Saffron
The dried stigmas of Crocus sativus, used as a deep-yellow food colourant and spice, most familiar in paella and risotto.
At doses well above normal cooking amounts, saffron can stimulate uterine contractions. Studies in pregnant women with high occupational exposure found a significantly higher miscarriage rate than in unexposed controls.
What is it?
Saffron is derived from the dried red stigmas of the Crocus sativus flower. Its vivid yellow-orange colour comes mainly from a carotenoid pigment called crocin, while safranal gives it its distinctive flavour and aroma. It is one of the world's most expensive spices by weight, requiring roughly 150,000 flowers per kilogram of dried stigmas.
What does it do?
Crocin dissolves readily in water and imparts an intense golden-yellow colour to food and drink. It also contributes a slightly bitter, honey-like flavour. The colouring effect is driven by crocin binding to food proteins and starches. JECFA (the UN/WHO food additive expert committee) classifies saffron as a food ingredient used for both flavouring and colouring purposes, rather than as a stand-alone food additive.
Where you will see it
Traditional dishes such as paella, risotto alla Milanese, bouillabaisse, and biryani. Also found in some liqueurs, confectionery, baked goods, and rice-based ready meals. On a UK food label it appears as 'saffron' rather than 'E164', because it is used as a food ingredient; 'E164' is the code assigned in older European additive frameworks but it does not appear in the current UK FSA or EU approved food additives list as an authorised food colouring additive.
What the science says
Uterine stimulant effects and pregnancy risk
Saffron contains compounds, particularly crocin and safranal, that can stimulate smooth muscle in the uterus. A prospective study of pregnant women working in Iranian saffron fields during harvest found a miscarriage rate of 10.6% among those with high saffron exposure, compared to 0% in protected controls. Animal experiments confirm uterine-stimulating activity at elevated doses. The effect appears strongly dose-dependent: the quantities involved in cooking are a tiny fraction of those linked to harm, but the signal is real.
A prospective case-control study of 79 pregnant women during saffron harvest found a miscarriage rate of 10.6% in the occupationally exposed group versus 0% in the protected control group, a statistically significant difference (P=0.03).
In experimental animal studies, saffron extract and its constituents crocin and safranal stimulated uterine contractions. Doses exceeding 5g per day in humans have been associated with uterine bleeding and abortion risk.
A 2016 PMC toxicology review confirmed that saffron's uterine contraction potential is documented in both human and animal data, and that doses over 10g have historically been used to induce abortion, with doses of 12-20g recorded as lethal.
High-dose toxicity
Saffron is far from toxic at the pinches used in cooking, but at doses of 5 grams or more the picture changes markedly. Symptoms reported at these higher levels include severe nausea, vomiting, bloody diarrhoea, and uterine bleeding. At 12-20 grams, deaths from multi-organ failure have been documented. These doses are vastly above anything achievable from food.
Acute oral LD50 for saffron extract in mice was approximately 4120 mg/kg body weight, indicating low acute toxicity by standard classification. Sub-acute exposures at 0.35-1.05g/kg for two weeks caused reduced haemoglobin and signs of liver and kidney stress in rats.
Clinical doses of saffron up to 1.5g per day for short periods showed no significant adverse effects on blood, liver, or kidney parameters in trials. Gastrointestinal upset was the most commonly reported adverse event at therapeutic (medicinal supplement) doses in a 2026 systematic review of 102 clinical trials.
Adulteration and undeclared synthetic dyes
Because genuine saffron is expensive and difficult to authenticate, the UK National Food Crime Unit (NFCU) issued a 2025 food crime alert after finding samples on the UK market adulterated with undeclared synthetic food dyes. These added colours contravene Regulation 1333/2008 and are not declared on labelling. The safety concern in this case is not from saffron itself but from the unlawful synthetic additives being passed off inside it.
The UK NFCU alert FSA-NFCU-A004-2025 identified adulterated saffron on the UK market containing undeclared synthetic food colours added in contravention of EU/UK food additive law.
Where it stands with the regulators
Who should be careful
Pregnant women should avoid saffron supplements and concentrated saffron extracts. At amounts well above those used in everyday cooking, saffron has been linked to uterine contractions and miscarriage. A pinch in a rice dish is a very different exposure to a supplement capsule or large medicinal dose. Look for 'saffron' in ingredient lists of herbal teas, supplement blends, and traditional-recipe ready meals if you want to minimise any intake during pregnancy.
The honest read
Saffron has been used as a food spice and colourant for thousands of years and the quantities used in cooking are minute. The uterine-stimulant and high-dose toxicity concerns come from occupational exposure studies and experimental data at doses many times what a dish of paella would deliver. The 2026 systematic review of 102 clinical trials found gastrointestinal side effects were the main complaint at medicinal supplement doses. That said, the miscarriage signal in occupationally exposed pregnant women is a real and documented finding, not a theoretical one. The uncertainty is whether trace culinary amounts carry any meaningful reproductive risk: the current evidence does not establish that they do, but no study has specifically cleared very frequent high-culinary intake in early pregnancy. The science on normal food intake is genuinely thin rather than reassuring.
Related additives
Common questions
Is E164 banned in the UK?
E164 is not listed as a banned food additive, but it also does not appear in the UK FSA's current approved food additives list or in EU Regulation 1333/2008's positive list of authorised food colour additives. Saffron itself is freely used as a culinary spice and food ingredient - the E164 designation is not used on UK labels.
Is saffron dangerous during pregnancy?
At the pinch-level amounts used in cooking, there is no established evidence of harm. However, saffron at higher doses (supplements, concentrated extracts, or heavy occupational exposure during harvest) has been linked to uterine contractions and a higher rate of miscarriage in a study of pregnant farm workers. Pregnant women are generally advised to avoid saffron supplements and large medicinal doses.
What foods contain E164?
Saffron appears in paella, risotto, biryani, bouillabaisse, some liqueurs, and certain baked goods and rice-based ready meals. It is always listed as 'saffron' on UK labels, not as 'E164'.
Is E164 vegan?
Yes. Saffron is the dried stigmas of the Crocus sativus flower, entirely plant-derived and suitable for vegan diets.
Sources
- UK FSA Approved Additives and E Numbers
- JECFA 29th Meeting - Saffron evaluation (TRS 733-JECFA 29/33)
- Hosseinzadeh & Nassiri-Asl, Toxicology effects of saffron and its constituents: a review, PMC 5339650
- Modaghegh et al., Increased Miscarriage Rate in Female Farmers Working in Saffron Fields, Asia Pacific Journal of Medical Toxicology
- Hasheminasab et al., Adverse Events of Saffron (Crocus sativus L.): Systematic Review of Current Evidence, Health Science Reports 2026
- UK NFCU Food Crime Alert FSA-NFCU-A004-2025 - Adulterated Saffron
- International Association of Color Manufacturers - Saffron colour profile
- EU Regulation (EC) 1333/2008 consolidated text (EUR-Lex)
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