Introduction

When the French philosopher Voltaire published Candide, or Optimism, 250 years ago, his purpose was to prove the opposite of what his character Pangloss claimed, that this is the “best of all possible worlds.” Candide was an attempt to show that the world is filled with horror and folly. After you have read my book, though, you may choose to side with Pangloss. Vitamin D could be such a panacea. From asthma to xeroderma pigmentosum and a lot in between, research suggests that vitamin D might be a modern version of a cure-all. Remember, there are two Ds in Candide!

For good reason, within the past few years a blood test for 25-hydroxyvitamin D has become commonly ordered in the United States. Doctors are finding many people whose blood levels have slipped below where some medical experts believe they should be. Low blood levels occur in all ages of Americans and throughout the world. Amazingly, reversing this lack of vitamin D is relatively easy and inexpensive, as you discover in Part III of this book.

What explains this lack of vitamin D in our bodies? First, many of us live in temperate zones where the rays of the sun aren’t powerful enough to produce vitamin D in our skin for much of the year. Second, even where the sun can produce sufficient vitamin D, we have been warned so often about the danger of the sun’s rays that we cover ourselves with sunscreen, clothing, and hats so that the healing power of the sun can’t penetrate. By the time you finish this book, you’ll know how to expose yourself for the right amount of time without risking wrinkles or skin cancer.

About This Book

This book has the latest information in the very fast-moving field of vitamin D and your health. As a long-time For Dummies author, I have written this book using everyday language so everyone can understand the material — no formal training in the sciences required.

Conventions Used in This Book

The following conventions are used throughout the text to make it consistent and easy to understand:

The unit in which 25-hydroxyvitamin D, the serum measure for how much vitamin D you have in your body, is measured in nanograms per milliliter (ng/ml) in the United States and nanomoles per liter (nmol/l) in Canada and much of the rest of the world.

Calcitriol is the biologically active form of vitamin D and does all of the things that we attribute, indirectly, to vitamin D.

All web addresses appear in monofont.

New terms appear in italic and are closely followed by an easy-to-understand definition.

Bold is used to highlight keywords in bulleted lists.

You should also know vitamin D comes in two forms. Chole-calciferol, the form of vitamin D that comes from the sun acting on your skin, is also called vitamin D3. This is also the form you get from foods that come from animals. Ergocalciferol, a form of vitamin D contained in many supplements and which is also found in some plants like irradiated mushrooms, is also called vitamin D2. I try not to use those long names again, but you should be aware of them.

What You Don’t Have to Read

From time to time, I explain some complicated subjects or include some information that’s interesting but not essential to your understanding of vitamin D. I’ve shaded this text in gray. This means that you can skip this information, but if you have a deep, questioning mind, you might want to read it. The information in gray is for the person who really wants to know the nuances of vitamin D.

Foolish Assumptions

As I wrote this book, I assumed that you know nothing about vitamin D. If you already know a little bit about vitamin D, you can skip the stuff you know and just go to the stuff you want to know. But you may miss out on some new findings or miss the opportunity to learn some things in much greater detail than what you may already know.

I expect that you’ll be amazed by the great potential of vitamin D as an agent that can protect your health. Feel free to highlight points that are of interest to you or that you want to find out more about. After all, you paid for the book (I hope).

How This Book Is Organized

This book has four parts. You don’t have to start at Part I, but I recommend that you do so. Each part is self-contained, so you can jump to Chapter 12 if that’s what floats your boat. Here’s a brief discussion of the contents of each part.

Part I: The Life History of Vitamin D

Part I is an introduction to vitamin D. It tells you what this so-called vitamin actually is and does, and how it performs its actions. It also tells you how to find out if you have enough in your body. You can find out which populations often lack sufficient vitamin D and how to overcome this. You will discover how vitamin D is measured and the problems associated with testing for vitamin D. Vitamin D also has an important sidekick, calcium, and you’ll read about that substance here as well.

Part II: Key Roles of Vitamin D

In Part II, you explore the role of vitamin D in the various organs of the body and how it prevents diseases. You quickly come to understand how important this nutrient has become in the last few years.

The chapters in these parts cover everything from the role of vitamin D in bone growth — where the function of vitamin D was thought to begin and end — to its potential role in preventing and treating heart disease, cancer, diabetes, and other common health concerns.

Part III: Getting Enough

Now that you’re convinced that you must maintain sufficient vitamin D in your body, Part III helps you do just that. Fortunately, you can build up your blood levels in many ways.

Chapter 11 describes how our bodies have gotten vitamin D for centuries for free, from the giver of life: our sun. The sun has gotten a bad name from skin doctors in the last few years, but I intend to set the record straight. The next best source is food, discussed in Chapter 12.

The next chapter takes up the subject of vitamin D supplements. What’s the best way to take it? How much and when should you take it? What should be the effect of a given dose? You can get 2,000 international units of vitamin D for so cheap that there’s no excuse for being low in vitamin D.

Part IV: The Part of Tens

Finally, Part IV is the traditional Dummies Part of Tens — in this case, ten myths about vitamin D and ten new functions of this vitamin. We may have to make this the Part of Twenties in future editions, given the research about vitamin D, but this works for now.

Icons Used in This Book

Icons throughout the book alert you to information you must know, information you may find helpful, and information you need to heed to live a healthy life.

When you see this icon, it means that the information is essential and you should be aware of it. Read it twice.

This icon marks important information that can increase the benefits of vitamin D on your health.

This icon alerts you to potential health pitfalls or setbacks.

Where to Go from Here

This book doesn’t have to be read starting at page 1 straight to the end. It’s not a novel, after all. (If you’d like to make it into a movie, though, let me know. I have just the right person for the leading role.)

If you want to know the basics of vitamin D, start with Chapter 1. If you have a disease or condition that you think might be affected by vitamin D, check it out in Part II. To make sure you’re getting enough vitamin D, check out Chapter 11 to see how you can get it from the sun, read Chapter 12 for food sources of vitamin D, and flip to Chapter 13 for what you need to know about taking vitamin D supplements.