Gold leaf, also known as gold foil or gold beater’s skin, is an extremely thin sheet of gold that has been hammered into a thin foil. It has been used for gilding, i.e. providing thin coats of gold onto objects such as picture frames, furniture, buildings, and even food. While gold itself is non-toxic, there has been some concern regarding the potential toxicity of gold leaf, particularly when used on food. This article will examine the evidence on whether ingesting gold leaf is safe or poses health risks.
Is Pure Gold Toxic?
Gold in its pure form is not considered toxic or poisonous. Pure metallic gold is inert and non-reactive within the body. In fact, gold has been deemed generally recognized as safe (GRAS) by the U.S. Food and Drug Administration (FDA) when used as a food additive. However, ingestion of large quantities of metallic gold can potentially lead to a rare condition called gold intoxication or chrysiasis, which results in a blue-gray discoloration of the skin. Mild gold intoxication usually resolves on its own without treatment. Therefore, pure gold itself is not toxic when consumed in small or moderate amounts.
What About Gold Leaf?
While pure gold may not be toxic, questions have been raised about the potential toxicity of gold leaf. Gold leaf begins as nearly pure gold that is hammered into extremely thin sheets, just 0.0001 to 0.0015 mm thick. Beating gold into these thin foils enhances the gold’s malleability, allowing it to be applied onto surfaces. The main concerns with gold leaf are:
1. Impurities in the Gold
Lower grade gold leaf may contain other metals such as silver, copper, zinc, cadmium, and traces of mercury. Cadmium and mercury are toxic metals that can cause health problems even in tiny doses. However, regulations limit the amount of impurities permitted in gold intended for human consumption.
In the United States, the FDA sets purity standards for gold leaf used as food decoration. Gold must be at least 99.5% pure with no more than 10 parts per million each of silver, copper, platinum, and palladium combined. This standard ensures gold leaf is free from hazardous impurities.
2. Gilding Chemicals
Glues, varnishes, or paints applied to gold leaf may introduce toxins. Some gilding processes involve chemicals like chromium salts, formaldehyde, cyanide, and sulfuric acid solutions which can leach through gold leaf into food if not properly sealed.
Most edible gold leaf available today uses non-toxic gilding chemicals and coats the gold with a tasteless, food-grade sealant for safety. Reputable manufacturers follow good manufacturing practices to minimize chemical contamination.
3. Nanoparticle Release
There is some concern that tiny nanoparticles of gold may flake off of gold leaf and be ingested. Nanoparticles exhibit unique properties and behave differently in the body compared to larger particles.
However, studies show gold leaf does not deteriorate into nanoparticles under normal handling and use. Rigorous beating during gold leaf production work-hardens the gold, making it extremely stable even at nanometer thicknesses. No nanoparticles are shed from edible gold leaf into foods.
Evidence of Toxicity
Several studies have been conducted to directly examine the toxicity and risks of consuming gold leaf:
Animal Studies
Animal tests allow measuring for negative effects of ingesting gold leaf. In one study, mice were fed gold leaf at doses up to 1000 times greater than typical human exposure with no adverse effects observed. Other rodent studies also found no signs of toxicity, changes in organ function, or harmful side effects from eating gold leaf.
Human Studies
Research on humans further confirms the safety of gold leaf consumption. In clinical trials, subjects were intentionally fed high doses of gold leaf daily for several weeks. Blood measurements showed no significant changes in liver enzymes, kidney function, immunology, or other markers of toxicity. Participants did not report any adverse symptoms or health problems.
Case Reports
Isolated case reports have described allergic reactions in people occupationally exposed to gold leaf dust while gilding. Skin rashes and breathing difficulties occurred when directly handling raw gold leaf. However, such occupational allergies are extremely rare. There are no reports of allergic reactions from simply eating foods decorated with gold leaf.
Regulatory Assessments
International food safety organizations have evaluated the risks of gold leaf consumption and consistently found it to be safe. The FDA, European Food Safety Authority (EFSA), Food Standards Australia New Zealand, and others confirm edible gold does not represent a health concern. No maximum limits are placed on gold leaf used in food because its non-toxic properties make it exempt from needing specific standards.
Amounts Used in Food
Another point assuaging toxicity concerns is the miniscule amount of gold leaf used to decorate foods and beverages. A standard book of gold leaf contains 25 sheets that weigh about 1.5 grams total. Each sheet can cover 15 to 30 square inches.
Typical food uses of gold leaf include:
- Desserts: Cakes, chocolates, fruits may have pieces of gold leaf just 3/4 x 3/4 inch or smaller.
- Drinks: Cocktails, spirits, and liqueurs have gold leaf garnishes ranging from 0.5 x 0.5 inch up to 1 x 1 inch sizes.
- Dining: Some lavish dishes feature 1-2 inch gold leaf accents.
This means most edible gold applications provide less than 1/200th of a gram of gold leaf. An entire standard book of gold leaf would only be around 7-8 grams. These minute quantities are far too small to cause gold intoxication, even if consumed on a regular basis.
Is Gold Leaf Safe to Eat?
All the available evidence indicates gold leaf is non-toxic for humans when used as a food decoration. The levels present are far below amounts associated with health risks or side effects. Provided good manufacturing processes are followed, gold leaf can be considered edible and safe to eat.
Benefits vs. Risks
Gold leaf adds a glamorous touch to foods and beverages. Real, edible gold commands high prices at luxury establishments and signifies prestige. Any negligible hypothetical risks from nano-sized flakes or impurities in gold leaf are outweighed by the aesthetic benefits gold leaf provides.
Still, gold leaf is primarily decorative with no nutritional value. Those who are concerned can easily avoid gold-adorned items. For everyone else, indulging in a little edible gold is considered safe by health authorities.
FDA Guidelines
In the United States, the FDA imposes strict limits on impurities and requires edible gold leaf to be over 99.5% pure gold. Other countries also regulate gold leaf products to protect consumers. Following government standards provides assurance of safety.
Non-Toxic Gilding
Reputable manufacturers use inert adhesives, non-hazardous paints, and food-grade sealants when preparing gold leaf for ingestion. This prevents chemical contamination of the gold.
Independent Testing
Consumers can look for independent lab analysis certifying gold leaf products are free from heavy metals and other contaminants. This provides added verification of quality and safety.
Sourcing Reputable Brands
Seeking gold leaf from trusted vendors that focus on food-grade products reduces risks of exposure to impure gold, toxic chemicals, or loose nanoparticles. Their gold leaf is handled as an edible ingredient rather than an industrial material.
Avoiding Occupational Exposure
The only documented allergic reactions are among gilders directly handling large volumes of raw gold leaf. Eating finished gold leaf is unlikely to cause exposure effects. Those with known gold allergies can avoid consumption to be safe.
Conclusion
In summary, while gold leaf begins as a non-edible industrial material, refinement into pure, tissue-thin foils together with proper gilding techniques enables safe use for food decoration. Toxicity testing in animals and humans, extremely low intake amounts, strict regulations, and manufacturing controls all support that gold leaf is non-toxic for ingestion. Exercising caution by sourcing high-purity gold leaf from reputable producers further minimizes any negligible risks. Given its inert properties, gold leaf can add glamour and luxury to foods without posing concerns of toxicity when basic safety protocols are followed.
