Explainer: Some supplements may not have what it takes | Science News for Students

Explainer: Some supplements may not have what it takes

Environment and growing conditions can vary the amounts of useful chemicals in a plant’s tissues
Mar 22, 2016 — 7:15 am EST

Many studies have shown diets rich in pomegranates or their juice can be healthy for the heart. Yet some supplements that claim to be made from this fruit appear to lack the heart-healthy chemicals.

Samantha Forsberg/Flickr (CC-BY 2.0)

Some dietary supplements are made in a lab, like drugs. Others are derived from plants. But there’s another big difference between these supplements than just where they came from. Those plant-based ones may sound healthier, because they have a natural source. But there’s no guarantee that plant-based supplements contain the chemicals that are supposed to make them healthful.

If a drug says it contains 200 milligrams of the pain-reliever ibuprofen, it should have exactly that amount. If a company sells you more — or less — than the labeled amount, they’re breaking the law. But supplements that are made from plants don’t contain an exact amount of some chemical. Instead, their labels usually say the pills contain a certain amount of the starting plant, such as ginseng or ginger. These plants have chemicals that can be helpful to the human body. But there’s a problem: The amount of those chemicals can vary widely from plant to plant and, thus, from one package of some supplement to another.

A plant is made of more than a single chemical. Its tissues contain many chemicals, sometimes thousands of them. And the amounts of each can vary greatly between any two plants — even if grown on the same farm.

Many of the plant chemicals sought by the makers of diet supplements are defense compounds. They may be poisons that plants make to deter predators. Others may be compounds — such as antioxidants — that the plants make to protect or repair damaged tissues. If a plant is very stressed, it may make more of these chemicals. If it isn’t, it may make few of them.

carrotsThe amount of nutrients in the soil also can affect a plant’s chemical content. When the proportion of nutrients is wrong, a plant may not be able to to make or use the chemicals it needs to grow — including the chemicals that diet studies have shown to be healthy for people.

Supplements may lack healthy chemicals

Science News published a big story on the problem back in 2003. Then it published a follow-up story six years later. Back then, the magazine asked: “How do we know what’s in those [food] supplements?” The answer, it found: “We don’t.”

This can prove especially true for supplements that are not made from recipes that include well-defined chemicals, such as creatine or magnesium citrate.

For instance, in one study, researchers at the Geffen School of Medicine at the University of California, Los Angeles, looked at supplements containing chemicals from pomegranates. A host of studies had found that eating this fruit or drinking its juice could lower the risk of heart disease. This benefit showed up both in lab animals and in people. Many studies had linked the health benefits from pomegranates to chemicals called tannins.

But fresh pomegranates can be expensive. They also are not in season all year round. So some supplement companies began offering capsules, tablets and soft gels claiming to hold pomegranate chemicals. However, the UCLA study found that of the 27 pomegranate supplements it tested, 17 (roughly two-thirds) had no tannins in them. And five more that did had just tiny traces. Some supplements either contained no pomegranate or had lost vital parts of the fruit as it was processed to make a food supplement, the researchers concluded.

Be careful what you ask for 

Sometimes even when a product contains exactly what it claims to, a user may still lose out. Consider the case of vitamin E.

Many studies have shown that foods rich in this vitamin can help reduce tissue damage (and perhaps disease) in the lungs and other tissues. It’s supposed to do this by quashing molecules known as free radicals. Chemicals that fight free radicals are known as antioxidants. They fight oxidation. This a potentially damaging reaction that can destroy cells. And vitamin E is known to be a very effective antioxidant.

In plants, vitamin E tends to occur as a mix of several related types of tocopherols and tocotrienols (Toh-koh-TRY-eh-nawls). These chemicals come in what are known as alpha-, beta-, gamma- and delta forms. Because alpha-tocopherol tends to occur in the highest amounts, some companies have sold it alone as vitamin E.

Yet several studies have suggested that alpha-tocopherol doesn’t have the same properties when consumed on its own that it may have when accompanied by the other forms. So people who want the benefits of vitamin E may need to make sure the supplement they buy has the entire mix of related compounds. And it may help if the chemicals are consumed in the proportions that tend to occur naturally in a plant.

That's why many doctors and food chemists now argue that the safest way to build a healthy body is to get your nutrition from eating a variety of whole foods. And here’s an interesting fact: Many of the healthiest compounds in plant-based foods come from the pigmented molecules in them. That’s why nutrition experts recommend eating a diet rich in colorful fruits and veggies.


Power Words

(for more about Power Words, click here)

alpha-tocopherol    One compound in a mix of natural plant-based chemicals that make up what is known as vitamin E. Those chemicals are various forms of tocopherols and tocotrienols.

antioxidant Any of many chemicals that can shut down oxidation — a biologically damaging reaction. They do this by donating an electron to a free radical (a reactive molecular fragment) without becoming unstable. Many plant-based foods are good sources of natural antioxidants, including vitamins C and E.

chemical     A substance formed from two or more atoms that unite (become bonded together) in a fixed proportion and structure. For example, water is a chemical made of two hydrogen atoms bonded to one oxygen atom. Its chemical symbol is H2O. Chemical can also be an adjective that describes properties of materials that are the result of various reactions between different compounds.

chemistry   The field of science that deals with the composition, structure and properties of substances and how they interact with one another. Chemists use this knowledge to study unfamiliar substances, to reproduce large quantities of useful substances or to design and create new and useful substances. (about compounds) The term is used to refer to the recipe of a compound, the way it’s produced or some of its properties.

creatine     A nitrogen-based compound made naturally by animals with backbones. It helps their bodies supply energy to cells, especially the making up muscle

deter   An event, action or material that keeps something from happening. For instance, a visible pothole in the road will deter a driver from steering his car over it.

diet    The foods and liquids ingested by an animal to provide the nutrition it needs to grow and maintain health.

free radical    A charged molecule (typically highly reactive and short-lived) having one or more unpaired outer electrons. It will attempt to steal electrons to make itself whole again through a process known as oxidation.

molecule    An electrically neutral group of atoms that represents the smallest possible amount of a chemical compound. Molecules can be made of single types of atoms or of different types. For example, the oxygen in the air is made of two oxygen atoms (O2), but water is made of two hydrogen atoms and one oxygen atom (H2O).

nutrient     A vitamin, mineral, fat, carbohydrate or protein that a plant, animal or other organism requires as part of its food in order to survive.

nutrition   The healthful components (nutrients) in the diet — such as proteins, fats, vitamins and minerals — that the body uses to grow and to fuel its processes.

oxidation     A process that involves one molecule’s theft of an electron from another. The victim of that reaction is said to have been “oxidized,” and the oxidizing agent (the thief) is “reduced.” The oxidized molecule makes itself whole again by robbing an electron from another molecule. Oxidation reactions with molecules in living cells are so violent that they can cause cell death. Oxidation often involves oxygen atoms — but not always.

pigment     A material, like the natural colorings in skin, that alter the light reflected off of an object or transmitted through it. The overall color of a pigment typically depends on which wavelengths of visible light it absorbs and which ones it reflects. For example, a red pigment tends to reflect red wavelengths of light very well and typically absorbs other colors. Pigment also is the term for chemicals that manufacturers use to tint paint.

predator    (adjective: predatory) A creature that preys on other organisms for most or all of its food.

quash    To completely suppress, destroy, neutralize or extinguish.

tannin    A reddish and bitter plant chemical used to tan leather. Tannins are also a natural pesticide. Pesticides kill vermin, such as rats, insects and lice.

tissue    Any of the distinct types of material, comprised of cells, which make up animals, plants or fungi. Cells within a tissue work as a unit to perform a particular function in living organisms. Different organs of the human body, for instance, often are made from many different types of tissues. And brain tissue will be very different from bone or heart tissue.

supplement     (verb) To add to something. (in nutrition) Something taken in pill or liquid form — often a vitamin or mineral — to improve the diet. For instance, it may provide more of some nutrient that is believed to benefit health.

stress     (in biology) A factor, such as unusual temperatures, moisture or pollution, that affects the health of a species or ecosystem. It an organism’s usual state of being or places increased demands on it.

tocotrienols     A family of structurally related chemicals whose activity in the body resembles or matches that normally attributed to vitamin E. These chemicals often occur in plants along with alpha tocopherol, the primary chemical referred to as vitamin E.


  • MS-PS1-3
  • MS-LS1-5
  • MS-LS1-7


U.S. Food and Drug Administration. “Questions and answers on dietary supplements.” Updated April 28, 2015.

Y. Zhang et al. Absence of pomegranate ellagitannins in the majority of commercial pomegranate extracts: Implications for standardization and quality controlJournal of Agricultural & Food Chemistry. Vol. 57, August 26, 2009, p. 7395. doi: 10.1021/jf9010017.

Further Reading

J. Raloff. “Herbal supplementation can be an empty gesture.” Science News blog. August 25, 2009.

J. Raloff. “Vitamin E shields lungs from smog effects.”Science News blog. March 18, 2009.

S. Gaidos. “Foul play?” Science News for Students. April 9, 2008. 

E. Sohn. “The buzz about caffeine.” Science News for Students. September 9, 2007.

J. Raloff. “Food colorings: Pigments make fruits and veggies extra healthful.” Science News. January 8, 2005.

J. Raloff. “A carrot rainbow (with recipe).” Science News blog. November 18, 2004.

J. Raloff. “A forget-me-not dietary supplement?” Science News blog. November 20, 2003.

J. Raloff. “Herbal lottery.” Science News. Vol. 163, June 7, 2003, p. 359.

J. Raloff. “E is for effort from athletes.” Science News blog. May 28, 2002.

J. Raloff. “Health benefits of another vitamin E (gamma tocopherol).” Science News. Vol. 151, April 5, 1997, p. 207.

Sports Supplements.” TeensHealth.