Functional foods and dietary supplements are closely related in that they both provide essential nutrition for humans. Both contain vitamins and minerals, and both have proven benefits for general health as well as certain ailments. Yet there are some distinct differences between the two that deserve consideration.
The Case For Supplements
For one thing, it is much easier to slam down a fistful of assorted pills and capsules with the morning coffee than try to eat four or five pieces of fruit, so-and-so many grams of this and half a bar of this-and-that at each meal. You don't run out of important ingredients, and they stay good for several months or even years, as opposed to foods that may start wilting or spoiling within days of purchase.
Furthermore, there's a cost difference involved. It is much cheaper to buy purified fish oil capsules than to have a slice or two of salmon each day, and let's not forget that key word, "purified." Some foods are notoriously hard to keep clean (salmon is high up in the food chain and almost guaranteed to either accumulate environmental pollutants in the wild, or the same in a farmed setting) while those capsules are chemically engineered and guaranteed to have most or all heavy metals removed.
Finally, there are therapeutic uses of supplements, like megadoses of vitamin C being used to fight infections, common colds and even cancer, that are just plain impossible to do without supplements. Linus Pauling, two-time Nobel prize winning nutritional expert, advocated taking several thousand milligrams of vitamin C per day to combat colds (he took 12,000 mg per day year-round) with spikes up to a whopping 100,000 mg per day for fighting cancer. One full cup of fresh-squeezed orange juice provides about 100 mg. While the scientific community in general question the benefit of such otherworldly large doses, it should be fairly obvious you simply can't get anywhere near that level by non-supplemental means.
The Case For Functional Foods
Functional foods are foods that are particularly high in specific nutrients, or have specific health benefits. For example, a low-fat yogurt smoothie packed with acai, blueberries, black currant, and a handful of other fruits/berries full of naturally occurring antioxidants can be said to be an excellent functional food.
The benefit of this approach vs. pills and capsules is that you take a lot of the mumbo-jumbo factor out of the equation. If you go buy a box of fresh blueberries at your local farmer's market, you know what goes into you. You can't say the same for the yellowish pill by a brand name you've never heard of that you found at the bargain shelf in the Dollar Store. In fact, a good percentage of the world's supplements are now produced in China; a country not exactly known for high production standards. How do you know where your supplements came from? Simple answer is: you don't. However, if it's cheap, odds are the bulk of the stuff inside came from the lowest bidder somewhere on the Chinese plains, far from the watchful eye of the USDA or FDA.
To further underscore the importance of potential impurities, it should be noted that the European Union has been cracking down on the supplement industry for years. Germans regulate supplements almost as tightly as full-blown drugs. There are certainly downsides to this, notably availability and options, but it should be noted that the United States is in a rapidly shrinking club of Western countries where the supplement industry is running practically unchecked.
Finally, remember the part about using supplements for therapeutic doses of vitamins? Vitamin C, as in our example, is water soluble and hardly toxic at all. Other vitamins and minerals are considerably tougher and can make you quite sick once you've accumulated sufficient amounts in your body. With functional foods, it's difficult to eat such quantities that this becomes an issue, but with supplements it's just a matter of how many pills you shake out into your palm each day.
Using Functional Foods and Dietary Supplements
The conclusion isn't necessarily to go with one or the other. Functional foods and dietary supplements are not mutually exclusive. In fact, either approach is likely to be beneficial as long as you let common sense be your guiding light, but the best solution is to pick the best of both worlds. Use functional foods as far as you can, then fill the gaps that are not practical and/or economically viable with supplements, or in the case with the fish oil capsules, where it actually makes sense to go the path of lesser resistance. Good luck!