"Why not just eat a vitamin pill and some cake?" she asked. "From observational studies of what people actually eat, and whether or not they die early, we are certain that eating vegetables and fruit makes a difference.
"But what is their content and what is the minimum you should consume? One portion a day will give you all the vitamin E that you need, so only one per cent of the population would benefit from eating more in this regard."
She contended that belief in antioxidant properties of some bioactive compounds is misplaced. "Just eating antioxidants won't change your antioxidant level beyond an initial fluctuation," she pointed out.
"A lot of previous research was barking up the wrong tree. People think that if they get rid of free radicals they will live longer, but it doesn't work that way. Free radicals are actually a symptom of the ageing process and too much of some antioxidants such as beta-carotene can actually increase the risk of cancer."
Instead, the only way so far proven to slow down the body's ageing is to eat less overall, Brandt insisted. "But an appropriate amount of certain natural pesticides found in vegetables and which we are adapted to may be good for us. A bitter taste is a good indicator of health benefits. People first have to eat them though. One possible reason why children particularly in the UK don't like the taste of vegetables is they aren't introduced to it through their mother's milk." She added that mothers in the UK tend to breastfeed for shorter periods than in other countries.
As to what health claims suppliers could make for fruit and vegetables, she said: "You can't say 'eat this carrot, it will reduce your risk of getting cancer', because the evidence isn't there. But we can design experiments to get that evidence.
"EFSA (the European Food Safety Agency, which rules on what health claims can be made for foodstuffs) requires human studies. But it's realistic to achieve that without huge investment. Some of the science has already been done. Walnut producers already did this successfully, and it's something the fresh-produce industry could do too."