Unfortunately, most nutrition information is downright wrong and nearly all of it is unscientific. Even government guidelines are highly suspect and the government is powerfully influenced by many food- and farm-lobbies that stand to gain or lose enormous amounts of money from endorsements or lack thereof. There are simply too many people with too much money at stake to enable objectivity. Even if everyone was held to high ethical standards -and they are not- the field would be heavily biased and unsuitable for scientific discovery.
For example, the Washington Post reported recently that a campaign by Health and Human Sciences Department to advocate breast feeding was very successfully toned down at the request of infant nutrition companies. Such things can and do happen and they happen a lot.
Government officials are beleaguered by diary farmers that want you to drink milk and eat cheese, by cattle ranchers who want you to eat beef, and by the poultry industry advocating eggs and chicken. Not to mention the fishermen who want to sell fish and the corn farmers who want to douse everything and everyone in high fructose corn syrup. The list of constituents with something at stake is just endless. Unfortunately, no science can be done in this type of climate.
Athletic food intake is, if anything, even more problematic. The specialty food industry is one of the most rapidly growing market segments and that means lots of interest from business and politico's alike. Everyone loves a growing market and nobody wants to spoil the party. Nobody would even dare to attempt to, and doing so would mean a certain DOA.
Food also has important cultural and religious overtones. Nearly all religions regulate food intake, often prescribing what people can eat and when. Against such forces, no objectivity can prevail. Science practitioners are human too, with their own ideas, cultural baggage, religious beliefs, and prejudices. As Michael Pollan pointed out, nutritionism, as the ending "ism" suggest is not a scientific subject but an ideology. And "ideologies are ways of organizing large swaths of life and experience under a set of shared but unexamined assumptions."
Fortunately, humans have an elaborate digestive system, and one function or benefit of such a system is that it makes one largely independent of what and when you eat. That is especially true now that a veritable treasure trove of clean, high-calorie food is readily available. If anything, we have too much good food that is too easily accessible.
It is therefore a total irony that people think they need supplements, vitamins, and other "magic" potions. It is safe to say that any such items are totally unnecessary and a waste of money. If anything, these useless items can only lead to disease, and hypervitaminoses are more of a problem in the West than lack of vitamins.
There is absolutely no reason whatsoever to take any vitamin or nutritional supplement. Once again I never have and I never will. It is a total waste of money and can only harm you. Yet nobody has the guts to admit to it. Most coaches will tell you to take a multi-vitamin. It is baloney and serves no purpose.
You don't need vitamins, mineral supplements, protein supplements, lycopene or quercetin or any other supplements to perform or stay healthy. These things do not work and the "scientific evidence" backing them up is not there.
The golden rule for food is, eat but don't eat too much so you stay lean. Weight is the great enemy of most endurance athletes. Always eat a variety of foods and be careful with carbohydrates. Carbohydrates, or sugars, provide a quick energy boost but it is easy to eat too much as carbs do not signal satiety as protein and fats do. A diet based most only carbs will leave you perpetually hungry and presents a great risk of overeating.
Unlike what you may think, fats do not make you fat. Carbs do. Ask any cattle-farmer what they use to fatten the cows. Ever heard of corn-fed beef?
Nutrition is the one area where you will do better the less you listen to the "experts" and the more you stick to nature. Never eat prepackaged and prepared foods unless you have no other option and are in danger of acute starvation. A candy bar is great while cycling, but it is not nutrition and should not be treated as such.