Nutrition Hotline
by Reed Mangels, PhD, RD
This issue's Nutrition Hotline addresses two concerns about soymilk: whether the body can absorb some calcium compounds better than others and if carrageenan in some brands of soymilk is dangerous. It also looks into the health benefits of a vegetarian diet for African-Americans.
QUESTION: “I use fortified soymilk as a source of calcium. The brand that I use is fortified with calcium carbonate. I read in Vegetarian Journal that calcium from soymilk is absorbed at only about 75 percent of the amount absorbed from cow's milk, but that study used soymilk fortified with tricalcium phosphate. Is the calcium from calcium carbonate better absorbed than the calcium from tricalcium phosphate?” C.S., via e-mail
ANSWER: Cheryl Sullivan, MA, RD, contacted White Wave, the makers of Silk Soymilk, a brand that is fortified with calcium carbonate. They reported that their product has not been tested specifically to see how well the calcium is absorbed; however, in studies of calcium sources, about 28 percent of the calcium in calcium carbonate is absorbed (Nutrition Reviews 1994; 57:221-232). This would mean that about 84 milligrams of calcium would be absorbed from a cup of calcium carbonate-fortified soymilk containing 300 milligrams of calcium.
Approximately 32 percent or 96 milligrams of calcium are absorbed from a cup of cow's milk (Am J Clin Nutr 1994; 59[suppl]:1238S-41S), compared to 24 percent or 72 milligrams absorbed from a cup of soymilk fortified with tricalcium phosphate. This suggests that calcium from soymilk fortified with calcium carbonate may be somewhat better absorbed than calcium from soymilk fortified with tricalcium phosphate, although these differences are fairly small. Many factors, including other foods, medications, age, and health, can affect absorption. However, we can certainly conclude that calcium-fortified soymilk is a good source of calcium.
Also, to maximize absorption, be sure to shake your soymilk well! The sludge at the bottom of some cartons of soymilk is probably calcium. If this is not incorporated into the soymilk by shaking, it gets discarded with the carton.
QUESTION: “I wanted to get your take on the use of carrageenan in products such as soymilk. I need as much info as I can gather in order to present it to my students who are freaking out about it!” M., via e-mail
ANSWER: Carrageenan is a product that is derived from red seaweed, a type of seaweed found in the Atlantic Ocean near Britain, Europe, and North America. It is used as a food additive to gel, thicken, and stabilize foods. Products that may contain carrageenan include some brands of soymilk, pie fillings, salad dressings, and chocolate products.
Recently, several websites have labeled carrageenan as dangerous, saying it can cause cancer in humans. These reports are based on studies that were mainly conducted on animals, although some have used cells from humans. These studies, however, have not used the type of carrageenan used in foods. They have used degraded carrageenan, which differs chemically from food-grade carrageenan. Degraded carrageenan is not approved for use in food products, although it has been used in Europe as a medication.
Some have expressed concern that, during the process of digestion, carrageenan is degraded into a harmful form. At this point, there is no evidence that this happens. Studies have shown that food-grade carrageenan in the digestive tract is either not degraded or not degraded in the same way as the harmful form of carrageenan.
The safety of carrageenan for use in foods has recently been assessed by the European Commission's Scientific Committee on Food; in the UK, by the Food Advisory Committee and by the Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment (COT); by the Joint FAO/WHO Expert Committee on Food Additives (JECFA); and by the U.S. Food and Drug Administration (FDA). All have concluded that the levels of carrageenan found in foods do not pose any hazard to health.
We will certainly follow reports of research in this area and share them with Vegetarian Journal readers, but, at this point, it does not appear that food-grade carrageenan should be avoided.
If you are interested in learning more about carrageenan, the British Nutrition Foundation website has a helpful fact sheet.
QUESTION: “Do you know of any study that has compared the longevity of African-American vegetarians to African-Americans who are not vegetarians? ...Common diseases that disproportionately afflict African-Americans are exactly those that are less common in vegetarians.” J.A., MN
ANSWER: There have only been a few studies that examined African-American vegetarians, and none looked at longevity. Results of these studies do suggest that African-Americans benefit from vegetarian diets. All studies have been conducted on black Seventh-day Adventists. Benefits of a vegetarian diet include lower weight,1 lower blood pressure,1,2 and less hypertension.1,2 Additional benefits include lower levels of blood cholesterol, triglycerides, and LDL-cholesterol.3 Interestingly, African-American vegans have lower total cholesterol and LDL-cholesterol than African-American lacto-ovo vegetarians.4 Blood pressure does not appear to be affected by the type of vegetarian diet.4 Diets of African-American lacto-ovo vegetarians tend to be lower in fat, cholesterol, and calories than those of African-American non-vegetarians.1
While African-American vegetarians in some of these studies tended to have higher blood pressure than whites, they still had a lower prevalence of hypertension and lower average blood pressure than did African-American non-vegetarians.1,2
Given the current high rates of heart disease and hypertension among African-Americans, it certainly seems reasonable to turn to vegetarian diets as one way of reducing risk and of possibly increasing life expectancy.
References
- Melby CL, Goldflies DG, Toohey ML. 1993. Blood pressure differences in older black and white long-term vegetarians and nonvegetarians. J Am Coll Nutr 12:262-69.
- Melby CL, Goldflies DG, Hyner GC, et al. 1989. Relation between vegetarian/nonvegetarian diets and blood pressure in black and white adults. Am J Publ Health 79:1283-88.
- Melby CL, Toohey ML, and Cebrick J. 1994. Blood pressure and blood lipids among vegetarian, semivegetarian, and nonvegetarian African Americans. Am J Clin Nutr 59:103-109.
- Toohey ML, Harris MA, Williams D, et al. 1998. Cardiovascular disease risk factors are lower in African-American vegans compared to lacto-ovo vegetarians. J Am Coll Nutr 17:425-34.
