Welcome to the November 2021 edition of Research Extracts. “The Extracts” is designed to keep busy practitioners and savvy consumers up to date on the latest research on diet, nutrients, botanicals, the microbiome, the environment, and lifestyle approaches to good health. Our medical team, which includes NDs, MDs, PhDs, RDs, an MS, and an LAc, has summarized the essence of several interesting recent studies.

In this issue you will find new studies on: (1) fitness instead of weight might be more important for mortality risk, (2) the minimum exercise needed to preserve fitness, (3) infant meat consumption and asthma, and (4) a Mental Health Moment: fish and mood.


Does Increasing Physical Activity Reduce the Health Risks Associated with Obesity?

Although there has been an increased focus on weight loss over the years, obesity continues to increase in the United States and worldwide. Repeated attempts to lose weight can also lead to weight cycling, a behavior strongly associated with increased health risks. A recent literature review questions whether focusing on increasing physical activity and cardiorespiratory fitness might be a better approach to reducing long-term health risks than focusing on weight loss.

Historically, a higher body mass index (BMI) has been associated with increased mortality risk; however, more recent studies find a less clear-cut relationship between BMI and health risk, with some studies finding the lowest mortality among older adults considered overweight according to BMI. Many of these studies have not included physical activity or cardiorespiratory fitness as part of their analysis when considering the relationship between BMI and mortality.

When looking at reductions in mortality risk, intentional weight loss does not consistently result in improved mortality risk. Cardiorespiratory fitness and increased physical activity, however, are consistently associated with significant reductions in both cardiovascular disease and all-cause mortality risk. The review authors recommend a weight-neutral strategy for reducing health risk associated with obesity, focusing on physical activity and cardiorespiratory fitness as essential vital signs and a consistent emphasis from health-care professionals on the benefits of physical activity regardless of weight loss.

Contributed by Jennifer Greer, ND, MEd


The Minimum Exercise Needed to Preserve Endurance and Strength

This research review identifies the minimal dose of exercise (frequency, volume, and intensity of training) needed for the general population to maintain adaptations of endurance training (VO2 max) or strength training (strength and muscle size) when a period of exercise cessation lasts beyond 2-4 weeks. A review of more than 60 peer-reviewed studies found the key to maintenance to be exercise intensity, and that frequency or volume is not always associated with greater gains for all populations.

To maintain a one repetition max (1RM; how much you can lift if you only had to do it once), one session a week of one set to failure with a heavy load (lifting a weight until you can’t lift it again) helps preserves max strength. To maintain muscle mass, younger adults (ages 20-35) only need one weekly session of one set per exercise when you lift until you can’t continue lifting. Older adults (ages 60-75) need two weekly sessions of 2-3 sets per exercise with the same max load intensity.

For shorter endurance (lasting 4-8 minutes), to maintain a VO2 max in a general population, only two weekly sessions are needed, as long as the volume and intensity are maintained as high as reasonably possible for 13 minutes each. Intensity can be reduced to 82-87 percent of heart rate max, as long as frequency and volume of training are maintained.

For longer endurance exercise (max bouts of 1-3 hours), the minimum frequency is unknown, although the researchers suggest maintaining exercise frequency at or near the typical training level. Volume can be reduced by 33 percent, to as little as 26 minutes per session, as long as frequency and intensity are maintained. The goal is to maintain exercise intensity as high as reasonably possible to match a typical training intensity.

This review did not include the minimal dose of exercise required to maintain body weight, body composition, physiological adaptations (e.g., bone mineral density, cardiac function), or health status (e.g., insulin sensitivity or blood pressure). The researchers intend to expand the review to professional athletes, military groups, and extreme non-use situations (e.g., spaceflight).

Contributed by Laura Kunces, PhD, RD


Infant Meat Consumption Might Contribute to Asthma

As a naturopathic physician, I often counseled new moms on when to introduce solid foods into their baby’s diet. The general theme was to not introduce the most common allergenic proteins too soon – cow’s milk, eggs, gluten, soy. This new study seems to turn on its ear some of what I thought to be true.

A new study from data derived from 1,400 infants in two birth cohorts – PASTURE and LUKAS2 – found that when meat consumption is the primary source of protein in the first year of life, the odds of a child developing asthma by age six increased more than eight times (OR: 8.47; p=0.001). In infants who were only breast fed through week 19, the odds increased 12-fold, compared to a 4-fold increase in infants who were breast-fed for a longer time. The cohorts were from rural areas in five European countries (France, Germany, Switzerland, Austria, and Finland) where home-grown meat is available. Store-bought meat increased the risk of developing asthma a bit more than home-grown meat. The group with the highest risk of developing asthma was also characterized by very little consumption of milk and yogurt – termed by the researchers as unbalanced meat consumption (UMC).

The infants’ intestinal microbiome was also studied using 16S rRNA sequencing. The UMC group had higher amounts of bacterial species associated with iron overgrowth and metabolism, such as Acinetobacter.

Contributed by Kathi Head, ND


Thorne Mental Health Moment: Fish Oil and Mood

Doctors and researchers have long had evidence that fish oil from supplements, as well as from higher dietary levels (such as the Mediterranean diet), can be supportive for mood.1 Research over the past few decades also shows there is a connection between inflammation,2 particularly in the brain, and the development of low or depressed mood. However, studies looking at traditional anti-inflammatory treatments have really not produced results, leaving questions as to whether this finding is meaningful.3

New data now brings researchers closer to understanding how the fatty acids in fish oil (omega-3 fatty acids) influence the normal inflammatory processes in the brain to benefit mood. A new study conducted by researchers in the United Kingdom and Taiwan4 looked at the molecular mechanisms underlying how these dietary fats impact the brain in cell cultures, and also conducted a small human trial to determine if they could find the same effects.

In the cell culture, the fatty acids in fish oil (EPA / eicosapentanoic acid and DHA / docosahexanoic acid) protected cells from being destroyed by inflammatory chemicals that occur naturally in the brain; essentially, they prevented the cells from dying.

In the follow-up human study, 22 adults were given either EPA (3 g/day) or DHA (1.4 g/day). Over a 12-week period, mood improved significantly in both groups, and researchers were able to find the same protective metabolites they found in the cell cultures in these subjects. The researchers also observed that higher levels of the protective metabolites correlated with better improvement.

Despite the positive findings, the researchers cautioned that, because mood changes naturally wax and wane, much longer and larger studies are needed to determine if these improvements would endure over time. Still, these findings add to a long list of benefits associated with having higher levels of fish oil and the essential fats they provide. If you are curious about adding fish oil to your diet, but are not sure of where to start, then we have a great quiz to get you going.

Contributed by Jacqueline Jacques, ND

References

  1. Ghasemi Fard S, Wang F, Sinclair A, et al. How does high DHA fish oil affect health? A systematic review of evidence. Crit Rev Food Sci Nutr 2019;59(11):1684-1727. 
  2. Kohler O, Krogh J, Mors O, Eriksen Benros M. Inflammation… and the potential for anti-inflammatory treatment. Curr Neuropharmacol 2016;14(7):732-742.
  3. Eyre H, Air T, Proctor S, et al. A critical review of the efficacy of non-steroidal anti-inflammatory drugs in depression. Prog Neuropsychopharmacol Biol Psychiatry 2015;57:11-16.
  4. Borsini A, Nicolaou A, Camacho-Muñoz D, et al. Omega-3 polyunsaturated fatty acids protect against  i  inflammation through production of LOX and CYP450 lipid mediators: relevance for major depression and for human hippocampal neurogenesis. Mol Psychiatry. 2021:1-16.