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Recently, everything we thought we knew about eating and drinking healthily was turned on its head.
First, a damning new study in the British Medical Journal showed that - after all we have been told to the contrary - saturated fat is good for you. Far from being the great risk to our health and hearts, it turns out that most people who eat butter, milk, cream and full-fat yoghurts generally have better heart health, less risk of Type 2 diabetes, and are even slimmer than those who eat fat-free. It seems that there is a connection between our 30-year war on saturated fat and our terrifying obesity epidemic.
Read more: Fatty food warnings should have been ignored - research
Now experts are saying instead that carbohydrates are the real killer.
Later in the week, more research was published in the British Medical Journal, suggesting that despite what we have always thought, the benefits of drinking wine have been overstated.
Read more: Doubts cast on benefits of alcohol moderation
So what can we safely eat these days? And what had we better avoid? Here, the experts give their "definitive" verdict...
What the line has been: Avoid butter at all costs and replace with low-fat polyunsaturated spreads.
What we now know: Butter can be good for you in small amounts.
"We used to think that if you ate saturated fat, it raised your cholesterol levels and increased your risk of heart attack," says Dr Michael Mosley, the science journalist. "It turns out that dairy fats don't work like that in your bloodstream. When you look at all the big studies, the proof that butter is bad for you isn't there."
Recommended amount: A moderate amount, which may even do you good.
What the line has been: Better to drink semi-trim or trim.
What we now know: Full-fat milk contains a lot of healthy fats and is just as good for you - if not better than -reduced-fat versions. "People have this misconception that full-fat milk is fattening, but now we know that just because a food is fatty doesn't mean it's bad for you, as there are different types of fat," says Mel Wakeman, a senior lecturer in nutrition at Birmingham City University. "I've gone back to drinking full-fat milk to ensure I get all the goodness."
Recommended amount: Up to 250mL of full-fat milk a day.
What the line has been: Eggs are full of cholesterol and you should limit your intake.
What we now know: Eggs are good for you and have no link to health problems. "Repeated studies have now shown that dietary cholesterol does not increase cholesterol levels in the blood," says Ms Wakeman. "Eggs are full of all sorts of nutrients and vitamins, and are very good for you. They contain protein, so will also keep you fuller for longer."
Recommended amount: You can eat eggs three or four times a week.
What the line has been: Olive oil is a wonder-ingredient that is key to better health.
What we now know: Olive oil is fine on salads but is carcinogenic when heated and should not be used for frying. "Olive oil is very good for you but has a very low smoke point, and produces carcinogens when heated," says Dr Glenys Jones, a nutritionist. "For frying, I recommend rapeseed oil, which has similar nutritional benefits, but has a high smoke point."
Recommended amount: A tablespoon a day.
What the line has been: Carbohydrates should make up 50 per cent of your food intake.
What the line is now: Brown carbohydrates are good, but white are deadly. "I'm a big supporter of carbohydrates," says Ms Wakeman, "but they must be wholegrain. White spaghetti, bread and rice are not our friends. Once they hit the bloodstream, they convert into pure sugar, and this puts us at risk of obesity, heart problems, Type 2 diabetes and cancer. Plus, the fibre and minerals have been stripped from white carbohydrates."
Recommended amount: Wholegrain carbohydrates should make up 50 per cent of your food.
What the line has been: A small amount of alcohol, particularly red wine, is good for the heart.
What we now know: The benefits of drinking have been over-stated. "New research shows that the benefits of even a small amount of red wine may have been exaggerated, but there has been a lot of conflicting research," says Ms Wakeman.
"It's certainly good for post-menopausal women because red wine makes the blood less sticky so lowers the risk of heart disease. In younger women, however, the research shows that there is an indisputable connection between levels of alcohol intake and breast cancer."
Recommended amount: A small glass of red a day is probably fine, with a couple of days off a week.
What the line has been: Fine in moderation.
What the line is now: There are strong links between eating processed meat and the risk of heart attacks, bowel cancer and strokes. "Processed meats, including bacon, sausages, Parma ham, ham and salami, have a very high salt content and the act of processing itself is associated with an increase of heart disease, bowel cancer and stroke," says Dr Michael Mosley. "One esteemed scientist I know called Dr David Spiegelhalter told me that if you crunch the numbers, every bacon sandwich you eat knocks half an hour off your life."
Recommended amount: A couple of times a week if you really have to - but no more.
What the line has been: Stick to the low-fat variety.
What the line is now: Full-fat may be better. "There is now strong evidence that eating full-fat yogurt is likely to cut your risk of heart disease and diabetes, and is associated with effective weight loss in a way that eating low-fat yogurt isn't," says Dr Mosley. "The problem with low-fat yogurts is that they remove the fat but stuff them full of sugar to improve the taste.
"Also, when you get rid of the fat, you lose a lot of the fat-soluble vitamins, so you lose the goodness, and also the yogurt becomes less filling so you eat more later."
Recommended amount: Switch to full-fat and you may eat regularly if you like.
What the line has been: There is no such thing as a superfood.
What the line is now: There has been much debate over how to define a "superfood" but it is now clear that certain foods - mostly fruits and vegetables - are extraordinarily nutrient-dense.
"There is strong evidence that some foods deliver far more micro-nutrients than others," says Dr Mosley.
"Watercress, beetroot and spinach, for example, all seem to deliver a record number of vitamins and micro-nutrients."
Recommended amount: As much as you like.
What the line has been: Fruit juice is good for you.
What we now know: Many commercial fruit juices contain unhealthy amounts of sugar, the equivalent of 10 teaspoons per glassful. "I've been banging on about the dangers of fruit juice for some years," says Dr Mosley.
"Many fruit juices have a similar sugar content to Coca-Cola. Commercial juices get rid of the fibre, which is the good stuff, and you're also consuming a lot of sugar in one drink, which isn't good for you. It also doesn't affect your appetite so you don't eat any less at your next meal."
Recommended amount: Making your own is better but it's a treat, not a health drink.
What the line has been: Red meat is bad for you.
What the line is now: Red meat from grass-fed animals can be good for you. "If you look at American studies, there does seem to be evidence of a small increase of risk to your heart from eating red meat, but when you look at similar studies from Europe there is no link," says Dr Mosley. "This is probably because American meat is reared on concrete lots, fed corn and given a lot of antibiotics and growth hormones, whereas beef in Europe is often fed on grass and hasn't been pumped full of all the bad stuff."
Recommended amount: 100g three or four times a week is fine.
What the line has been: Bread is good for you.
What the line is now: Only wholegrain breads are good for you. "They key thing with bread is to always make sure you are eating bread made from wholemeal flour," says Ms Wakeman. "White flour will just convert to sugar the minute it hits your bloodstream. Just because bread is covered in seeds doesn't mean it has been made from wholemeal flour. Lots of healthy-looking artisan breads are made with white flour, so always read the label. There's no difference in terms of nutrition if you buy sliced bread."
Recommended amount: Two to four slices a day is fine.
What the line has been: Up to six cups of coffee or tea a day is fine.
What we now know: Many of us punctuate our day with cups of coffee or tea, and caffeine has long been associated with increased wakefulness, yet caffeine is now thought to come with health risks. "Caffeine is highly addictive, bad for blood pressure and has been linked to heart disease," says Dr Jones.
Recommended amount: Up to two cups of coffee or four cups of tea a day - no more.
What the line has been: Chocolate is bad for you.
What we now know: Dark chocolate is good for the heart. "Research now conclusively shows a link to eating small amounts of dark chocolate and lowered blood pressure," says Mel Wakeman. "But don't kid yourself that milk chocolate is good for you. It's just fat and sugar with very little cocoa in it."
Recommended amount: Two squares of 70 per cent cocoa dark chocolate a day.
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