Breaking Down Food: A Closer Look at What You Eat

Finding Nutritious Foods

Macronutrients make up the bulk of the calories you eat each day. They provide the nutrients that your body needs to make energy. They also give your cells important building blocks needed for all their different functions, like fighting diseases.

Your body needs only small amounts of each micronutrient. But they are critical for healthy development and disease prevention.

Experts advise adults to stay within their recommended calorie limits while choosing food and drinks that are rich in nutrients. The guidelines suggest getting 10% to 35% of your calories from protein; 25% to 35% from fat; and 45% to 65% from carbohydrates. Learn how to personalize nutrition recommendations at MyPlate (USDA).

To find the amounts of different nutrients in a food, look at the Nutrition Facts label. You can also find resources about nutrients in foods at Nutrition.gov (USDA).

Meeting Your Body’s Needs

Your body still might be able to function when it’s not getting enough of the different macronutrients, says Samantha Adas, a nutritionist at NIH, “but that doesn’t mean it’s optimal.”

Proteins are needed for cells to perform critical functions in your body. They’re broken down by your body into amino acids. Amino acids are used by cells to build muscle, skin, and organs; break down toxins; and do many other critical jobs.

Proteins can also be used for energy. “They give a stronger sensation of fullness than carbohydrates,” says Dr. Christopher Lynch, the acting director of the NIH Office of Nutrition Research.

But, explains Adas, “carbohydrates are the body’s preferred source for energy because they provide energy right away.”

Your body turns carbohydrates into glucose, a type of sugar. Nearly every cell in your body uses glucose as its main fuel source.

There are three different types of carbohydrates: simple carbohydrates (sugars), complex carbohydrates (starches), and fiber.

Simple carbs are made of one or two sugar molecules. Your body digests and absorbs these quicker than complex carbohydrates. Complex carbs are larger chains of sugars, so they take longer to break down and move into your blood.

Simple carbohydrates may raise your blood glucose higher and faster than complex carbs. Having blood sugar levels that are too high over time can lead to many health problems.

Limiting how much added sugar you eat to no more than 10% of your daily calories can help lower your health risks. So can choosing more complex carbohydrates, like whole grains, beans, legumes, and starchy vegetables. Complex carbs can help you get more fiber, too. Fruits and vegetables are also a great source of fiber and are rich in micronutrients.

“If you eat a meal that is high in fiber, you feel fuller longer,” says Dr. Katherene Anguah, a nutrition researcher at the University of Missouri. This can help you better control your calories.

Most Americans aren’t getting the recommended 14 grams of fiber for every 1,000 calories. Anguah is studying the health benefits of consuming a fiber-rich diet.

Foods rich in fiber are important for gut health. They can also lower the amount of fat and cholesterol (a waxy, fat-like substance) in your blood. Fat and cholesterol buildup can lead to heart disease and stroke. High-fiber foods may help protect against these and other health conditions, like diabetes.

Although too much fat can cause trouble, you still need some in your diet. Fats are broken down into fatty acids. Your body uses these to make energy, build certain cell structures, absorb certain vitamins, and protect your organs. Some organs, like your heart, prefer to use fat as fuel.

Experts recommend limiting a certain type of fat called saturated fats to less than 10% of your daily calories. Saturated fats are solid at room temperature, such as the fats in red meats, lard, and full-fat milk and dairy products. Meanwhile, fats found in nuts, seeds, vegetable oils, and fatty fish have been shown to be beneficial for heart health.

“Healthy fats have a place in the diet, but within reasonable calorie limits,” says Dr. Alison Brown, a nutrition scientist at NIH. It’s important to watch how much of them you eat. Fats have more than twice as many calories per gram as protein or carbohydrates, so can add extra calories to your day. Eating too many calories can lead to weight gain. Excess weight and obesity can increase your risk for many serious diseases.

Getting Personal

Our genetic makeup interacts with our diet and may affect how each person’s body breaks down food. Scientists are now digging deeper to better understand these differences. NIH has launched a precision nutrition study to learn more about how various food components affect people differently. The study is enrolling 10,000 people to learn what factors predict how people’s bodies will respond to different types of foods.

The researchers hope to learn how to tailor what you eat based on your genes, culture, and environment to improve your health. Learn more at Nutrition for Precision Health.

Getting Better Nutrition:

• Stay within your recommended daily calorie limit. How many calories you need depends on many factors, including your sex, height, age, and activity level.
• Choose a healthy mix of foods: vegetables, fruits, whole grains, proteins, low-fat or fat-free dairy, and oils.
• Limit saturated fat to less than 10% of daily calories. Replace foods containing it (like butter or lard) with healthier unsaturated fat options, like plant oils.
• Limit salt to no more than 2,300 mg per day.
• Limit added sugars to less than 10% of daily calories.
• Vary your protein sources. Include lean meats, poultry, eggs, seafood, beans, peas, lentils, nuts, seeds, and soy products.
• Replace highly processed or high-fat meats (e.g., hot dogs, sausages, bacon) with healthier protein sources.
• Eat plant-based foods. Plants often contain healthy fats and important vitamins and minerals.