What are goitrogens?

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What are goitrogens?

JoAnn Guest

Nov 12, 2006 14:14 PST

 

 

 

Goitrogens are naturally-occurring substances that can interfere

with function of the thyroid gland. Goitrogens get their name from

the term " goiter, " which means an enlargement of the thyroid gland.

If the thyroid gland is having difficulty making thyroid hormone, it

may enlarge as a way of trying to compensate for this inadequate

hormone production. " Goitrogens, " like circumstances that cause

goiter, cause difficulty for the thyroid in making its hormone.

 

The link between isoflavones and decreased thyroid function is, in

fact, one of the very few areas in which flavonoid intake has been

called into question as problematic.

Isoflavones appear to reduce thyroid hormone output by

blocking activity of an enzyme called thyroid peroxidase. This

enzyme is responsible for adding iodine onto the thyroid hormones.

 

(Thyroid hormones must typically have three or four iodine atoms

added on to their structure in order to function properly.)

Isothiocyanates are the category of substances that have been

associated with decreased thyroid function. Like the isoflavones,

isothiocyanates appear to reduce thyroid function by blocking

thyroid " peroxidase " , and also by disrupting messages that are sent

across the membranes of thyroid cells.

 

In the absence of thyroid problems, there is no research evidence to

suggest that goitrogenic foods will negatively impact your health.

In fact, the opposite is true - organic tofu and vegetables have

unique nutritional value, and intake of these foods have been

associated with decreased risk of cancer in research studies.

 

Because carefully controlled research studies have yet to take place

on the relationship between goitrogenic foods and thyroid hormone

deficiency, healthcare practitioners differ greatly on their

perspectives as to whether a person who has thyroid problems, and

notably a thyroid hormone deficiency, should limit their intake of

goitrogenic foods.

 

Most practitioners use words like " overconsumption " or " excessive "

to describe the kind of goitrogen intake that would be a problem for

individuals with " thyroid hormone deficiency " .

Here the goal is not to eliminate goitrogenic foods from the meal

plan, but to limit intake so that it falls into a reasonable range.

 

Ingredients like textured vegetable protein (TVP) and isolated soy

concentrate may appear in foods that would rarely be expected to

contain soy. A standard, one cup serving of cruciferous vegetables 2-

3 times per week, and a standard, 4-ounce serving of tofu twice a

week is likely to be tolerated by many individuals with thyroid

hormone deficiency.

It's worth it to try and include these foods in a meal plan because

of their strong nutritional value and great track record in

preventing many kinds of health problems.

 

The effect of cooking on goitrogens

Although research studies are limited in this area, cooking does

appear to help " inactivate " the goitrogenic compounds found in food.

Both isoflavones and isothiocyanates (found in

cruciferous vegetables) appear to be " heat-sensitive " , and cooking

appears

to " lower the availability " of these substances. In the case of

isothiocyanates in cruciferous vegetables like broccoli, as much as

one third of this goitrogenic substance may be " deactivated " when

broccoli is boiled in water.

 

Although for many people goitrogens do not seem to pose a health

concern, certain individuals who have thyroid problems may be

advised by their healthcare practitioner to limit " excessive "

consumption of foods that contain these compounds. As cooking seems

to help to inactivate the

goitrogenic compounds found in food, it seems reasonable to conclude

that for individuals with deficient thyroid hormone production,

steaming of cruciferous vegetables like broccoli makes good sense,

as does consumption of tofu in cooked versus raw form.

 

 

References

 

Conaway, C. C.; Getahun, S. M.; Liebes, L. L.; Pusateri, D. J.;

Topham,

D. K.; Botero-Omary, M., and Chung, F. L. Disposition of

glucosinolates

and sulforaphane in humans after ingestion of steamed and fresh

broccoli. Nutr Cancer. 2000; 38(2):168-78.

 

Fowke, J. H.; Fahey, J. W.; Stephenson, K. K., and Hebert, J. R.

Using

isothiocyanate excretion as a biological marker of Brassica

vegetable

consumption in epidemiological studies: evaluating the sources of

variability. Public Health Nutr. 2001 Jun; 4(3):837-46.

 

Getahun, S. M. and Chung, F. L. Conversion of glucosinolates to

isothiocyanates in humans after ingestion of cooked watercress.

Cancer

Epidemiol Biomarkers Prev. 1999 May; 8(5):447-51.

 

Liggins, J.; Bluck, L. J.; Runswick, S.; Atkinson, C.; Coward, W.

A.,

and Bingham, S. A. Daidzein and genistein contents of vegetables. Br

J

Nutr. 2000 Nov; 84(5):717-25.

 

Toda T, Uesugi T, Hirai K, Nukaya H, Tsuji K, Ishida H. New 6-O-acyl

isoflavone glycosides from soybeans fermented with Bacillus subtilis

(natto). I. 6-O-succinylated isoflavone glycosides and their

preventive

effects on bone loss in ovariectomized rats fed a calcium-deficient

diet.Biol Pharm Bull 1999 Nov;22(11):1193-201

 

 

JoAnn Guest

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www.geocities.com/mrsjoguest/Diets