Eat Food.

Michael Pollan, author of The Omnivores Dilemma, comments on current day nutrition in this outstanding article.

That, more or less, is the short answer to the supposedly incredibly
complicated and confusing question of what we humans should eat in
order to be maximally healthy. I hate to give away the game right here
at the beginning of a long essay, and I confess that I’m tempted to
complicate matters in the interest of keeping things going for a few
thousand more words. I’ll try to resist but will go ahead and add a
couple more details to flesh out the advice. Like: A little meat won’t
kill you, though it’s better approached as a side dish than as a main.
And you’re much better off eating whole fresh foods than processed food
products. That’s what I mean by the recommendation to eat “food.” Once,
food was all you could eat, but today there are lots of other edible
foodlike substances in the supermarket. These novel products of food
science often come in packages festooned with health claims, which
brings me to a related rule of thumb: if you’re concerned about your
health, you should probably avoid food products that make health
claims. Why? Because a health claim on a food product is a good
indication that it’s not really food, and food is what you want to eat.

Don't be shellfish...