Dietary supplements elbow their way into discussions of human longevity in a very unhelpful way. The loudest voice in the room when it comes to aging is not the research community, but rather the collective megaphone wielded by the salespeople of the "anti-aging" marketplace - a well-funded army ever ready to puff up thin evidence, misrepresent research, propagate outright lies, and sell you whatever happens to be sitting in their warehouses right this instant. They're just as good at deceiving themselves as anyone else; the best salespeople are the true believers.
The simple truth is that no (presently available) supplement or collection of supplements can be shown to achieve anything close to the benefits to health and longevity produced by exercise and calorie restriction. Everyone should take a decent multivitamin, as it costs next to nothing and there is much evidence, both historical and contemporary, in support of the negative effects brought on by a diet lacking one or more essential micronutrients. The more adventurous can do as they please in the vast wilderness of studies showing very narrow statistical benefits in mice or specific populations - but only spend the money you can afford to throw away, and bear in mind you'd be better off donating it to efforts like the SENS Foundation that aim to actually repair and reverse aging rather than just slow it down. You'll never know whether or not all your investigations and supplements did any good: based on a broad reading of the work out there to date, any plausible effects from supplementation will be washed out by the consequences of your specific level of calorie intake and exercise.
This focus on supplements is, I think, some kind of oral fixation aspect of magical thinking. It's a mythic inheritance from the days of consuming a beast's heart to gain its courage. Researchers learn something about our biochemistry, spread the word, and that then manifests in our broader culture as an urge to consume some aspect of that knowledge - and so the pill sellers and potion manufacturers prosper in every age, regardless of the actual merits of what they sell.
I have to say that I am disappointed that Ray Kurzweil places so much emphasis on supplements in his thoughts on engineered longevity. He should throw that all out and focus on exercise and calorie restriction - that's where the science is far more settled, and the effects on health are large, noteworthy, and inarguable. But of course that isn't going to happen now that he has a business in the Life Extension Foundation vein going on that side, selling thin evidence to people who would rather follow the mythic path of eating knowledge than actually get up and exercise, or sanely reduce their intake of calories.