Risk Factors of Kidney Stones

In the following table, all risk factors of kidney stones are described in details^[1-5]:

Risk Factors	Descriptions
Calcium	Calcium stone formers generally have a high urinary calcium. Calcium is the most abundant mineral in kidney stones. More calcium is absorbed from the upper intestine while more oxalate is available in the lower intestine. Reducing urine calcium should be a goal for stone formers, but not via dietary restriction. Counterintuitively, calcium reduction may promote stone formation, and doctors should encourage patients to continue consuming calcium-rich foods.[17] A 5-year randomized clinical trial of men with a history of calcium oxalate stones found that a normal calcium, decreased sodium, and decreased animal protein diet was more effective for reducing stone events than was a restricted calcium diet (Borghi et al., 2002). Clearly, strong research evidence now supports adequate calcium intake for patients who form kidney stones. Low-fat dairy products, green leafy vegetables, broccoli, fortified foods, and almonds are excellent sources. Patients should avoid calcium supplements in favor of calcium-rich foods (see [12]; the new research has associated calcium supplements with an increased kidney stone risk). Low-calcium diet is bad for two reasons: Lower bone density If you are on a low-calcium diet, your bone problem is going to get worse, particularly as you grow older. There is growing evidence to indicate that stone formers as a group have lower bone densities than the general population. Higher urinary oxalate Calcium and oxalate bind in the gut and in the urine to form a nonabsorbable compound. Low dietary calcium permits greater free oxalate to be absorbed in the gut and excreted in the urine, which may be counterproductive for calcium oxalate stone formers. Ordinarily, there is an excess of calcium over oxalate in the first part of your intestine. Since calcium and oxalate combine easily, most of the oxalate in your diet unites with calcium in the upper intestine. In essence, tiny calcium oxalate stones form inside your bowl. Since the intestine is so wide, these tiny stones make no differences. There is, however, very little oxalate available as your food moves to the last part of the intestine, the colon. And it is in the colon that most oxalate is absorbed by the body. In other words, with ordinary bowel function, only a very small part of the ingested oxalate is absorbed because most of it combines with calcium in the first part of the intestine. In a recent study, men over 40 on low-calcium diets made more stones than men on medium-calcium diets. The increased oxalate absorption may have been a factor.
Oxalate	Oxalate is a component, with calcium, of the majority of kidney stones. Oxalate is present in more than 75% of all stones. What most people with kidney stones don't know is that oxalic acid, like calcium, performs a vital function. 98 % of the oxalic acid in the body is produced internally and is used for moving food through the digestive tract by peristalsis. Oxalic acid also aids in the absorption of calcium into the cells[7]. Based on [7], leftover oxalic acid, along with excess calcium, is removed from the blood by the kidneys and passes into the urine. Calcium oxalate permeates the urine generally, but only in those people whose urine is overloaded with acid waste does it form stones. [7] also says that eating greens high in oxalates in moderate amount should be OK if they are raw. Calcium oxalate is a very insoluble salt. Though only 10% to 20% of urinary oxalates come from dietary sources (Morton, Iliescu, & Wilson, 2002), dietary reduction is commonly advised for calcium oxalate stone formers. It has been suggested that because there is much less oxalate in the urine than calcium in the urine, urinary oxalate concentration is much more critical to the formation of calcium oxalate crystals than is the urinary calcium concentration; reducing urine oxalates may have a more powerful effect on stone formation than can reduction of urine calcium (Morton et al., 2002). Oxalate is found only in plant foods, and the highest concentration are in dark green, leafy vegetables such as spinach, and in rhubarb, chocolate, tea, okra, nuts, beans, beets, wheat bran, and strawberries. A thorough oxalate list can be found on the Web site of the Oxalosis and Hyperoxaluria Foundation (http://www.ohf.org/diet.html). For a simple list of high-oxalate foods, visit http://www.gicare.com/pated/edtgs29.htm. Because it binds vital nutrients such as calcium, long-term consumption of foods high in oxalic acid can be problematic. Healthy individuals can safely consume such foods in moderation, but those with kidney disorders, gout, rheumatoid arthritis, or certain forms of chronic vulvar pain (vulvodynia) are typically advised to avoid foods high in oxalic acid or oxalates. There are four sources of the oxalate that appears in the urine. large amount of protein excess amounts of vitamin C Excess amounts of vitamin C can be excreted in the urine as oxalate. Vitamin C is an acid (ascorbic acid). It tends to lower urinary pH, which in turn lowers urinary citrate, a natural inhibitor of kidney stones. Recent data suggest that even small amounts of vitamin C supplements-doses of 250 mg to 500 mg-can raise urinary oxalate in some patients. waste products of general metabolism seven foods that greatly enhance urinary oxalate excretion: spinach In various food tests, spinach seems to produce the greatest rise in urinary oxalate. rhubarb beets nuts chocolate tea One patient who started to keep a large pitcher of iced tea on his desk at work. He was consuming 4 to 6 large glasses a day. He formed his first stone 2 months later. For those with excessive urinary oxalates, black and iced tea should be eliminated because both teas are high-oxalate beverages [5&8]. wheat bran However, the "bioavailability" of the oxalate may be different in various foods. In other words, some oxalate-containing foods are more problematic than others. Each person absorbs and excretes various dietary elements differently. The problem with oxalate recommendations Oxalate is difficulty to measure in both food and body fluids. The oxalate content of food can vary greatly from one batch of a given food to another. It is believed that aging increases the amount of oxalate in plants. Although oxalate has no known function in animals, it is believed to help plants dispose of calcium. Animals have kidneys that excrete excess calcium. Plants do not. The theory is that the oxalate binds to the excess calcium, trapping it in the leaves, bark, and skin. As older leaves are shed, the plant disposes of unwanted calcium. As the plant gets older, the oxalate content tends to increase. The bioavailability of oxalate differs in foods. Strawberries and spinach are both high-oxalate foods. However, the oxalate in spinach is more bioavailable than it is in strawberries. If oxalate is present as oxalic acid (the form found in younger plants), it is more bioavailable. If it is present in food as a calcium oxalate salt (the form found in older plants), it is less bioavailable in the intestines, and absorption decreases. Key issues in oxalate control (note that reduction of high oxalate foods is the goal for typical stone formers rather than strict avoidance of all oxalate-containing foods which would be very difficult): control portion size control fat intake In people prone to the overabsorption of oxalate, a high-fat diet will cause more oxalate to be absorbed. avoid vitamin c supplements Dr. Rodman advises his stone-forming patients not to take vitamin C supplements beyond what is in a balanced diet. watch for hidden oxalates the peanut oil used to cook in most Chinese food. drink two large glasses of water-or more when you know you have overindulged.
High Blood Uric Acid (See Also High Animal Protein Intake)	Saturation levels of uric acid in blood may result in uric acid stones. There is no inhibitor of uric acid crystal formation (Menon & Resnick, 2002), so dietary measures focus on reducing uric acid and increasing urine volume. Some patients with gout eventually get uric kidney stones.
Acid Urine	If the urine is acid most of all of the time, you are at risk for making uric acid stones. An acid urine also decreases citrate formation (the natural inhibitor of stones) by the kidneys, making a calcium oxalate stone more likely. Normal urinary pH levels range between 5.0 and a little over 8.0. This varies with the time of day, food consumption, age, and other factors.
Lack of Fluids (or Dehydration)	Less urinary flow (due to less fluid intake) increases the relative frequency of stone formation. Addressing fluid intake is the only therapeutic recommendation needed for some female stone formers. It is also one of the most important aspects of treating urinary tract infections in women. Dilution of urine is necessary "24/7," or all day, every day. Patients must accept the necessity of getting up at least twice at night to urinate, and should consume more water each time they rise to void [5]. What fluids to drink? For stone formers, you should drink more water and avoid excess caffeine, black tea, and grapefruit and apple juices. Lemonade is often recommended, as it supplies dietary citrate, a stone inhibitor and pH buffer when excreted later in the urine. [5].
High Animal Protein Intake	After low urinary volume, a high animal protein intake is the most important factor influencing the frequency of kidney stone disease. The effect of excess animal protein (purine=>uric acid) is most obvious for the uric acid stone former. High dietary protein is associated with increased urinary calcium. Thus, there is a link between meat consumption and both uric acid and calcium stone formation. Too much protein can cause dehydration, which is a cause of kidney stones[6] For every 50 grams of protein digested, your body must contribute 3 cups of water to dilute the resulting uric acid that is excreted. In comparison, metabolizing an equal amount of fat or carbohydrates consumes less than 1/2 cup of water. A study of 18 hypercalciuric stone formers found that a 15-day protein restriction had many positive effects on urinary markers of stone risk. Namely, significant decreases were seen in urine calcium, urine uric acid, urine phosphate, and urine oxalate. And, for unclear reasons, a beneficial increase in urinary citrate was observed (Giannini et al., 1999). Diets high in animal protein will increase the chance of forming both uric acid and calcium oxalate stones for 3 related but slightly different reasons: Animal protein contains high purines, whose end product is uric acid. More uric acid in the urine means that you are more likely to make a uric acid stone. In addition, one form of uric acid, urate, can act as a seed for calcium oxalate stones. The excessive consumption of animal protein will lower the pH of urine, making it more acid. This lower urinary pH makes uric acid less soluble and thereby favors the formation of uric acid stones. It also suppresses citrate formation by the kidney, which reduces one the body's natural inhibitors of calcium oxalate formation. One of the amino acids in all proteins, glycine, is metabolized to oxalate. Another amino acid, methionine, drives out more calcium in the urine. A diet higher in protein will therefore increase urinary calcium even though the amount of calcium in the diet remains constant.
Alcohol	By itself, alcohol does not contribute to stone formation. However, it does have two effects that may set the stage for stone formation. alcohol makes you pass more urine and can lead to dehydration. alcohol indirectly inhibits the ability of the kidneys to excrete uric acid.
Sodium	By itself, the sodium in your diet has only a minimal effect on the tendency of the urine to make stones. However, an increase in dietary sodium increases the urinary calcium.
Late dinner	Late-night eating is conducive to the formation of kidney stones. The tendency of more families to follow late eating habit in the 1980s and 1990s may be one reason for the rising incidence of stone disease.
NSAIDs and Acetaminophen	Taken in large quantities over long periods of time (no longer than 10 days, Dr. Oz has warned), analgesics such as NSAIDs and acetaminophen can cause damage to the papillae of the kidney. Injured papillae can seed a stone as well as complicate the stone-forming process.
Diamox or Acetazolamide	Some people with glaucoma form kidney stones while they are on carbonic anhydrase inhibitors (e.g., Diamox or acetazolamide) to lower eye pressure. These medicines can lower urinary citrate and increase urinary calcium. Patients can take potassium citrate supplements under doctor's supervision while the acetazolamide is continued, to minimize the tendency to make stones.
Rapid Weight Loss	Rapid weight loss is as bad as, or potentially worse than, overeating protein when it comes to causing stone disease. Doctors frequently give potassium bicarbonate and potassium citrate supplements to stone formers who are beginning a weight loss diet. The best way to lose weight is to combine a nutritionally balanced diet with exercise and behavior modifications.
Hot Climates	Kidney stones often occur in people who move to hot, dry climates and in people whose work or exercise causes them to perspire heavily.
Fat Malabsorption	Fat malabsorption can lead to an increased net oxalate absorption and, finally, to increased urinary oxalate.
Problems with Voiding	Problems with voiding make bladder stones more likely. The most common cause of bladder outflow problems is enlargement of the prostate gland in the older male.
Pregnancy	Pregnancy can increase stone risk due to the following factors: Her diminished bladder capacity As the fetus grows, there is less room in the pelvis for a full bladder. The pregnant woman has to provide enough calcium in her blood to form a whole new skeleton. Urinary calcium will rise to its highest levels in the last trimester. Therefore, stone formation can result from this low urine flow and high urinary calcium.
Genetic Predisposition	If one or both of your parents made stones, there is a greater chance that you will make stones.
Men vs. Women	Stone disease is much more common in men than in women because of the following factors: Men generally have a larger muscle mass than women. Hence they have more of the daily breakdown and rebuilding of tissue that results in metabolic waste. And an increase in metabolic waste predispose people to stone formation. Men generally eat more meat than women do. The male urinary tract is more complicated than the female urinary tract.

Warning

This article is not intended as and does not substitute for doctor's advices - the content presented is for your information only. Please see your personal physician for further evaluation of your individual case.

Reference(s)

1. Stamatelou, Kiriaki K.; Francis, Mildred E.; Jones, Camille A; Nyberg Jr., Leroy M.; Curhan, Gary C. (2003). "Time trends in reported prevalence of kidney stones in the United States: 1976–1994"
2. Taylor EN; Stampfer MJ; Curhan GC (2004). "Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up."
3. No More Kidney Stones by John S. Rodman, M.D., R. Ernest Sosa, M.D., and Cynthia Seidman, M.S., R.D, with Rory Jones.
4. The Complete Idiot's Guide to Detoxing Your Body by Delia Quigley.
5. The Role of Diet in the Prevention of Common Kidney Stones: Dietary Changes to Prevent and Reduce Stone Formation
6. The Swiss Screte to Optimal Health by Thomas Rau, M.D. with Susan Whler
7. The Acid Alkaline Balance Diet by Felicia Drury Kliment
8. Iced Tea Can Contribute to Painful Kidney Stones
9. Acid-Alkaline Balance
10. Building Strong Bones
11. Types of Kidney Stones
12. 6 Health Risks of Calcium Supplements
13. A Diet to Prevent Kidney Stones: Foods Vary
• Low-sodium diet is healthy for the kidneys as well as the heart.
• People can also reduce their risk of developing kidney stones and improve their health in general by increasing their intake of melons and citrus fruits like lemons, limes and oranges, says Dr. Monga.
14. 9 Unknown Signs You’ll Get Kidney Stones and How to Prevent Them
15. Alpha-lipoic acid prevents kidney stones in mouse model of rare genetic disease
16. How Not to Die from Kidney Disease | NutritionFacts.org
17. Kidney Stones: Water, Calcium and the DASH Diet
18. Antibiotics, High-Fat, High-Sugar Diets and Microbial Oxalate Metabolism
19. Mechanisms facilitating the persistent colonization of oxalate-degrading bacteria
20. What Are the Best Foods for Kidney Health?

Health Benefits of Phytochemicals

Antioxidants are vitamins, minerals, and phytochemicals  (plant-chemicals or phytonutrients) that aid the body in removing "free radicals" and controlling free-radical production.

• Without sufficient antioxidants, an excess of free radicals creates inflammation and leads to premature aging
• Vitamin C, vitamin E, folate, selenium, and alpha- and beta- carotene, as well as various other phytochemicals, have antioxidant effects

Science has since demonstrated that the positive health effects attainable from an antioxidant-rich diet are more likely caused by stimulating the body’s natural defenses against aging, including boosting the production of the body’s enzymes that eliminate free radicals, not as a result of the antioxidant activity itself.^[12]

Video 1.  The Best Diet for Diabetes (YouTube link)

Phytochemcals

Researchers in Japan found that phytonutrients in such plant foods as fruits, vegetables, tea leaves, and beans can block the effects of dioxins in vitro. The only catch was that these phytonutrient effects lasted only a few hours, meaning you may have to keep eating healthy foods, meal after meal.^[3]Other than blocking toxins, phytonutrients have been studied widely for their potential health benefits.  

Several hundred phytochemical plant nutrients have been identified and about 150 have been studied in detail.

For example, phytochemicals can

• Protect body against diseases
• The lack of a wide assortment of plant-derived phytochemicals in their native form is responsible for the development of most preventable diseases, including cancer.^[10]
• A phytochemically deficient diet is largely responsible for a weak immune system.
• There is a general consensus that the elements of a whole-foods plant-based diet—legumes, whole grains, fruits, vegetables, and nuts, with limited or no intake of processed foods and animal products—are highly beneficial for preventing and treating type 2 diabetes.^[13]
• Populations with a much higher intake of vegetables have much lower rates of cancer, and the longest-living populations throughout history have been those with the highest intake of vegetables in the diet.^[7]
• A review of more than 206 epidemiological studies shows that the consumption of raw green vegetables has the most consistent and powerful association with reduction of cancer of all types, including stomach, pancreas, colon, and breast.^[2]
• Have immune-modulating functions
• Multiple micronutrients, including lutein, lycopene, folate, bioflavonoids, riboflavin, zinc, selenium, and many others have immune-modulating functions.^[9]

In various studies, phytochemicals have been found to play protective roles not covered by vitamins and minerals, including the following:

1. Inducing detoxification enzymes
2. Controlling the production of free radicals
3. Deactivating and detoxifying cancer-causing agents
4. Protecting cell structures from damage by toxins
5. Fueling mechanisms to repair damaged DNA sequences
6. Impeding the replication of cells with DNA damage
7. Inducing beneficial antifungal, antibacterial, and antiviral effects
8. Inhibiting the function of damaged or genetically altered DNA
9. Improving immune cells' cytotoxic (destructive) power--that is , the power to kill microbes and cancer cells.

The list could be condensed into one primary role: 

Phytochemical are the fuel that runs our body's anticancer defenses.

 

Western Diets

The increase in consumption of processed foods, "fake" foods, food additives, and all the cancer-causing elements these things contain, our current food environment is compromising our health.  Poor nutrition only only makes us more susceptible to viruses but significantly impacts the length and severity of an illness.

The Kaiser Health Foundation studied this issue in depth, determined that 1/3 of medical spending is devoted to services don't improve health or the quality of care--and may make things worse!

Importance of Micronutrients

When our body is deficient in plant-derived miccronutrients, we weaken our immune system and leave ourselves exposed to infections and cancer.  Then key to superior nutrition is to get adequate of miccronutrients, while at the same time not consuming excess calories.

To get optimal amounts of immune-protective miccronutrients, we have to eat lots of vegetables. Fortunately, vegetables are relatively low in calories, so large amounts can be consumed without overeating on calories.  A study on relatively malnourished children in Vietnam illustrated this:^[3] 

Young children (five months to two years old) were randomly selected and assigned based on local areas to one of two groups, nutritional intervention or control.   

The intervention group received more vegetables and other micronutrient-rich food, while the control group was left on the typical rice diet.  During follow-up, children in the intervention communes had approximately half the respiratory illness experienced by those in comparison communes.

Figure 1.  A higher intake of cruciferous veggies is associated with a reduced risk of many cancers thanks to Sulforaphane and DIM (Diindolylmethane).

Conclusions

Phytochemicals are bioactive, plant-derived chemical compounds important for the growth and survival of the plant; they came about for the benefit of the plant world.   However, the human immune system evolved dependent on these phytochemicals for its optimal functioning.  

In summary, phytochemcials in the diet fuel the miraculous self-healing and self-protective properties already built into the human genome:^[1] 

• The whole is greater than the sum of its parts
• A combination of these compounds is more effective than a single agent, even in a high dose.
• Antioxidants aid the body in removing "free radicals" and controlling free-radical production
• Without sufficient antioxidants, an excess of free radicals creates inflammation and leads to premature aging.
• Phytochemicals protect body against diseases
• To have normal immune function we require hundreds of additional phytochemicals in addition to vitamins and minerals
• Phytochemicals are compounds that maximize cell function, thus enabling the healing properties of immune cells

References

1. Super Immunity by Dr. Joel Fuhrman
2. Steinmetz KA, Potter JD.  Vegetables, fruit, and cancer prevention: a review.  J Am Diet Assoc 1996, Oct; 96(10):102739.
3. Sripaipan T, Schroeder DG, Marsh DR, et al.  Effect of an integrated nutrition program on child morbidity due to respiratory infection and diarrhea in northern Viet Nam.  Food Nutr Bull 2002; 23(4): 70-77.
4. Author Jo Robinson discussed her book “Eating on the Wild Side: The Missing Link to Optimum Health”.  (Listen the audio from 24:25)
5. Higher Dietary Flavonol Intake Is Associated with Lower Incidence of Type 2 Diabetes Journal of Nutrition (​2013;143(9):1474–1480)
6. Boussiba; Sammy, V.; Avigad, C.; et al. (2000) Procedure for large-scale production of astaxanthin from haematococcus.
7. Belgian Researchers Discover Way to Block Cancer Metastasis
• The free radical involved in the metastacism of tumor cells is superoxide. Tests in mice on melanoma and breast cancer cells showed that administering an antioxidant stopped the production of superoxide. That, in turn, prevented cell changes that would lead to metastasis.
8. Differences in Biological Response Modifier-like Activities According to the Strain and Maturity of Bananas
• Since the highland variety is cultivated for a longer period and under a more severe environment, the content of dopamine, with its anti-oxidative effects, may be a useful self-defense mechanism. 
9. The dark side of antioxidants (important)
10. Top Women’s Mental Health Issues Infographic
11. Consumption of 85% cocoa dark chocolate improves mood in association with gut microbial changes in healthy adults: a randomized controlled trial
• Collectively, given the role of the gut microbiota in polyphenol bioavailability and metabolism as well as brain function, our findings suggest that daily intake of polyphenol-rich chocolate gradually alters gut microbial diversity, resulting in beneficial impacts on the host's mood.
12. Lifespan: Why We Age—and Why We Don't Have To
13. The Best Diet for Diabetes

Health Benefits of Selenium

Selenium (Se) is an essential trace element (for example, you only need to eat 1-2 Brazil Nuts per day; see Table 2) of high importance for human health . Studies have already identified associations between selenium deficiency and increased morbidity and mortality from viral infections, cardiovascular, and thyroid diseases, as well as prostate, gastrointestinal, and breast cancers. But, you do need to avoid overdosing on Se as warned by CDC:^[17]

Brazil nuts contain very high amounts of selenium (68–91 mcg per nut) and could cause selenium toxicity if consumed regularly. Acute selenium toxicity has resulted from the ingestion of misformulated over-the-counter products containing very large amounts of selenium. In 2008, for example, 201 people experienced severe adverse reactions from taking a liquid dietary supplement containing 200 times the labeled amount. Acute selenium toxicity can cause severe gastrointestinal and neurological symptoms, acute respiratory distress syndrome, myocardial infarction, hair loss, muscle tenderness, tremors, lightheadedness, facial flushing, kidney failure, cardiac failure, and, in rare cases, death.

Figure 1.  10 foods high in Selenium (Source: dietingwell.com)

Figure 2.  Selenium absorption, metabolism, and distribution (Source: [12])

Absorption/ Metabolism / Distribution

Selenium is found in foods and nutritional supplements in 2 forms

• Organic form
• selenomethionine, selenocysteine, seleniummethylselenocysteine
• Inorganic form
• selenate and selenium

After intestinal absorption, selenium forms are converted into hydrogen selenide (H2Se), a metabolic intermediate incorporated into selenoproteins, in the form of selenocysteine. 

Figure 3.  Selenium supplementation boosts T_FH cells in mice and humans (Source: [7])

Important Roles of Selenoproteins

Se performs its main functions in the form of selenoproteins.  A wide range of these selenoproteins are linked to redox signaling, oxidative burst, calcium flux, and the subsequent effector functions of immune cells being grouped into families such as:

• Glutathione peroxidases (GPXs)
• Iodothyronine deiodinases (DIOs) 
• Thioredoxin reductases (TrxRs)
• Methionine sulfoxide reductase B1 (MSRB1)
• Selenophosphate synthetase 2 (SEPHS2)

In addition, the Selenoprotein P (or SELENOP) acts as the main selenium transporter for peripheral tissues also performing extracellular antioxidant function (see Figure 2). 

Thus, selenium plays a role in antioxidant, anticarcinogenic, anti-inflammatory, redox and immune-cell function as well as in the regulation of thyroid hormone metabolism:

• Anti-inflammatory
• Findings suggest that UV damage to the epidermis affects deeper layers of the skin and even blood and other tissues
• Diets enriched with antioxidant nutrients, including selenium, beta-carotene, vitamin E, and vitamin C, inhibit the formation of UV-induced tumors.^[4]
• A major role of the exogenous antioxidants, vitamins C and E (a-tocopherol), b-carotene, and selenium, is to act as efficient scavengers of reactive oxygen radicals, thereby protecting against oxidative damage.^[14]
• Antiviral
• Se/selenoproteins are relevant in the viral pathogenicity, notably reducing proliferation of T cells, lymphocyte-mediated toxicity and NK cell activity, all of which are crucial for antiviral immunity. 
• Selenoproteins partly reduce oxidative stress generated by viral pathogens.
• The available studies support the belief that selenium may be of relevance in the infection with SARS-CoV-2 and disease course of COVID-19.
• There is a mechanism proposed by Zhang et al.^[10] by which selenium might suppress the life cycle and mutation to virulence of SARS-COV-2 while attenuating viral-induced oxidative stress, organ damage and the cytokine storm.
• Redox
• Selenoproteins also regulate or are regulated by cellular redox tone, which is a crucial modulator of immune cell signaling. 
• The cellular redox environment is a balance between the production of reactive oxygen species (ROS), reactive nitrogen species (RNS), and their removal by antioxidant enzymes and small-molecular-weight antioxidants.
• Redox-active selenium metabolites are involved in the anti-viral action of selenium in mice and humans.^[15]
• Immune-cell activity
• Se is useful for the competency of the cellular component of both innate and adaptive immunity.
• Inhibition of ferroptosis (i.e., a form of regulated cell death) via selenium supplementation promotes the survival of follicular helper T cells (T_FH), boosting the germinal center and antibody response following vaccination in mice and people (see Figure 3).^[7]
• On a cellular level, Se status may influence various leukocytic functions including adherence, migration, phagocytosis, and cytokine secretion. 
• Regulation of thyroid hormone metabolism
• Selenium in iodothyronine deiodinase, as selenocysteine, plays a crucial role in determining the free circulating levels of T3. Selenium deficiency can have implications in fall of T3 levels.
• In target tissues, T4, the most abundant circulating thyroid hormone, can be converted to T3 by selenium-containing enzymes known as deiodinases.^[11]

Table 1: Selenium Content of Selected Foods [16]

Food	Micrograms (mcg) per serving	Percent DV*
Brazil nuts, 1 ounce (6–8 nuts)	544	989
Tuna, yellowfin, cooked, dry heat, 3 ounces	92	167
Halibut, cooked, dry heat, 3 ounces	47	85
Sardines, canned in oil, drained solids with bone, 3 ounces	45	82
Ham, roasted, 3 ounces	42	76
Shrimp, canned, 3 ounces	40	73
Macaroni, enriched, cooked, 1 cup	37	67
Beef steak, bottom round, roasted, 3 ounces	33	60
Turkey, boneless, roasted, 3 ounces	31	56
Beef liver, pan fried, 3 ounces	28	51
Chicken, light meat, roasted, 3 ounces	22	40
Cottage cheese, 1% milkfat, 1 cup	20	36
Rice, brown, long-grain, cooked, 1 cup	19	35
Beef, ground, 25% fat, broiled, 3 ounces	18	33
Egg, hard-boiled, 1 large	15	27
Bread, whole-wheat, 1 slice	13	24
Baked beans, canned, plain or vegetarian, 1 cup	13	24
Oatmeal, regular and quick, unenriched, cooked with water, 1 cup	13	24
Milk, 1% fat, 1 cup	8	15
Yogurt, plain, low fat, 1 cup	8	15
Lentils, boiled, 1 cup	6	11
Bread, white, 1 slice	6	11
Spinach, frozen, boiled, ½ cup	5	9
Spaghetti sauce, marinara, 1 cup	4	7
Cashew nuts, dry roasted, 1 ounce	3	5
Corn flakes, 1 cup	2	4
Green peas, frozen, boiled, ½ cup	1	2
Bananas, sliced, ½ cup	1	2
Potato, baked, flesh and skin, 1 potato	1	2
Peach, yellow, raw, 1 medium	0	0
Carrots, raw, ½ cup	0	0
Lettuce, iceberg, raw, 1 cup	0	0

*DV = Daily Value.

References

1. Health Benefits of Iodine (Travel and Health)
2. Beck MA. Antioxidants and viral infections: host immune response and viral pathogenicity.  J Am Coll Nutr 2001; 20 (5 Suppl): 384S-388S, discussion 396S-397S.
3. Garlic—a Vegetable, a Condiment, and a Medicine (Travel and Health)
4. Health Benefits of Carotenoids (Travel and Health)
5. What You Need to Know About Your Thyroid Health (Dr. Mercola)
6. Selenium (Harvard School of Public Health; good)
7. Selenium saves ferroptotic TFH cells to fortify the germinal center
8. Nutritional risk of vitamin D, vitamin C, zinc, and selenium deficiency on risk andclinical outcomes of COVID-19: a narrative review
9. Huang Z, Rose AH, Hoffmann PR. The role of selenium in inflammation and immunity: from molecular mechanisms to therapeutic opportunities. Antioxid Redox Signal 2012 Apr 1;16(7):705-43.
10. Zhang J, Saad R, Taylor EW, Rayman MP. Selenium and selenoproteins in viral infection with potential relevance to COVID-19. Redox Biol 2020 Oct;37:101715
11. Iodine (Linus Pauling Institute)
12. Selenium in Human Health and Gut Microflora: Bioavailability of Selenocompounds and Relationship With Diseases
13. The Role of Selenium in Inflammation and Immunity: From Molecular Mechanisms to Therapeutic Opportunities
14. Vitamin C and the risk of developing inflammatory polyarthritis: prospective nested case-control study
15. Yu L., Sun L., Nan Y., Zhu L.Y. Protection from H1N1 influenza virus infections in mice by supplementation with selenium: a comparison with selenium-deficient mice. Biol. Trace Elem. Res. 2011;141(1–3):254–261.
16. U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, 2019.
17. Selenium—Fact Sheet for Health Professionals (NIH)
18. Egg consumption improves vascular and gut microbiota function without increasing inflammatory, metabolic, and oxidative stress markers