Categories: Food 301

Iodine Deficiency: A Hidden Cause of Hiking Fatigue

Backpacking fatigue is usually blamed on a heavy pack, steep inclines, insufficient training, or a poor trail diet. However, a connection almost no one thinks about is iodine deficiency. Iodine deficiency affects your thyroid, which dictates how effectively your body uses energy during hill climbs and exertion. Your metabolic “engine” relies heavily on iodine to keep your legs moving forward.

When most people think of iodine, they think of salt. However, salty foods do not mean they contain iodine. Backpacking meals — even those high in sodium, including processed food and snacks—do not supply iodine. And hikers making their own trail food often use “sea salt” or other specialty salts in their meal prep because they taste better. However, most are not iodized or contain far too little iodine to meet daily needs. Specialty salts, including sea salt, kosher salt, Himalayan salt, Celtic salt, and fleur de sel, do not contain enough iodine to meet daily needs. Sea salt is a product we use and recommend at Outdoor Herbivore, but it contains virtually no iodine.

For the weekend backpacker, iodine deficiency is less of a concern. But for thru-hikers and other long expeditions requiring reliance on backpacking food and processed snacks, it can be a major contributor to fatigue and muscle weakness. Healthier eaters, especially herbivores and those on low-sodium diets, are more likely to have iodine deficiency. Yet, iodine deficiency is rarely mentioned among hikers.

Here, we highlight iodine, one of the most common micronutrient deficiencies in the world.

Spotlight: How Iodine Affects Your Hike

Iodine is a trace mineral essential for the production of thyroid hormones (T3 and T4), which regulate metabolism, including protein synthesis, heart rate, digestion, energy levels, and overall cell growth.

Our cells need iodine to convert food into energy. If you do not get enough, your body makes fewer thyroid hormones, which can cause tiredness, weak muscles, weight gain, and trouble with body temperature.

If you become deficient, your metabolism slows down, leading to several issues that will show up during hiking and other exercise:

Muscle cramps or weakness: Low thyroid function can lead to slower muscle contraction and repair.
Reduced Cardiac Output: Your heart may not pump blood as efficiently to your extremities, making every switchback feel twice as hard.
Poor Thermoregulation: Iodine deficiency often makes people feel colder. On a hike, this can lead to quicker energy depletion as your body struggles to maintain its core temperature.
Brain Fog: Fatigue isn’t just physical. Low iodine can cause mental lethargy, which affects your coordination and trail decision-making.

Other signs that indicate a long-term iodine deficiency:

Persistent fatigue on “zero” or rest days.
Weight gain despite high activity.
Dry skin and thinning hair.
Goiter occurs if your iodine intake falls below approximately 10–20 mcg/day. Goiter is usually the earliest clinical sign of iodine deficiency, followed by hypothyroidism.[1]
Fibrocystic breast disease, characterized by lumpy, painful breast tissue, often occurs. Iodine helps regulate how breast tissue responds to estrogen. In an iodine-deficient state, breast cells can become hypersensitive to estrogen, leading to cell overgrowth and cyst formation.

No Iodine on the Nutritional Label: Tips For Getting Enough

Most nutritional labels do not list iodine because it isn’t a mandatory disclosure like Vitamin D or Calcium. If food contains iodized salt, it must be listed on the label. When a food naturally contains iodine, the iodine content does not have to be listed. This makes it difficult to know if you are getting enough. To support health naturally through diet, the goal is to reach the Recommended Dietary Allowance (RDA) of 150 mcg per day. Iodine is most concentrated in marine life (seaweed & seafood), but it can also be found in dairy and eggs if the animal feed is iodine-supplemented.

Vegetarian Food Sources of Iodine

Seaweed is the most potent source of iodine, but the amount varies wildly by species. Be cautious of the source. Some can contain high levels of arsenic.
- Kelp is an excellent source of iodine, but a little goes a long way. For instance, ¼ tsp (.75g) of granulated kelp contains over 2,000% of RDA. It is usually recommended to eat kelp only once a week or use it sparingly as a seasoning. We use and recommend Maine Coast Kelp Granules.
- Roasted Seaweed Snacks are thin sheets of Nori, which are incredibly light and delicate. While they don’t provide many calories and have rigid packaging to prevent crumbling, they are an iodine “bomb” and work great for backpacking if you add them to soups or rice dishes, or don’t mind them crumbling.
- Wakame, commonly found in miso soup, contains about 66 mcg per gram. A small serving is a great way to hit your daily goal without going overboard.
- Nori (Sushi Wraps) is much milder, providing about 16–43 mcg per sheet. Nori sheets make a good gluten-free wrap for Outdoor Herbivore’s trail salads. Try using two sheets as a wrap instead of a tortilla. You’ll need several sheets to meet your daily requirement.
Iodized salt supplies the very minimal amount of iodine you need. Keep in mind that high-sodium processed foods are not a source of iodine unless the label discloses added iodide or “iodized” salt.
- 1/4 teaspoon of iodized salt (one packet) contains about 71 mcg of iodine.
Dairy and egg products may contain trace amounts of iodine if the chicken feed is iodine-supplemented or if salt licks are iodized for cows. Approximate amount of iodine:
- Dried Eggs, 1 egg | 2 TB (9g) | 10-25 mcg
- Milk Powder (Cow) | 2 TB (21g) | 0–10 mcg
Low iodine with “goitrogen” foods like broccoli, kale, and soy contains compounds called goitrogens that can interfere with how your body uses iodine. You don’t need to avoid them, but if you eat a lot of these cruciferous vegetables or soy, your iodine needs are slightly higher.

Animal & Fish Sources of Iodine Common for Backpacking/Travel

When looking for high iodine content in shelf-stable, ready-to-eat (RTE) foil pouches, the general rule of thumb is that white fish (like cod and pollock) significantly outperforms oily fish (like tuna and salmon). Wild-caught ocean fish have higher iodine levels than farmed versions because they eat a natural marine diet (plankton and smaller fish) rich in iodine. While tuna and salmon are the most common pouched options, they appear relatively low in iodine compared to other marine life. That is because iodine is water-soluble and tends to concentrate in the lean muscle of white fish. Fatty fish like tuna and salmon show lower iodine levels because iodine is stored in their oil/fat, which is difficult to measure. Since iodine isn’t listed on pouched fish labels (as of 2026), these are approximate amounts.

Wild Alaska Pollock, Wild (Pouched) | 3.5 oz (100g) | 60–130 mcg
Salmon, Pink/Sockeye, Wild (Pouched) | 3 oz (85g) | 50–60 mcg
Mackerel, Wild (Pouched) | 3.5 oz (100g) | 30-40 mcg
Tuna, Wild (Pouched) | 3 oz (85g) | 10-17 mcg

A Note on High Iodine Intake without Selenium

Iodine works with selenium. Taking high amounts of iodine without enough selenium can stress the thyroid. Adding just two Brazil nuts a day to your diet is usually enough to cover your selenium needs and help your body process iodine safely.

Other Likely Causes of Hiking Fatigue

It’s worth weighing iodine against the more common causes of fatigue among hikers:

Factor	Symptoms	Relation to Iodine
Iodine Deficiency	Chronic lethargy, feeling cold, weight gain, swelling in the neck (goiter).	Impacts long-term metabolic rate.
Iron Deficiency	Shortness of breath on inclines, pale skin, extreme fatigue.	More common in high-endurance athletes/hikers.
Dehydration	Thirst, headache, dark urine, sudden “bonking.”	The most common cause of acute hiking fatigue.
Electrolyte Imbalance	Muscle cramps, dizziness, nausea.	Caused by sweating out salt/potassium/magnesium.

Summary

1 Iodine deficiency can cause fatigue and weakness on long hikes.

2 Most backpacking foods and specialty salts lack sufficient iodine.

3 Seaweeds and iodized salt are practical iodine sources for all hikers.

Backpacking meals and snacks often lack the vitamins and minerals your body needs to stay energized and healthy. For backpackers, whose recovery is closely tied to their overall trail diet and metabolic efficiency, micronutrients like iodine are fundamental in supporting the body’s metabolic engine.

If you need to increase your iodine intake, increasing your sodium intake is not the answer. Food manufacturers do not use iodized salt. Backpacking food, instant meals, and snacks almost never contain iodized salt. Many hikers making their own trail food often use “sea salt” or other specialty salts in their meal prep because they taste better. However, most are non-iodized or contain too little iodine to meet daily needs. If you don’t regularly salt your food with iodized salt, eat much sea vegetables, seafood, or dairy, you are probably not getting enough iodine in your trail diet. Just remember if using kelp, it is possible to get too much iodine—a sprinkle goes a long way.

References

[1] https://ods.od.nih.gov/factsheets/Iodine-HealthProfessional

Outdoor Herbivore