Nutrients

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Table of Contents
Nutritional Requirements And Sources
Am I Getting Enough Nutrients In My Diet?
Do I Need Supplements?
Vitamin A & Toxicity
Vitamin C & Antioxidant Supplements
Vitamin D
– Required amount of vitamin D
– Two types of vitamin D
– How much vitamin D is too much?
– Vitamin D from sunlight
– Food sources of vitamin D
– Vitamin D supplements
– Increasing levels of vitamin D
Calcium
– The importance of getting enough calcium
– How much calcium do you need?
– Post menopausal women calcium dose controversy
– Calcium and bone mineral density study
– Calcium fortified foods vs supplements
– Food sources of calcium
– Who may need a calcium supplement?
– Best type of calcium supplement
– Risks of high calcium supplementation
– Getting the balance right with calcium supplements
– How to take calcium supplements
– Specific dairy and breast cancer risk
– Kefir potentially for the lactose intolerant
Iodine
– The importance of iodine
– Who is at risk of iodine deficiency?
– How much iodine do I need?
– Food sources of iodine
– Iodine supplements
Further Reading And References

Nutritional Requirements And Sources

This BBC Good Food article discusses nutrient requirements at different life stages: (62).

The British Nutrition Foundation provides information about vitamins and minerals, sources and what each does for the body here. They also have an infographic containing details of food sources that provide specific nutrients that support the immune system here: (5).

Am I Getting Enough Nutrients In My Diet?

Dieticians and nutritionists are unlikely to provide a full nutrient breakdown of your current diet, due to the time that this would take. However, there is an excellent online tool that allows you to calculate this yourself for free. If you have time, it allows you to find out exactly what nutrients the food that you are eating contains. You have to sign-up (no fees), which provides you with an account so that you can save ‘recipes’. This means that for instance you could create a recipe for breakfast, lunch and dinner and then create a recipe using the breakfast, lunch and dinner recipes to find out whether you are reaching your RDA (recommended daily amount) values of nutrients for the day. The RDA values are US based and may vary slightly from those of the other countries. The link to the tool is below:

nutritionvalue.org

If you are short of any specific nutrients, you can also find out which foods contain these, so that you can make up the difference yourself.

This is not an absolute measure since it won’t show the levels of nutrients absorbed by your body, but at least it provides some form of guideline. NHS blood screening can test for specific nutrients such as calcium, copper, magnesium, phosphate, potassium, selenium, vitamins A, B12, D, E and zinc. However, these tend to be taken if your doctor has concerns about specific symptoms. Though there is no harm in asking your GP for these tests, if you believe that you have deficiencies due to the need to avoid certain foods to manage symptoms and can’t find alternative foods to get specific nutrients from. Calcium is difficult to test for since the body keeps the level of calcium in the blood in balance by taking calcium from bones if required.

Do I Need Supplements?

Some argue that everyone needs supplements due to the reduction in nutrients from food due to modern farming practices, including a decrease in nutrients in soil, but is this true?

In 1997, historical tables regarding the composition of 20 fruits and 20 vegetables from the 1930s and 1980s were compared in UK. The 1980s batch had lower levels of magnesium, copper and other micronutrients. A similar analysis was performed in the US in 2004 of 43 raw vegetables commonly grown in home gardens in 1950 and 1999. They found reductions in protein, calcium, phosphorus, iron, riboflavin and vitamin C in the 1999 batch.

The difficulty with these studies is the source of the data is not controlled with foods possibly coming from different countries, different soil types, have different degrees of ripeness, different climates and types of farming. There are also changes in sampling methods over time and modern laboratory testing has become more accurate. This means that these figures are highly controversial.

UK based Rothamsted Research, which is a non-profit research centre focussing on strategic agricultural science, has been running the longest scientific experiment in the world starting in 1843 and known as the Broadbalk long term experiments. The organisation holds 180 years worth of soil samples, crops, fertilisers and organic manures involving 300,000 samples. Their long term study covers British staples such as wheat, which makes up large part of daily food consumption providing 20% of the energy and protein consumed in the UK.

In a 2008 study by Rothamsted Research, nutritional quality and yield of wheat grains over 160 years was analysed. They found stable mineral concentrations between 1845 and 1967, but declines in zinc, copper and magnesium after 1968. Soil samples were also compared from 1865 to 2000. Soil micronutrients either remained stable or increased during this period, due to the use of inorganic fertilisers. It is to be acknowledged, however, that 60% of soils in the European Union are in an unhealthy state due to the reductions in bacteria, fungi, nutrients and other microbes in the soil attributed to agricultural practices such as tillage disrupting soil structure and growing the same type of crop in the same field year after year.

The study authors state that the 1968 decline is due to the timing of when new, high-yielding varieties of wheat were introduced rather than related to soil content. They found modern wheat contained fewer minerals, when grown side by side with older varieties, which corroborates reductions not being related to environmental factors. These new wheat varieties push up carbohydrates in the grain whilst diluting minerals.

A 2020 study achieved similar results with samples from 16 different countries, finding carbohydrates have increased and protein and minerals have declined in such crops. There is also a potential attribution to rising carbon dioxide levels, which stimulate growth but not nutrition. Field experiments show about 5% reduction in micronutrients.

The assessment of the scientific paper from which the above information was extrapolated does not suggest that people should be supplementing in the grand scheme of things. Of more importance is consuming a variety of plants foods as already recommended in dietary guidelines.

(66)

However, supplementation may be of use in specific circumstances. Some of these situations are discussed in the following sections.

Vitamin A & Toxicity

A Nutritional Therapist advised me to take a liquid vitamin A supplement to increase SigA (intestinal antibody) production to fight intestinal pathogens (1). I was already consuming a large amount of carrots (one of the vegetables that wasn’t affecting me at the time), which contains beta-carotene, which is converted to vitamin A by the body. I was concerned about too much vitamin A since it is stored in the body. After my findings below, I stopped taking the supplement:

Intakes of greater than 25,000 IU daily for 6 years and greater than 100,000 IU daily for 6 months are considered toxic. However, these limits regarding toxicity vary from person to person. (2)
A vitamin A dose of 100,000 to 200,000 IU daily for approximately 16 months was taken by an 18 year old woman for a skin disorder. She experienced fatigue and muscle stiffness particularly after exercise, then bone pain, headache, poor appetite, nosebleeds, dry and itchy skin. Examination uncovered cheilosis, an inflammatory condition that effects the corners of the mouth, dry scaly skin and enlargement of the liver and spleen. The woman stopped taking vitamin A and there was significant improvement in her symptoms within 2 months. (3)
Dry and fissured skin followed by general fatigue and abdominal swelling was experienced by a 63 year old man who had been taking 400,000 IU of vitamin A daily for 8 years. (3)
A 31 year old woman who took 3.5 million IU of vitamin A daily for 3 weeks for psoriasis, developed fatigue, severe headaches loss of appetite, weight loss, nausea and vomiting, thirst and pains in both legs during week 3. Into week 4 she developed jaundice, had an enlarged liver, thereafter anaemia and required blood transfusions of high doses of methylprednisolone. A few days after stopping vitamin A supplementation she experienced almost total hair loss. After 2 months without supplementing, her laboratory tests were normal, but her psoriasis, which had been helped by the supplement, returned. (3)

The best way to consume vitamin A is through foods containing good levels of beta-carotene such as carrots since your body will only convert the amount it needs of vitamin A from the beta-carotene and will eliminate the rest (6). This helps to avoid the toxicity problems discussed above.

Supplemental doses of beta-carotene or diets with high levels of carotenoid-rich food for long periods are generally not considered toxic. If beta-carotene is consumed to excess, at worst, a harmless condition which makes skin turn yellow-orange, called carotenodermia may develop. This side effect is reversed by stopping beta-carotene ingestion. However, 20mg/day of supplemental beta-carotene for 5-8 years was found to increase the risk of lung cancer and mortality in male smokers. The US based Food and Nutrition Board advises the general population not to take supplemental beta-carotene except as a provitamin A source to prevent vitamin A deficiency. (4)

Vitamin C & Antioxidant Supplements

The body has a process of programmed cell death (apoptosis), which removes abnormal or damaged cells, that can’t be repaired, from the body. If this process is prevented, it can lead to uncontrolled cell division and the development of a tumour. A study has shown that supplemental antioxidants (such as extra vitamin C, vitamin E and N-acetylcysteine) can keep cells alive that should be removed by this process. Ignoring apoptosis signals in this way is believed to be related to the development of cancers. (9)

Another study has suggested that vitamin C supplementation can impair sporting performance and your body might not see the improvements from exercise at a cellular level. (9) (10) (11)

It is better to obtain vitamins and minerals from food as far as possible. Our bodies have adapted over thousands of years to extract what it needs from foods. It seems that supplementing with some nutrients in their raw form may have unintended consequences.

Some foods that are high in vitamin C with the amount of vitamin C are listed below (7) (8):

Orange 53mg/100g
Red cabbage 55mg/100g
Strawberries 57mg/100g
Cauliflower 56mg/100g
Broccoli 79mg/100g (around a third of a medium sized head, fried in olive oil with garlic)
Brussels Sprouts 115mg/100g
Peppers – both green and red peppers contain a similar amount of vitamin C with 1 medium green pepper containing 192mg (around 120mg/100g)
Kale – 80mg per serving
Kiwi – 35.4mg per average sized kiwi

Some of the above may be a challenge for IBS sufferers.

Fruits that are low in vitamin C include:

Pear
Apricot
Raspberries

The NHS states that adults aged 19 to 64 need at least 40mg vitamin C per day (63). Whilst eating 2-3 fruit portions a day, an example of a daily adequate supply of vitamin C may be found in 1 orange or 2 kiwis or a strawberry serving each day paired with a low vitamin C fruit if needed.

Vitamin D

Required amount of vitamin D

Adults require 10mcg (400 IU) of vitamin D a day (12).

Two types of vitamin D

Vitamin D2 (ergocalciferol) & Vitamin D3 (cholecalciferol) (19)

Vitamin D3 is much better at raising vitamin D levels and increases vitamin D levels almost twice as much as vitamin D2 (64)

How much vitamin D is too much?

Long periods of excess vitamin D supplementation can cause a build up of calcium in the body (hypercalcaemia), which can weaken bones and cause kidney and heart damage (12).

10mcg a day will be sufficient for most people who choose to supplement (12).

Greater than 100mcg (4000 IU) of vitamin D a day, could be harmful and should be avoided (12).

Vitamin D from sunlight

Short periods of sun exposure with forearms, hands or lower legs uncovered without sunscreen from late March or early April to the end of September (particularly 11am to 3pm) can make enough vitamin D for most people (13).

October to early March sunlight doesn’t contain enough UVB radiation for our skin to be able to make vitamin D. Vitamin D from food sources (including fortified foods) and supplements will be needed during this period (12).

Studies show vitamin D is made most efficiently from sunlight at noon, when the sun is at its highest point with UVB rays most intense. At this time you only require a short time in the sun to make enough vitamin D. For example, 13 minutes three times a week in the summer in the UK will maintain healthy levels among Caucasian adults. However, those with darker skin may need 30 minutes to three hours longer to get enough vitamin D. A study in Oslo, Norway found 30 minutes of midday summer exposure was equal to consuming 10,000–20,000 IU of vitamin D. There is increased risk of dangerous skin cancers from afternoon sun according to a study, so short midday exposure to sun is not only more efficient for vitamin D production but also safer (14).

It is best to cover up or use sunscreen after 10-30 minutes of exposure depending on your skin to avoid sun burn (14).

Food sources of vitamin D

oily fish (e.g. salmon, sardines, herring and mackerel) (12)
red meat (12)
liver (12)
egg yolks (12)
fortified foods (e.g. some fat spreads and breakfast cereals) (12)
Note: UK cows’ milk is not fortified with vitamin D unlike some other countries, so isn’t a good source of it (12)
There is an interesting blog here (16) which discusses foods containing Vitamin D, one of which is mushrooms. UV-exposed mushrooms contain the highest amounts of vitamin D (17). It is possible to purchase vitamin D enhanced mushrooms from supermarkets (18). However mushrooms contain vitamin D2 rather than D3 (19).

Vitamin D supplements

Whether you need to supplement depends on your blood levels which will be influenced by your diet, your sunlight exposure, skin colour and how much you absorb from supplements since everyone is different. (20) There are testing kits for vitamin D levels available on the internet.

The measures of vitamin D are ug & IU. This calculator here (21) will convert vitamin D between ug & IU.

Supplements are available in liquid and tablet form. NOW liquid Vitamin D is available as 400IU per 4 drops and is reasonably priced for a 60ml bottle. NOW seems to be a trusted brand. (22) (23). Lamberts do a 400IU tablet form of vitamin D.

Increasing levels of vitamin D

The BBC Trust Me, I’m a Doctor TV program tested the vitamin D levels of people who obtained vitamin D from 3 different sources:

Group 1: sunshine exposure for 10 minutes every day, at lunchtime
Group 2: low dose vitamin D supplements daily
Group 3: 100g of oily fish, three times a week

All three groups increased vitamin D levels by roughly the same amount.

Oily fish is full of nutrients, but there are concerns over contaminants in oily fish, so you shouldn’t over eat them. 2004 government advice stated girls and women of child-bearing age are advised no more than two portions of oily fish a week.

(15)

Smaller oily fish such as mackerel, herring and sardines will contain fewer pollutants than larger oily fish such as tuna and swordfish (24).

Calcium

The importance of getting enough calcium

for healthy bones and teeth (26)
plays an important role in blood clotting (26)
assists muscle contraction (26)
helps to regulate normal heart rhythms and nerve functions (26)
regulates sleep cycle impacting the level of REM (rapid eye movement) sleep by using calcium to convert tryptophan into melatonin required for sleep. Those with low calcium levels may wake up hours after falling asleep, have difficulty getting back to sleep and may not have the full REM sleep needed to feel refreshed in the morning. (55) REM sleep is the stage of sleep where most dreams happen (25)
can lead to bone loss if not enough is consumed (26):
- the body regulates the amount of calcium in the blood stream to perform these vital functions
- parathyroid hormone (PTH) will signal the bones, which contain 99% of the body’s calcium, to release calcium into the bloodstream if the calcium levels in the blood are too low. 1% of the body’s calcium is found in blood, muscle and other tissues
- vitamin D may be activated to help intestinal absorption of calcium
- simultaneously, PTH signals kidneys to release less calcium in urine
- conversely calcitonin performs the opposite function when the body has sufficient calcium by preventing the release of calcium from bones and signalling the kidneys to remove calcium in urine
- the body obtains calcium either from foods or supplements containing calcium or by taking calcium from the body
- calcium will be removed from bones if insufficient calcium is consumed
- it is hoped that the calcium from bones will be replaced when there is sufficient calcium, but this may not always happen

How much calcium do you need?

The table below, from the British Dietetic Association, shows the daily calcium requirements for various circumstances (30).

The sections further below demonstrate the sometimes conflicting evidence around the required amount and form of calcium intake.

Group	Age (years)	Calcium (mg) per day
Infants	Under 1	525
Children	1-3 4-6 7-10	350 450 550
Adolescents	11-18	800 (girls) 1000 (boys)
Adults	19+	700
Those who are breastfeeding		1250
Coeliac Disease	19+	1000-1500
Osteoporosis	19+	700 (up to 1000 on osteoporosis drug treatments)
Inflammatory Bowel disease (while taking corticosteroids)* *Discuss need for supplementation with doctor or dietitian	19+	800-1000

Source: British Dietetic Association (March 2021, Review date March 2024 – Currently under review) (30)

(30)

Post menopausal women calcium dose controversy

In 1997, an Institute of Medicine panel raised the recommendation for calcium intake from 800 mg to 1,200 mg a day for women over 50. However, this was based on studies from the 1970s that only lasted a few weeks and not the years needed to determine calcium balance. Additionally, these studies did not investigate whether that level of calcium helped to prevent fractures. Nevertheless, this recommendation was carried forward. (31)

Two 2005 British studies and a 2006 report from the Women’s Health Initiative of 18,000 postmenopausal women who took a supplement containing 1,000 mg of calcium and 400 international units (IU) of vitamin D confirmed that calcium and vitamin D supplements don’t prevent fractures. In the latter study, the women supplementing were no less likely to break their hips than the equal number of women who took a placebo pill, except there was a slight increase in hip bone density, which may have been due to vitamin D rather than calcium. (31)

Calcium and bone mineral density study

A study of women aged 34-56 years found low BMD (bone mineral density) in those who had a very low intake of calcium from dairy products and restricted use of calcium supplements and/or consumption of calcium- fortified foods (32).

In the study, high BMD was achieved by women who had calcium intake from calcium-fortified foods and the consumption of calcium supplements, and – to a lesser extent – by calcium intake from dairy products with an average calcium intake (32).

This meant that calcium intake from dairy products was insufficient to reach high BMD values (32).

Calcium fortified foods vs supplements

For those who are dairy intolerant, vegans or individuals who do not care for dairy meeting daily calcium requirements can be a challenge. Calcium fortified foods, such as soy milk, tofu, whole-grain cereal and juice (in moderation), can be a safe approach to boost levels and are better than having calcium insufficiency. (33)

There is better absorption of calcium when consumed in smaller amounts and spread throughout the day. Calcium fortified foods tend to have these smaller amounts than supplements. Other nutrients are also needed for bone health including potassium, magnesium, zinc, vitamin C and vitamin K. This is why it is still important to have a healthful diet as far as possible in addition to calcium fortified foods. (33)

Food sources of calcium

Sources of calcium including the bio-availability of calcium in common foods can be found here.

There are further calcium related food lists here: (27) (28) (29) (30).

Who may need a calcium supplement?

Despite having a healthy balanced diet, some may find it difficult getting sufficient calcium, such as those who (35):

consume a vegan diet
restrict dairy products due to lactose intolerance
have large amounts of protein or sodium causing the excretion of more calcium
under long-term treatment with corticosteroids
have reduced ability to absorb calcium such as those with certain bowel or digestive diseases, such as inflammatory bowel disease or celiac disease
those affected may wish to speak with their doctor or dietitian about calcium supplementation and whether this is appropriate (35)

Best type of calcium supplement

Calcium citrate is the most absorbable form of calcium supplement. The colloidal liquid form of this supplement may irritate the intestinal wall less (34).

Risks of high calcium supplementation

Some studies have found risks associated with high levels of calcium supplementation, but not with calcium obtained through a regular diet:

increased risk of kidney stones. The Woman’s Health Initiative found that women taking supplemental calcium and vitamin D were at higher risk of developing kidney stones than those taking a placebo, since high doses of calcium from supplements may enhance stone formation by increasing urinary elimination of calcium. Conversely, high levels of dietary calcium are thought to offer protection against kidney stones (31)
potential increased risk of heart attack:
- 21 out of 732 who took 1,000 mg of calcium a day in a randomised study of 1,471 postmenopausal women in New Zealand had heart attacks, compared with 10 out of 736 who received a placebo. (31)
- calcium supplementation was linked to risk of heart attack in a 2010 analysis of 15 randomized controlled trials (31)
- in a 2016 reported study, 5,000 adults underwent a coronary artery calcium test (CAC), related to hardening of the arteries, at the beginning of the study and half of the people were re-tested 10 years later. Those with had calcium intake from foods had lower risk of heart problems and those from who took calcium supplements showed signs of heart damage (59)
- women who took calcium supplements were more likely to get calcifications in their aorta in a 2020 study (59)
- A 2020 review of 42 studies and a 2021 review of 15 studies found that calcium supplements did seem to harm the heart (59)
- conversely, data from 87,899 participants from 12 randomised controlled trials showed no link between calcium supplementation and risk of heart attack, stroke or heart failure admission (65)
- many scientific papers suggest that this is still a controversial area and not all scientists agree on the matter (59) (40)

Getting the balance right with calcium supplements

At least 700 mg of calcium from food should be enough for adults (31) and foods should be the primary source of calcium where possible (40).

If you suspect that you are not getting enough calcium from foods, perhaps due to food intolerances such as dairy, an approach might be to calculate the amount of calcium you are getting from your diet (see Am I Getting Enough Nutrients In My Diet?) to understand any short fall.

Discussion with your doctor or dietitian may be needed if you feel you need to make up a short fall with calcium supplements (31).

Consider using the smallest amount of calcium supplement (i.e., less than 500 mg) to complement dietary intake (40).

Calcium supplements may interfere with some medications or health conditions so it is important to discuss this with a health professional (35).

How to take calcium supplements

Taking a calcium supplement that also has vitamin D will aid its absorption (38)
Take no more than 500mg at a time (38)
Avoid taking calcium supplements with fibre, since fibre can interfere with absorption (39). Whole grains, seeds, legumes, some nuts contain phytates, which bind to calcium when eaten at the same time. When calcium is bound, the body cannot use it (41)
Take with a full glass of water, juice or other liquid to enhance solubility (39)
If taken only once per day, calcium supplements may be best taken in the evening (39)
If you need to take 250mg or more of magnesium, as well as calcium supplements, it is best to take them at separate times since they can compete for absorption (42)

Specific dairy and breast cancer risk

A 2019 study (43) of 61,000 women found:

dairy milk consumption is associated with risk of breast cancer – steeper rises in breast cancer risk were seen at intakes of dairy milk up to ¾ cup/day (43)
this is due to due to sex hormones found in milk particularly since 70% dairy cows are pregnant (43)
no associations were seen with cheese or yogurt (43)

A 2018 study of 184 women found similar results whilst also finding fresh cheese had a protective effect (44).

A 2020 study of 52,795 women confirmed these findings including full & reduced fat milks. The strongest risk was achieved at relatively low doses of less than or equal an 8 ounce cup per day. Again, no associations were seen with cheese or yogurt. (45) However, the American Institute for Cancer Research noted some limitations in that study. Their own study in conjunction with the World Cancer Research Fund found limited suggestive evidence that dairy lowered the risk of pre-menopausal breast cancer but noted that more research is needed (46).

Protections from breast cancer can be found in yoghurt, which is typically made using lactobacillus strains and even more so from kefir, which contains beneficial yeasts and bacteria. The probiotics in these products help to reinforce the intestinal barrier against harmful agents resulting in anti-cancer activities. 100% grass fed organic yoghurt is preferable to non-organic due to lower amounts of hormones and higher conjugated linoleic acid and omega 3 fatty acids. Low fat yoghurts contain even higher conjugated linoleic acid without the high saturated fat content. (47) (48) (49)

Kefir potentially for the lactose intolerant

Kefir is a dairy drink made with caseins. Bacteria in kefir break down much of the lactose, so those who are lactose intolerant may be able to consume kefir, though the amount of lactose may be reduced leaving trace amounts rather than eliminated entirely. (50)

According to research kefir may have antimicrobial and antifungal properties, may help the immune system and be anti-tumour (50).

Potential side effects of kefir include constipation and abdominal cramping. These side effects are most common when you first start taking kefir. (51)

Normally kefir relieves constipation (53), but some report it causes the opposite. Probiotics in kefir lower intestinal PH by producing a number of acids including lactic acid and acetic acid, which usually enhances peristalsis and decreases transit time. However, one study found that apple cider vinegar, which contains acetic acid, slowed emptying further for those already with slow digestion exacerbating constipation. Longer fermentation time will mean more acid and not necessarily more probiotics; more acid may lead to more constipation (52).

You can start slowly with kefir, taking 1 tablespoon per day for a week, then 2 tablespoon per day for a week and so on, up to 170ml a day (54).

Iodine

The importance of iodine

Iodine is an essential mineral used by the body to produce thyroid hormones, which have many bodily functions. Iodine must be obtained from your diet. Insufficient iodine can lead to a goitre (swelling of the thyroid gland) and hypothyroidism leading to fatigue, muscle weakness and weight gain (57).

Breasts and ovaries in women have high concentrations of iodine and increased requirements for it. Iodine deficiency has been linked with breast cancer in preliminary data (58).

Iodine alkalises the body, acts as a powerful antioxidant and is essential for a well functioning immune system (58).

Who is at risk of iodine deficiency?

Those who avoid fish and/or dairy products (e.g. due to allergy or intolerance) could be at risk of iodine deficiency. Additionally vegetarians and particularly vegans, who do not eat iodine rich foods, will be at risk. Such people may need to consider an iodine containing supplement (56).

How much iodine do I need?

Adults need 150mcg per day (56).

The European upper safety limit has been set at 600 mcg. However, Japanese consume around 100 times the RDA on a daily basis due to their seaweed rich diet. Of note is that Japanese have lower levels of breast, endometrial and ovarian cancer and less fibrocystic breast disease (58).

Food sources of iodine

These can be found here: (56), (57), (58) and (60).

Iodine supplements

The British Dietetic Association (BDA) recommends not exceeding the the daily adult requirement of 150 mcg when supplementing (56).

Supplements should be in the form of “potassium iodide” or “potassium iodate” (56).

Avoid seaweed or kelp supplements since they can provide too much iodine and the amount of iodine claimed on the label may not be reliable (56). There have also been concerns about seaweed being contaminated with heavy metals (61).

Potassium iodide was almost completely (96.4%) absorbed in humans in a small study (60).

Since I am unable to consume dairy, I take a 150mcg potassium iodide supplement on the days that I don’t consume fish. However, if considering this yourself, you might be advised to discuss this with your doctor first.