We’re told to eat more dairy: Harvard researchers disagree
A Harvard University review has questioned guidelines suggesting we consume more dairy products.
The average Australian eats about one and a half serves a day, while the guidelines recommend between two and a half and four serves of dairy a day, depending on your age.
Do we need more dairy? No, according to a new review.Credit:Getty
Harvard researchers, however, argue that these recommendations are not “justified”.
“The health benefit of a high intake of milk products has not been established, and concerns exist about the risks of possible adverse health outcomes,” write the authors, Walter Willett and David Ludwig in the New England Journal of Medicine. “Therefore, the role of dairy consumption in human nutrition and disease prevention warrants careful assessment.”
For their review, Willett and Ludwig explored the evidence, based on more than 100 studies, in relation to growth and development, bone health, body weight, blood pressure and cardiovascular disease, diabetes, cancer and total mortality.
They found that the outcomes typically depended on what dairy consumption was being compared with. For instance, dairy foods compared favourably with processed red meat or sugar-sweetened beverages but less favourably with plant-protein sources such as nuts.
Specifically, they found that, in childhood, dairy foods “can add important nutritional value”.
“Even with adequate overall nutrition, milk consumption augments longitudinal growth and attained height,” they wrote. For adults, the benefits were less clear.
Eating more dairy is encouraged largely to obtain calcium for bone health, however they found it does not reduce fractures or improve bone health and “in populations with generally adequate nutrition, high consumption of milk may increase the risk of fractures later in life”.
The relationship between dairy consumption and body weight as well as the risk of diabetes, cardiovascular disease and overall mortality was not established, though consuming full cream milk (presumably because it is more satiating) and yoghurt was generally linked to better weight outcomes than low-fat alternatives.
While there are “major limitations” in the existing literature, “high consumption of dairy foods is likely to increase the risks of prostate cancer and possibly endometrial cancer but reduce the risk of colorectal cancer”.
If diet quality is high, increased intake is unlikely to provide substantial benefits, and harms are possible.
The balance of evidence led to Willett and Ludwig to conclude: “If diet quality is low, especially for children in low-income environments, dairy foods can improve nutrition, whereas if diet quality is high, increased intake is unlikely to provide substantial benefits, and harms are possible.”
Calcium and vitamin D requirements can be met with other foods, including kale, broccoli, tofu, nuts, beans, and fortified orange juice or supplements.
“In our opinion, the current recommendation to greatly increase consumption of dairy foods to 3 or more servings per day does not appear to be justified,” they wrote.
Accredited practising dietitian Melanie McGrice says it is “important to note” that the paper was not a systematic review, which is based on all the available evidence.
“Although it is true that the nutrients found in milk can be sourced from other foods, milk is a nutritious, scalable and affordable source of nutrition, so for most Aussies, 2-3 serves of milk every day is still a wise option,” she said.
Public health nutritionist Dr Rosemary Stanton said she agrees with the paper’s authors that the recommended dietary intakes (RDIs) for calcium “are higher than the evidence justifies”.
“Sadly, on each revision, RDIs tend to increase and my cynical view sees this as related to the fact that some of the scientists who set these levels have food industry ties,” she said.
Stanton added that there is “reasonable evidence” that fermented dairy products (which includes yoghurt and possibly cheeses) are beneficial for our health and dairy plays “a positive role within the diet” for dietary nutrient-density.
“But that doesn't make 'more better',” she said.
“The major message from this study is that it's way too simplistic to think any single food is either sinner or saint – at least after weaning age. (As they acknowledge, modified cow's milk can be a lifesaver for an infant who is not breastfed.) But for fractures, weight, diabetes, cardiovascular disease and all-cause mortality, milk itself is neither sinner or saint.
“Canada's most recent dietary guidelines don't put milk ‘on the plate’. Australia's Dietary Guidelines urgently need a revision for many reasons.”
Source: Read Full Article