When you are looking at diet pill formulations do you only look at the key ingredients listed in the supplement facts? If so, you are not alone. That’s what most people do. Very few people take note of the “other” ingredients or “additional ingredients” that are generally presented in smaller print underneath.

We’ve all done it but failing to take note of the additional ingredients can cause problems further along the line. This poorly presented ingredient information often has important details such as the presence of gelatin in the capsule shell. If you are vegan or vegetarian, that’s something you will definitely want to know about.

However, the average Vegan is used to scrutinizing products closely. As are most vegetarians, it’s unlikely they will be caught out.

It’s not just a case of checking for animal extracts though. We all need to take careful note of all ingredients in diet pills and other supplements we are considering using. Some of the extra ingredients, such as rice and soy, can cause certain people to experience allergic reactions. Other products have ingredients in them that have raised health concerns or have not been sufficiently studied.

This is not only a problem with natural supplements. Some medicines contain dubious conclusions too.

The picture at the top of this page shows the inactive ingredients in Alli and several of them are associated with health concerns.

Alli is a low-strength version of the prescription weight loss medication Orlistat and it contains these additional ingredients too.

Despite the health concerns some experts raise, the American FDA still permits small quantities of these ingredients to be used. So do similar regulatory bodies in other countries, although the European Food Safety Authority (EFSA) is generally a slightly tougher nut to crack.

Over-the-counter supplements, such as diet pills, present greater concerns than medications because their production is not so closely monitored.

Fortunately, many of the additional ingredients in diet pills are unlikely to cause problems. By acting as binders and fillers, they can be very useful.

However, we all have the right to understand what we are putting into our bodies and to decide which ingredients we are happy to welcome inside and which ones we’d prefer to turn away.

In this article, I’m going to explain why certain types of ingredients are included. I’m also going to help you to understand which ingredients you may want to avoid and why.



Most diet pills have filler ingredients in them. That’s okay. Supplement fillers serve a purpose but lots of ingredients can serve the same purpose and some may be more acceptable to you than others.

Supplement filler ingredients are there to provide bulk. Some ingredients, such as vitamins and minerals are minuscule. Pills and powders that contain a lot of these ingredients need to have fillers or it would appear there was nothing there.

Think about it, if you bought a multi-vitamin tablet that was almost too small to see or a diet pill capsule that was only one-quarter full, how would you feel. I bet you’d find it hard to believe you were getting good value for money.

By providing extra bulk, fillers make products look more substantial. In the case of tablets, they also make them easier to pick up and handle.

A few filler ingredients:

  • Salt
  • Calcium
  • Sugar
  • Rice flour
  • Vegetable gum
  • Talc

As you can see some of the above fillers (there are many more), such as rice flour, may be unacceptable to some people.

But what of talc? Many people may not be offended by the idea of talc in their supplement, but it has very dubious credentials. More on that later.



Binders are another useful type of ingredient that’s present in many diet pills. They are especially important for compressed tablets because, as the term “binder” suggests, they help bind the ingredients and hold the tablet together.

Some binder ingredients are sugar derivatives, such as sucrose or liquid glucose. Starch paste or acacia gum are also quite common and cellulose is a popular option too but there are many more.


​Flow Agents

Flow agents are additional ingredients that prevent the other ingredients from sticking to the machinery that produces consumable pills and powders. They also stop the ingredients in capsules from clumping together.


​Tablet Coatings & Capsule Shells

Some manufacturers use additional ingredients to coat their pills and make them easier to swallow. A nice smooth coating can be a godsend for people who have difficulty swallowing pills.

Capsules often have pull-apart casings that hold the key ingredients inside. Traditionally these were often made from gelatin. This is still the case with many pill-type supplements but a growing number of manufacturers are switching to vegetable-based cellulose casings instead.


​Ingredients That Add Color and Flavor

Many supplements, including a lot of diet pills, contain extra ingredients to improve the color and flavor. Manufacturers have a variety of choices when it comes to choosing their ingredients.

Some choose natural options such as plant and fruit extracts. Others use chemicals and the chemical colorants in some diet pills have concerns surrounding their use. Lots of people prefer to stick with the natural options and it’s a very good stance to take.


​How “Other Ingredients” Can Influence Key Ingredient Absorption

Some of the additional ingredients in diet pills can reduce the bioavailability of the key ingredients making them harder to absorb.

Others may increase bioavailability. Piperine is one example. It’s such an important ingredient most manufacturers list it as a key ingredient but some manufacturers throw it among the small print that lists the additional ingredients.

Piperine is an alkaloid. It comes from black pepper. Bioperine is the best form. It’s standardized to be 95 percent piperine.

Lots of diet pills have piperine in them and it’s especially useful in formulas that contain curcumin. The body struggles to digest curcumin but research shows piperine can boost absorption rates by up to 2,000 percent.

However, if the additional ingredients contain sources of iron, and the key ingredients include zinc, the iron may reduce the amount of zinc you can absorb. (https://pubmed.ncbi.nlm.nih.gov/9701159/)

Zinc is a key ingredient in many diet pills aimed at people who like to train and at bodybuilders hoping to ditch extra fat. Manufacturers add zinc because it boosts testosterone. It won’t be able to do this if there are other ingredients present that prevent it from being absorbed.


​The Extra Ingredients You May Want to Avoid

Now you know the various roles the various extra ingredients play, it’s time to look at some of the ones you may want to avoid.


​Magnesium Stearate

Magnesium stearate is sometimes used as a flow agent in diet pills and other supplements. It works well in this role but there are several concerns you need to be aware of.

Some experts believe magnesium stearate may block drug and nutrient absorption. There are also concerns that it may weaken the immune system by interfering with T-cell function.

Magnesium stearate has FDA approval for use in food and supplements. The National Center for Biotechnology Information (NCBI) also believes it is safe but recommends a maximum of 2,500 mg (per kg of body weight) per day. That’s a lot more than you’d be likely to get from supplements.

In the end, only you can decide if you are comfortable using supplements that contain this ingredient. Here’s a link to a trusted source that provides information to help you make up your mind: https://www.webmd.com/vitamins-and-supplements/what-is-magnesium-stearate


​Talc (Magnesium Silicate)

Athletic Woman Looking at Talc on her Hands

Talc is sometimes used as a cheap filler in supplements. It also has value as a flow agent.

There are concerns that talc may be contaminated with asbestos. That may surprise you. Most of us have breathed talc in without suffering ill effects but some experts believe talc presents an unacceptable threat and advise against consuming it or breathing it in.

Unfortunately, researchers don’t appear to be able to agree about the dangers of talc. Some studies suggest it may cause cancer, others suggest it does not.

The truth is, there’s a need for further investigation and several alternative ingredients can do the same job.

Is it safe to take supplements with talc in them? That’s not for me to say. Here’s a link to an article that may help you decide for yourself: https://www.drugwatch.com/talcum-powder/does-talc-cause-cancer/


​Artificial Colors

Artificial colors are present in many diet pills and lots of foods and candies. There are concerns about many of them.

Here’s a list of a few food dyes that are currently approved by the FDA:

  • FD&C Blue No. 1
  • FD&C Blue No. 2
  • FD&C Green No. 3
  • FD&C Red No. 3
  • FD&C Red No. 40
  • FD&C Yellow No. 5
  • FD&C Yellow No. 6

And here’s a link to a report on the toxicology of food dyes: https://pubmed.ncbi.nlm.nih.gov/23026007/

The report points out Red 3 causes cancer in animals, while Red 40, Yellow 5, and Yellow 6 have been found to be contaminated with benzidine and carcinogens.

Red 40 and Yellow 5 cause hypersensitivity as well. It’s just one report but a lot is going on.

I’m not an expert on food dyes, but here’s a link to an article by a doctor who knows more than me: https://www.drtaniadempsey.com/post/food-coloring-toxic-health-risks


​Titanium Dioxide

Titanium dioxide is another chemical nasty that often finds its way into diet pills and supplements. It’s a color-providing ingredient. We’ve covered them already but titanium dioxide has so many potential problems attached to its usage I thought it deserved a special mention.

Titanium dioxide is used as a colorant in supplements and cosmetic products. It’s also used to add color to foods.

There are many concerns about the risks it may present.

When inhaled, titanium dioxide may have the potential to cause lung damage. The research suggesting this was conducted on rabbits, not people, but it still suggests a need to tread carefully.

Research indicates titanium dioxide may be capable of causing minor DNA damage too. That’s rather disturbing because a lot of people ingest the ingredient every day via vitamin pills and similar supplements.

A retracted study involving mice suggests the ingredient may also be hard on the liver

Again this study did not involve humans and the fact that was retracted questions its value. Still, though, it’s hard not to find it concerning.

Despite the questions, many experts raise about the safety of titanium dioxide, the FDA permits it to be used as a food additive, albeit in very low amounts.

For a long time, regulatory bodies in Europe considered titanium oxide a safe food additive too. That changed in May 2021 when the European Food Safety Authority updated its safety assessment.

The EFSA has concerns about genotoxicity and the ingredient’s ability to accumulate in the body. You can learn more about the assessment and findings at the EFSA website.


​Final Thoughts

Although many of the binders and fillers and other extra ingredients can be useful additions to medicines, diet pills, vitamin tablets, and supplements; some of them appear to be more trouble than they are worth.

In writing this article, my aim is to encourage people to take a close look at all the ingredients in weight-loss supplements before they allow them into their bodies. I’ve also provided information about some ingredients you should look out for but there could be many more. There are limits to my knowledge and studies of many ingredients is ongoing so I encourage you to do your own research.

We all have the right to decide what products we use but we also have the right to be told about everything they contain. Some diet pills are sold with lots of big promises and little or no information about the ingredients at all. I strongly advise against buying any health and wellness products that are marketed in this way. If you don’t know what something contains, you cannot know what it may do ‒ good or bad.

I’d like to end this article by pointing out I’m a diet pill and supplement reviewer, not a doctor. The information I provide is the result of detailed research, not a medical education. This article is not intended to be a substitute for expert medical advice.

If you are considering using a new supplement for the first time and fear there may be risks or doubt its suitability, it’s always best to visit your doctor, take along the supplement information (ingredient list, etc.) and let them be your guide.

Ninja Sword