Soy

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February 11, 2000

Soy: FDA Takes Bean's Benefits to Heart

From The January issue of Herb & Dietary Supplement Report

In October, the FDA ruled that soy protein products can carry

cholesterol-lowering health claims on their labels. While the FDA's

ruling

is based on evidence from clinical trials, there is potential for the

consumer to be misled. Healthcare professionals must help consumers

understand the differences between soy products.

By Hoeckh, R.Ph.

Recently, the FDA ruled that manufacturers of soy protein products can

claim

on product labels that 25 g/day of soy protein, as part of a diet low in

saturated fat and cholesterol, may reduce the risk of coronary artery

disease. The FDA ruling is based on studies showing that dietary

consumption

of soy protein can lower total and low-density lipoprotein (LDL)

cholesterol

levels. The FDA reviewed approximately 40 human studies published

between

1976 and 1999. Some of the studies reviewed are summarized below.

* Researchers conducted a meta-analysis of 38 clinical trials on soy's

effects on cholesterol levels ( et al). Most of the studies

included

both men and women, while four studies included only children. Decreases

in

total cholesterol occurred in 34 of 38 studies. The type of soy protein

used

was either isolated soy protein or texturized soy protein. Soy intake

averaged 47 g/day. When compared with control diets, ingestion of both

isolated and textured soy protein decreased total and LDL cholesterol by

9.3

and 12.9 percent, respectively. Individuals with the highest baseline

cholesterol concentrations had the greatest reductions in total and LDL

cholesterol. High-density lipoprotein (HDL) cholesterol did not change

significantly and triglycerides decreased by 10.5 percent.

* Investigators concluded that 25 g/day of isolated soy protein, with

or without soybean fiber, can reduce total cholesterol in men who have

elevated cholesterol levels(>5.7 mmol/L) (Bakhit et al). These findings

support the hypothesis that soy protein, not soy fiber, is responsible

for

lipid reduction.

* In a randomized, double-blind, crossover trial, 20 g of soy protein

powder reduced total and LDL cholesterol in perimenopausal women by 6

and 7

percent, respectively (Washburn et al).

Source: Food vs. Supplements

Healthcare professionals should be ready to answer patients' questions

about

whether the FDA's ruling applies to soy supplements (e.g., tablets,

capsules, and powders). The FDA ruling pertains to low-fat soy protein

products and does not specifically refer to soy isoflavones, which are

sold

as dietary supplements for symptoms of menopause in tablet and capsule

forms. (Isoflavones are estrogen-like components in soy.) At this time,

the

evidence for isoflavones' effects on serum lipids is inconsistent. In

addition, the long-term consequences of ingesting concentrated

isoflavones

is unknown. Because soyfoods, including powders, have shown positive

effects

on cholesterol, individuals should consume soyfoods, as opposed to

isoflavone supplements, for cholesterol-lowering purposes. (See table

below.)

ISOFLAVONE AND PROTEIN CONTENT OF SOYFOODS

Food Serving (g) Protein (g/100g) Isoflavones/(mg/100g^)

Soy protein concentrate 28 63.6 Daidzein/* Genistein/* Total

isoflavones/*

Soy protein isolate 28 92 Daidzein/33.6 Genistein 59.6 Total

isoflavones/97.4

Tempeh, uncooked 114 17 Daidzein/17.6 Genistein/24.9 Total

isoflavones/43.5

Tofu, firm, uncooked 114 15.8 Daidzein/11.1 Genistein/15.6 Total

isoflavones/27.9

^ Planting season, growing conditions, and processing influence

isoflavone

content of soybeans. * Depending on how it is processed, soy protein

concentrate may have a large or small concentration of isoflavones;

alcoholic extraction, compared with aqueous extraction, results in a

significant loss of isoflavones.

The Bottom Line

In the preceding studies, soy-based diets and control diets were similar

in

fat and cholesterol content. Changes in total and LDL cholesterol were

directly related to initial cholesterol concentrations. Some studies

have

demonstrated soy's ability to reduce triglycerides, yet it does not

appear

to have significant effects on HDL. The actions of isolated isoflavones

are

conflicting, and soy fiber does not appear to affect lipemia. The FDA

moved

in the right direction with its ruling that 25 g/day of soy protein can

reduce cholesterol levels. However, a number of questions still remain:

What

is soy protein's mechanism of action; what is soy's effect on blood

pressure; and, does it interact with other medications?

Note: In the next issue, Hoeckh will present an overview of the

existing research on soy for women's health, specifically osteoporosis

and

breast cancer.