Jack Norris RD

I just updated VeganHealth.org with information from an April 2009 review on soy infant formulas (link). Here is an excerpt from the paper:

“Even though soy isoflavones can bind and activate [estrogen receptors (ER)], they do not behave like typical estrogen agonists but rather as selective ER modulators and, in addition, have many other actions that are ER independent, eg, tyrosine kinase inhibition. It is unfortunate that soy isoflavones have been called “phytoestrogens,” because they are not estrogens and are not truly estrogenic at nutritionally relevant concentrations. The weak isoflavone potency for activating the ERs combined with competition with endogenous estrogens for the ERs make isoflavone-related ER activity minimal when fed in amounts similar to those found in [soy formula], even when fed during early development. Moreover, although some studies have shown similar gene expression profiles for genistein (the major soy isoflavone) and [estrogen] in some tissues in vitro and in vivo, ingestion of soy foods results in a complex mixture containing hundreds of phytochemicals and peptides being introduced to the gastrointestinal tract, many of which are absorbed and have biological actions. This situation is not unlike the mixture of phytochemicals found in a typical meal containing a mixed salad and vegetables.”

I just updated Another Internet Soy Article on VeganHealth.org with information on breast cancer. Link. It’s too much to reprint here but it is all good news, with decent evidence that eating soy in moderate amounts can actually decrease the risk of breast cancer. I wouldn’t go so far as to claim that we know it does, but at the very least we can conclude that it doesn’t increase the risk for breast cancer.

Ginny Messina has a blog post on a just-released study putting people on a vegan, Atkins-like diet.

The study is The Effect of a Plant-Based Low-Carbohydrate (”Eco-Atkins”) Diet on Body Weight and Blood Lipid Concentrations in Hyperlipidemic Subjects.

I just added the following to the VeganHealth.org article on disease markers of vegans, and thought it might be of some interest to readers:

Recent research has shown that a BMI of 22.5 to 25.0 is associated with the lowest mortality rate. It has been known for some time that a lower BMI has been associated with an increased risk of death, but that was thought to be due mostly to smoking-related diseases. A 2009 meta-analysis of 900,000 people found that even in those who never smoked, there is a slight increase in mortality below a BMI of 22.5. (1)

The excess mortality below 22.5 has not been explained. One theory is that the excess mortality might be due to lower fat-free mass, which would most likely be lower muscle mass (though could also technically be bones, or even some organs). (1, 2) Studies on BMI and mortality to date have not differentiated between fat and fat-free body mass.

1. Prospective Studies Collaboration, Whitlock G, Lewington S, Sherliker P, Clarke R, Emberson J, Halsey J, Qizilbash N, Collins R, Peto R. Body-mass index and cause-specific mortality in 900 000 adults: collaborative analyses of 57 prospective studies. Lancet. 2009 Mar 28;373(9669):1083-96.

2. Wändell PE, Carlsson AC, Theobald H. The association between BMI value and long-term mortality. Int J Obes (Lond). 2009 May;33(5):577-82.

Alpha-linolenic acid (ALA) is the main omega-3 fatty acid found in plant foods, and it is found in large amounts in flax seeds. A number of studies have found a link between ALA and prostate cancer, but others have not. Until recently, the best review of the literature claimed that ALA does not cause prostate cancer. I thought its logic was sound, but it came from the Flax Council of Canada.

Now a new meta-analysis says that ALA does not cause prostate cancer. The abstract states:

When examined by study type (ie, retrospective compared with prospective or dietary ALA compared with tissue concentration) or by decade of publication, only the 6 studies examining blood or tissue ALA concentrations revealed a statistically significant association. With the exception of these studies, there was significant heterogeneity and evidence of publication bias. After adjustment for publication bias, there was no association between ALA and prostate cancer (RR: 0.96; 95% CI: 0.79, 1.17).

I’ve updated the VeganHealth.org article Omega-3 Fatty Acid Recommendations for Vegetarians with this information.

Nothing major, but I just updated the vitamin D page of VeganHealth.org with results from a study on vitamin D supplementation in older people. It’s short, so I will just cut and paste it here.

Older People

As mentioned in the recommendations, elderly people need 30 minutes a day of direct sunlight in order to produce adequate vitamin D.

A 2009 study from Ireland showed that people aged 64 years or older needed 15 mcg (600 IU) per day to bring vitamin D levels from an average of 55 nmol/L to 74 nmol/L. The researchers estimated that it would take about 40 mcg (1600 IU) per day to raise 97.5% of the participants’ vitamin D levels to 80 nmol/L.

Although some researchers recommend maintaining vitamin D levels at 80 nmol/L, there is not enough evidence to know that there is much of a difference between 74 and 80 nmol/L. For this reason, the recommendation of 25 mcg (1,000 IU) should suffice for people aged 64 and older.

In April, a cross-sectional study was published looking at the bone mineral density (BMD) of vegan, Buddhist nuns in Vietnam:

Ho-Pham LT, Nguyen PL, Le TT, Doan TA, Tran NT, Le TA, Nguyen TV. Veganism, bone mineral density, and body composition: a study in Buddhist nuns. Osteoporos Int. 2009 Apr 7. [Epub ahead of print]

The nuns were lifelong and mostly vegan (some ate some dairy). They were matched with meat-eaters from the community. Participants were 50 to 85 years old. The nuns had the same BMD as the meat-eaters, while only eating about half the calcium: 330 mg per day vs. 682 mg for the meat-eaters. The researchers reported that the osteoporosis rates in these groups were about the same as in the greater population (approximately 20%).

Cross-sectional studies are very limited in their ability to determine cause-and-effect. We do not know if there were nuns who stopped being vegan after getting osteoporosis. It seems that the researchers could have made an effort to investigate this possibility, but they didn’t report that they did.

While this was good news for these nuns, it concerns me that the take home message is that vegans only need 300 mg/day of calcium.

A more relevant study – the most important to date on vegan bone health - is a 2007 analysis from EPIC-Oxford which found that vegans had higher rates of fracture than those in other diet groups. When they adjusted for calcium intake, they found that vegans who ate 525 mg of calcium per day had the same fracture rates as the other diet groups. This was a prospective study which means they followed vegans (and other diet groups) through time, which is a better way to find associations than are cross-sectional studies. It is the only prospective study ever done on vegan bone health.

To date, the best evidence shows that vegans should get at least 525 mg of calcium per day. I recommend at least 700 mg for adults and 1,000 mg for teens.

For more detailed information on vegans, calcium, and vitamin D click here.

It has long been thought that exercise is good for bones because the stress stimulates the bones to become stronger. Heavier people generally have higher bone mineral density (BMD), presumably due to the higher stress put on their bones.

Some time ago, I was giving a talk and mentioned that exercise is good for bones. Someone asked if you need to exercise your upper body in order for bones in your upper body to benefit from exercise. I didn’t know the answer; it didn’t seem unreasonable to me that any exercise could stimulate increased BMD via hormones circulating throughout the entire body.

I finally got around to looking into it today. I found a number of abstracts of experiments and meta-analyses looking at whether exercise improves BMD. Most indicated that exercise does improve BMD in certain spots, especially the hip and spine.

I only found one study that compared upper body exercise to lower body exercise:

Winters-Stone KM, Snow CM. Site-specific response of bone to exercise in premenopausal women. Bone. 2006 Dec;39(6):1203-9. Epub 2006 Jul 28.

People who did upper and lower body exercise had more improvement in their lower back BMD compared to people who only did lower body exercise. Unfortunately, it appears that they didn’t measure the spine in the upper back or other upper body areas which would have been interesting information.

This is just one study and I don’t think it’s conclusive, but so far it appears that at least some of your bones will benefit from doing upper body resistance exercise in addition to lower body exercise.

I just read a very engaging article about vitamin D (and that is saying a lot, I find most nutrition articles to be drowse-inducing). It is an interview with one of the world’s foremost vitamin D experts, Michael Holick. It is free on the web here.

A quick summary of the main points:

- 30 to 80% of the US population is vitamin D deficient.
- Vitamin D can protect against cancers, autoimmune diseases, infections, and bone problems.
- If you live north of Atlanta, your skin can’t make vitamin D from November through March.
- Both children and adults need 1,000 IU a day to keep their vitamin D levels above 30 ng/ml (about 75 nmol/L), which is the most healthy level.
- You need massive amounts of vitamin D to overdose. 5,000 IU per day, indefinitely, is probably safe.
- Vitamin D2 is as effective as D3.
- The sun is the most efficient way to receive vitamin D and may have important health benefits beyond vitamin D production.

For sun exposure, Dr. Holick says:

“I typically recommend people go out for a period of time—depending on the time of the year, the time of day, the latitude, and the degree of skin pigmentation—if you know you’re going to get a mild sunburn after 30 minutes, I typically recommend about 10, no more than 15, minutes of arms and legs exposure, or if you’re in a bathing suit, abdomen and back exposure as well, 2 to 3 times a week. Always wear sun protection on your face because that’s the most sun-damaged area and it’s only about 9% of your body surface, so it doesn’t provide you with that much vitamin D. Go out, enjoy yourself, get some sensible sun exposure, then put sunscreen on if you plan to stay out for a longer period of time. People with a higher degree skin pigmentation, such as African Americans, are walking around with an SPF of 8 to 15. That’s why they need to be exposed for much longer periods of time and why people of color are at especially high risk of having vitamin D deficiency.”

I have just updated VeganHealth.org with info on vegetarians’ vitamin D levels from the Adventist Health Study-2 which were recently released.

The good news is that vegetarians were no worse off than non-vegetarians. The bad news was that many of them were deficient, especially African Americans.

You can read more here.

And make sure you are following the vitamin D recommendations.