I think Americans generally pay more attention to the gasoline they put in their cars than to the food they put in their mouths. We are a society of excess, and one of our more impressive excesses is the way in which we eat and what we choose to put in our mouths.

We are the leading country in the world in almost everything, yet our mortality rates, our cancer rates, and our neonatal death rates don’t rank among the best in the world. We lead in research, we lead in academic training, we lead in freedom of information, yet we don’t lead in taking care of our health.

We have all the knowledge in the world about everything in life, but that has made no impact on our health. Why? I think nutrition is part of the reason, and I think I know why.

No one is ever taught about nutrition. We certainly don’t teach the subject in grammar school, and it’s rarely taught in high school. Some colleges may offer it as an elective. But our parents certainly don’t talk to us about carbohydrates and proteins the way they do about the birds and the bees. If you combine this lack of knowledge with our appetite for diversity, taste, and presentation, what you have is a lot of people who know nothing about the food on their plate.

It’s never too late to learn about nutrition. The fundamental issue with nutrition is learning how to balance your caloric intake with the number of calories you burn. Everything we eat has a caloric value. If you take in more nutrients that contain a lot of calories and you don’t burn them up, the excess caloric energy is going to be stored as fat, and you’re going to gain weight. That weight and that fat will then interfere with all the normal functions of your body.

On the other hand, if you consume too few calories, say fewer than 1,200 calories a day, then your body doesn’t have sufficient energy to maintain adequate functioning. The caloric intake for a normal adult should range between 1,500 and 2,000 calories a day.

The body requires certain nutrients in order to work properly. Nutrients are the chemicals our body gets from food. These nutrients are used to build muscles, improve cell-to-cell transmission, and manufacture hormones. In describing nutrients, the word “essential” means that the body must consume them; it cannot produce them on its own. The nutrients we need include:

Essential amino acids.

The body requires amino acids to produce new body proteins and replace damaged proteins to build and maintain the body.

Vitamins and minerals.

These are recognized as essential nutrients that are specifically linked to the functionality of cells. If we’re deficient in vitamins and minerals, we develop a weak immune system, cell metabolism disorders, premature aging, scurvy, goiters, and bone loss.

Fatty acids.

Also essential, fatty acids are crucial for maintaining the body’s normal health. They are responsible for the normal formation of hormones and creation of some of the biological pathways responsible for dealing with inflammation and cell repair.

Sugars.

They are essential because they provide the fuel our cells need to function adequately, which allows the other nutrients to be utilized properly. If cells don’t have the sugar molecule necessary to generate the energy required for repairing, functioning, transmitting, and utilizing nutrients, then cellular damage and disease will result.

Each nutrient carries out one or more unique tasks your body needs to function. And because you need many nutrients to stay healthy—protein, fat, carbohydrates, vitamins, minerals—you have to eat a wide variety of foods to get them all.

It’s when we don’t recognize the necessity of all those elements that we begin getting into trouble. It’s like filling your gas tank with gasoline and forgetting to change the oil every 3,500 miles, or forgetting to put water in the radiator. The car needs the gasoline, the oil and the water, all in the proper proportions, in order to function properly. The same is true of the human body.

The problem, as I’ve mentioned before, is that about one-third of all American meals are prepared foods. And the problem with prepared foods is that their contents are not nutritionally balanced.

Our lack of knowledge of nutrition, combined with our obsession with processed foods, is really damaging our health. So we have to get back to fundamentals, a good example of which is the diet of people who live in the Mediterranean. Their diet is well balanced with vegetables and fruit, fish and lean meat, and the good unsaturated fats like olive oil.

Today, many people think that if they stick to low-fat or nonfat foods, they won’t gain weight. That’s a myth, because gaining weight has to do with calorie intake. If you take a salad and you add cheese and eggs and everything else in the book, even if you select low-fat ingredients, you’re still consuming a tremendous load of calories. And size matters, too; the size of your portions does make a difference in terms of the total amount of calories consumed. It’s just a plain mathematical calculation.

There are no magical foods that are going to help you burn calories or increase your cell metabolism either. There is no such a thing as a food that is more active in the body than others. People think that eating a grapefruit each day or having cabbage soup for lunch is going to burn off their fat. But that’s a myth. There is only one way to burn off those extra calories: exercise, any exercise at all.

How to Eat

It’s not just what or how much we are eating that’s the problem these days, it’s the way most of us eat. Many people skip breakfast, gulp down a quick lunch at noon, and then consume a large meal at seven o’clock at night.

Trouble is, they don’t need all that fuel at night. They need a little bit throughout the day when they are active—either moving, thinking, or both.

So what happens in the middle of the day if this is the way we eat? Without a supply of energy, our metabolism gets altered. Our blood sugar level is erratic. Our hormones go haywire trying to figure out where to obtain the fuel we need. People are always telling me, “I don’t eat, so how come I’m not losing weight?”

That’s the answer. Their metabolism is out of whack, and they need to get it back in order.

Supplements

If you eat a balanced diet with fruits, vegetables, grains, fish, and all the rest, you don’t need to take supplements. But how many of us really eat such a balanced diet?

And even if we do, because we are all predisposed for certain diseases and the aging processes, being proactive and adding certain supplements to our diet may be a good idea. But before popping supplements like candies from a bag of M&M’s, check with your doctor about what’s best for you. Some supplements can be toxic. Others may cause allergies or cross reactions with medications you may be taking. But there is no doubt that certain supplements can have specific health benefits and can lower the cost of health care at the same time.

An Important Word About Supplements

Many supplements contain active ingredients that can have strong effects on your body, and some supplements can interfere with prescription medicines. Always consult with your doctor or pharmacist before taking supplements.

I am particularly bullish on five supplements that have been well studied and are proven to support optimal health.

Omega-3 Fatty Acids

I love the omega-3 fatty acids. They are an important contributor to the improvement of human health. Some studies have shown that omega 3s are good for the prevention of heart disease, as well as for depression, rheumatoid arthritis, and asthma. You can get omega 3s by eating leafy greens and fish or by taking a fish oil tablet. Omega 3s assist with fat metabolism and help maintain a balance of good and bad cholesterol.

Calcium

Calcium is another very good supplement, specifically calcium with vitamin D. Calcium intake is an important factor in bone health and may play a role in the prevention of colon cancer, though it doesn’t appear to be the silver bullet that everyone hoped it would be. Research has shown that calcium supplements can significantly lower the occurrence of hip fractures among those aged 65 and older.

Folic Acid

Folic acid and folate are forms of a water-soluble vitamin B that occur naturally in leafy vegetables such as spinach and turnip greens, dry beans and peas, fortified cereal products, and some other fruits and vegetables. Folic acid supplements have been a lifesaver in the prevention of neural tube defects in children. They are also very beneficial for cell function and the prevention of heart disease.

Glucosamine

I also like glucosamine. It has good anti-inflammatory effects, especially for individuals with arthritis. It doesn’t prevent arthritis, and it doesn’t repair or rejuvenate cartilage, but I think it’s a very good supplement because it helps promote joint function and relieves the symptoms of inflammation and pain.

Other supplements that are thought to make a positive contribution to health include saw palmetto, the fruit of the fan palm, for men. Native Americans consumed it as food and used it to treat urinary and genital problems. Some research has shown that it could be effective for the treatment of an enlarged prostate in men. It increases urinary flow and has no known safety hazards.

Click here to check out Dr. Manny's book The Check List (Harper Collins, 2007), from which this article was excerpted.

Dr. Manny Alvarez is the managing editor of health news at FOXNews.com, and is a regular medical contributor on the FOX News Channel. He is chairman of the Department of Obstetrics and Gynecology and Reproductive Science at Hackensack University Medical Center in New Jersey. Additionally, Alvarez is Adjunct Professor of Obstetrics and Gynecology at New York University School of Medicine in New York City.

Dr. Manny Alvarez serves as Fox News Channel's senior managing health editor. He also serves as chairman of the department of obstetrics/gynecology and reproductive science at Hackensack University Medical Center in New Jersey. Click here for more information on Dr. Manny's work with Hackensack University Medical Center. Visit AskDrManny.com for more.