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Monday, 31 July 2017

Low fat dairy recommendations for children completely lack an evidence base, to put it mildly

"There is no finer investment for any community than putting milk into babies."

— Sir Winston Churchill (1874-1965) Radio broadcast (March 21, 1943)

After reading about the Toddler Paradox on the Care Factor Critical blog, I wondered what evidence was cited in New Zealand to support recommendations for low fat milk, lean meat, and so on in the diets of children. These recommendations were revised in 2015, so should be based on up-to-date science. And, if not, they should at least be based on science, right? Totality of the evidence and all that - if there's evidence that bears directly on the question, it should be cited?

Not in the background document for these recommendations - none of it is cited. Perhaps because none of it supports the recommendations? Surely not. Perhaps because the scientists signing off on the document were too busy to check? Who knows.

Here is the background document:

Ministry of Health. 2012. Food and Nutrition Guidelines for Healthy Children and Young People (Aged 2–18 years): A background paper – Revised February 2015. Wellington: Ministry of Health.

It contains the following statement, reinforced - with great specificity - in all menu examples –

Reduced- and low-fat milk is suitable for children aged two years and over, as long as growth is occurring normally. Therefore, it is recommended that children transition from standard homogenised (dark blue) milk to low-fat (green or yellow) milk from two years of age.

1) The Boyd Orr Cohort is selectively cited

There are few if any relevant citations in the document - the Boyd Orr cohort is interesting because it follows the long-term health of children raised in an era - the 1930's - when many fatty animal foods were considered health foods. Sources of saturated fat in these diets were dairy and meat, and tallow used for deep frying in in fish and chip shops, which were the only fast food outlets. There are two relevant Boyd Orr papers, but only one, from 1998, was cited.

[1] Gunnell DJ, Frankel SJ, Nanchahal K, et al. 1998. Childhood obesity and adult cardiovascular mortality: a 57-year follow-up study based on the Boyd Orr cohort. American Journal of Clinical Nutrition 67: 1111–18. LINK
Is cited to support the claim that childhood obesity increases the risk of cardiovascular disease and early mortality.

Compared with those with BMIs between the 25th and 49th centiles, the hazard ratio (95% CI) for all-cause mortality in those above the 75th BMI centile for their age and sex was 1.5 (1.1, 2.2) and for ischemic heart disease it was 2.0 (1.0, 3.9)

However the 2005 Boyd Orr cohort paper relating to saturated fat intake and cardiovascular and all-cause mortality was not cited.

[2] Ness AR, Maynard M, Frankel S, et al. Diet in childhood and adult cardiovascular and all cause mortality: the Boyd Orr cohort. Heart. 2005;91(7):894-898. doi:10.1136/hrt.2004.043489.

In this paper fat and saturated fat were not associated with the outcomes attributed to obesity in the earlier paper, and were non-significantly protective, making it unlikely that higher fat and saturated intake in this cohort either contributed to childhood obesity or had any adverse effect on the outcomes strongly associated with childhood obesity, i.e. all-cause mortality and cardiovascular disease.

The age, energy, and sex adjusted rate ratio between the highest and lowest quartiles of total fat intake was 0.89 (95% CI 0.46 to 1.72, p for trend 0.80). The fully adjusted rate ratio between the highest and lowest quartiles of total fat intake was 0.87 (95% CI 0.38 to 2.00, p for trend 0.80). The age, energy, and sex adjusted rate ratio between the highest and lowest quartiles of saturated fat intake was 0.70 (95% CI 0.38 to 1.29, p for trend 0.30). The fully adjusted rate ratio between the highest and lowest quartiles of saturated fat intake was 0.62 (95% CI 0.28 to 1.37, p for trend 0.30).

The 2005 Boyd Orr cohort paper bears directly on recommendations made often in the 2015 document and is from a body of research which was found evidential enough to be included as the 1998 paper; it should have also been included.

2) observational studies on low fat vs whole milk and dairy in children

No papers were cited in the document that directly support (or otherwise directly relate to) the recommendation to drink “Low fat calcium enriched milk” in place of whole milk.

There are, as well as relevant papers that were available at the time of writing the document, also more recent papers showing that whole milk consumption is associated with leaner BMI in children.

[3] Vanderhout SM, Birken CS, Parkin PC, Lebovic G, Chen Y, O’Connor DL, Maguire JL; TARGet Kids! Collaboration. Relation between milkfat percentage, vitamin D, and BMI z score in early childhood. Am J Clin Nutr 2016;104:1657–64. LINK

Among the 2745 included children there was a positive association between milk-fat percentage and 25(OH)D (P = 0.006) and a negative association between milk-fat percentage and zBMI (P less than 0.0001). Participants who drank whole milk had a 5.4-nmol/L (95% CI: 4.32, 6.54) higher median 25(OH)D concentration and a 0.72 lower (95% CI: 0.68, 0.76) zBMI score than children who drank 1% milk. Milk volume consumed modified the effect of milk-fat percentage on 25(OH)D (P = 0.003) but not on zBMI (P = 0.77).”

The following paper is important for ruling out a role of reverse causation in the others.

[4] Prentice P, Ong KK, Schoemaker MH, et al. Breast milk nutrient content and infancy growth. Acta Paediatrica (Oslo, Norway : 1992). 2016;105(6):641-647. doi:10.1111/apa.13362.

Higher HM TCC was associated with lower 12‐months body mass index (BMI)/adiposity, and lower 3–12 months gains in weight/BMI. HM %fat was inversely related to 3–12 months gains in weight, BMI and adiposity, whereas %carbohydrate was positively related to these measures. HM %protein was positively related to 12‐months BMI.”

[5] Rolland-Cachera MF, Maillot M, Deheeger M, Souberbielle JC, Peneau S, Hercberg S. Association of nutrition in early life with body fat and serum leptin at adult age. Int J Obes (Lond) 2013;37:1116–22. LINK

In adjusted linear regression models, an increase by 100 kcal in energy intake at 2 years was associated with higher subscapular skinfold thickness (β=6.4% SF, 95% confidence interval 2.53–10.30, P=0.002) and higher FFM (0.50 kg, 0.06–0.95, P=0.03) at 20 years. An increase by 1% energy from fat at 2 years was associated with lower subscapular skinfold thickness (−2.3% SF, −4.41 to −0.18, P=0.03), lower FM (−0.31 kg, −0.60 to −0.01, P=0.04) and lower serum leptin concentration (−0.21 μg l−1, −0.39 to −0.03, P=0.02) at 20 years."

[6] Alexy U, Sichert-Hellert W, Kersting M, Schultze-Pawlitschko V. Pattern of long-term fat intake and BMI during childhood and adolescence—results of the DONALD study. Int J Obesity Relat Metab Dis. 2004;28: 1203–9. LINK

The mean BMI during the study period differed significantly, with the highest BMI in the low fat intake cluster.

Consistent with a review of the evidence in adults

[7] Kratz M, Baars T, Guyenet S. The relationship between high-fat dairy consumption and obesity, cardiovascular, and metabolic disease. Eur J Nutr. 2013;52:1–24. LINK

The observational evidence does not support the hypothesis that dairy fat or high-fat dairy foods contribute to obesity or cardiometabolic risk, and suggests that high-fat dairy consumption within typical dietary patterns is inversely associated with obesity risk.”

One Brazilian study which could be interpreted as supporting the recommendation - though it is at best ambiguous - found that higher full-fat dairy consumption was associated with higher triglycerides in obese and overweight children eating fewer servings of full-fat diary than recommended in that country. However no comparison with low-fat dairy was available. Saturated fat and full-fat dairy were not associated with higher LDL cholesterol (non-significant correlation of full-fat dairy with lower LDL, multivariate linear regression coefficient −0.38 (−0.77;0.01) p=0.06)

[8] Rinaldi AEM, de Oliveira EP, Moreto F, Gabriel GFCP, Corrente JE, Burini RC. Dietary intake and blood lipid profile in overweight and obese schoolchildren. BMC Research Notes. 2012;5:598. doi:10.1186/1756-0500-5-598.

3) trial evidence.

Few trials have tested the effect of increasing fat and saturated fat from dairy in the diets of children, due to current recommendations to do the opposite. However the available example shows that this does not result in harm in the context of a nutritionally adequate diet.

[8] van der Gaag EJ, Wieffer R, van der Kraats J. Advising Consumption of Green Vegetables, Beef, and Full-Fat Dairy Products Has No Adverse Effects on the Lipid Profiles in Children. Nutrients 2017, 9(5), 518; doi:10.3390/nu9050518.

"In children, little is known about lipid profiles and the influence of dietary habits. In the past, we developed a dietary advice for optimizing the immune system, which comprised green vegetables, beef, whole milk, and full-fat butter. However, there are concerns about a possible negative influence of the full-fat dairy products of the diet on the lipid profile. We investigated the effect of the developed dietary advice on the lipid profile and BMI (body mass index)/BMI-z-score of children. In this retrospective cohort study, we included children aged 1–16 years, of whom a lipid profile was determined in the period between June 2011 and November 2013 in our hospital. Children who adhered to the dietary advice were assigned to the exposed group and the remaining children were assigned to the unexposed group. After following the dietary advice for at least three months, there was a statistically significant reduction in the cholesterol/HDL (high-density lipoproteins) ratio (p < 0.001) and non-HDL-cholesterol (p = 0.044) and a statistically significant increase in the HDL-cholesterol (p = 0.009) in the exposed group, while there was no difference in the BMI and BMI z-scores. The dietary advice has no adverse effect on the lipid profile, BMI, and BMI z-scores in children, but has a significant beneficial effect on the cholesterol/HDL ratio, non-HDL-cholesterol, and the HDL-cholesterol."

The diet advice in this trial also resulted in a decrease in respiratory infections, possibly an outcome of interest with regard to the New Zealand population and the incidence of rheumatic fever.

Thus it appears that the Ministry of Health document was prepared without a proper literature search, and that no-one involved in the 2015 version was familiar with the extensive literature regarding a specific recommendation that was being made.

I'm aware that there are controversies in nutrition science, but this does not appear to be one. The evidence is all on one side, and yet it is being ignored by people who think they know better.

With what results we see.


Galina L. said...

Low fat milk is the perfect protein choice if you want to fatten a pig. It is the situation that since the beginning of the year I give a diet advice to humans, and it happens again and again - people have troubles with loosing weight with any milk products in their diet even while lowcarbing. Due to my experience I have reconsidered my attitude to milk products in general. High fat products like cream are fine but in limited amounts, cheese is limited, butter is fine.No yogurt or country cheese for thous who in need to loose weight.

George Henderson said...

Yes, the comparison is whole milk vs reduced fat milk = lower BMI in kids
Milk vs no milk is still higher BMI for adults, but less so with whole milk.

Bob said...

Dairy seems a great way to "pig out" on saturated fat. I do a "healthy" amount of sour cream, some "sweet" cream, and moderate cheese. Of course, Galina specifically mentions people who need to lose, and I am not in that category. So I suppose one's mileage may vary.

Michael B said...

I think it is obscene that these low-fat recommendations are still being inflicted on children. When I talk to friends about cutting out carbs and getting more fat there is such a fearful reaction because of all these recommendations that never had a firm scientific basis. Will there ever be a day when these organizations start looking at actual evidence and admitting they have been wrong? (Or is the correct question "When will pigs fly?)

Thanks for the article and all the good citations. This is something I will send to friends and family with children.