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Genghis Khan supposedly believed eating yogurt instilled bravery in his warriors, and in the Bible, Abraham’s longevity was attributed to his yogurt consumption [1]. Although there isn’t scientific evidence that yogurt encourages people to storm through Mongolia or helps them live to be 175 years old, yogurt does have numerous demonstrated health benefits that could influence both vitality and life span—it has been shown to reduce inflammation and improve gut and cardiovascular health [2], and dairy foods, including yogurt, are associated with improvements in insulin sensitivity and a lowered risk for type 2 diabetes [3].

These myth-busting properties of yogurt and dairy were highlighted in two new population-based studies [4, 5]. The first study [4] focused on the potential for dairy foods to influence cardiovascular health in patients who have suffered from a myocardial infarction (MI, more commonly called a heart attack). In healthy patients, dairy food consumption has shown either a neutral or favorable association with cardiovascular health [6], but the influence of dairy foods on heart health was unknown for individuals that had alterations to their cardiovascular system due to a heart attack and who use medications, such as statins, to lower cholesterol and control inflammation.

The study followed 4,365 Dutch men and women between 60 and 80 years of age for 12 years. All participants had suffered an MI no more than 10 years from the start of the study. At enrollment, patient diet over the previous month was assessed with a food frequency questionnaire (FFQ) that included 42 dairy items (including plain yogurt, hard cheeses, fermented dairy, and milk). The Dutch team took a food matrix approach and focused on frequency of consuming whole dairy foods, rather than calculating daily intakes of individual nutrients, such as saturated fat. Nutrient interactions in the dairy food matrix can have important implications for cardiovascular health [4]. For example, a cup of low-fat yogurt contains two grams of saturated fat, which is usually considered bad for heart health. But in dairy foods, that saturated fat is delivered in the milk-fat globule, which is metabolized differently than sources of saturated fat such as red meat or palm oil and is digested alongside fat-binding calcium and high-quality proteins. Yogurt also provides probiotics that influence the nutritive and bioactive properties of other ingredients, such as increasing the bioavailability of calcium [7].

Study participants who consumed more than 50 grams of plain yogurt per day (about 0.20 cup), regardless of fat content, had a lower risk of mortality due to cardiovascular disease (CVD) and a lower mortality risk from all other causes of death (except ischemic heart disease) compared with participants that consumed less than 25 grams of yogurt per day [4]. The researchers also found that every 25 grams per day increase in yogurt intake was associated with a 4% lower risk of CVD mortality over the 12-year study period [4]. To put these findings in perspective, a single serving container of yogurt from the grocery is usually between 150 and 200 grams. The amount of daily yogurt consumption needed to show an effect on cardiovascular health and mortality was quite small—spoonfuls rather than full cups.

On the other hand, total milk consumption showed only a neutral association with CVD and all-cause mortality. Although not as significant as the association with yogurt, total fermented dairy product consumption tended to be associated with lower mortality risks [4]. Taken together, these findings suggest that the heart-health benefits are likely the result of probiotics working in the dairy food matrix, particularly those found in yogurt.

The Dutch study did not measure specific markers of immune function or inflammation in participants, but several intervention studies [8-10] previously demonstrated an association between yogurt consumption and chronic inflammation and suggest a potential pathway for improved CVD health. Lowered levels of inflammatory markers, such as IL-6 and TNF-a, could provide protective effects on the cardiovascular system in much the same way as statins or other medications with anti-inflammatory effects that are regularly prescribed after a heart attack [4].

The second population-based study [5] highlights other potential pathways for improved health. In this study, researchers compared self-reported dairy consumption (via an FFQ) from 1,833 Spanish participants to their plasma metabolite profiles, with the goal of identifying dairy-specific metabolites. Microorganisms in the gut help with food digestion and produce metabolites—small molecules such as amino acids or fatty acids—when they break down carbohydrates, fats, and proteins. Although produced in the gut, these metabolites can have physiological actions throughout the body, including influencing cardiovascular health and insulin sensitivity [5].

The research team identified 38 dairy-specific metabolites [6]. Of these 38, three (C14:0 sphingomyelin, C34:0 phosphatidylethanolamine, and γ–butyrobetaine) were highlighted for their consistent association with both total dairy intake and specific dairy foods, including yogurt. Using statistical models to create a metabolic profile “score” for each study participant (and controlling for other diabetic risk factors), they found that a higher total dairy intake-related metabolic score was associated with a lower risk for type 2 diabetes [5].

These 38 metabolites could be biologically relevant to understanding the roles dairy foods play in type 2 diabetes, cardiovascular health, and perhaps even cancer. Are they involved in reducing inflammation or enhancing the immune response? Do they influence how insulin is moved in the body and taken up by cells? Do probiotics from yogurt and other fermented dairy foods augment the production of metabolites that have protective effects? Genghis Khan was not thinking of the way that yogurt’s ingredients interacted with one another and with the gut microbiome, but research that does take this perspective could potentially make sense of his mythical musings and help inform dietary guidelines to improve health outcomes.

References

Red meat, fish, beans, and cow milk are all good dietary sources of B vitamins. But what about human milk? The answer is more complicated than a simple yes or no. Unlike cow mothers who have bacteria in their rumen that synthesize vitamin B12 during food digestion, human mothers rely on their diet to supply milk with B vitamins [1]. Because populations in many parts of the world suffer from vitamin B deficiency due to poor quality diets or dietary preferences that exclude animal products (e.g., vegetarian and vegan diets), human milk B vitamin composition varies widely across mothers [1–10].

The impact of this variation on infants could be critical. B vitamins play a role in neurodevelopment and inadequate intakes of these micronutrients during infancy could negatively influence growth and development [1–6]. As a result, research on milk B vitamin content has focused on identifying dietary patterns associated with lower levels of B vitamins in milk and developing intervention strategies to improve infant outcomes.

Vitamin B12

Most studies to date have investigated human milk vitamin B12 and thiamin (B1) content, but there are eight different vitamins that make up the B vitamin complex. They are grouped together because they are all water soluble (i.e., not stored in the body) and all play a role as co-enzymes in cellular functions (i.e., they help enzymes complete biochemical reactions).

Vitamin B12 is supplied by animal products including red meat, fish, poultry, and dairy. Diets with limited access to these foods or those that exclude them purposefully are at risk for vitamin B12 deficiency. In South America, the prevalence of vitamin B12 deficiency is estimated at 40% of the population and as high as 60% in parts of Asia and Africa [4, 7, 9]. In infants, vitamin B12 deficiency has been associated with failure to thrive and developmental delays [4].

The relationship between maternal vitamin B12 status, vitamin B12 dietary intake, and milk vitamin B12 levels is complicated. On the one hand, levels of milk vitamin B12 from well-nourished populations with regular access to these foods—which are used as the standard to determine adequate intake of micronutrients for infants—are consistently higher than milk vitamin B12 levels from populations with poor nutrition or whose diets lack animal products [1, 3, 4, 8, 10]. (For comparison, the mean value from well-nourished populations is 300 picomoles per liter with a range from 150-700 pmol/L and in vitamin B12-deficient populations, values are usually between 100-200 pmol/L) [1, 3, 4, 8]. On the other hand, milk vitamin B12 levels decrease over the first six months of lactation even in well-nourished populations with consistent intake of vitamin B12 by mothers [3, 4, 8]. These findings suggest that factors in addition to current dietary intake regulate milk B12 content over the course of lactation.

One potential factor influencing milk vitamin B12 levels could be the increased vitamin B12 requirements during pregnancy and lactation [4]. Studies that provided vitamin B12 supplements to mothers during pregnancy and lactation [9] found a greater increase in milk vitamin B12 levels than those that only provided a supplement during lactation [4]. It is possible that mothers who are deficient during pregnancy are never able to catch up during lactation, with their bodies prioritizing sending available vitamin B12 to their liver rather than milk [3, 4]. Decreases during lactation, even among well-nourished mothers, further suggest the cost of maintaining milk vitamin B12 levels for six months may be challenging regardless of maternal vitamin B12 status [3]. However, despite decreased milk vitamin B12 values, infants of well-nourished mothers do not demonstrate developmental delays associated with vitamin B12 deficiency [3]. Adequate intake early in lactation may be sufficient to prevent developmental delays observed in vitamin B12-deficient populations.

With that in mind, intervention strategies have focused on improving maternal vitamin B12 status during pregnancy and lactation among vitamin B12-deficient populations. A study in Cameroon [10] found that vitamin B12 fortification of flour had a greater influence on milk vitamin B12 levels than did a high-dose supplementation. This finding suggests a higher nutrient transfer to milk with dietary sources compared with vitamins and/or improved absorption with smaller amounts of vitamin B12 throughout the day compared with a single dose [7]. Given the observation that milk vitamin B12 levels drop once supplementation stops [9], an intervention that can be maintained throughout the course of pregnancy and lactation—like fortification of foods that the women are likely to consume—is ideal. These foods would also benefit developing infants consuming mixed diets (mother’s milk and other foods) or those that are completely weaned, increasing their impact on infant health.

Thiamin

Thiamin is found in pork, fish, green vegetables, and brown rice. White rice, however, is thiamin poor, and diets high in polished white rice (particularly those that are also high in carbohydrates) are susceptible to thiamin deficiency [5, 6]. In infants, thiamin deficiency could lead to long-term cognitive impairments and neuronal damage [5, 6].

Two newly published studies [5, 6] investigated the relationship between maternal supplementation, milk thiamin levels, and infant cognitive, motor, and language development in a Cambodian population. Thiamin deficiency in Cambodia is estimated to affect 27% of women of reproductive age and 38% of infants 6-12 months of age [3]. A randomized supplement study [6] of nursing mothers provided either a placebo, 1.2 mg thiamin, 2.4 mg thiamin, or 10 mg thiamin daily from week 2 through week 24 of lactation. They found the 1.2 mg supplementation was sufficient to produce milk levels similar to those from populations in the U.S. and Finland where thiamin intake is sufficient (i.e., approximately 200 micrograms per day for infants less than 6 months of age) [6]. However, they also noted a dose-dependent relationship between the amount of thiamin mothers received and infant scores on learning and language assessments; infants of the mothers in the 10 mg group performed significantly higher than infants in all the other groups, particularly placebo [5]. Unfortunately, language scores decreased in all supplement groups—but most rapidly in the 10 mg group—after supplementation ended at 24 weeks through 52 weeks of age [5]. This highlights the need for continued maternal thiamin supplementation throughout lactation, as well as the need to provide thiamin-rich (or thiamin-fortified) complementary infant foods to maintain the neurocognitive gains [5].

Additionally, the researchers found a positive association between milk thiamin concentrations at week 2 of lactation (before supplementation) and measures of infant cognition at 12, 24, and 52 weeks of age [5]. This suggests that maternal thiamin status during pregnancy could be critical for optimal infant development and supplementation during lactation alone may not be sufficient.

Improving Maternal Status

Considering the influence B vitamins have on infant development alongside the rates of B vitamin deficiencies across the globe, it seems imperative to provide appropriate interventions to improve infant outcomes. But as the studies summarized above make clear, the real goal is not simply increasing milk values of these vitamins. Interventions must focus on achieving adequate nutritional intakes for mothers—throughout their reproductive life span.

References

Food allergies can be a real kick in the guts, causing a range of symptoms from mild discomfort to life-threatening anaphylactic reactions. About 2–3% of babies and young infants have allergic reactions to proteins in cow’s milk, making this the most common food allergy in early childhood [1].

“Beta-lactoglobulin is a pretty major protein in milk, and if you’ve got that allergy, it would be a good thing if you don’t have this protein in milk,” says Dr. Alison Van Eenennaam of the University of California at Davis.

There are a number of processing technologies, such as enzymatic hydrolysis, that can reduce the allergenicity of milk proteins. But these technologies are expensive and may not fully remove the allergens from milk [4].

As a result, researchers have attempted to use genetic methods to disrupt BLG production in animals. Knocking out the genes for BLG production could result in animals that produce hypoallergenic milk that doesn’t contain BLG.

“The beauty of genetics is that it’s cumulative and permanent,” says Van Eenennaam. “If you can do it genetically, then it’s done forever and it gets passed on from generation to generation, whereas if you have to remove it some other way then you’re going to have to keep removing it that other way,” she says.

Genetic approaches are already being attempted for other food allergies. “Certainly there are other groups trying to remove allergens from eggs, for example, and obviously some plants have gluten and things like that that people are trying to work on, so it’s a reasonable approach,” says Van Eenennaam.

While researchers have had the ability to knock out genes for decades, newer genome editing technologies such as CRISPR-Cas9 and TALENS have made the process more efficient, precise, and easier to use, including in livestock [5–8]. “There are groups working on cattle to introduce heat tolerance, disease resistance such as tuberculosis resistance, and there are groups working to eliminate horns so that dairy cows don’t need to be de-horned,” says Van Eenennaam.

In a new study, researchers combined cloning techniques with genome editing to create a cow cell line that lacks the genes for producing BLG [9]. They used the same cloning technology used to clone Dolly the sheep, called somatic cell nuclear transfer (SCNT), along with CRISPR genome editing to knockout the genes responsible for BLG production. The researchers thus obtained an embryonic fibroblast cell line lacking the genes responsible for BLG production. Transplanting these cells to recipient animals is expected to create cows without the ability to synthesize BLG, which would thus produce BLG-free hypoallergenic milk [10].

SCNT cloning and CRISPR are not new technologies. “We’ve had clones since Dolly, and CRISPR editing is not novel, so there is not a lot of novelty there,” says Van Eenennaam. But the new study shows that combining these techniques could help eventually produce BLG-free milk. However, it’ll require a few more steps to get to that point.

“The researchers still have some not insurmountable technical issues to deal with, so they’re at least three or four years away from having the knockout cow,” says Van Eenennaam. “Once they have the knockout cow, if they want to produce a line of it then they’re going to have to genome edit the other sex to get a clone of that if they want to start breeding,” she says. “And then basically you’re going to have to keep breeding within those knocked out animals to make something that’s inherited, assuming it doesn’t hurt them in any other way,” says Van Eenennaam.

Researchers have previously used a different approach to create cattle producing BLG-free milk. In an earlier study, researchers injected TALENS genome editors into zygotes instead of combining SCNT and CRISPR [11]. They used this approach to generate BLG-knockout calves and showed that they did not produce BLG in their milk. They also characterized the BLG-free milk and showed that there was a slight increase in protein and lower lactose content, although fat and lactose levels remained within the normal range.

These studies indicate that regardless of the specific approach used, genome editing could be a viable technique for producing BLG-free hypoallergenic milk. But at least in the US, it may take a while before such milk makes it to your grocery store. “It’s a multi-year, multi-million-dollar regulatory process before they can enter the food supply,” says Van Eenennaam.

As a result, it’s unclear when genome-edited hypoallergenic milk will be approved for food use. But certainly for those suffering from milk allergies, it can’t come soon enough.

References

As the popular adage goes, you are what you eat, and a new study published in the Journal of Dairy Science (in a loose sense) seems to support that. A research team from the Netherlands has characterized the tastes and smells of human milk and discovered a correlation between the mother’s diet and the taste of her milk. In particular, the scientists were interested in teasing apart the sensory differences in fore and hind milk and focused on whether bitter tastes would show up through the mother’s milk [1].

“There’s an important element of breastfeeding that comes with the smell and taste of human milk,” explains Bernd Stahl, the Director of Human Milk Research & Analytical Science at Danone Nutricia Research Utrecht and Associate Professor at Utrecht University, Netherlands. “It’s a biologically important interaction between a mom and her baby.”

Different flavors from the mother’s milk could be an opportunity for the infant to get acquainted with different tastes, which can later influence their food preferences growing up [2,3]. That’s why it’s valuable for the breastfeeding mother to eat a [4–6] variety of foods so that their child can develop a taste for those foods as they grow.

Previous analytical studies looking at the chemical composition of human milk have shown that flavors from the mother’s diet, such as vanilla, carrot, and garlic, are showing up in breast milk [7–9], but very few studies have examined the sensory perception of human milk. This new study takes this more holistic approach in getting the mothers to characterize the smells and tastes of their own milk.

The aims of the study were multi-fold. For one, the research team wanted to characterize the tastes and smells of both the fore milk and the hind milk [1]. “The fore milk is the first sip of milk and the hind milk is the last sip of milk in one given breastfeeding session,” explains Stahl. “The first sip is really rich in carbohydrates and proteins but very limited in fats, but the last sip is very rich in fat.” Second, the researchers wanted to see if components of milk such as fats or sugars could be discerned in the tastes and smell of milk, and thirdly, they wanted to know if the mother’s diet could influence the taste of their milk, with a focus on bitterness [1].

To do this, the research team worked with a group of 22 lactating mothers. At the start of the trial, the mothers underwent taste training to standardize how the mother’s ranked tastes. They then tasted their own fore milk and hind milk and recorded taste, smell, and mouthfeel attributes such as sweet, creamy, or watery. Then, the volunteers kept a food diary for a day to record their diets, and the next day, repeated the tasting [1].

Overall, the research team found that human milk was most often described as having a neutral, creamy, and sweet odor, mostly sweet and some bitter tastes, and a thin, watery, smooth, and fatty mouthfeel. The hind milk was reported to have a more intense vanilla flavor and creamy odor compared with the fore milk, and the mouthfeel was described to be more creamy, fatty, less watery, and less thin [1]. This finding corroborates past research that has found that hind milk is richer in fats [10], which would account for the creamier mouthfeel.

Interestingly, on the second day, the investigators reported that the mothers who ate more bitter foods scored their fore milk but not their hind milk as more bitter, showing that tastes from their foods were transferred to their milk. Reasons for the fore milk having bitter tastes rather than the hind milk are unclear, but researchers speculate that it could be because the fore milk is more watery, how the milk is formed during lactation in the mammary gland, or the bitter tastes being masked by the high fat content in the hind milk.

The correlation between the mother’s diet and the taste of her milk supports the recommendation for lactating mothers to consume a variety of foods. According to Stahl, when the infant is consuming milk, “there’s stable intake of proteins, carbohydrates, and fats, but then it’s decorated with those flavors and smells. I think that makes it more exciting.” Stahl speculates that giving the nursing baby different flavors will be a more interesting and varied taste experience, and this may help breast-fed infants develop healthier food preferences in later life.

Stahl also emphasized that mothers shouldn’t be worried about restricting their diet because of the finding that bitterness is appearing in milk. “I think it’s our obligation to do whatever we can to support breastfeeding,” he says.

Stahl said that one limitation of the study would be an innate sensory bias when the mothers were tasting their own milk. For example, if a mother consumed a lot of garlic, her system might be so flooded with the scent that she might not be able to detect it in her own milk. But in spite of that, the researchers still found that the mothers were able to detect more bitter tastes [1].

For future studies, Stahl thinks it would be ideal to use the sensory approach taken with this study and combine it with the analytical methods used in other studies. Corroborating the two approaches would give a more robust and in-depth understanding of how diet can affect the smells and taste of milk.

References