Health myths busted: Can too much sleep kill you and is popcorn is good for you?

Science is busting myths we’ve long believed true, which might make you think differently about your lifestyle.

Myth: The slimmer you are, the longer you’ll live

Truth: Carrying a few extra pounds could help you live longer according to a new study by State University New York. It found moderately overweight people were less likely to die from heart problems than those who were underweight.

“We can only speculate why,” says lead researcher Dr Abhishek Sharma, “but it may be that overweight patients are more likely to be prescribed heart-protective medications such as beta blockers and statins, so their hearts are better able to cope under strain.”

It’s not the first study with similar ­findings – previous research has found that a higher BMI protects against death from many diseases, despite the fact it can also trigger them.

Being obese is still viewed as unhealthy, but scientists suspect that people who carry just a little extra weight may have more fat reserves to call upon should they lose weight due to ill health as they get older.

Myth: You should exercise five times a week for 30 minutes

Truth: The current recommended 150 minutes per week of moderate ­exercise may not be the most efficient way to work out. The latest research shows that shorter, higher intensity exercise – even as little as six minutes per week – could be more effective.

Heriot-Watt University in Edinburgh reported substantial benefits when ­volunteers did 30-second sprint sessions three times a week on an exercise bike.

It does mean working at a harder level than normal, but in such short bursts it’s bearable, plus it makes fitting exercise into a busy week a whole lot easier.

Myth: Red meat is bad for your heart

Truth: Eaten as part of a balanced diet, red meat doesn’t cause heart disease and has lots of health benefits.

According to diet expert Dr Michael Mosley, the idea that saturated animal fat, as found in red meat and butter, clogs the arteries stems from a paper by American scientist Ancel Keys in 1953.

From then until very recently, people were warned to cut down on meat and dairy ­products and ­encouraged to switch to starchy carbohydrates and vegetable oils to reduce their risk of heart disease.

But now the latest research is pointing to sugar as the greater dietary evil, and this year a British Heart ­Foundation review of 72 previous studies found no evidence that saturated fats cause heart disease.

Good quality lean red meat is one of the best sources of ­important nutrients often lacking in the British diet, including iron, zinc, vitamin A, vitamin D, ­magnesium, selenium and ­potassium, according to British Nutrition Foundation research.

Myth: Raw fruit and ­vegetables are healthier

Truth: Cooking all food makes it far easier to digest, meaning you absorb more nutrients from it.

Fans of raw food claim that cooking vegetables kills the vitamins and minerals, but studies have found that while cooking may destroy some vitamin C, it boosts your uptake of the disease-fighting ­nutrients known as antioxidants.

A 2008 study found that carrots, spinach, mushrooms, asparagus, cabbage and peppers all supplied more antioxidants when cooked than when eaten raw.

Bridget Benelam from British Nutrition Foundation explains: “This is because cooking breaks down thick ­vegetable cell walls, making it easier to absorb the ­nutrients they contain.”

Myth: Peanut butter is bad for you

Truth: Harvard Medical School researchers recently reported that snacking on peanut butter five days a week can halve the risk of a heart attack because nuts are high in ­mono-unsaturated fat that has a protective health effect.

Numerous other studies have shown that people who regularly include nuts or peanut butter in their diets are less likely to develop heart disease or type 2 diabetes, and find it easier to stay slim than those who rarely eat nuts. This may be in part because nuts are packed with protein, helping people stay full longer, so they’re less likely to snack on sugary treats.

Myth: Pork scratchings are fattening

Truth: Two-thirds of the fat in these pub snack favourites is mono and ­polyunsaturated fats, which are beneficial for heart health, while 13% of the fat comes from stearic acid, a type of saturated fat that doesn’t raise cholesterol levels.

Nutritionist Linda Foster says: “Plus, because what you’re eating is effectively concentrated collagen from skin, it has an incredibly high protein content to keep you feeling full, and helps maintain bone strength and muscle tone.”

Myth: Full-fat milk is unhealthy

Truth: Evidence suggests that, on balance, whole milk could be a better choice than low-fat skimmed. Not only does it only contain around 4% fat, it’s far more nutritious because the important fat-soluble vitamins A, D, E and K are found in the cream.

Plus it could help your diet – one study by Cardiff University found full-fat milk helped ­slimmers burn more calories.

Myth: There’s no such thing as too much sleep

Truth: Sleeping for too long – classed as more than 10 hours a night – is as damaging as getting less than six hours, according to a recent study by the ­American Academy of Sleep Medicine.

It’s thought longer sleepers sleep badly, plus spending long periods lying ­horizontal can slow the flow of blood to organs and affect blood sugar levels leading to an increased risk in heart disease, stroke and diabetes. Seven to nine hours a night is the healthiest amount of kip.

Myth: Marathon runners are super healthy

Truth: Latest evidence shows that long-distance runners are more prone to arthritis, infections and hip replacements. Plus, according to new US research, jogging more than 20 miles per week can reduce your lifespan for reasons related to heart health that are not yet clear.

Another study by Leicester University found that after long, taxing workouts such as marathons, immune systems were depleted for weeks, leading to a three times higher risk of picking up cold and flu infections. But that’s no excuse to stay on the sofa – a moderate amount of weekly exercise was found to boost immunity.

Myth: Popcorn is a diet disaster

Truth: Skip the sugar, and popcorn is a pretty healthy wholegrain snack. Indeed a study at University of Scranton, ­Pennsylvania, found that a portion of this cinema favourite was brimming with more disease-fighting nutrients than your average serving of fruit and veg!

Researchers discovered one serving contains up to 300mg of antioxidants – nearly double the 160mg for fruit per serving. Choose the air-popped, salted variety over sweet to keep it healthy.

Myth: Olive oil is the ­healthiest fat to cook with

Truth: It becomes unstable and potentially bad for us at high temperature, such as when frying. This is because when over-heated to smoking point, olive oil, and some other oils, release ­chemicals called lipid ­peroxides, which can react with DNA in ways that are linked to a higher risk of cancer and heart disease.

As a result, some experts recommend cooking with oils with a smoking point that’s a higher temperature, such as sunflower, peanut or coconut oil. Keep olive oil, particularly extra virgin oil, for salad dressings and drizzling over food.

Myth: Celeb superfoods like goji berries and kale make you healthier

Truth: Many fad foods are an ­expensive waste of money and may even be bad for you! Nutritionist Petronella Ravenshear last year claimed so-called wonder-food kale “can interfere with thyroid function”, goji berries should be consumed “with caution, especially if you have arthritis”, chia seeds can “inhibit the ­absorption of certain minerals”, and quinoa contained “potentially gut-irritating compounds”. Not all nutrition experts agree, but many are quick to point out that bog-standard foods such as eggs, tinned salmon and onions might not sound as sexy, but have just as good nutritional ­properties as the latest miracle foods.

Linda Foster adds: “There’s also the danger that people think than eating lots of one superfood will combat their other bad food choices.”

Myth: Eating plenty of fruit is a good thing

Truth: Too much fruit could increase your risk of diabetes and obesity. Although fruit contains ­vitamins and fibre, it’s also very high in fructose (fruit sugar), which recent research has suggested is a type of sugar that doesn’t make you feel as full.

Normally when we eat sugar, our body releases the hormone insulin, which tells the brain we’ve had enough to eat.

However fructose doesn’t trigger the body to produce insulin and the hormones that suppress appetite.

As a result, we’re more likely to overeat, leading to fatty substances building up in the liver, raising our risk of obesity and type 2 diabetes. Linda advises: “Don’t dodge fruit altogether as it’s a very healthy food in moderation. Just stick to two pieces a day, avoid juices, which are pure liquid sugar hits, and make up the rest of your ­recommended 5-a-day from veg.”

Myth: Salad is the ultimate health food

Truth: That salad staple, iceberg lettuce, contains very few nutrients and consists mostly of water.

Plus, studies have shown pre-packaged salad leaves are a common source of food poisoning.

Research by Imperial College London found that the salmonella bacteria could poison salads by ­gripping the leaves with their flagella – spiny propellers which they use to move around.

They can spread to any veg ­fertilised with contaminated manure or through contact with other products.

For a healthier salad, pick darker leaves such as rocket and spinach, which contain iron and the important B vitamin folate for plenty of energy. And wash all leaves in running water – even if pre-washed.