This forum is about wrong numbers in science, politics and the media. It respects good science and good English.
After doing a bit of checking, it looks like you did not mishear the 800 g of fruit and vegetables per day figure. This BBC news article gives more details:
A 'portion' is apparently 80 grams (or just under 3 ounces), so 10 portions would be 800 g. On a weekly basis, that would be 5.6 kg or 12.3 lb of fruit and vegetables being consumed.
The news article also quotes a figure of 7.8 million 'premature deaths' being avoided per year by following this advice. The 'premature deaths' figure is of course based on the imaginary scenario where the whole UK population is currently eating 10 portions per day, whereas they're not eating anything like 10, or even 5, I'd estimate the average member of the British public is eating more like 1 or 2 per day. I believe that the most commonly eaten vegetable in the UK, the potato, is not allowed to be included in this fruit and vegetables consumption exercise.
The key piece of information that would need to available for anyone to make a decision regarding a health issue, that is what is the change in lifespan for the average person that is supposedly achieved by following this advice, is as usual missed out.
Yet somehow, Milk and Potatoes can keep one alive.
But then we get to start talking about epigenomes...
I use lots of vegetables when I cook. I sneak extra in because if I eat enough vegetables, my challenges with post ingestion gas goes away.
I think we can take most nutritional advice with a pinch of salt, including the advice to have less salt.
The original "5-a-day" advice was nothing more than a marketing ploy dreamt up by the Produce For Better Health Foundation. They came up with the slogan in 1991
Here's the list of their donors - It's like a who's who of the Big Food industry
As this is the NumberWatch forum, here are plenty of numbers to show that fruit and veg don't actually have a great deal to offer in terms of vitamins and minerals
The Perfect 5-A-Day
Entirely agree that the occasional or even regular fasting day is easily coped with and has beneficial effects. On both weight and energy levels.
For the past 20 odd years, whenever I find myself getting a bit floppy round the midriff I have a near fasting (breakfast only) day once a week until normal geometry is re-established. Usually 4 to 6 weeks does the trick. Nice thing about this method of weight control is that, unlike a the usual long term restricted calorie intake diet, it doesn't seem to push the body into low food mode so there is little risk of rapidly putting the weight back on once you come off the diet and go back to normal eating. If you do put a bit of weight on then a few fasting days soon gets rid of it.
A couple of years ago there was a book published advocating combining two near fasting days once a week with five normal eating days. I understand there were plenty of recipe suggestions for both normal eating and fasting days to help ensure you got decent supplies of all nutrients. 5-2 Diet or something. Might be worth looking into.