Severely malnourished? Whey beats soy yet again

Severely malnourished? Whey beats soy yet again

Three weeks ago I wrote about a study comparing a whey-based ready-to-use therapeutic food (RUTF) to a soy-based RUTF in the treatment of moderate malnutrition. The results showed a clear advantage to the whey-based RUTF, with a significantly greater 3.4% recovery rate, despite a markedly lower amount of calories (-8%) and protein (-33%). What’s more, this study showed that this superior product was similarly affordable, costing a mere $1.36 more per child who recovers from malnutrition.

Not everyone agrees that this price is affordable. In a recent study by Bahwere et al, it was argued that “the high milk content of this formulation makes it very expensive for sustainable use in resource-poor settings and increases the proportion of ingredients that have to be imported into developing countries.” Accordingly, they conducted a study comparing the efficacy of a RUTF made from soy, maize, and sorghum (SMS-RUTF) to the efficacy of a peanut paste-based RUTF (P-RUTF) that contained milk powder.

The goal of this research wasn’t to see if the SMS-RUTF was superior to the P-RUTF, but only to show that it wasn’t worse. Why? Because if it performs similarly and costs less to produce, then it would be a viable alternative to the standard P-RUTF already being used globally to treat malnutrition. This would certainly benefit the company that developed the SMS-RUTF (Valid Nutrition), therefore making it unsurprising that half the study authors, all of which participated in the study design, implementation, and data interpretation, are employed by this company (one is even the director).

The set-up

The researchers recruited infants and young children aged 6-59 months from the Democratic Republic of Congo, Africa who were admitted into the government-run malnutrition program. All the children were diagnosed with severe acute malnutrition and consumed a diet poor in dairy and other animal foods. Over the course of 12-months, study participants attended an outpatient treatment center for 8 hours each day to receive standardized treatment protocols, including administration of the RUTFs.

Children were randomized to receive either the SMS-RUTF or P-RUTF, but there was no blinding to the researchers or participants. The outcomes of interest were the recovery rate, amount of weight gain, and length of stay.


The two RUTFs did not differ only in their ingredients, but also in their nutrient composition (figure 1). Replacing the peanut paste and skim milk of the P-RUTF with dehulled soybean, degerminated maize, and whole grain sorghum of the SMS-RUTF markedly increased the phytic acid content by 65%. This was compensated for by nearly doubling the amount of vitamin and mineral premix added to the SMS-RUTF, so that the iron and zinc to phytic acid ratios met World Health Organization recommendations. Of course, this also meant that many other vitamins and minerals were greater in the SMS-RUTF vs the P-RUTF.

B2ap3 Large Malnutrition Wheysoy Fig 20160319 221747 1

To further increase iron bioavailability, additional vitamin C was added to the mix, so that its content was ultimately over 6-fold greater than the P-RUTF. The omega-6 content was also lowered and omega-3 content increased to achieve an omega-6 to omega-3 ratio less than 5. Finally, the amount of calories and protein were greater in the SMS-RUTF, albeit by only 4% (23 kcal and 0.6 grams per 100 grams of RUTF, respectively).

Recovery rate, weight gain, and length of stay

A total of 875 children “exited” the study, meaning that they either recovered, didn’t recover after 90 days of treatment, died, or defaulted (refused to continue treatment or were absent for 5 consecutive days).

Overall, the SMS-RUTF showed lower recovery rates, higher mortality rates, lower weight gain, and longer lengths of stay than the P-RUTF. However, the only difference considered statistically significant was the difference in recovery rate among infants aged 6-24 months.

B2ap3 Large Malnutrition Wheysoy Fig2

This is one area where that potential conflict of interest arises. The thresholds for determining whether the SMS-RUTF was inferior to the P-RUTF were arbitrarily determined by the researchers. For recovery rates, a 10% difference was considered acceptable, meaning that the SMS-RUTF could have up to a 10% lower recovery rate than the P-RUTF and not be considered inferior from a statistical standpoint. For weight gain, the difference could be up to 1.2 kg per day. For length of stay, a difference of 14 days was acceptable.

These values seem rather large, in my opinion, especially considering that the previous malnutrition study I wrote about noted a 3.4% difference in recovery rates as significant. In the current study, recovery and mortality rates among children aged 24-59 months were 88.3 and 1.7 % for the SMS-RUTF and 90.3 and 0.4% for the P-RUTF. Among infants aged 6-24 months, P-RUTF recovery and mortality rates were 75.1 and 1.0 % compared to 54.3 and 3.4 % in the SMS-RUTF. In both cases, the P-RUTF shows a clear advantage, especially among the infants.

Weight gain and length of stay in the outpatient clinics show similar findings. Average daily weight gain in the SMS-RUTF was 0.7 kg less than the P-RUTF in both age groups of children. Length of stay in the SMS-RUTF was 2.4 and 3.9 days longer for participants aged 24-59 months and 6-24 months, respectively, compared to the P-RUTF.

RUTF intake, acceptability, and tolerance

One potential explanation for the observed differences could be owed to differences in food consumption. Although adverse side-effects were similarly low (2-3%) among both RUTFs, a dislike of the SMS-RUTF was reported to be 19.2% compared to 13.3% with the P-RUTF. Accordingly, consumption of the P-RUTF was about 24.6 grams and 28.9 grams greater than the SMS-RUTF for children aged 6-24 months and 24-59 months, respectively. This translated to a 16-18 kcal/day greater intake in both age-groups for the P-RUTF. Although a possibility, it does seem rather unlikely this difference in energy intake would be of clinical significance.

Peanuts and milk beat soy, maize, and sorghum

This study suggests that a peanut paste and skim milk RUTF, currently considered the standard for treating malnutrition by the World Health Organization, is more effective than a cheaper RUTF based on soy, maize, and sorghum, especially among infants. This is despite notably higher vitamin and mineral content of the latter, which was necessary to help overcome the intrinsically unfavorable properties of legumes and grains (e.g., phytic acid).

According to the current researchers, the results show that their product is similar among older children, but this is based on arbitrary thresholds determined by them. If we scale the findings upwards to the nearly 20 million children under five years of age that are severely malnourished, then the 2 and 1.3% difference in recovery and mortality rates, respectively, corresponds to 400,000 and 260,000 children. This assumes that all severely malnourished children were older than 2 years, and if we accounted for the 20.8 and 2.4 % differences in recovery and mortality rates among infants less than 2-years, the argument in favor of the P-RUTF only grows stronger.

Taken in conjunction with the previous study I wrote about, it does thus appear that peanut paste RUTFs using skim milk or whey protein are more effective at treating both moderate and severe malnutrition.

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