E223 (sodium metabisulfite)

E223 is sodium metabisulfite, a sulfite salt used as a preservative and antioxidant. In foods it can release sulfur dioxide-related forms and belongs to the broader sulfite system E220-E228. Its technological role is to slow oxidation, browning, flavor changes, and the growth of some microorganisms. It may appear in wine-related products, preserved foods, some marinades, dried fruit, processed vegetables, and other products where shelf stability is needed.

How metabisulfite differs from sulfite

Sodium metabisulfite differs chemically from sodium sulfite E221 and sodium bisulfite E222, but in food practice all of them belong to the sulfite group. For a technologist, the form matters because it affects solubility, pH, sulfur dioxide release, method of addition, and behavior in a particular formula. For the consumer, the practical message is that anyone sensitive to sulfites should consider E223 together with other additives in this group.

The word sodium in the name does not make E223 an electrolyte supplement. Sodium can indeed be important on keto, but it is obtained from salt, broth, mineral water, or electrolyte formulas. Sodium metabisulfite is not used to replenish salt; it is used by manufacturers to protect the product. Assessment therefore begins with the food category and sulfite tolerance, not with sodium benefit.

Where it matters for keto and LCHF

In low-carb eating, E223 itself does not add sugar. But the foods containing it may be very different. Dry wine with metabisulfite may remain low in carbohydrates, but alcohol, sleep, appetite, and personal response matter separately. Dried fruit with sulfites almost always remains high in carbohydrates because of natural sugars. Marinades and sauces should be judged by sugar, starch, syrups, acids, salt, and portion size.

For that reason, E223 cannot be used as the single marker of allowed or forbidden. A more accurate order is carbohydrates and food type first, then frequency of use, then individual response. Occasional dry wine that is well tolerated is one situation. Daily dried fruit, ready-made marinades, and several sulfite-containing products in the same day are a different issue because total exposure and sugar load add up.

Sulfite sensitivity

Sulfites may trigger reactions in susceptible people. Possible symptoms include coughing, wheezing, stuffiness, headache, flushing, itching, skin reactions, nausea, or irritation of mucous membranes. People with asthma and reactive airways are usually advised to pay particular attention. If symptoms repeat after wine, dried fruit, or foods labeled as containing sulfites, E223 and related additives are worth considering as possible factors.

At the same time, E223 rarely exists in isolation. Wine contains alcohol and may contain biogenic amines. Dried fruit delivers concentrated sugar. Marinades may be acidic, salty, or spicy. A reaction may be cumulative, so it is useful to record not only the sulfite but also the food, portion, timing, foods eaten with it, and symptoms. This prevents blaming one code when the whole food matrix is involved.

Practical conclusion

EFSA considers sodium metabisulfite within the sulfur dioxide and sulfite group because total sulfite exposure is relevant for safety. For someone eating LCHF, the practical meaning is clear: E223 is not a carbohydrate problem, but it may be a tolerance problem. The more often wine, dried fruit, industrial preserves, and ready-made marinades appear in the diet, the more attention total sulfite load deserves.

If the diet is mostly fresh food, home cooking, and short ingredient lists, E223 will be a rare label line. If sulfite-containing products appear regularly and are followed by headaches, respiratory symptoms, skin reactions, or digestive irritation, reducing the whole group and discussing persistent symptoms with a clinician is more sensible. For home storage, tested recipes, refrigeration, acidity, and short storage are more reliable than trying to copy industrial preservation with one salt.

In practice, E223 is especially relevant for people who notice reactions to wine, dried fruit, marinades or ready-made sauces: headache, blocked nose, cough, itching, hives or worsening asthma. Such reactions are not necessarily about carbohydrates or histamine; sulfite treatment may be the important factor. When intolerance is suspected, it is more useful to compare not only sugar content but also the presence of E223, E224, E220 and other sulfite additives.