Iodine is an essential trace mineral that is vital for thyroid hormone production and many other important functions in the body. Many people don’t get enough iodine in their diets, which can negatively impact thyroid health. Choosing foods high in iodine can help ensure you meet your daily iodine needs.
Why is iodine important?
Iodine is a mineral that is naturally present in some foods and added to others. The body needs iodine to make thyroid hormones. Thyroid hormones control the body’s metabolism and many other important functions.
Getting enough iodine is crucial, especially during pregnancy and for young children. Even mild iodine deficiency during pregnancy and early childhood can negatively impact brain development.
Some of the main reasons iodine is so important include:
- Production of thyroid hormones T3 and T4
- Growth and development, especially of the brain
- Metabolic function and energy production
- Healthy immune system function
Without sufficient iodine intake, you are at risk of developing iodine deficiency disorders like hypothyroidism, goiter, mental retardation, heart disease, and infertility.
How much iodine do you need?
The Recommended Dietary Allowance (RDA) for iodine is as follows:
- Infants 0–12 months: 110 mcg/day
- Children 1–8 years: 90 mcg/day
- Children 9–13 years: 120 mcg/day
- Teens 14–18 years: 150 mcg/day
- Adults 19+ years: 150 mcg/day
- Pregnancy: 220 mcg/day
- Breastfeeding: 290 mcg/day
As you can see, iodine needs increase during pregnancy and breastfeeding. Without sufficient iodine intake, pregnant women are at high risk of thyroid problems.
Iodine in food
There are several excellent food sources of iodine:
- Seaweed and sea vegetables
- Fish and shellfish
- Dairy products
- Eggs
- Iodized salt
- Some fruits and vegetables
The amount of iodine in different foods can vary substantially based on the soil content where plants are grown and what marine life eats. Seaweed and seafood typically provide more significant amounts of iodine.
Vegetables highest in iodine
Although seaweed and sea veggies are the absolute highest in iodine, most people don’t eat these on a regular basis. Several more common vegetables also contain good amounts of iodine.
Here are some of the top vegetables highest in iodine, according to data from the United States Department of Agriculture (USDA):
| Vegetable | Serving | Iodine (mcg) |
|---|---|---|
| Baked potato with skin | 1 medium (173g) | 60 |
| Sweet potato | 1 medium (114g) | 19 |
| Corn | 1 cup (164g) | 14 |
| Green beans | 1 cup (125g) | 3 |
As you can see, the potato is by far the highest in iodine. One medium baked potato with skin provides 60 mcg of iodine. That supplies 40% of the RDA for an adult.
Why is the potato highest in iodine?
There are a few reasons why potatoes contain more iodine than other common vegetables:
- Potatoes are grown in the soil that typically contains traces of iodine.
- The potato skin is concentrated in nutrients like iodine.
- Potatoes are good absorbers of iodine compared to other vegetables.
Make sure to eat the potato with the skin on to get the most iodine content from this vegetable. Peeling potatoes can remove up to half the iodine content.
Other vegetables containing iodine
In addition to potatoes, sweet potatoes, corn, and green beans, several other veggies contain small amounts of iodine:
- Carrots
- Broccoli
- Cauliflower
- Spinach
- Asparagus
- Onions
- Tomatoes
- Eggplant
- Celery
- Cabbage
Eating a diet high in fresh fruits and vegetables can help you consume more iodine from produce. However, most people need to rely on additional sources to meet their daily iodine needs.
Other dietary sources of iodine
In addition to potatoes and other veggies, make sure to include these good iodine sources:
Seaweed
Seaweed such as nori, wakame, kombu, and kelp are the most concentrated food sources of iodine. Just one gram of dried seaweed may contain up to 2,984 mcg of iodine. However, different types contain varying amounts.
Fish and shellfish
Fish and shellfish contain significant iodine levels. This includes fish like cod, tuna, salmon, and perch and shellfish like oysters, mussels, shrimp, and clams. Three ounces of fish can provide 11–178 mcg iodine.
Dairy products
Milk, yogurt, and cheese are fairly good sources of iodine. One cup of yogurt or milk contains around 55–90 mcg. The iodine content comes from the animal feed and use of iodine-based cleaning solutions in the dairy industry.
Eggs
One large egg contains around 16 mcg iodine. The iodine content in eggs depends on the diet of the hen who laid it.
Iodized salt
Iodized salt contains added iodine to prevent iodine deficiency. Using iodized instead of regular salt helps increase iodine intake. One teaspoon of iodized salt has around 400 mcg iodine.
Foods that are goitrogenic
Some foods can impair iodine absorption when eaten in large amounts. These foods are known as goitrogens and may interfere with thyroid function if consumed excessively.
Some goitrogenic foods include:
- Soybeans
- Peanuts
- Strawberries
- Spinach
- Sweet potatoes
- Broccoli
- Cauliflower
- Cabbage
Eating these foods in moderation is fine for most people. But those with hypothyroidism or autoimmune thyroid disease may want to limit intake.
Iodine supplements
Dietary sources are the best way to meet iodine needs. However, some people may require iodine supplements in addition to a healthy diet:
- Those with hypothyroidism or thyroid disease
- People who don’t use iodized salt
- Vegetarians and vegans
- Women who are pregnant or breastfeeding
- Individuals restricting salt or sodium intake
Before taking an iodine supplement, talk to your healthcare provider to determine your individual dosage needs. Too much iodine can also cause health problems.
Signs of iodine deficiency
Some signs and symptoms may indicate you have an iodine deficiency, including:
- Goiter (swelling of the thyroid gland)
- Hypothyroidism
- Difficulty concentrating
- Fatigue
- Weakness
- Weight gain
- Dry skin
- Hair loss
Make sure to consume adequate iodine if you are experiencing any of those conditions and consult with your healthcare provider.
Checking your iodine levels
Doctors can perform a urinary iodine test to check your iodine levels if a deficiency is suspected. This measures the amount of iodine in a urine sample.
Blood tests can also detect thyroid hormone levels associated with iodine status in the body.
Iodine sensitivity
Some people may experience negative reactions or allergies to consuming higher amounts of iodine. This is known as iodine sensitivity.
Those more likely to experience iodine sensitivity or allergies include:
- People with existing thyroid conditions like Graves’ disease, Hashimoto’s, or goiter
- Individuals who have undergone thyroid surgery
- Those with a family history of autoimmune thyroid disease
Symptoms of iodine sensitivity can include swelling of the thyroid glands, rash, upset stomach, and changes in thyroid hormone levels. If you experience any sensitivity to iodine-rich foods or supplements, stop consuming them and speak to a doctor.
Conclusion
Getting sufficient iodine from your diet is crucial for thyroid health, metabolism, growth, and many key functions. The potato is the highest in iodine among common vegetables.
Aim to eat potatoes regularly along with other iodine-rich foods like dairy, eggs, seafood, and seaweed. Additionally, using iodized salt helps increase your levels. If you still suspect an iodine deficiency, consider supplements under the guidance of your healthcare provider.