Manufactured ascorbic acid has become a swear word in the USA!

In September 2023, consumers in the USA filed a 23-page lawsuit against PepsiCo, arguing that the company “falsely advertised” that its Ceres juice drinks contained no preservatives and were 100% juice. The lawsuit alleges that the products “in fact contain[s] the artificial ingredient ascorbic acid, a type of artificial Vitamin C, which acts as a preservative”; and that “although there is a naturally occurring form of ascorbic acid, it is most commonly produced synthetically, “through extensive chemical processing”. Similar lawsuits were issued against Walmart, Target and others. Other arguments include that synthetic vitamin C is often derived from GMO maize, and that synthetic vitamin C may be advertised as ‘natural’.

Vitamin C (also known as ascorbic acid or ascorbate) is an essential water-soluble vitamin and micronutrient for humans. It is the most encountered ascorbic acid. It is obtained through diet primarily from citrus, other fruits, and vegetables. It is required for the functioning of several enzymes, and importantly, for healthy immune system function. Vitamin C acts as a cofactor for numerous biosynthetic enzymes required for the synthesis of amino acid-derived macromolecules, neurotransmitters and neuropeptide hormones, and is also a cofactor for various hydroxylases involved in the regulation of gene transcription and epigenetics. A deficiency of vitamin C causes scurvy.

In fact, ascorbic acid exists as two enantiomers (mirrorimage isomers), commonly denoted ‘L’ (for ‘levo’) and ‘D’ (for ‘dextro’). The term ‘vitamin C’ always refers to the L-enantiomer and its oxidised forms, such as dehydroascorbate (DHA). In contrast, D-ascorbic acid has no significant biological role, i.e. no ‘vitamin C’ effects. Both forms are used throughout the world, as food preservatives or antioxidants, in a wide range of food categories, with the highest permissible level of 250–1 500 mL/kg or mg/L in different food categories.

Is there a difference between synthetic and natural vitamin C?

Chemically speaking, food-derived vitamin C (L-ascorbic acid) and synthetic vitamin C (derived from glucose, for instance) are identical. If they were not identical molecules, their structures would look different!

The body cannot differentiate between these two sources. There is some evidence that any differences between ‘natural’ and ‘synthetic’ vitamin C exist only in the so-called matrix effects; in other words, ‘natural’ vitamin C comes from fruit and vegetables rich in numerous micronutrients, dietary fibre and phytochemicals (e.g. bioflavonoids), and these may play a role in the absorption (and thus the bioavailability) of vitamin C.

Although the majority of animal studies have shown differences in the comparative bioavailability of synthetic versus natural vitamin C, results have varied depending on the animal model, study design, etc. However, bioavailability studies in humans have shown no differences between synthetic and natural vitamin C, regardless of subject population, study design or intervention used, except for some small, transient comparative differences with minimal physiological impact. Extracting natural vitamin C from fruit removes its benefits from the fruit, and adding synthetic vitamin C to fruit juice adds the same benefits.

In South Africa, the NRV (Nutrient Reference Value) for vitamin C is 100mg. Freshly squeezed 100% orange juice contains 46mg vitamin C per 200ml (46% NRV). Ceres mango-flavour juice, consisting of purified water, orange juice, sugar, mango puree, vitamin C (E300), citric acid (E330) and natural flavours, claims 90mg ascorbic acid per 200ml. (‘E300’ designates the vitamin C as an antioxidant.) Compared to one orange, which contains 70mg vitamin C, one guava contains 125mg vitamin C, which exceeds the daily NRV.

It’s debatable whether vitamin C in factory-manufactured fruit juice occurs naturally, or is intentionally added for preservative or antioxidant effects, or to increase vitamin C content. Regardless, the physiological effect is the same.

If vitamin C is added to a food with the purpose of creating a health ‘halo’ effect, consumers are entitled to feel aggrieved if the levels are insufficient to contribute any significant benefit. Some vitamin manufacturers tout the benefits of high-dose oral vitamin C, without robust evidence to support their claims. There is no evidence that high-dose vitamin C has any effect on reducing or preventing the common cold. In fact, studies have shown that at very high concentrations, vitamin C can switch roles and act as a tissue-damaging pro-oxidant instead of an antioxidant.

The effects of vitamin C in very high doses on humans remain unclear, but are unlikely to be harmful, except for digestive upset and/or diarrhoea; it can also lead to increased risk of kidney stones.

So what exactly is the issue? Is it primarily that PepsiCo has advertised Ceres juices “as ‘100% juice’ with ‘no preservatives’, while the drink actually contains ascorbic acid, an artificial ingredient with vitamin C that acts as a preservative”? The lawsuit argues that this supports a “deceptive marketing campaign”, allowing PepsiCo to achieve a higher price for Ceres juice. Are consumers scientifically ‘naïve’, or are they demanding 100% ‘truthfulness’ from the industry?

Ironically, many plant-derived sources of vitamin C are deliberately fortified with synthetic vitamin C; because otherwise, their vitamin C content would be too low.

References are available.

As published in SAAFoST’s FST magazine (South African Food Science and Technology), pages 12-13.
Author: Harris Steinman is a researcher, medical doctor and CEO of FACTS (Food & Allergy Consulting & Testing Services).