Archive for the ‘Bones’ Category

Protein Intake and Bone Health

Thursday, December 3rd, 2009

A meta-analysis looking at protein intake and bone health was published this month in the American Journal of Clinical Nutrition (1).

In terms of bone mineral density (BMD), the authors reported:

“Overall, there was very little evidence of a deleterious influence of protein intake on BMD, with most cross-sectional surveys and cohort studies reporting either no influence or a positive influence. Thus, 15 cross-sectional surveys found a statistically significant positive relation between protein intake and at least one BMD site. However, 18 studies found no significant correlation between protein intake and at least one BMD site.

“The cohort studies also identified little evidence of any deleterious influence of protein intake on bone. … [N]o studies showed a significant increase in BMD loss with increased protein intake, and only one study showed a significant decrease in BMD loss with increased animal and total protein intakes.”

In terms of bone fracture rates, the authors reported:

“Overall, the [seven] cohort studies indicated either a benefit or no effect of protein intake on hip fracture relative risk, with only one study reporting a significant increase in risk with increasing animal protein intake and increasing animal to vegetable protein ratio. Three studies found a decreased relative risk of hip fracture with increasing animal, total, and vegetable protein intakes. Two studies found no significant association of animal protein with fracture risk, whereas 2 studies found no association of total protein with fracture risk. Last, 2 studies found no relation between fracture risk and vegetable protein.”

In summary:

“Overall, the weight of the evidence shows that the effect of dietary protein on the skeleton appears to be favorable to a small extent or, at least, is not detrimental. However, the long-term clinical importance of the effect is unclear, and a reduction in fracture risk was not seen. More research is required to resolve the protein debate. In the meantime the protein intakes and balance of different protein sources as indicated in the current healthy eating guidelines represent appropriate dietary advice.”

Reference

1. Darling AL, Millward DJ, Torgerson DJ, Hewitt CE, Lanham-New SA. Dietary protein and bone health: a systematic review and meta-analysis. Am J Clin Nutr. 2009 Dec;90(6):1674-92. Epub 2009 Nov 4.

Soy and Hip Fractures

Thursday, October 29th, 2009

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.

What Supplements Does a Vegan Dietitian Take?

Tuesday, October 27th, 2009

Updated January 2018

Every month or so, someone reads my recommendations for vegans, checks out some vegan multivitamins, and then writes me asking about the high levels (many times the RDA) of some individual vitamins in many of the vegan multivitamins.

B vitamins—including folic acid—and vitamin C can be very high in multivitamins.

There have been concerns that taking folic acid could be linked to cancer, but a 2013 meta-analysis found no link between folic acid and cancer in the many clinical trials that have been performed using large amounts of folic acid. (1)

I’m not aware of any risks in taking B vitamins and vitamin C in the amounts found in typical vegan multivitamins.

There’s also evidence that taking vitamin A—as retinol, retinyl palmitate, or retinyl acetate—can cause osteoporosis at typical amounts of 1,500 mcg (5,000 IU) found in vitamins. Vitamin A as carotenoids doesn’t cause osteoporosis and is what is typically found in vegan vitamins. See Vitamin A at the Linus Pauling Institute for more info.

I thought it might interest readers to hear what supplements I take:

Calcium
I drink a glass of calicum-fortified orange juice with my morning oatmeal.

Zinc
I take 10-13 mg of zinc per day depending on the supplement I currently have in stock.

Vitamin B12
I take half a Trader Joe’s High Potency B “50” tablet once a day. This provides 25 µg of vitamin B12. I also suspect I can use a bit extra riboflavin which this provides.

Iodine
Since I almost never eat seaweed, I take one-quarter of a 225 µg kelp tablet each day.

Vitamin D
During the warmer months (when sunburn is possible) I get out in the sun a lot, probably too much. During the colder months, I take a vitamin D supplement of 1,000 IU each day. Vitamin D2 supplements should be fine. I had my vitamin D levels tested in September of 2011 and they were at 34 ng/ml (84 nmol/l).

Vitamin A
I’m pretty good about eating yellow vegetables every day.

Omega-3s
I’m a bit of an anomaly so don’t adhere to my own recommendations. Around 2002, I had my blood clotting time tested. Being a vegan, I wanted to make sure I was getting enough omega-3s and that my blood wasn’t clotting too fast. Well, it turned out that it was actually clotting a bit too slowly. I’d been taking one teaspoon of flaxseed oil per day for a couple years and decided to stop. I’ve had my clotting time tested a number of times since then and it’s always a bit slower than normal. So for omega-3s, I’ll take a DHA tablet once in awhile, but by no means as often as I recommend for other vegans.

Creatine
I’m a recreational weightlifter, lifting three times per week with short but intense workouts. For a long time, I supplemented with creatine off and on, but I think I’m finally done with that. It might benefit elite vegetarian athletes, but I didn’t find any consistent enough results to justify the cost or inconvenience.

Reference

1. Martí-Carvajal AJ, Solà I, Lathyris D, Karakitsiou DE, Simancas-Racines D. Homocysteine-lowering interventions for preventing cardiovascular events. Cochrane Database Syst Rev. 2013 Jan 31;1:CD006612.

Vitamin D in Older People

Tuesday, May 19th, 2009

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.

Bone Mineral Density in Vegan Buddhist Nuns in Vietnam

Friday, May 8th, 2009

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.

Upper Body Exercise & Bone Density

Thursday, May 7th, 2009

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.