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New advice suggests that for a longer life, we need to eat 10 portions of fruit and vegetables a day, but how realistic is this and is it only a diet for the wealthy?

"Healthy foods are three times more expensive calorie-for-calorie than unhealthy foods so there's a very strong price differential in a typical basket," says Anna Taylor, executive director of the independent think tank Food Foundation.

Vegetables are getting cheaper but, she says, there are people who "haven't got enough money to put food on the table, so for them, trying to secure 10 portions of fruit and veg a day in their diets would be impossible."

The study by Imperial College London, calculated that increasing our fruit and veg intake to 10-a-day could prevent 7.8 million premature deaths each year.

But currently only around a quarter of adults in the UK achieve the five-a-day target.

The British Heart Foundation did a survey which found that a third of UK adults are struggling to afford to eat healthily. So is 10-a-day realistically affordable?

"For some people it is," says Victoria Taylor, senior dietitian at the BHF.

"But for others it would take some serious thought and commitment in terms of working out which fruit and vegetables will be affordable. But it's important to keep in mind that our target is five a day and this study found that the best effects were seen for people who are currently getting below this number.

"The focus on 10 is, in a sense, moving the goalposts and it would be a shame if this put people off aiming for five, or even just having one more portion a day."

The British Dietetic Association says: "What it tells us is that the benefits of eating fruit and vegetables are incremental - in other words eating five portions a day is great, but 10 a day is even better."

So any improvement in your fruit and vegetable intake is a benefit.

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Victoria Taylor says cost is not the only reason we don't eat enough fruit and veg.

"There are numerous factors that influence our food choice. Cost is important but so is taste, cooking skills, storage facilities and ability to get to and from the shops. It's hard to say how much is specifically due to the price of food as all of these issues are interrelated."

Tips on buying fruit and veg

Buy seasonally and check prices online or with in-store flyers before you do your shop

Most supermarkets do weekly fruit and veg deals, and the own brand or economy fruit and veg is cheaper

Frozen fruit and veg can be an affordable choice - it's ready prepared and cuts down on wastage

Buy fruits like berries and cherries frozen or when they are in season and freeze extra yourself

Meat is usually more expensive so swapping in pulses as an alternative source of protein some of the time will save you money

Buying loose can be half the price of buying pre-packaged

Fruits and vegetables that are in season locally are normally better value as well.

If something is about to go out of date, use it in a stew or soup rather than throwing it away - or freeze it

Do not have too much fruit juice and dried fruits as they are higher in sugar

Source: BHF and BDA

The Food Foundation is hosting a conference in June bringing together businesses, farmers, retailers and government departments which aims to make it easier for people to eat vegetables.

Some of the ideas they will be looking at are current pilots in America where if food stamps are spent on fruit and veg, they can be doubled in value so "you create a positive incentive for people to spend their vouchers on fruit and veg because you're giving them more value".

Another scheme sees people who have early stage type 2 diabetes or are pre-diabetic being prescribed fruit and veg and getting vouchers to spend in local markets "to help them rethink their diets and get their diets on track".

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Why did we write this article?

We asked BBC readers to send us their questions about the 10-a-day diet and then our health team wrote this piece to try to answer as many as possible.

A lot of people asked about the cost implications of trying to achieve a 10-a-day diet.

Gary asked: "Should fruit and vegetables be heavily subsidized by the government to encourage further consumption?"

Gary explained to us the thinking behind his question:

"Simple consumer habits dictate that people consume more of something when it is cheaper. I believe the same economic principle can be applied to fruit and vegetables. When people go shopping, they have to make the choice of what to buy, and usually, the best value items win."

With concern over the cost of healthy eating, some have asked whether the government should subsidise fruit and veg?

At the moment, the government has "measures in place to support low income families, pregnant women and children under four through Healthy Start Vouchers. These can be spent on milk, fresh or frozen fruit and vegetables."

They also point out that all infant pupils can now get free school meals and they've announced £10m funding a year to expand breakfast clubs in up to 1,600 schools.

Currently only 70% of those eligible get the healthy start vouchers and Anna Taylor says the Food Foundation will debate whether that programme should be expanded to include a broader income group or wider age range at its conference. As she points out, this "would create a positive pull of demand - and thereby help to strengthen the British horticulture sector at the same time."

And she thinks in the post-Brexit world there is a big opportunity to help farmers.

"Doesn't it make sense to join up our farming policy with our health policy and think about - could we increase consumer subsidies to really drive up demand so our horticulturalists benefit as well - it's win-win."

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"There are lots of different ways we could make it easier to eat veg - which go beyond price and much more about our whole food environment and to what extent fruit and veg is a strong part of that and encouraging us to eat it."

She points out when you look at advertising only "1% of food and soft drink advertising spend goes on fresh veg".

But she believes we need to change our whole way of thinking about fruit and veg and the messages we send - even down to children's TV where, she says, it is "demonised".

"It's set against delicious and junk food or cream cakes, and fruit and veg is the yucky thing that kids don't want to eat. There's a bit of that subliminal stuff that happens in kids' TV because it's funny but it's kind of normalising that this is stuff that you don't want to be eating - so there's a job of work there beyond advertising, in broadcasting to try and not normalise that this is worthy but not tasty."