Personal update: I have, for all intents and purposes, finished the article on soy that I worked on for over 3 months. But, it is not yet live. I’m hoping it will be soon. In the meantime, I’m getting to the back log that built up during the time I was working on it.

And without further ado, here is some information on hair loss and iodine:

QuasiVegan’s post Hair Loss on the Vegan Diet, brought my attention to the fact that thyroid problems can cause hair loss, something that I was not aware of previously.

I have updated the VeganHealth.org article, Hair Loss, with the following:

Summary: Occasionally, women who become vegetarian or vegan report experiencing hair loss. If there is a dietary cause, the most likely are rapid weight loss, thyroid problems, or iron deficiency. Zinc deficiency and not getting enough of the amino acid lysine could also be culprits.

According to Mayo Clinic, an overactive or underactive thyroid gland can lead to hair loss. Upon going vegetarian or vegan, people might increase their soy intake. Soy can affect the thyroid, especially when iodine levels are not adequate or someone is predisposed to thyroid problems. Making sure you get enough iodine, by taking 75 to 150 µg per day from a supplement, should prevent any hair loss problems that could be due to iodine or soy. If you are predisposed to thyroid problems, limiting soy might also help.

A study from the USA was released Feb 25 showing that consuming up to 1/2 serving of soyfoods per day did not increase breast cancer recurrence among women previously diagnosed with breast cancer, and was even associated with lower mortality among such women.

The Women’s Healthy Eating and Living (WHEL) study is a randomized controlled trial of a high fruit/vegetable/fiber and low fat dietary intervention in early stage breast cancer survivors in the USA. It had a median follow-up of 7.3 years from the time of enrollment. Soy intake was measured post-diagnosis (median 2 years, range: 2 months to 4 years) using a food frequency questionnaire that included specific items for “Meat Substitutes (such as Tofu, Veggie Burgers),” and “Soy Milk”, as well as an opportunity to include other soy foods and supplements.

Isoflavone intake (the marker for soy) was unrelated to the risk of recurrence regardless of hormone receptor status or Tamoxifen use. No significant increased or decreased risk was associated with any specific level of intake. Risk of death tended to be lower as isoflavone intake increased (p for trend=0.02). Women at the highest levels of isoflavone intake (>16.3 mg/day isoflavones; equivalent to at least 1/2 cup soymilk or 2 oz tofu) had a non-significant 54% reduction in risk of death compared to the lowest quintile of soy intake.

The authors state:

Our study is the third epidemiological study to report no adverse effects of soy foods on breast cancer prognosis. These studies, taken together, which vary in ethnic composition (two from the US and one from China) and by level and type of soy consumption, provide the necessary epidemiological evidence that clinicians no longer need to advise against soy consumption for women diagnosed with breast cancer.

Reference

Caan BJ, Natarajan L, Parker BA, Gold EB, Thomson CA, Newman VA, Rock CL, Pu M, Al-Delaimy WK, Pierce JP. Soy Food Consumption and Breast Cancer Prognosis. Cancer Epidemiol Biomarkers Prev. 2011 Feb 25. Link

Just added to Another Internet Soy Article:

A 2010 study found that low (1.64 mg/day) or high (61.7 mg/day) isoflavone consumption for 8 weeks did not significantly affect semen volume or sperm concentration, sperm count, total motile sperm count, or sperm motility in a sample of 32 healthy adult males (15).

62 mg is the amount of isoflavones found in about 2.5 cups of soymilk.

Thanks, Marco!

Reference

15. Beaton LK, McVeigh BL, Dillingham BL, Lampe JW, Duncan AM. Soy protein isolates of varying isoflavone content do not adversely affect semen quality in healthy young men. Fertil Steril. 2010 Oct;94(5):1717-22. Link

Just added two paragraphs to Another Internet Soy Article on VeganHealth.org:

Thyroid

A 2010 study found that 3 years of a daily dose of 54 mg of the isoflavone genistein, in postmenopausal women, did not harm the thyroid in any way compared to placebo (12). They measured 11 different thyroid health parameters. This is the amount of genistein contained in about (14.7*) 4 cups of soymilk, and the amount of isoflavones you would find in about (8.7*) 2 to 3 cups of soymilk (13).

*Correction: I was contacted by a soy expert who said, “54 mg genistein is the amount found in about 100 mg total isoflavones from soyfoods. One serving of a traditional soyfood, such as a cup of soymilk made using the whole soybean (think Silk) provides about 25 mg isoflavones. So 4 cups will provide 54 mg genistein.” Upon closer inspection of the USDA list of isoflavones in food, I noticed more entries for soymilk and a range of genistein from 1.5 to 6.7 mg per 100 g for genistein and a range of 2.6 to 10.7 mg per 100 g for total isoflavones.

Sperm Characteristics

In a 2008 study on soy intake and sperm characteristics, researchers found that sperm counts among men with higher soy intakes did not differ from those who ate no soy. Men who ate more soy had lower sperm concentrations, but this was due to a higher semen volume; this finding was more pronounced in overweight and obese men than among lean men (14).

References

12. Bitto A, Polito F, Atteritano M, Altavilla D, Mazzaferro S, Marini H, Adamo EB, D’Anna R, Granese R, Corrado F, Russo S, Minutoli L, Squadrito F. Genistein aglycone does not affect thyroid function: results from a three-year, randomized, double-blind, placebo-controlled trial. J Clin Endocrinol Metab. 2010 Jun;95(6):3067-72. Link

13. USDA Database for the Isoflavone Content of Selected Foods Release 2.0. (2008) Link

14. Chavarro JE, Toth TL, Sadio SM, Hauser R. Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. Hum Reprod. 2008 Nov;23(11):2584-90. Link

A new paper has been published on the feminizing effect of soy on men:

Messina M. Soybean isoflavone exposure does not have feminizing effects on men: a critical examination of the clinical evidence. Fertil Steril. 2010 May 1;93(7):2095-104. Epub 2010 Apr 8. Review.

You can read the abstract at the link above, and here is a little more info from the June 2010 issue of Soy & Health.

Dear Jack,

I recently got into a debate with a friend who insisted that quinoa, hemp, amaranth, buckwheat, and spirulina are all complete proteins. When I told him soy is the only complete vegetarian protein, he told me he avoids all soy due to its negative effect on men’s health. I wondered where this guy learned this and a quick google search on vegetarian complete proteins got me here. I checked out your page on protein. That chart listing the essential amino acids in so many plant foods made me realize that in fact many plant foods do contain all the essential amino acids but at such low levels it’s hard to list them as ‘complete proteins’ in the true meaning intended. So my take is that the only vegetarian protein that comes close to really being a complete protein (meaning it has essential amino acid levels similar to those of animal proteins) is soy. Would you agree?

Answer:

[As an aside, the research to date indicates that moderate amounts of soy do not harm men’s health.]

Because this question about complete proteins comes up on a regular basis, I decided to do some number crunching to get to the bottom of it. Mind you, there are many more numbers to crunch if someone wanted to take the time, but I think I’ve covered enough to draw some conclusions.

I see two ways of looking at the question of whether a food has complete protein:

If you look at Table 3 of Where Do You Get Your Protein?, you will see what it takes to meet the RDA for each EAA for a variety of foods.

I have taken some of the data from Table 3 and constructed the table below to look more closely at what foods might contain a “complete protein”. In the table below, the numbers in the right-hand column represent the following equation:

Where:

From the chart above, it appears that tuna is the most complete protein with a range of only .4 servings and only 1.7 servings required to meet the RDA for all the EAA. Chicken, beef, edamame (whole, cooked soybeans), lentils, and pinto beans all do quite well. I think it’s fair to consider all of them a “complete protein”. Tofu, milk, quinoa, soy milk, and eggs do significantly better than most grains and nuts which have a much wider range.

As for spirulina…not so much.

One thing to note about this is that all the numbers depend on the serving size. I tried to pick what I thought were reasonable (or common) serving sizes for each food (you can see what they are in Table 3).

The USDA database has a lot of specific entries for some of the food categories above (like ground beef). I chose what looked like a common version of the food, but I did not average the data across more than one version.

As for the remaining, supposed complete proteins mentioned in the original question above, here is what I found:

Amaranth
The USDA lists 9 g of protein per cup of cooked amaranth. That’s a good amount when compared to other grains, but I’m not sure if it’s as easy to eat a cup of amaranth as a cup of, say, rice or corn. The USDA had no amino acid info.

Hemp
There was no info in the USDA database. I found many sources saying that it is a complete protein but none that I know to be reliable.

Nutritional yeast
No info in the USDA database. According to this site, it has 9 g of protein per 3 tbsp serving. That’s a decent amount, but I’m not sure if we can trust that info.

In conclusion, edamame, lentils, and pinto beans fared pretty well with chicken and beef for being a complete protein. Tofu, soymilk, and quinoa were on par with eggs and milk.

A month old now, but I finally got around to sending out a link to this article Ginny Messina wrote, Hexane in veggie burgers: little science behind the claims.

Article from Men’s Fitness. Link.

Thanks, Matt!

I just updated Another Internet Soy Article with the following:

A 2009 report from the Shanghai Breast Cancer Survival Study showed that women with a prior diagnosis of breast cancer (including estrogen-positive), who ate more soy, had lower rates of death and cancer recurrence (12). The study followed women for an average of 3.9 years after a diagnosis of breast cancer. The researchers measured a beneficial effect of up to 11 grams of soy protein per day. Table 3 shows the results.

12. Shu XO, Zheng Y, Cai H, Gu K, Chen Z, Zheng W, Lu W. Soy food intake and breast cancer survival. JAMA. 2009 Dec 9;302(22):2437-43.

A study was just published showing that Chinese women living in Singapore who ate more soy had a reduced risk of hip fractures. Compared with women in the lowest one-fourth of intakes for tofu, soy protein, and isoflavones, those in all three of the higher intake categories had a 21%–36% reduction in risk. Soy did not show any benefit for men.

Koh WP, Wu AH, Wang R, Ang LW, Heng D, Yuan JM, Yu MC. Gender-specific associations between soy and risk of hip fracture in the Singapore Chinese Health Study. Am J Epidemiol. 2009 Oct 1;170(7):901-9. Epub 2009 Aug 31.