Quick summary:
Poor iodine and selenium status in
this German population, lower iodine and selenium status in vegetarians, and even lower in vegans.
[My conclusion:
The Vegan Society’s supplement Veg1
is a helpful supplement for vegans in Germany.
Veg1 contains:
Vitamin D2: 10 mcg
Vitamin B2: 1.6 mg
Vitamin B6: 2 mg
Vitamin B12 (cyanocobalamin): 10 mcg
Folic acid: 200 mcg
Iodine: 150 mcg
Selenium: 60 mcg]
A doctoral thesis (MD) from southern
Germany from January 2015 is centred around a study comparing iodine,
selenium, zinc, and iron status in vegans, vegetarians, and omnivores.
As far
as I’m aware these results haven’t been published in a journal, and haven’t
been published in English at all. (The doctoral thesis, including the summary,
is available in German only).
Because the results seem relevant for the field of vegan nutrition I have translated the most relevant findings
into English.
1. Study
- Cross-sectional
study
- Published as a dissertation
(doctoral thesis, MD) at Ludwig-Maximilians-Universität (LMU) Munich, Germany
- Dissertation title (translation): “Significance
of the iodine/selenium quotient and of ferritin for the occurrence of
autoimmune thyroiditis (AIT) in subjects following an omnivorous, vegetarian or
vegan diet”
- “Vegetarian” was defined as “no
meat, poultry or fish”, i.e. ovo-lacto-vegetarian – so the vegetarian group did
NOT include pescatarians or semi-vegetarians
1.1 Study period
May–December 2009 (southern Germany)
1.2 Study participants
- Total n = 283
- Age range: 14–65 y
- At least 6 months on their respective
diets
- No known history of thyroid
disease
- No other chronic diseases
- Percentage of study participants who did not supplement iodine or selenium
(neither of the two):
82% (68/83) of vegans
91% (92/101) of vegetarians
93% (92/99) omnivores
TABLE 1: Study particpiants
|
|||
diet group
|
omnivore
|
vegetarian
|
vegan
|
number
|
99
|
101
|
83
|
number (women)
|
n = 70 (71%)
|
n = 72 (71%)
|
n = 56 (67%)
|
number (men)
|
n = 29 (29%)
|
n = 29 (29%)
|
n = 27 (33%)
|
age (mean ± SD)
|
43.6 ± 12.5 y
|
39.1 ± 13.9 y
|
38.9 ± 13.1 y
|
age (median)
|
45 y
|
40 y
|
38 y
|
age (range)
|
16–65 y
|
14–63 y
|
15–65 y
|
2 Results
2.1 Summary of results:
1. No clear correlation between iodine/selenium quotient and
AIT (autoimmune thyroiditis)
2. Clear correlation between ferritin deficiency and AIT
3. Still high prevalence of iodine deficiency in Germany
(despite iodine prophylaxis)
4. Poor selenium status in Germany
5. Vegetarians and especially vegans have worse iodine and
selenium status
6. Incidence of AIT is higher in vegetarians, and especially
vegans
7. Sonography test results typical of AIT more common in
vegetarians and vegans
8. All three diet groups (omnivores, vegetarians, vegans) were
within the reference range for zinc, but lower status in vegetarians, and yet
lower in vegans
2.2
Table
TABLE
2: Concentrations of trace elements in the three diet groups
|
||||||
SePP
(mg/L)
|
Selenium
(μg/L)a
|
Iodine
in urine (μg/L)
|
Ferritin
(μg/L)
|
Zinc
(μg/L)
|
||
Reference ranges
|
±
3 mg/L
|
70–140
μg/L
|
100–200
μg/L
|
30–300 μg/L
|
650–1200 μg/L
|
|
Omnivores
(n = 99)
|
mean
|
2.78
|
84.72
|
67.1
|
94.9
|
1141.71
|
SD
|
± 0.55
|
± 21.18
|
± 50.9
|
± 93.7
|
± 1037.56
|
|
median
|
2.68
|
83.2
|
50.7
|
65
|
988.1
|
|
range
|
1.51–4.17
|
49.6–189.4
|
3.47–252.97
|
5–586
|
403.3–2190.2
|
|
Vegetarians
(n = 101)
|
mean
|
2.6
|
69.4
|
55.7
|
38.63
|
961.65
|
SD
|
± 0.6
|
± 16.48
|
± 56.03
|
± 30.5
|
± 248.66
|
|
median
|
2.56
|
68.9
|
33.01
|
29
|
920
|
|
range
|
1.53–4.32
|
36.9–114.5
|
2.06–305.5
|
5–154
|
412.8–2353.1
|
|
Vegans
(n = 83)
|
mean
|
2.26
|
59.43
|
24.4
|
46.65
|
883.29
|
SD
|
± 0.52
|
± 19.02
|
± 33.09
|
± 41.1
|
± 186.77
|
|
median
|
2.24
|
56.7
|
13.15
|
39
|
865.7
|
|
range
|
1.16–3.92
|
21.7–125.7
|
0.28–168.64
|
10–318
|
581.5–1519.2
|
|
a Note that the author gives a
different reference range for plasma selenium on page 33/32: 50–120 μg/L. The vegan participants’ mean and median values are
within this range. But the author writes that more and more experts recommend
the lower value for plasma selenium to be at least 80–95 μg/L.
|
||||||
SD: Standard
deviation
SePP: Selenoprotein P
|
||||||
2.3 Further results
Selenium:
- Selenium status: vegetarians and
vegans deficient, omnivores in low reference range
- Insufficient selenium status (<3 mg/L SePP):
91.6% of vegans
74.3% of vegetarians
67.7% of omnivores
- GPx activity was normal in all three diet groups.
Iodine:
- Iodine status: all groups
deficient, vegans had most evident deficiency
- 66.3% of vegans had severe iodine
deficiency (iodinuria <20 μg/L); 6% of vegans had optimal
iodine status (iodinuria 100 – 199 μg/L)
- Sonography test results of thyroid typical of AIT
(autoimmune thyroiditis): 14% (n = 12) of vegans; 11% (n = 11) of vegetarians;
10% (n = 10) of omnivores
- Mean TSH was normal in all three diet groups.
- Mean TSH levels: 1.92 μg/mL in vegans; 1.64 μg/mL in vegetarians; 1.52 μg/mL in
omnivores [see TABLE 23 “Tab. 23” in the thesis]
Iron:
- Plasma
iron was normal in all three groups
- Ferritin <30 μg/L: 36% of vegans; 51% of vegetarians; 21%
of omnivores
Zinc:
- [Plasma] zinc: all groups within the reference range, but
vegetarians lower than omnivores, and vegans lower than vegetarians
3 Additional information
- The author concluded that if selenium, iodine and ferritin
levels are too low the risk for AIT is increased.
- 25% of women and 10% of men in
Germany seem to have a goiter.
- In Crohn’s disease, rheumatoid
arthritis, and asthma, plasma selenium levels and GPx activity correlate inversely
with severity of symptoms.
- The thyroid gland contains large
amounts of selenium.
- Reference range for TSH at LMU
Munich and in this study: 0.3–4.0 µIU/mL
- Recommended daily intake of iodine
(according to the author) for adequate thyroid function: 150–250 µg
- 100 µg/day prevent iodine
deficiency symptoms.
- According to the WHO iodine intake
in Germany – due to consistent iodine prophylaxis [iodized salt] – is high
enough so that iodine deficiency associated mental retardation hardly [!] occurs.
- The food industry and large-scale
caterers (canteens etc.) in Germany are supposed to use iodized salt by law
[I’m not sure how widely this is done and to what extent it is obligatory].
Because of this iodine intake in the general population in Germany is almost
adequate. There generally seems to be no risk of iodine excess in Germany.
- DGE (German Society for Nutrition)
recommendations for iodine intake: adults <50 y: 200 mcg/d; adults >50 y
180 mcg/d. The typical German diet does NOT provide these amounts.
- DGE food recommendations to
improve iodine status: 1–2 portions of sea fish (150 g each) per week. However à
example: if consumed as salmon: 300–600 µg iodine per week ß
still clearly below the weekly recommendation of 1,400 µg.
- The selenium content in plants
depends on the selenium content in the soil [other factors apply].
- Author: Up to 50% of selenium
intake can potentially come from plant foods.
- The author names "dates and mushrooms" as potential plant sources of zinc (other than
legumes, whole grains and nuts/seeds). [Dates however seem to contain little selenium, and I'm not sure about the bioavailability of selenium from mushrooms. If the bioavailability is high, they might be good sources of selenium.]
- When
selecting participants the researchers looked for people who did not supplement
their diets with selenium or iodine.
- Recruiting vegans was more difficult than expected.
- Since 1979 15 studies have determined plasma selenium levels
in Germany with means between 63 μg/L and 94 μg/L
- Selenium intakes in Austria: 37–68
µg/d [Typical selenium intakes in Germany aren’t given.]
- To maximize SePP plasma concentrations a selenium intake of
more than 90 μg/d seems to be necessary.
4 Quotes from the dissertation
- “A further factor that surely applies to all three diet
groups, is that one can eat an unbalanced or balanced diet in each of the diet
groups – which is something that also became apparent during the course of this
study.”
„Ein weiterer Faktor, der sicher
für alle drei Ernährungsgruppen zutrifft, ist, dass man sich in jeder Ernährungsgruppe
einseitig oder ausgewogen ernähren kann, was im Rahmen der Studie auch deutlich
wurde.”
- “For this reason further intensive strategies with the aim
to ensure an additional supply of iodine and selenium for the population should
be discussed.”
„Aus diesem Grund sollten weiterhin
intensive Strategien zur zusätzlichen Versorgung der Bevölkerung mit Jod und
Selen diskutiert werden.”
- “The
importance of a balanced diet and the necessity of fortification with iodine
and selenium should therefore reach the awareness of the public to a greater
extent, in order to avert long-term negative health outcomes.”
„Die Wichtigkeit einer ausgewogenen
Ernährung und die Notwendigkeit der Anreicherung von Jod und Selen sollte daher
noch mehr ins Bewusstsein der Bevölkerung vordringen, um langfristige Schäden
abzuwenden.”
-
“The evidence presented here should reinforce the efforts to further improve
iodine intakes in Germany and to think about potential solutions regarding the
progressive selenium deficiency in Germany.”
„Die hier erbachten Nachweise sollten die
Bemühungen bestärken, die Jodversorgung in Deutschland weiter voranzutreiben
und über Lösungsansätze bezüglich des progredienten Selenmangels in Deutschland
nachzudenken.”
5 Reference
- Hildbrand SM: Bedeutung des
Jod/Selen-Quotienten und des Ferritins für das Auftreten einer
Autoimmunthyreoiditis (AIT) bei omnivor, lakto-vegetarisch und vegan sich
ernährenden Personen. Eine epidemiologische klinische Querschnittsstudie.
Dissertation zum Erwerb des Doktorgrades der Medizin.
Ludwig-Maximilians-Universität München (2015) https://edoc.ub.uni-muenchen.de/18155/