What Is the Element Composition of Our Body

The late, great Carl Sagan in his personal exploration of the cosmos said that we are made up of "star stuff." What he meant was that our body is made up of many of the very same elements that make up planets and other celestial bodies in the universe. We humans, as well as other life-forms on our planet, have simply borrowed these elements. Interestingly, four of these elements, namely oxygen, carbon, hydrogen, and nitrogen, make up greater than 90 percent of our body weight. Since the majority of these elements are found in our body as part of substances such as water, proteins, carbohydrates, fats, and nucleic acids (DNA and RNA), it only makes sense that these substances must be the major chemicals of

Table 1.1 Elements of Our Bodies

Major Elements (>0.1% Body Weight)

Percentage of Body Weight

Minor Elements (<0.1% Body Weight)

Percentage of Body Weight

Oxygen (O)

63

Iron (Fe)

<0.1

Carbon (C)

18.0

Selenium (Se)

<0.1

Hydrogen (H)

9.0

Copper (Cu)

<0.1

Nitrogen (N)

3.0

Cobalt (Co)

<0.1

Calcium (Ca)

1.5

Fluoride (F)

<0.1

Phosphorus (P)

1.0

Iodine (I)

<0.1

Potassium (K)

0.4

Molybdenum (Mo)

<0.1

Sulfur (S)

0.3

Manganese (Mn)

<0.1

Sodium (Na)

0.2

Vanadium (V)

<0.1

Chloride (Cl)

0.2

Chromium (Cr)

<0.1

Magnesium (Mg)

0.1

Boron (B)

<0.1

Zinc (Zn)

<0.1

Aluminum (Al)

<0.1

Tin (Sn)

<0.1

Silicon (Si)

<0.1

Arsenic (As)

<0.1

our body. For example, a lean, young adult male's body weight may be approximately 62 percent water, 16 percent protein, 16 percent fat, and less than 1 percent carbohydrate. Most of his remaining weight (about 5 percent) would be attributed to minerals. We will spend a lot more time talking about the finer details of body composition in later chapters.

Our body is mostly made of water, fats, protein, carbohydrate, minerals, DNA, and other special molecules.

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