Hidden dangers of oxalates and goitrogens in green smoothie for thyroid and kidney

Many are taking green smoothie as high valued healthy diet as it’s major parts of nutrients remain intact. But if you are taking green smoothie regularly you also need to know about the dark side. When I am writing an article about how to reduce gointrogen and oxalates from vegetables I felt I should also write an article about green smoothie as many people are taking green smoothie as healthy option. If you are taking green smoothie you should also aware of Hidden dangers of oxalates and goitrogens in green smoothie for thyroid and kidney stone

Hidden dangers of oxalates and goitrogens in green smoothie for thyroid and kidney

Your green smoothie

If you are taking green smoothie recipe may contains like spinach, broccoli, kale, orange, berries, almond milk and some other similar. In green smoothie there are no major loss in antioxidant part and some vitamins. In contrast some losses occur mainly in antioxidant, vitamin C while minerals remain almost same. But there are some other concerns of raw foods. Raw foods may contain higher percentage of goitrogens as well as oxalates.

Your green smoothie may contain goitrogens and impair thyroid function

Your thyroid gland needs iodine for thyroid hormone synthesis. Goitrogens more importantly progoitrin interfere with iodine uptake and that impairs production of T4 thyroid hormone. Other form of goitrogen in cruciferous vegetable is thiocyanate. However researchers found as the maximum thiocyanate increase would be on the order of 10 μM from 100 g of fresh vegetable weight. As this increase is much less than naturally occurring thiocyanate concentration in human body hence thiocyanate from crucifers unlikely would have significant adverse effects on thyroid function. Other form of goitrogen as progoitrin converts to goitrin. Researchers reported 194 μmol of goitrin but not by 77 μmol of goitrin inhibited iodine uptake. Therefore found as reasonable to conclude less than 70 μmol of progoitrin unlikely to impair thyroid function.

Therefore researchers concluded consumption of typical serving sizes of raw broccoli, Chinese cabbage, turnip, bok choy, broccoli rabe correspond to low concentration of goitrogenic compound progoitrin and thiocyanate unlikely to impair thyroid health. In contrast 100g of fresh Chinese kale, Russian kale, Kale(B. Napus), collard greens has higher amount of progoitrin than 70 μmol. (1)We disscussed these with our earlier article in more and also mentioned about way to reduce goitrogens.

You can see the list of vegetables with progoitrin concentration here.

You green smoothie may have higher concentration of kidney stone developing oxalates

Green leafy also contains oxalates with varying amount. Oxalates occur mainly in two forms soluble and unsoluble. Soluble oxalates bind with calcium as well as other minerals and thus make them less bioavailable to absorb. In contrast insoluble oxalates excrete in feces after ingestion. More problems occur when soluble oxalate is absorbed through intestine and circulates in bloodstream. There it form calcium oxalate by binding with circulating calcium and accumulates in excretory organs kidney. In fact approximately 75% of kidney stones contain calcium oxalates.(2) However major part of oxalate excreted in urine produced by the body, rather than absorbed from food.(3)

Gut health determines oxalates absorption

Individual with healthy gut absorb only small amount of oxalates. In contrast oxalates absorption increases with increased intestinal permeability or leaky gut through paracellular “leak” pathway. (4,5) Gut also bacteria degrades oxalates and thus helps to reduce oxalate concentration.(6,7) Thus if you have compromised gut function you need to be more careful.

In study people with Crohn’s disease had much higher rate oxalate absorption. Researchers concluded oxalate abosorption or kidney stones has major implications for the general health in patients with Crohn’s disease.(8)

Similarly in a study published in PLoS One concluded the diagnosis of Crohn’s disease, intestinal surgery, prolonged NSAID or nonsteroidal anti-inflammatory drugs use, disease activity and duration and bowel stenosis were significantly associated with development of kidney stone in IBD. (9)

Gut Bacteria and Oxalates

Some gut bacteria reduce oxalates by degrading it. Oxalobacter formigenes significantly reduces the oxalate amount your body absorbs.(10) Other bacteria that may play role in degradation of oxalates includes but not restricted to Eubacterium lentum, Enterococcus faecalis, Lactobacillus family such as L. acidophilus, L. plantarum, L. paracasei, L. bulgaricus and Bifidobacterium family such as B. breve, B. longum, B. infentis, B. lactis. (11,12,13, 14). Therefore probiotics can play role here in oxalate degradation.

Other way of reducing oxalates

Researchers reported that cooking reduces oxalates. Boiling significantly reduced soluble oxalate content by 30-87% followed by steaming 5-53%. (15) However while removing the water it also loss nutrients. It also has been informed that a low fat milk as cooking medium with neutral pH can maximize the oxalate reduction.(16) One experiment was conducted with consumption of spinach as grilled spinach in one way and spinach with diary product with calcium. Researchers found highest urinary oxalates with people who had eaten grilled spinach. On the other hand people who had ingested spinach with diary product had lowest urinary calcium excretion.(17) That indicates soluble oxalate when consume with calcium bind with calcium and made them less bio-available. Such less bio-available calcium prevent absorption and thus excreted less in urine.

However in present days change of breed of cows also changed the milk structure more specifically proteins part with raise of some serious concerns.

Greens with oxalates

As soluble oxalate gets absorbed and binds with minerals, mainly problems come from soluble oxalate than insoluble part. Some vegetables and fruits such as spinach, rhubarb, beets, nuts more specifically almonds, turnips, kale, Parsley, collard greens, strawberries, carrot, raddish, etc contains higher percentage of oxalates. There also very healthy some other ways. I have shared a link here you can see the list for more information. Unfortunately I have no separate list for soluble oxalate right now.

On the other hand beet also help to improve health by improving vascular health, brain function, stamina, beauty and more.

Genetic Factor and Kidney Stone

Around 75% of kidney stone contains calcium oxalate. And if you have genetic factor or family history your probability of calcium oxalate accumulation tends to be more. Approximately 40 percent of people who form kidney stones have a positive family history for stones. Individual with genetic factor or family history more tend to accumulate calcium oxalate. (18,19,20,21) Additionally individual with tendency of developing should also check their sodium intake. Apart from direct preparation of foods sodium also hides in many package foods.

Green vegetables may contain heavy metal

Another possible concern includes possible chance of having heavy metal toxicity. (22) Therefore factors like source, cultivating soil, chemical used etc matters. It is better to choose organic for eating raw.

Bottom Line

Lastly I am not going to discourage you from healthy eating rather than alert you from hidden risk of foods looking as healthy. Greens contain varying amount of goitrogens as well as oxalates with them. Therefore it is wiser to perform accordingly. And gut health is a must. You can’t completely escape from oxalates also you need not. Many plants source of foods contains varying amount of oxalates. Missing those foods you are going to miss some vital nutrients. What you need to check the oxalates content more specifically soluble oxalate and take some preventive measure or limit. And even more specifically if you have genetic or family history or/and unhealthy gut. More is not always better, moderation is the key.

And I wish like to hear from you if you have something with you in this subject.

Disclaimer: Information provided here are generalized information 
for educational purpose only,  not intended to provide one to one 
health consultation or replace practice of a qualified 
practitioner. Different people may have different health 
condition and may have different reaction to the same food. Hence 
it has been advised to consult with health care provider before 
application of any of above information.
1.Peter Felker, Ronald Bunch, and  Angela M. Leung, 
Concentrations of thiocyanate and goitrin in  human plasma, their 
precursor concentrations in brassica vegetables, and  associated 
potential risk for hypothyroidism, Nutr Rev. 2016 Apr; 74(4): 
248–258 
2.Sumana Ghosh Das,Geoffrey Peter Savage,Total and Soluble 
Oxalate Contentof Some Indian Spices,Plant Foods for Human 
Nutrition 67(2):186-90 · April 2012  
3.Holmes RP, Goodman HO, Assimos DG.,  Contribution of dietary 
oxalate to urinary oxalate excretion, Kidney Int. 2001 
Jan;59(1):270-6    
4.https://med.nyu.edu/medicine/nephrology/sites/default/files/nep
hrology/C alcium%20oxalate.pdf  
5.Felix Knauf et. al.,Net Intestinal Transport of Oxalate 
Reflects Passive Absorption and SLC26A6-mediated Secretion,J Am 
Soc Nephrol. 2011 Dec; 22(12): 2247–2255 
6.Abratt VR, Reid SJ.,Oxalate-degrading bacteria of the human gut 
as probiotics in the management of kidney stone disease,  Adv 
Appl Microbiol.2010;72:63-87  
7.Sivasamy Gomathi et. al.,Screening of Indigenous Oxalate 
Degrading Lactic Acid Bacteria from Human Faeces and South Indian 
Fermented Foods: Assessment of Probiotic Potential,The Scientific 
World Journal, Volume 2014, Article ID 648059, 11 pages
8.Hueppelshaeuser R, von Unruh GE, Habbig S, Beck BB, Buderus S, 
Hesse A, Hoppe B.,Enteric hyperoxaluria, recurrent urolithiasis, 
and systemic oxalosis in patients with Crohn's disease, Pediatr 
Nephrol. 2012 Jul;27(7):1103-9
9.Stefania Fagagnini,Henriette Heinrich,Jean-Benoît Rossel,Luc 
Biedermann,Pascal Frei,Jonas Zeitz,Marianne Spalinger,Edouard 
Battegay,Lukas Zimmerli,Stephan R. Vavricka,Gerhard 
Rogler,Michael Scharl,Benjamin Misselwitz,(2017) Risk factors for 
gallstones and kidney stones in a cohort of patients with 
inflammatory bowel diseases. PLoS ONE 12(10):e0185193. 
https://doi.org/10.1371/journal.pone.0185193 
10. David W. Kaufman,Judith P. Kelly,Gary C. Curhan, Theresa E. 
Anderson, Stephen P. Dretler,Glenn M. Preminger, and  David R. 
Cave,  Oxalobacter formigenes May Reduce the Risk of Calcium 
Oxalate Kidney Stones,  J Am Soc, Nephrol. 2008 Jun; 19(6): 1197–
1203 
11. Liebman M, Al-Wahsh IA., Probiotics and other key 
determinants of dietary oxalate absorption,  Adv Nutr. 2011 
May;2(3):254-60. 
12. Paul E, Albert A, Ponnusamy S, Mishra SR, Vignesh AG, 
Sivakumar SM, Sivasamy G, Sadasivam SG,Designer probiotic 
Lactobacillus plantarum expressing oxalate  decarboxylase 
developed using group II intron degrades intestinal  oxalate in 
hyperoxaluric rats, Microbiol Res. 2018 Oct;215:65-75 
13. Giardina S, Scilironi C, Michelotti A, Samuele A, Borella F, 
Daglia M,Marzatico F., In vitro anti-inflammatory activity of 
selected oxalate-degrading  probiotic bacteria: potential 
applications in the prevention and treatment of hyperoxaluria,  J 
Food Sci. 2014 Mar;79(3):M384-90
14.Turroni S, Bendazzoli C, Dipalo SC, Candela M, Vitali B, Gotti 
R, Brigidi P., Oxalate-degrading activity in Bifidobacterium 
animalis subsp.lactis: impact of acidic conditions on the 
transcriptional levels of the oxalyl coenzyme A (CoA) 
decarboxylase and formyl-CoA transferase genes,
Appl Environ Microbiol. 2010 Aug;76(16):5609-20.                  
15.Chai W, Liebman M.,Effect of different cooking methods on 
vegetable oxalate content, J Agric Food Chem. 2005 Apr 
20;53(8):3027-30  
16.Simpson TS, Savage GP, Sherlock R, Vanhanen LP.,Oxalate 
content of silver beet leaves (Beta vulgaris var. cicla) at  
different stages of maturation and the effect of cooking with 
different  milk sources, J Agric Food Chem. 2009 Nov 
25;57(22):10804-8.
17.Brogren M, Savage GP.,Bioavailability of soluble oxalate from 
spinach eaten with and without milk products, Asia Pac J Clin 
Nutr. 2003;12(2):219-24 
18.Carla G. Monico, and  Dawn S. Milliner, Genetic Determinants 
of Urolithiasis,  Nat Rev Nephrol. 2011 Dec 20; 8(3): 151–162. 
19.John A. Sayer,Progress in Understanding the Genetics of 
Calcium-Containing Nephrolithiasis,  J Am Soc Nephrol. 2017 Mar; 
28(3): 748–759
20.Filippova TV, Alyaev YG, Rudenko VI, Asanov AY, Gadzhieva ZK, 
Subbotina TI, Perekalina AN,  [Genetic aspects of urolithiasis],
Urologiia. 2016 Apr;(2 Suppl 2):95-102 
21.https://www.uwhealth.org/urology/genetic-heritability-for-
kidney-stones/11212
22.Jana Pavlíčková , Jiří Zbíral , Michaela Smatanová , Petr 
Habarta, Pavlína Houserová & Vlastimil Kubáň,Uptake of thallium 
from naturally-contaminated soils into vegetables, Food Additives 
& Contaminants Volume 23, 2006 - Issue 5