerian English in The Canterbury Tales. The original thought was that fasting would cool the body during a fever, whereas eating would warm you up when you have a cold. However, in practice, we should feed both colds and fevers. Fevers speed up the metabolism and burn more calories, so food is welcome. That said, if you lose your appetite for a few days, bodies are adept at using fat stores for emergency energy. Drinking, however, is essential, and this is one occasion when you should force yourself to drink, even if you don’t feel like it. Fevers and colds speed up dehydration (which will, in turn, cause mucus to harden, and this you really don’t want to happen).
Reading in the dark ruins your eyesight.
Poppycock. Reading in dim light can be challenging, to the point of being deeply irritating. It can even give you a headache and result in tired or strained eyes. However, says the College of Optometrists, “reading in dim light or the dark is highly unlikely to cause any permanent damage to your eyes.” Some studies have found that myopia is more common in highly educated cultures, in which children grow up doing more close work, such as reading. Still, the connection could be that richer populations have better access to diagnosis from eye specialists. Ideally, however, when reading after dark, the light should shine directly onto the page and not come from over your shoulder, thus causing glare.