Have you ever found yourself standing in front of a store shelf, picking up bottle after bottle of “natural” vitamins and flipping them over to read the label? If the answer is yes, you may already know that many so-called natural vitamins actually use significant amounts of synthetic ingredients in their formulas.

How does that even happen, and does it matter? We’ll dive into those answers today – plus how to spot the synthetic stuff and natural forms to look for – and in a follow-up post I’ll explain what I use and why.

So, what’s the difference between natural and synthetic vitamins?

Natural can mean a lot of things depending on who you ask, but for the purposes of this article we’ll define things this way:

Natural, bioavailable supplements – Derived from whole foods such as acerola cherry, these supplements contain a variety of phytonutrients that work together to support vitality in ways that we are still discovering. They can be in capsule or pill form (dried, ground herbs for example) or a liquid form such as herbal tincture extracts.

Synthetic supplements with low bioavailability – Usually made in a lab, these supplements are typically isolated nutrients. They tend to be chemically identical to their natural counterparts, but not molecularly. If it’s been awhile since you picked up a chemistry textbook, when something is chemically identical it has all the same ingredients, and when something is molecularly identical it has all the ingredients arranged in exactly the same pattern.

Manufactured (some would say synthetic) supplements with high bioavailability – In this category there are two kinds of supplements: Those that were created in a lab and those that were refined from natural ingredients into isolated nutrients. The important thing to know about them is that they are both chemically and molecularly identical to the way they are found in nature.

In other words, although they are not “natural” in the sense that they were manufactured or processed to the point that they don’t resemble their whole-food origin, they do use the natural, optimally bioavailable form of the nutrient.

4 Concerns With Synthetic Supplements

Unfortunately, just because a synthetic vitamin is chemically (and even molecularly) identical to the natural form does not automatically mean it will have the same effect. Two hormones – oxytocin and pitocin (synthetic oxytocin) – are identical, but they have different effects on the body.

The same can be said for some synthetic supplements. Here’s why:

1. They don’t use natures “secret recipes”

Let’s say your friend bakes amazing carrot cakes and she walks through the door with a beautiful baking tin in her hands. Your mouth is already watering by the time she lifts the lid to reveal . . . carrots, eggs, baking soda and all the other ingredients that go into her recipe. All the right ingredients are there, but they’re not in a form that you or I would recognize as carrot cake.

The same things can happen with certain synthetic nutrients. Just like we immediately recognize carrot cake when all the ingredients are assembled in the right way, our bodies recognize nutrients when they’re structured in a particular way.

Nature has it’s own “secret recipes” that combine nutrients in an optimal way, and there is so much innate wisdom about these “formulas’ that we are still discovering. (1)

When the constituents are isolated and used separately they have less therapeutic benefit. Carrots alone do not count as carrot cake, and isolated nutrients aren’t the same as their whole-food form.

For example, it was once thought that a medicinal herb had an “active constituent” that was the sole source of its therapeutic benefits. Over time, though, we’ve learned that there are usually several supporting constituents that amplify the therapeutic effect of the primary constituent. When isolated, it often becomes far less effective.

2. Our bodies don’t always know how to use them

In nature, vitamins have either a right (D) form or left (L) form called optical rotation. In plain English, that means they’re chemically identical, but instead of being structurally identical they’re mirror images of each other. (Think right and left handed gloves.)

Some nutrients are “right-handed,” while others are “left-handed.” For example, vitamin C occurs in nature as l-ascorbic acid instead but not d-ascorbic acid.

Some nutrients naturally occur in both forms, but our bodies are only able to use one form. The amino acid arginine is an example: Both l-arginine and d-arginine exist in nature, but only the l-form is considered to be biologically active. (2)

To understand why one mirror-image works but not the other, imagine you’re trying to put together a puzzle and you find two pieces that fit together. That’s what happens when a vitamin attaches to a cell receptor site – the cell locks onto it because it fits just right.

Would the same piece work if you flipped it over and tried to put it in place? Nope, because although it’s the exact same piece it’s not oriented correctly.

That the issue with some synthetic nutrients. Even when they’re chemically identical to what’s found in nature, they’re not always structurally. When that’s the case, our bodies can’t use them well.

Take vitamin E, for example. In this study, researchers found that natural vitamin E was absorbed twice as efficiently as the synthetic version.

In another study, natural vitamin K was compared with synthetic K1, and researchers concluded that just 1/4 the dose of the natural form was more effective than the synthetic form.

3. They may clog cell receptor sites

Poor absorption is not the only problem, though. When the wrong form is given to our bodies, it may clog the receptor sites that could be used by truly bioavailable nutrients.

Folic acid, for example, is a synthetic compound that many people (especially those with the MTHFR mutation) cannot use efficiently. When consumed, it attaches to receptor sites that are then blocked for use by a more bioavailable form such as methylfolate.

4. They come in unnaturally high doses

Manufacturers often use higher doses to try to overcome the low absorption issue, but there are downsides to that approach.

Research suggests that because our bodies don’t metabolize folic acid (which is synthetic) well, it may build up in the body and increase the risk of cancer. (3) (4)

Another study found that 1 gram of daily synthetic vitamin C impaired mitochondrial function and reduced athletic performance. (5)

There also one more thing to consider: Some nutrients – calcium and magnesium, for example – compete for absorption, so taking excessive amounts of one can throw off another. This can happen even when the lab-created supplement uses the natural, bioavailable form.

How do I know if my supplement is natural or synthetic?

Here are a few things to look for:

If the label says it’s made from 100% plant or animal sources, it’s natural

If it just says “natural” or “whole food-based,” it may have natural ingredients that are spiked with synthetic vitamins to make it appear more potent. Remember, natural vitamins are better absorbed than synthetic ones so we don’t need megadoses. However, high dosages seem like a good idea to many consumers and marketers use that to their advantage.

An example a 100% plant based supplement would be ground turmeric in a cellulose capsule. Cod liver oil (without synthetic vitamin A or D added in) would be a 100% natural animal product.

If a vitamin is listed in “dl” form, it’s synthetic

For example, natural vitamin E is d-alpha-tocopherol and synthetic vitamin E is dl-alpha-tocopherol.

If the label says “derived from,” dig deeper

“Labels often proclaim ‘natural’ B vitamins, derived from yeast. But companies manufacturing yeast add laboratory-synthesized B vitamins to the food fed to the yeast during its growth, and then fortify the yeast further with additional B vitamins once it has grown. This allows the production of yeast of any B-vitamin potency desired, which is then used to formulate vitamin pills labeled ‘B vitamins derived from yeast.’”

This can happen with other nutrients as well, but I don’t think that every supplement which uses “derived from” wording is using this kind of approach. For me, seeing that phrase is a sign that I need to talk to the manufacturer and ask some questions.

If it lists isolated nutrients like “vitamin C” or “ascorbic acid,” it’s most likely synthetic

If a product that claims to have vitamin C lists a whole food ingredient such as rosehips or acerola cherry powder on the label, it’s natural.

However, as I mentioned above, some supplements are refined into isolated nutrients from natural sources in a way that I feel comfortable with. More on when I opt for nutrients in this category below.

All mineral supplements are natural

Even when synthesized, all mineral supplements are sold in forms that are found in nature. However, some are better absorbed than others – oxides and chlorides tend to have low absorption rates. Also, as is true with other supplements, they are often coated in hydrogenated fats such as magnesium stearate and stearic acid which inhibit absorption.

Are synthesized or isolated nutrients ever a good idea?

I think so. If one of my kids develops a urinary tract infection, you can bet I’m breaking out the d-mannose. Yes, it’s an isolated nutrient and in general I opt for nutrients that have all of their natural co-factors, but d-mannose is an exception. To get enough from food, my children would have to eat a ton of fruit, which would increase their sugar intake and potentially make the UTI worse.

In cases like the one I just mentioned, using the “natural” or bioavailable form of a nutrient – regardless of how it was manufactured – can be incredibly helpful. Of course, whenever I use a supplement like this as an intervention I also look for ways to address the root cause of the issue going forward.

Although they are isolated nutrients, lab-created supplements that are in their “natural” or bioavailable form can be helpful for targeted supplementation. By that, I mean targeted supplementation can help to correct a deficiency while the individual works on lifestyle factors to address the root cause of that deficiency.

Common Names of Natural & Bioavailable Vitamins

Most of the time if a particular vitamin is listed on a label, it’s an isolated nutrient that has been added to the formula. However, there are exceptions. The fish oil I buy does not have synthetic vitamin A and D added in, but because consumers want to know exactly how much of these vitamins it contains they specify that on the nutritional label.

This list is not exhaustive, but hopefully, you’ll find it helpful in identifying whether the nutrients in your supplements are optimally bioavailable.

  • Vitamin A (Retinol) – As I mentioned in this article on eating healthy during pregnancy, nutrition labels often say that a food has “X” amount of Vitamin A, but what they really mean is that it contains carotenoids such as beta-carotene. Unfortunately, beta-carotene is not biologically active, and therefore not the same as the bioavailable form of Vitamin A (retinol) found in animal products. Most of us do not possess enough of the enzyme needed to efficiently convert beta-carotene into bioavailable Vitamin A – in fact, this study found that only about 3% is converted, and about 45% of adults can’t make the conversion at all. (source 1, source 2)
  • Vitamin B1 (Thiamine) – Thiamine pyrophosphate; Thiamine triphosphate
  • Vitamin B2 (Riboflavin) – Riboflavin-5-phosphate; Flavin mononucleotide
  • Vitamin B3 (Niacin) – Nicotinamide (adenine dinucleotide)
  • Vitamin B5 (Pantothenic Acid) – Pantethine Pyridoxine
  • Vitamin B6 (Pyridoxine) – Pyridoxal-5-phosphate
  • Vitamin B9 (Folate) – Folinic acid; 5-methyl tetrahydrofolate
  • Vitamin B12 (Cobalamin) – Methylcobalamin; Adenosylcobalamin
  • Choline – Phosphatydlcholine
  • Vitamin C – The l-ascorbic acid found in orange is both chemically and molecularly identical to the synthetic version. However, I personally believe that the benefits of vitamin C are strongly tied to the co-factors found in whole food forms, so I opt for food and whole-food supplements such as dried acerola cherry.
  • Vitamin D – D3 (However, supplementing with vitamin D may not have all the same benefits as sunshine)
  • Vitamin K2 – menaquinone-7 (MK-7)

Article sources:

1. Liu, RH (2003) Health benefits of fruit and vegetables are from additive and synergistic combinations of phytochemicals. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/12936943

2. Drugbank, supported by the Canadian Institutes of Health Research. D-Arginine. Retrieved from https://www.drugbank.ca/drugs/DB04027

3. Sweeney, MR et. al. (2007) Folic acid fortification and public health: report on threshold doses above which unmetabolised folic acid appear in serum. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/17378936

4. Ebbin, M et. al. (2009) Cancer incidence and mortality after treatment with folic acid and vitamin B12. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/19920236

5. Gomez-Cabrera, Mari-Carmen et. al. (2008) Oral administration of vitamin C decreases muscle mitochondrial biogenesis and hampers training-induced adaptations in endurance performance. Retrieved from https://academic.oup.com/ajcn/article/87/1/142/4633311

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Posted by Dr. Katherine Jenkins

Dr. Katherine Jenkins is a functional-medicine expert who consults people nationally and locally in Austin, Texas. Her specialization is customizing health programs for digestive disorders. She was awarded the prestigious R. Wieland prize by American Nutrition and Dietetics Association. Dr. Jenkins is a regular contributor to Sharp & Healthy.