Soy Good or Not Soy Good?

Even dietitians occasionally question their recommendations due to myths or fears circulating in the public. People read all sorts of propaganda online, and some of it is so convincing it can be hard to decipher fact from fiction.

Recently, I’ve heard a lot about soy foods. When I asked people about the source of their beliefs, their response was often “I don’t know, but I know I heard it somewhere” or “I’m not sure, but I heard it wasn’t good so I just avoid it.” So, I went searching for a more concrete answer.

I first turned to Google to see what was being said, and I found some pretty scary stuff out there. The problem is, none of what I found was backed up by solid research. One person went so far as to call soy, and all beans for that matter, “evil food.” I then turned to more research driven search engines such as PubMed, Google Scholar, and Web of Science. All I could find there were studies reporting soy’s positive influence on health. No wonder there is so much confusion!

So, what’s with all of the contradiction? A lot of what it has to do with is the amount and type of research out there. But hopefully by the end of this article things will be a bit more clear.

The back story…

To start, soy is a plant native to Asia that has been around for at least 5,000 years (that’s a looooong time). It has been a part of Chinese culture since the 2^nd century, and came to the US in the 1700’s. It is an economically important crop, is easy to grow, and provides an excellent source of protein for both humans and animals. In 1999, soy crops made up 27% of the total crop area in the United States¹.

Whole soy (like edamame) is chiefly made up of proteins, isoflavones, lecithin, fiber, and phosophlipids (see diagram below)². Soy is an excellent form of vegetable protein, but is not a complete protein because it lacks the essential amino acid methionine¹.  Isoflavones are compounds chemically similar to estrogen in the body – also called phytoestrogens (no boys, it will not give you man-boobs). The two main types of isoflavones are genestein and daidzen. Lecithin is a preservative found naturally in a number of different foods as well as soy foods. Fiber is found mainly in fruits, vegetables and whole grains, and to learn more read my previous blog entry.

 

Soy components not in equal proportions as indicated. Image only for demonstration.

 Cardiovascular Disease

According to the Mayo Clinic², numerous human studies report that adding soy protein to the diet can moderately reduce blood cholesterol levels and low-density lipoprotein (LDL) levels - the "bad" cholesterol. Furthermore, according to the majority of these studies, soy’s heart healthy effects can be linked to phytoestrogens found naturally in the plant.

Cancer

The estrogen found in our bodies is linked to the progression of hormonally-sensitive cancers (like breast and prostate cancer)³. In these types of cancers tumors grow when estrogen locks to estrogen receptor cells, causing a series of signals that instruct tumors to grow. However, phytoestrogens are weak imitations of estrogen, and when it comes to tumor growth some studies indicate phytoestrogens can help slow tumor growth. They do this by locking with estrogen receptors and blocking estrogen from ever attaching to receptor sites³. However, other studies like that of Dr. Bill Helferich, found that injecting genestein into mice made breast tumors grow.⁴ It is important to note is that these studies are not as influential on dietary recommendations because they occur in rodents and in isolated periods of time. So, as of now, natural soy (tofu, edamame, milk, temphe, miso ect.) is thought to have a protective effect against breast and prostate cancer.

If you take a look at studies of Asian populations, where soy is a regular part of the diet, researchers have found that cancer risk is about 24% lower in people who ate more soy when compared to those who ate less.³  Some studies suggest that the protective effects of soy for breast cancer in Asian cultures is due to the fact that consumption of soy begins at an early age, when breast tissue is still developing ³. The jury is still out on that fact, but it will be interesting to see if adding soy into the diet early on has any benefit.

Additionally, when it comes to cancer, natural soy has antioxidant properties, which help reduce the formation of cancer-causing free radicals.^{3, 5}

Menopause

Because of soy’s high concentration of phytoestrogens it was, at one time, believed that soy supplements were effective. However, an article published in the New York Times states that American Menopause Foundations and the North American Menopause Society suggest that moderate soy supplementation is ineffective in the treatment of menopause.⁴

Pediatrics

Many parents are naturally concerned about everything they feed their child, and that’s a good thing. Most children go through a “picky” phase making meal-time and nutrient intake challenging. So making sure your child gets enough nutrition can be nerve racking! Furthermore, with the prevalence of food allergies parents are more aware than ever of potential allergens in our food supply.

Natural soy is an excellent source of protein and can be a good alternative when allergies persist. However, if your child is allergic to peanuts there is some evidence to suggest that they may also be allergic to soy milk as well.¹ So why not just supplement right away with almond or rice milk? A great idea, but the problem is bioavailability, rather, how much your child actually ends up absorbing. ¹

When it comes to available nutrition, nothing is better than cow’s milk- see diagram below. But if your child has an allergy, or you prefer non-animal sources, I would first choose fortified soy milk, then almond milk, then rice milk. But always choose a fortified alternative to make sure they’re getting enough calcium to help bone development.

Milk/"Milk" Comparison chart (per 1 cup)*
	Calories	Fat/Saturated	Protein	Carbo- hydrate	Fiber	Calcium	Vitamin D
Cow’s	80-150 (nonfat to whole)	0.5-8 g fat/ 0-5 g saturated	8-9 g	12-13 g	0 g	30% DV	25% DV
Goat's	90-150 (nonfat to whole)	2.5-8 g fat/ 1.5-5 g saturated	7-8 g	9-12 g	0 g	30% DV	Up to 30% DV
Soy	60-130	2-6 g fat/ 0-0.5 g saturated	4-12 g	5-15 g	0-4 g	4-30% DV	Up to 30% DV
Rice	110-120	2.5 g fat/ 0 g saturated	1 g	20-24 g	0 g	2-25% DV	Up to 25% DV
Almond	60-80	2.5-4.5 g fat/ 0-0.5 g saturated	2-9 g	5-11 g	0-4 g	20-30% DV	Up to 25% DV
Hemp	110-130	3-7 g fat/ 1 g saturated	4-5 g	6-20 g	1 g	2-46% DV	Up to 25% DV
*Data reflects a sample of 20 readily available milks/“milks.” For plant-based “milks,” we included only plain varieties—both sweetened and unsweetened, when available.  Source: eatingwell.com6

(Tip: shake the container before pouring any calcium fortified juice or milk. Calcium is a heavy element and will often sink to the bottom of the container reducing the amount of calcium you get per serving!)

Challenges in research

Every piece of literature I uncovered touting the benefits of soy stressed the importance of further research to determine weather or not soy can be recommended as a way to help prevent cancer. At this time the belief is that natural soy (tofu, edamame, milk, temphe, miso ect.) may help protect against cancer when eaten in moderation.⁵

As referenced earlier in the article, several rodent studies have suggested that soy might encourage tumor growth. The difficulty with animal studies is that this type of research occurs in a vacuum, where rodent subjects are fed (typically injected) with only one type of food for defined period of time. While this type of research is really important, we cannot make the direct link to humans because, well, rats aren’t humans, we don’t live in cages, and we eat a lot of different things.

According to the International Agency for Research on Cancer (IARC)⁷, several types of epidemiological studies (human studies) are considered when determining the cancer-causing effects of agents in our environment. While I won’t bore you with them all, the IARC suggests that intervention studies can provide strong evidence in determining something as cancer causing, much like the studies linking smoking cessation to lung cancer did. But this is not as easy when conducting dietary studies since our diets are so variable.

In the end…

It is my guess that all of the fear and confusion comes from the varied results among research. It’s natural to want to “air on the side of caution” when it comes to preventing cancer, especially since their appears to be some things we still don’t know.

However, when in doubt, I’m going to remind myself that soy has been around for over 5,000 years! And, as of now, research suggests that soy may help prevent heart disease and cancer.

Bottom line: Consume natural forms of soy knowing that you’re doing something good for yourself. If you want to prevent cancer DO NOT use any form of tobacco ever (that includes cigarettes, cigars, and chewing tobacco), eat a variety of fruits and vegetables, limit meat, exercise, and visit your doctor regularly.

1.     Friedman, Mendel; Brandon, David L. (2001). Nutritional and Health Benefits of Soy Proteins. Journal of Agricultural and Food Chemistry, 49, (3), 1069-1086.

2.     Natural Standard: The Authority on Integrative Medicine. (2012). Soy (Glycine max). Retrieved from http://www.mayoclinic.com/health/soy/NS_patient-soy

3.     McCullough, Marji ScD, RD. (2012). The Bottom Line on Soy and Breast Cancer Risk. Retrieved from http://www.cancer.org/cancer/news/expertvoices/post/2012/08/02/the-bottom-line-on-soy-and-breast-cancer-risk.aspx

4.     Tarkan, Laurie. (2004, August 24). As a Substitute for Hormones, Soy is Ever More Popular, but Is It Safe?. The New York Times. Retrieved from http://www.nytimes.com/2004/08/24/health/as-a-substitute-for-hormones-soy-is-ever-more-popular-but-is-it-safe.html?pagewanted=all&src=pm

5.     Miller, Paige F. PhD, MPH, RD; Snyder, Denise C. MS, RD, CSO, LDN. (2012). Phytochemicals and Cancer Risk: A Review of the Epidemiological Evidence. Nutrition in Clinical Practice,  27 (5), 599-612.

6.     Meredith Corporation. (2013) A Buyers Guide to Milk Alternatives. Retrieved from   http://www.eatingwell.com/healthy_cooking/healthy_cooking_101/shopping_cooking_guides/a_buyer_s_guide_to_milk_part_ii

7.     The World Health Organization International Agency on Research for Cancer. (2006). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Preamble. Pg. 8, Lyon, France.

The Real Master Cleanse

As a dietitian some of my most regularly, pardon the suggestion, doled out advice is related to the subject of fiber and bowel health. Fiber is important to include in our daily diets, but some of you may be wondering why we need it and what it is. 

Lesson One – Fiber does way more than help us stay regular. 

Fiber is known to reduce our risk of heart disease, diabetes and some cancers - in addition to promoting weight loss.(1) And, as if that weren’t enough, a high fiber diet (consisting of 25 grams or more of fiber a day) has also been shown to reduce the incidence of death! That’s right, in a study published in the Archives of Internal Medicine men and women who ate a high fiber diet, mostly from whole grains, had a lower risk of death. With the popularity of low carb and gluten free diets grains have developed a bad rap. But remember, grains are REALLY important to include in our diets. Not to mention they’re delicious. 

Lesson Two – Eating Fiber is the best way to keep your gut healthy. 

Despite what your naturopath or that cleansing advertisement tells you, resting your bowels is never a good idea!  I always hear people talking about going on a “juice fast” or a “bowel cleanse” to promote health and general wellbeing. But when I went poking around for research I could barely find anything - which is usually my first clue that something is not right.

What I found was a review in the American Journal of Gastroenterology(2) stating that there is little published about the benefits of cleansing, but a wealth of information about its adverse effects (take a moment to Google bowel perforation, YIKES!). In this case, I’d rather stick to what I know, and what I know is that fiber promotes regular bowel movements and prevents intestinal disease.

Fiber creates an environment in our bowels where healthy bacteria can flourish. We need bacteria in our colon to prevent unhealthy bacteria from invading our gut.(3) Furthermore, the slower our bowels move the better. This gives time for healthy bacteria to do its thing, and ensure we get all we can out of the food we eat. Diets that are low in fiber usually move through our guts too quickly, not to mention they are typically higher in calories and sugar. If you’re juicing, for example, you can almost guarantee that you’re taking in more sugar than you would if you were to eat a regular high fiber diet. Not to mention you’re probably starving between meals.

Remember, your intestines are muscles too. Just like your biceps and abs, you need to work them out. Eating fiber is a great way to make sure your gut stays in shape! 

Third Lesson – Nutrition can be confusing. 

Fiber is a form of carbohydrate, and if I teach you anything, it is that carbohydrate is not a dirty word. Formally, dietary fiber consists of the structural and storage polysaccharides and lignin in plants that are not digested in the human stomach and small intestine (4). Say what? Basically, fiber is the part of plants that we don’t digest.

There are generally two types of fiber, soluble and insoluble. Soluble fiber helps us feel full, promotes bowel health, and reduces cholesterol. Insoluble Fiber absorbs water and helps produce soft stools.(5) For our purposes let’s just say their both good. And good news is, most high fiber foods are made up of both types of fiber.

You may see food labels that say “Added Fiber”, “Dietary Fiber”, or “Total Fiber”. Dietary fibers are all of the non-digestible carbohydrates found naturally in the foods that we eat. Added fibers (also called functional fibers) are isolated, or manufactured, fibers that are beneficial to humans and typically added to foods. (6) And total fiber is the sum of dietary and added fiber (4). Typically, breads and cereals high in fiber are high in fiber because of added fiber; which isn’t bad, it’s just something to think about.

Final Thoughts 

My feeling is that people generally turn to juice fasts, low carb diets, and other fad diets because their regular eating habits don’t make them feel good. However, the solution is never the most extreme option, and the results are usually mental and temporary. I can guarantee that you’ll feel better if you eat healthier foods regularly, steer clear of high fat foods, large portions, alcohol, and sweets. So take a look at your regular diet and start making small changes there. Rather than spend all that cash on silly juices call a dietitian for a more permanent fix.

Bottom line, again pardon the suggestion, try to eat whole grains, vegetables, and fruits as much as you can. And as you increase your fiber intake make sure to drink plenty of water. 

1.  Park, Yikyung Sc.D; Subar, Amy F. PhD.; Hollenback, Albert  PhD. Et al. (2011). Dietary fiber intake and mortality in the NIH-AARP Diet and Health Study. Arch Intern Med, 171(12): 1061–1068.

2.  Acosta, Ruben D., MD; Cash, Brooks D. MD, FCAP, FACG, AGAF (2009). Clinical Effects of Colonic Cleansing for General Health Promotion: A Systematic Review. Am J Gastroenterol 2009; 104:2830–2836.

3.  Salvin, Joan (2013). Fiber and Prebiotics: Mechanisms and Health Benefits. Nutrients, 5, 1417-1435.

4.  ADA Reports (2002). Position of the American Dietetic Association: Health implications of dietary fiber. Journal of the American Dietetic Association, 102 (7): 993-1000.

5.  Roche Dietitians (2001). Clinical Indications of Drug-Nutrient Interactions and Herbal Use: A Guideline for Practitioners. Illinois, Roche Dietitians, L.L.C.

6.  Johnson, Kimball MD (2012). The Benefits of Fiber for Your Heart, Weight, and Energy. WebMD Retrieved From http://www.webmd.com/diet/fiber-health-benefits-11/compare-dietary-fibers.