| Selenium | |||||
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- Why selenium is good for you
- Important selenium facts
- Groups at risk of selenium deficiency
- Symptoms of selenium deficiency
- Selenium and health
- Selenium in foods
- Selenium recommended daily intake (RDI)
- Selenium works best with
- Overdosage, toxicity and cautions for selenium
Selenium is another important mineral for the health of the thyroid gland - it helps it to work properly and reduces goitre. It is helpful in fighting infections since it stimulates increased antibody response to infections and promotes more energy in the body. Selenium is a potent antioxidant.
One of the main activities of selenium is its anti-aging properties and its ability to help rid the body of free radicals, as well as toxic minerals such as mercury, lead and cadmium.
Selenium helps with alleviating menopausal symptoms in women and it also assists men in producing healthy sperm. Tissue elasticity and pancreatic function is also dependent on this mineral.
- People living in areas where the soil is poor in selenium, should pay attention to their selenium intake
- Selenium supplements should contain methionine as it detoxifies excess amounts of selenium
- Sodium selenate is also less toxic than sodium selenite
Groups at risk of selenium deficiency
- Men - men need more selenium than women as it is lost in the seminal fluid
- Chronically ill patients - muscular weakness, muscle wasting, and cardiomyopathy (inflammation and damage to the heart muscle) have been noted in these patients.
- People with large sections of their small intestine removed - these people have impaired absorption of selenium and may need supplementation
- People with severe gastrointestinal problems, such as Crohn's disease - these people have impaired absorption of selenium and may need supplementation
- People on specialised medical diets to treat metabolic disorders - people on these diets (ie one for as phenylketonuria - PKU), are often low in selenium due to the restrictions of their diet and may need supplementation
People in these groups at risk of deficiency should talk to a medical professional about selenium supplements BEFORE taking them.
Symptoms of selenium deficiency
Selenium deficiency occurs when there is <40mcg intake of selenium per day. Selenium deficiency is associated with problems with the thyroid gland.
The following are two diseases which are caused by selenium deficiency:
Keshan's Disease:
This is a disease which affects the heart and it occurs mainly in selenium-deficient soils in certain regions of China. The acute form of Keshan's disease is characterized by the sudden onset of cardiac insufficiency, while the chronic form results in moderate to severe heart enlargement with varying degrees of cardiac insufficiency. The incidence of Keshan disease is closely associated with very low dietary intakes of selenium and poor selenium nutritional status. Selenium supplementation has been found to protect people from developing Keshan disease but cannot reverse heart muscle damage once it occurs.
Kashin-Beck Disease:
Kashin-Beck disease is characterized by the degeneration of the articular cartilage between joints (osteoarthritis) and is associated with poor selenium status in areas of northern China, North Korea, and eastern Siberia. The disease affects children between the ages 5 and 13 years. Severe forms of the disease may result in joint deformities and dwarfism, due to degeneration of cartilage forming cells. Unlike Keshan disease, there is little evidence that improving selenium nutritional status prevents Kashin-Beck disease.
- Cancer - in studies with animals it has been shown that high (therapeutic) levels of selenium reduces cancer in animals. Geographic studies have shown that people who live in areas with low soil selenium and also have relatively low selenium intakes have higher cancer mortality rates. In one trial undertaken in an area of China, higher selenium intake showed a 35% reduction in cancers. Other studies, in other areas have confirmed this result
- The heart - selenium's antioxidant properties are helpful in making the blood less "sticky", which is helpful in preventing heart attacks and strokes
- The immune system - selenium deficiency has been associated with impaired function of the immune system. Good selenium levels stimulate the immune system into action to protect the body for viral or bacterial infection
- Viruses - some researchers have shown that in selenium-deficient animals a harmless virus can mutate into a virulent form capable of causing more severe ill health and death - this has also been followed up ad confirmed by other studies
People who wish to take an selenium supplement should talk to a medical professional BEFORE taking it.
FUTURE RESEARCH
- HIV/AIDS - there is evidence that selenium levels decrease as the disease progresses, even before malnutrition is presented. Several studies are underway and show some improvement in symptoms of people with HIV/AIDS with selenium supplement but do not decrease mortality or disease progression. More research is underway
People who wish to take an selenium supplement should talk to a medical professional BEFORE taking it.
| FOOD | AMOUNT | selenium (mg) |
|---|---|---|
Crab meat |
85g | 40 |
Salmon |
85g | 40 |
Halibut |
85g | 40 |
Noodles, enriched |
1 cup | 35 |
Prawns (shrimp) |
85g | 34 |
Pork |
85g | 33 |
Brazil nuts |
30g (6-8 nuts) | 30 |
Chicken (light meat) |
85g | 20 |
Rice, brown |
1 cup | 19 |
Beef |
85g | 17 |
Whole wheat bread |
2 slices | 15 |
Milk |
1 cup | 5 |
Walnuts, black |
30g | 5 |
Selenium recommended daily intake (RDI)
| RDA | lifestage | age | AMOUNT |
|---|---|---|---|
| INFANTS | 0-6mths 7-12mths |
15mcg 20mcg |
|
| CHILDREN | 1-3yrs 4-8yrs |
20mcg 30mcg |
|
| CHILDREN | 9-13yrs 14-18yrs |
40mcg 55mcg |
|
| ADULTS | 19-50yrs |
55mcg | |
| SENIORS | 51+yrs | 55mcg | |
| PREGNANT | 60mcg | ||
| LACTATING | 70mcg | ||
| TOLERABLE UPPER LIMIT | lifestage | age | AMOUNT |
| INFANTS | 0-6mths 7-12mths |
45mcg 60mcg |
|
| CHILDREN | 1-3yrs 4-8yrs |
90mcg 150mcg |
|
| CHILDREN | 9-13yrs 14-18yrs |
280mcg 400mcg |
|
| ADULTS | 19-50yrs |
400mcg | |
| SENIORS | 51+yrs | 400mcg | |
| PREGNANT | 400mcg | ||
| LACTATING | 400mcg | ||
| Toxic Levels | >1000mcg | ||
The tolerable upper limits should only be taken for short periods and only under medical supervision.
- Vitamin B3 (Niacin)
- Vitamin C
- Vitamin E (Tocopherol)
- Co Enzyme Q10
- Cysteine
- Glutathione
- Methionine
- Iodine
- Iron
- Zinc
Overdosage, toxicity and cautions for selenium
Toxicity >2mg - birth defects, dermatitis, fatigue, garlic breath odour, stomach upsets, irritated eyes, liver impairment, metallic taste in mouth, nausea, weakness, yellow skin
references
- USDA National Nutrient Database - provides nutrient values for foods (accessed 5 January 2005)
- Osiecki, H. The Nutrient Bible. Bio-Concepts Publishing QLD, 2002
- Whitney EN, Cataldo DB, Rolfes SR. Understanding Normal and Clinical Nutrition, 6th Edition. Wadsworth/Thomson Learning, 2002
