Nutrient Facts: Nutrients and Their Functions

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If you ever wanted to see if some food was healthy, you probably just checked the Nutrition Facts label at the back of the box. Most people just look at the calories and maybe how much fat or sugar it has. But have you ever wondered about what the other nutrients and their functions are?

The Nutrition Facts label contains a surprising amount of information, and it can help you make better choices when it comes to food. So here’s a guide about all those nutrients and their functions.

Types of Nutrients

Nutrients are divided into two categories: macronutrients and micronutrients. Macronutrients are nutrients that the body needs large quantities of, and they also provide energy. Fats, carbohydrates, and protein belong in this category. Water is also sometimes listed as a macronutrient despite being zero calories because you need a large amount of it. Micronutrients are substances that the body needs in relatively small quantities. Vitamins and minerals belong in this category. You need proper amounts of both categories to stay healthy.

Macronutrients and Their Functions

Fats, carbohydrates, and protein are often the focus of dieters (low-fat, low-carb…). But they’re more complicated than you think. The quality of these nutrients matters way more than the quantity. So, in addition to watching how much of these you eat, choosing the right kinds is also very important.

Fats

Of all the nutrients, fat probably has the worst reputation. When I was growing up, low-fat and non-fat foods were all the rage, and even now they’re still quite prevalent. And at 9 kcal/g (1 kcal = 1 food calorie), the most calorie-dense of all the macronutrients, it’s not surprising to see why. But now people have come to realize that there are good and bad fats. The good ones are cis unsaturated fats (monounsaturated and polyunsaturated), and the bad ones are saturated fat and trans unsaturated fat (aka trans fat). Cholesterol is typically separate from the total fat section of the Nutrition Facts label (it doesn’t provide food calories), but it’s a lipid, so it’s technically a kind of fat.

Fats in moderation are vital to health. In addition to being an energy source, they are necessary for helping the body absorb fat-soluble vitamins (A, D, E, and K). They also help maintain skin and hair and play a role in cell function (mainly maintaining cell membranes and their fluidity).

Cis Monounsaturated and Polyunsaturated Fats

Both of these fats in moderation help lower LDL (“bad cholesterol”) when used in place of saturated and trans fats.

They also increase cell membrane fluidity, which improves cells’ function. This is because unsaturated fats have one (monounsaturated) or more (polyunsaturated) double bonds in their chemical structure, which causes them to be bent instead of completely straight in the case of saturated fats. As a result, this bent structure prevents them from being packed together as tightly in the cell membrane, allowing proteins and other molecules embedded in the membrane to travel around easier.

Polyunsaturated fats in particular are also the source of the essential omega-3 and omega-6 fatty acids. They’re called essential fatty acids because your body can’t make them. Both improve cardiovascular health in a variety of ways, such as reducing the chance of arrhythmia (irregular heartbeat) and heart attacks. In addition, docosahexaenoic acid (DHA), an omega-3 fatty acid, is a primary component of your brain (especially grey matter), skin, and retina.

Major sources of cis monounsaturated fats are some plant oils (olive, canola, and sunflower for example), nuts, some kinds of meat, and avocados.

Major sources of cis polyunsaturated fats are fish, walnuts, flax seeds, sunflower seeds, sesame seeds, and some plant oils (canola, avocado, and safflower for example).

Saturated Fat

There is some debate on the extent of saturated fat’s effects on cardiovascular health, but it’s widely accepted that saturated fats increase LDL (a risk factor for cardiovascular disease) and should be limited and replaced by healthier cis monounsaturated and polyunsaturated fats whenever possible.

Major sources of saturated fat are meat, some plant oils (palm and coconut for example), whole milk dairy products, and many processed foods.

Trans Unsaturated Fat

Trans fats are the worst kind of fat in terms of health. These fats are identical to their cis versions except for the orientation of their double bonds (the bond(s) is in the trans configuration instead of the cis configuration). Here’s an example:

A cis monounsaturated fatty acid (oleic acid)... — A cis monounsaturated fatty acid (oleic acid)…

...and its trans version (elaidic acid). — …and its trans version (elaidic acid).

Notice that the trans fat example above is straighter, making it more similar to a saturated fat in shape. What makes trans fat worse than saturated fat is that in addition to raising LDL like saturated fat, it also lowers HDL (“good cholesterol”). It also impairs the metabolism of essential fatty acids, which leads to changes in the fatty acid composition of the aorta and other arteries around the heart (it stiffens their walls). As a result, this leads to a buildup of plaque in those arteries and increases the risk of coronary artery disease.

Trans fat is found in any food that contains partially hydrogenated oils, but it’s rare in nature.

Cholesterol

Cholesterol is different from the previous kinds of fat in that it’s a sterol (a steroid alcohol). It’s vital to health, and it has a wide variety of functions:

It’s used in cells as a sort of regulator for the fluidity of the cell membrane. Cholesterol in cell membranes acts like filler material between the phospholipids that make up the membrane. This ensures that the membrane isn’t leaky but still flexible.
Cholesterol helps with cell membrane processes. It’s vital for some forms of endocytosis, which is the process where the cell membrane envelops and takes in stuff from the outside. Cholesterol also helps out with the formation of lipid rafts in the cell membrane, which help with cell signaling.
Cholesterol is used to make all steroid hormones. These include cortisol, aldosterone, progesterone, estrogen, and testosterone
It’s needed for the body to make vitamin D.
The liver adds cholesterol to bile. It helps with the digestion of fats and allows the body to absorb fat-soluble vitamins.
It helps protect neurons. The myelin sheath that covers neurons is rich in cholesterol, an electrical insulator. It allows the neuron to send electrical signals more efficiently.

So what about LDL and HDL, the supposed “bad” and “good” cholesterol? Actually, LDL and HDL aren’t cholesterol. Instead, they’re complex molecules that HOLD cholesterol. In fact, the cholesterol in both of them is the same.

LDL stands for low-density lipoprotein, and HDL stands for high-density lipoprotein. Cholesterol is a lipid, which means it doesn’t dissolve in blood easily. In order for it travel in the bloodstream effectively and reach cells, it needs to be transported inside these molecules.

LDL is the main transporter. But if there’s too much LDL floating around, more of it gets oxidized (it’s random but more LDL means more chances it can happen). Macrophages, the body’s trash collectors, pick up these oxidized LDL molecules. But they get engorged in the process, forming foam cells, and get stuck in blood vessel walls. When this process keeps happening, it forms cholesterol-filled plaques along the vessels’ walls, which constrict blood flow and cause cardiovascular problems.

HDL transports cholesterol from cells (including foam cells) back to the liver for disposal or reuse. That’s why having higher amounts of HDL is beneficial.

Major sources of cholesterol are animal-based products like meat and eggs. But it’s not really important because your gut can’t absorb most of the cholesterol you eat. The body creates its own cholesterol as well and adjusts its production based on how much you absorb. So the end result is that cholesterol concentration in blood doesn’t budge very much in the long run after you eat it. The things that change cholesterol levels the most are the aforementioned trans and saturated fats and exercise. There are some people who are more sensitive to dietary cholesterol, but they’re relatively rare, and it’s likely due to genetics.

Carbohydrates

The carbohydrates you eat are divided into three main categories: sugars, starches, and dietary fiber. The Nutrition Facts label clearly lists sugar and dietary fiber in the total carbohydrate section, and the rest is usually starch (the “Other Carbohydrate” if it’s even there at all).

Carbohydrates contain about 4 kcal/g, and the amount varies slightly depending on what type it is. The exception is dietary fiber (at least for us), which is mostly indigestible for humans and doesn’t provide as much energy.

The primary function of sugars and starches is providing energy for the body. But some starches also have the added effect of fermenting in the gut. This process provides energy to the microbes in the large intestine, but also produces gas as an unfortunate side effect.

It’s pretty obvious what the major sources of sugar are (pretty much anything sweet). But too much sugar is a major risk factor for type-2 diabetes.

Major sources of starch are grains, root vegetables like potatoes, peas, bananas, chestnuts, and many kinds of beans.

Of the three carbohydrates, dietary fiber is probably the most important in relation to health. Dietary fiber has two categories: soluble and insoluble. Both have beneficial functions related to digestive health.

These are the functions of soluble fiber:

Soluble fiber ferments in the colon and helps maintain the microbe ecosystem there. The beneficial microorganisms in the gut outcompete harmful ones and help digestion.
Soluble fiber also slows down the digestive process by increasing the viscosity of the stuff in the digestive tract. This extends that “full” feeling.
Due to the increased viscosity, it also slows down the absorption of sugar and reduces the absorption of cholesterol.

These are the functions of insoluble fiber:

It contributes to bulking (it absorbs water and holds it), which eases bowel movements and makes them more regular.
Some types ferment in the colon like soluble fiber, providing the same benefits.

In addition to the above effects, both types of fiber increase food volume without adding as many calories. So eating stuff with more fiber helps you reduce the amount of calories you eat.

Major sources of dietary fiber are vegetables (including root vegetables), fruits, grains, legumes, nuts, and seeds.

Protein

Proteins are essential parts of a healthy diet because they provide essential amino acids. Like carbohydrates, they provide 4 kcal/g.

There are nine essential amino acids: phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine. The body can make the other amino acids we need. Meat, dairy products, eggs, and soy are sources of complete protein (they contain all the essential amino acids). But for people who don’t eat these foods, they need to get the complete set by eating a combination of other plants. If you don’t get enough protein, your body will start breaking down your own muscles to get enough.

The body uses protein for a wide variety of purposes. In addition to providing energy, it’s also used to build and repair bodily tissues like muscles and blood cells. When broken down to amino acids, it forms the basis for nucleic acids (like DNA), enzymes, hormones, molecules needed for immune response, and many others. It’s an absolutely vital nutrient.

Micronutrients and Their Functions

Even though we need relatively smaller amounts of vitamins and minerals, they are no less important than macronutrients. The body needs them for a wide variety of functions, so getting too little will cause health problems. But getting too much of many of them also causes problems. So it’s important to stay relatively close to the recommended daily intake as noted on the Nutrition Facts label.

Vitamins

These micronutrients are organic molecules that we need to survive. Some of these vitamins aren’t actually one substance but are actually a group of similar substances called vitamers. There are 13 vitamins that we need.

Vitamin A

Vitamin A is actually a group of fat-soluble substances, the main one being retinol. You can get already-made vitamin A from animal-based foods. You can also get vitamin A in provitamin form (substances that the body changes into a vitamin) from plant sources, the main one being beta-carotene. Major sources of vitamin A include meat, dairy products, leafy vegetables, orange and yellow vegetables (like carrots and squash), some fruits (like cantaloupe and mango), and fortified breakfast cereals.

Vitamin A helps with vision (the retina specifically), gene transcription, immune function (specifically T cell formation), bone growth (including teeth), skin health, reproduction, and the formation of blood cell components. It’s also an antioxidant (it prevents damage from free radicals).

Vitamin B₁ (Thiamin)

Thiamin is a water-soluble vitamin that’s present in whole grains, legumes, eggs, and some kinds of meat. Since a lot of foods use processed grains (the processing removes most of the thiamin), fortified cereals and flour add it back in.

Thiamin helps with breaking down sugars and amino acids.

Vitamin B₂ (Riboflavin)

Riboflavin is a water-soluble vitamin that’s present in fortified foods, dairy products, eggs, mushrooms, leafy vegetables, meat, legumes, and almonds. It’s not as soluble in water compared to the other B vitamins.

Riboflavin helps with cellular respiration (converting nutrients to energy) and other cellular processes.

Vitamin B₃ (Niacin)

Niacin is a water-soluble vitamin that’s present in fortified foods, nuts, meat, beans, and whole grains.

It helps with cell signaling, regulating cholesterol production, DNA repair, nervous system function, and breaking down macronutrients and alcohol.

Vitamin B₅ (Pantothenic Acid)

Pantothenic acid has the Greek root “pan” in it because it’s present in just about every food. However, you’ll find the highest amounts in fortified whole grain cereal, egg yolks, liver, and mushrooms. It’s water-soluble.

Pantothenic acid helps with metabolizing macronutrients. It also plays a role in making fatty acids, cholesterol, and the neurotransmitter acetylcholine.

Vitamin B₆

Vitamin B₆ is actually a group of similar water-soluble substances, the most common one in supplements being pyridoxine. It’s present in fortified breakfast cereals, some meats, non-citrus fruits, chickpeas, potatoes, and pistachios.

It plays a role in a huge number of enzyme reactions (over 100 of them) involving metabolizing macronutrients. It also helps with gene expression and with making hemoglobin, histamine, and neurotransmitters.

Vitamin B₇ (Biotin)

Biotin is a water-soluble vitamin that’s present in a wide variety of foods. You don’t need much, and intestinal bacterial make it (which your body then absorbs).

It helps with metabolizing macronutrients, cell growth, making proteins, and with metabolic reactions involving carbon dioxide transfer.

Vitamin B₉ (Folate)

Folate is a water-soluble vitamin that’s present in fortified grain products (like breakfast cereals), leafy vegetables, strawberries, nuts, certain seeds like sesame, beans, peas, avocados, asparagus, and some kinds of meat. The form you find the most in supplements and on the Nutrition Facts label is folic acid.

It’s necessary for cell production and maintenance, making DNA and RNA, preventing changes to DNA, fertility, and for processing certain amino acids. Folate is especially important for pregnant women and infants because of its role in cell division (embryos and infants have rapid cell growth). Pregnant women need to get enough to prevent neural tube defects and other birth defects.

Vitamin B₁₂ (Cobalamin)

Cobalamin is a water-soluble vitamin and is also the largest and most structurally complex vitamin. Since it’s mostly present in animal-based foods and rare elsewhere (and the only organisms that produce it are certain microorganisms), people who don’t eat them need to get cobalamin from fortified foods (like breakfast cereals).

Every cell needs cobalamin for metabolism, and it also helps with preventing certain kinds of anemia and with making DNA, myelin, and red blood cells.

Vitamin C (Ascorbic Acid)

Ascorbic acid is a water-soluble vitamin present in many fruits (including citrus, strawberries, and kiwis), broccoli, Brussels sprouts, and raw bell peppers. Cooking or storing foods decreases their ascorbic acid content.

It’s an important antioxidant, and it also helps with producing collagen (for skin and wound healing) and certain neurotransmitters, with the function of many enzymes, and with immune function.

Vitamin D

Vitamin D is actually a group of fat-soluble secosteroids, the most important ones being ergocalciferol (vitamin D₂) and cholecalciferol (vitamin D₃). It’s present in very few foods. Instead, your skin makes the vitamin D you need using a process involving sunlight. However, some people who don’t get enough sunlight might need to get it from supplements, fortified foods, egg yolks, saltwater fish, or liver.

Vitamin D’s main function is helping the intestines absorb calcium (for bone growth and maintenance), magnesium, and phosphate. It’s especially important in preventing osteoporosis (bone weakening) and rickets (soft and easily bendable bones). It also helps maintain calcium and phosphorus levels in the blood, regulate cell growth, make proteins important for neuron function, make glutathione (an important antioxidant), and helps muscle and immune function.

Vitamin E

Vitamin E consists of a group of four tocopherols and four tocotrienols. It’s fat-soluble and is also an antioxidant. Vitamin E is present in fortified foods, vegetable oils (like sunflower and safflower), green vegetables (like broccoli and spinach), nuts, seeds, and peanuts. People who don’t get enough generally have a problem with digesting or absorbing fat not because they have a diet that’s low in vitamin E (though that can cause a lack of vitamin E too).

Vitamin E is mostly important for its antioxidant properties. It also affects gene expression for controlling enzyme activity and plays a role in smooth muscle growth (like blood vessels).

Vitamin K

Vitamin K is a group of fat-soluble substances, the most important ones being phylloquinone (vitamin K₁, the “plant form” of vitamin K) and menaquinone (vitamin K₂). The main sources of it are green, leafy vegetables.

Vitamin K helps make proteins for blood coagulation and for controlling the binding of calcium in bones and other tissues.

Minerals

In contrast with vitamins, minerals in the nutritional sense are chemical elements. There are 15 minerals we need (cobalt is one of them but you get it in the form of vitamin B₁₂, so I won’t talk about it here).

Sodium

You get most of your sodium from salt, and since salt is in so many kinds of foods, you usually don’t have to worry about not getting enough. In fact, you probably get way more than you need. But in some cases like strenuous exercise, you may need to replenish your supply of sodium.

Sodium plays a role in regulating blood volume, blood pressure, osmotic equilibrium (balancing the concentration of solutes inside and outside the cell), and pH. It also works in tandem with potassium as an electrolyte to conduct electrical signals in neurons.

Potassium

Potassium is in all vegetables, fruits, and meats, but particularly good sources are yams, apricots, nuts, potatoes, bananas, tomatoes, milk and yogurt, beet greens, fruit juices, and spinach.

It plays a role in a wide variety of processes including hormone regulation, blood pressure control, pH regulation, glucose and insulin production, and kidney function. As mentioned before, it also works with sodium as an electrolyte to conduct electrical signals in neurons.

Chlorine

You get chlorine (the Nutrition Facts label lists it as chloride) from salt, so like sodium, you probably get more than enough of it.

Chlorine plays a role in metabolism, the production of stomach acid, pH regulation, and in immune response (specifically neutrophils, a kind of white blood cell).

Calcium

Most of the calcium you get comes from dairy products and grains (not a good source but people eat a lot of grains). Some other sources are fortified foods, canned fish with bones, leafy vegetables like spinach, and tofu.

You probably already know you need calcium for strong bones and teeth. It also functions as an electrolyte, supports blood cell production and function, regulates muscle and blood vessel contraction, regulates blood clotting, and acts as an anchor for cell membrane proteins.

Phosphorus

You get phosphorous generally from the same sources as you get protein from (meat, dairy, nuts, beans…). So as a rule of thumb, if you’re getting enough protein and calcium, you’re getting enough phosphorous.

Phosphorous is an important structural component of DNA, RNA, and cell membranes. It also acts as an energy source and regulator for cells (both in the form of ATP) and helps stiffen bones.

Magnesium

Magnesium is present in lots of different foods including fortified foods, whole grains, wheat bran, dairy products, nuts, leafy vegetables like spinach, pumpkin seeds, beans, peas, and bananas.

Its interaction with phosphate ions is essential for nucleic acid chemistry in all cells. In fact, over 300 enzymes need magnesium, including ones that build DNA and RNA and all enzymes using and producing ATP. It also helps with building proteins and bone and with regulating muscle and nerve function, blood sugar, and blood pressure.

Iron

Iron is pretty common in foods. But especially good sources of iron include fortified foods, meat, lentils, beans, dark green vegetables, tofu, and chickpeas.

The main function of iron is to carry oxygen, which it does as hemoglobin (from lungs to everywhere) and myoglobin (to muscles). It’s also needed for some enzymes and hormones and for building connective tissue.

Zinc

Zinc is in both animal and plant products, but the amount in plant-based ones varies depending on the soil. Good sources of zinc include fortified foods, meat (especially oysters), dairy products, eggs, whole grains, seeds, nuts, beans, and blackcurrants.

Over 300 enzymes and 1000 transcription factors (gene regulators) need zinc to function. In fact, it’s the only metal in humans present in all enzyme classes. As such, it has a huge amount of functions. These include sending chemical signals inside cells, regulating apoptosis (programmed cell death), aiding brain neuron function, helping reproductive organ growth and function, regulating carbon dioxide, digesting proteins, helping the body’s immune response, and speeding up wound healing. It also helps with growth and development (especially in pregnancy, infancy, and childhood), making proteins and DNA, and with our sense of taste and smell.

Manganese

You can get manganese from beans, nuts, pineapples, spinach, yams, and whole grains.

It forms a critical component of many proteins and enzymes. Manganese also helps with the metabolism of macronutrients, bone and cartilage formation, preventing damage from free radicals, and with wound healing.

Copper

Good sources of copper include organ meats like liver, crustaceans and shellfish, nuts, seeds, lentils, cocoa, whole grains, green olives, and avocados.

Copper works with iron in red blood cells to help transport oxygen. It also helps with iron absorption, bone formation, collagen and other connective tissue formation, converting nutrients to energy in cells, neutralizing free radicals, and with nervous system function.

Iodine

Iodine is in many different kinds of seafood (fish, seaweed, and shellfish). It’s also in many animal and plant products that came from organisms that received enough iodine. In an effort to stop iodine deficiency, people created iodized salt, which is probably where you get a lot of your iodine from.

The main function of iodine is the creation of thyroid hormones. These hormones regulate metabolism, bone and brain development (especially during pregnancy and infancy), and reproductive functions.

Chromium

You can find chromium in many foods, but only in small amounts. But you only need very small amounts, so it’s usually not a problem. Like with iodine, the amount of chromium in animal and plant-based foods depends on how much the organisms received. Foods with relatively high amounts include broccoli, fruits (and their juices), meat, spices like basil, and whole grains.

Chromium’s full effects on human health are still somewhat unclear. But it does appear to increase the effect of insulin, which is critical to the metabolism and storage of macronutrients.

Molybdenum

Molybdenum is present in nuts, beans, peas, and whole grains. But the molybdenum content of these foods depends on the amount in the soil where they grew.

Only four enzymes (that we know of so far) use molybdenum. Among them is sulfite oxidase, which helps us process sulfites in food. Molybdenum is also in tooth enamel.

Selenium

You get selenium mostly from nuts (especially Brazil nuts), whole grains, and mushrooms. Some other animal and plant-based foods also contain it, but the amount depends on how much the organisms received.

Selenium acts as an antioxidant and also helps thyroid, reproductive, and immune function. In fact, every cell that uses thyroid hormone uses selenium.

Yue’s Recommendation

I keep track of the calories I eat in a day (I stick close to 1800). So sometimes I might not be eating as many nutrients as I should be eating because well I don’t eat that much, period. That’s why I make sure to eat a multivitamin every day. It ensures that I get the proper nutrition in case I happen to miss something in my diet.

The multivitamin I eat is Centrum (specifically the formula for adults). I highly recommend it because it’s incredibly comprehensive. It has significant amounts of just about every vitamin and mineral I talked about in this post. The tablet is also relatively small, so it’s easy to swallow. I’ve been taking one every day for more than two decades with no adverse health problems. My medical tests also show no nutritional deficiencies. Centrum’s a great multivitamin overall.