"If I eat a healthy diet, do I need to use nutritional supplements?" This is one of the most important questions we get, and it deserves a thoughtful answer.
There is no doubt that the best scenario is that your lifestyle provides all the nutrients you need through healthy eating. With Vitamin D, we have to add in healthy sunshine exposure. The absolute best way to get Vitamin D is through healthy sun exposure. Whether you believe in evolution or creation (or some combination of the two), we can all agree that life is dependent on the sun. We are learning more and more every day that the sun does a whole lot more than just stimulate Vitamin D production.
So, to rephrase, the best way to get your nutrients is from a lifestyle of healthy food and healthy sun exposure. This is the way that we were created/evolved. The question becomes: "Is it working? Is your lifestyle providing adequate levels of nutrients?"
One of the great aspects of living in modern times is we can test for many of these nutrients. Testing answers the question and eliminates confusion. If you are being intentional about your diet and sun exposure and then you test your blood and discover that your level is in the optimal range, you can find great peace in knowing that your strategy is working. If you test your blood level and discover that you don't have healthy Vitamin D levels, you are empowered to re-evaluate your lifestyle and tweak aspects to make it better.
For most people, supplementation will be crucial for certain nutrients for several reasons:
Some nutrients are very difficult to get from food. In particular, Vitamin D and Omega-3 Essential Fatty Acids are difficult to get from diet.
With Vitamin D, most people don't spend enough time in the sun. Most people work indoors under artificial light, especially during the winter months. Also, many people have been taught to be afraid of the sun, so they cover up or use sunscreen.
With many important nutrients, some simple Google searching will help you discover that it's easier to get them from food. We all know that B vitamins are important, but they tend to be readily available in meat, poultry, eggs, other animal products, legumes, leafy greens, etc. Someone eating a healthy diet will likely be getting adequate levels of B vitamins. Again, the best way to know is to test.
Another example: We all know that Vitamin C is important. A quick search will reveal that Vitamin C is readily available in a wide variety of fruits and vegetables. I would speculate that most people are not deficient in Vitamin C because it's relatively easy to get from diet.
Omega-3 and Vitamin D are different. It's more difficult to get these from food. It's well known that wild-caught Alaskan Salmon and flax seeds are a good source of Omega-3. Most people are not eating these every day, so there's a good chance that most people are not getting enough Omega-3. Testing helps answer this question and clear up confusion.
The same is true with Vitamin D. Salmon, sardines, and liver are good sources of Vitamin D. But, how many people do you know that are eating these things regularly? Nearly 90% of American adults surveyed had below-optimal levels of Vitamin D, with about 50% considered deficient.
Conclusion: The best way to get your nutrients is the way that you were created/evolved to get them, through food and for Vitamin D: sunshine. We should take advantage of technology and test for nutrient levels that are likely low, like Vitamin D and Omega-3. With these two nutrients in particular, the dangers associated with deficiency are so serious that the need to supplement a healthy lifestyle may be necessary.