Saturated fats in dairy foods
Dairy foods are controversial in terms of their health impacts. Although dairy contains high amounts of high-quality protein and calcium, it also contains high amounts of saturated fats. Over the past 50 years, health authorities have recommended limiting intakes of saturated fats, such as those in dairy products, especially the full-fat versions.
Risk of stroke
Researchers in the Netherlands and China conducted a systematic review and meta-analysis of cohort studies that investigated links between dairy products and risk of stroke. The 18 included studies came from Western (N=11) and East Asian (N=7) countries. For all countries, each 200 gram intake of milk predicted a significant 7 percent lower risk of stroke. However, no significant relationship existed for Western countries. Higher intake of high-fat milk predicted a small (4 percent) but significant higher risk of stroke. Curiously, both low-fat and high-fat dairy (milk and yogurt and cheese) predicted small (3 and 4 percent) but significantly lower risks of stroke. The lowest risk of stroke for milk and cheese occurred for 125 and 25 grams per day intake of milk and cheese, respectively. Based on this review, increased intake of dairy products won’t much affect your risk of stroke.
Risk of mortality
Dietary guidelines commonly recommend minimizing consumption of whole-fat dairy products, which are a source of saturated fats and presumed to increase LDL-cholesterol, thereby increasing the risk of cardiovascular disease and mortality. The Prospective Urban Rural Epidemiology (PURE) study is a large multinational cohort study of individuals aged 35–70 years enrolled from 21 countries in five continents. Consumption of dairy products (milk, yogurt, and cheese) for 136,384 individuals was recorded using country-specific validated food frequency questionnaires. The average follow-up was 9.1 years. Compared to those with no dairy consumption, those with two or more daily servings of dairy had 17, 23, and 34 percent lower risk of all-cause mortality, cardiovascular mortality, and stroke, respectively. No significant association occurred with heart attack. Compared to those with no milk intake, those with at least one serving per day had 10 and 14 percent lower risk of any cardiovascular event. Cheese and butter consumption were not significantly associated with the number of total cardiovascular events. Dairy consumption was associated with lower risk of mortality and major cardiovascular disease events.
Focus on specific foods
Noted nutrition researcher Darius Mozaffarian outlined a shift in nutrition policy and research over the past century. He noted that the past focus on single nutrients, such as vitamins, which can prevent certain diseases, such as rickets, that arise from a single factor does not work well for chronic diseases, such as cardiovascular disease, type 2 diabetes, and obesity. Mozaffarian contends that the focus should be on specific foods, such as dairy products, rather than on a single nutrient (fat, calories) or a suite of nutrients (calcium, vitamin D). Current evidence suggests that dairy products don’t promote weight gain. Rather, increased intake of cheese and unsweetened yogurt may help limit weight gain. Fermented and unsweetened dairy products, such as cheese, yogurt, kefir, may lower the risk of cardiovascular disease and type 2 diabetes. Little evidence supports low- or non-fat dairy products over the full-fat versions.
Modestly higher risk of all-cause mortality
Researchers at Harvard used data from three, long-term cohort studies to determine whether higher consumption of dairy foods predicted risk of all-cause and cause-specific mortality. The three cohort studies included the Nurses’ Health Study (74,805 females), Nurses’ Health Study II (93,348 females), and Health Professionals Follow-up Study (49,602 males). Intakes of total dairy, milk, cheese, and yogurt were calculated from food-frequency questionnaires updated every four years. After pooling data from the three studies and compared to the lowest quartile of total dairy consumption, participants in the highest quartile had a significant 7 percent higher risk of all-cause mortality over follow-up of 29-32 years. Compared to participants in the lowest quartile of whole milk consumption, participants in the highest quartile had a significant 11, 9, and 11 higher risks of all-cause, cardiovascular, and cancer mortality, respectively. Consumption of higher levels of skimmed or low-fat milk and cheese did not significantly alter risk of all-cause or cause-specific mortality. The lowest risks of all-cause, cardiovascular and cancer mortality occurred with moderate total dairy consumption of 1.15 to 1.5 cups per day.
Risks of cancers
The US Department of Agriculture recommends that adults and children over age 9 consume three 8-ounce servings of milk (or the equivalent of yogurt, cheese or other dairy products) daily. This recommendation contrasts with the actual average intake of 1.6 servings per day for adults. The USDA recommendation seeks to maintain adequate levels of calcium intake to support bone health. However, the recommendation is based on a methodology that may not be valid. A recent review of the scientific evidence relating to milk and health does not support the current recommendation. In fact, evidence suggests that the risks of high milk consumption may outweigh the benefits. For example, some studies show higher risk of breast, prostate, and other cancers with high milk consumption. On the other hand, high milk intake is linked to reduced risk of colorectal cancer. Fermented dairy products such as yogurt and kefir may promote gut microbiome health. As a protein source, milk appears to be more healthful than eggs or processed meat; similar to unprocessed meat, fish, and chicken; and less healthful than plant-protein sources such as legumes. Reduced fat milk is not linked with weight-loss. For food-insecure people living on a low plane of nutrition, milk is probably healthful. But most Americans probably don’t need to drink more milk.
Dairy matrix
The concept of the food matrix has been applied to dairy products, especially fermented ones such as yogurt, cheese, and kefir. The idea is that combinations of nutrients and the processing that some foods undergo can substantially affect health value. Three researchers shared their views on dairy products, particularly with regard to the dairy matrix, at the American Society of Nutrition’s 2022 Live Online Conference. A new article summarized those findings. The dairy matrix may confer health benefits aside from any benefits of dairy products’ composition, such as high amounts of protein and calcium. Hypothesized benefits included more favorable blood fat profiles, reduced body weight or composition and reduced risks of cardiovascular disease and type 2 diabetes. Fermented dairy products, such as yogurt, cheese and kefir, seem to promote better blood fat profiles that does milk. The saturated fat in dairy products consists of more than 400 types of fatty acids that differ in their properties. The LDL cholesterol particles in dairy products appear to be relatively benign compared to those of carbohydrates.
Dairy or not?
The current evidence suggests that fermented dairy products, such as plain yogurt (unsweetened), cheese, and kefir, as well as low-fat milk, promote better health. Evidence is equivocal with regard to full-fat dairy. For people who lack sufficient protein in their diets or who are otherwise food insecure, dairy products are especially likely to be healthful. Of note: Some of the authors of the above articles are employed by or receive financial support from the dairy industry.
