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Metabolism & Nutrition – Tutorial 7: Eatmeter

During the last tutorial in the RuG Metabolism & Nutrition course, Janine used the aggregated data from all the eatmeter food logs submitted by Group C to bring much of the course’s material closer to home.

The average calorie count in group C correspond with the national average. Although there are fewer ♂♂ than ♀♀ in Group C, the variance within the ♂ segment is greater. Also, the only data points above the 3000 kcal/day line were in the male group. (I am definitely one of the guilty ones there.) Much of the variance in energy intake can probably be explained by differences in activity and BMR. The latter is influenced by, for example, height, muscle mass, ambient temperature, gender, age. It was again emphasized that energy requirement calculations from Lecture 2 are not accurate for very fat or very muscular individuals.

The variance in fat consumption is greater than the variance in carb consumption within our group.
Janine reminded us that “fat is bad, mkay?” LDL gets attacked by macrophages and ends up causing artherosclerose. Serum LDL concentration is regulated by LDL receptors in the liver. LDL level has a big genetic determinant, and is also lowered by exercise, both of which may explain why my LDL is in the low range, dispite the consumption of copious amounts of (saturated) fats. (My mother’s LDL is also low.) I derive most of my saturated fats from animal products and from coconut oil. Interestingly, margarine is sometimes enriched with plant sterol, which, by mimicing LDL cholesterol, can actually contribute to keeping actual LDL levels low.

Alcohol, the “liquid fat”

When discussing fat metabolism during Lecture 2, Bert Groen mentioned the energy density of the important groups of macronutrients: E(fat) = 9 kcal/g » E(carb) = E(protein) = 4kcal/g. What he didn’t mention was something I was confronted with when entering a late-night glass of rum in the Eatmeter on the first morning that I started logging: that alcohol has a high energy-density. With 7kcal/g, alcohol is sometimes called “liquid fat”.

Dietary fibers

Fiber intake is lower than advised for most students in Group C. Fibers are an important food source with a number of functions:

  • stommach filling;
  • bulk forming and nutrient dilution causing slower absorption in small intestine and less glucose spiking, while food uptake remains efficient;
  • fiber-nutrient interaction;
  • longer transit time;
  • a food source for microbiota.

Microbiotic fermentation products

Among the fermentation products of our microbiome are short chain fatty acids (acetate, propionate, butynate) which are important as an energy source, and also perform signalling functions (satiety). Propionate is anti-inflammatory. Its anti-inflammatory effect is mediated through GPR43. Short chain fatty acids are the fermentation product of polysaccharides.

Another fermentation product of the gut microbiome is TMA, which is the fermentation product of choline. TMA is further converted by FMO3 enzymes in the liver to TMAO, which is implicated in the development of CVD.
To research this relationship in mice, GM LDL-receptor knockout mice have to be userd, because normal mice do develop plaques, but no CVD; compared with humans, mice have a very different lipo-profile (VLDL:LDL:HDL), with much higher HDL counts. [More on this in the CVD tutorial.]

Our own cells can produce primary bile acids from cholesterol, but these van only be converted to secondary bile acids with the aid of microbiota. Secondary bile acids are important ligands for nuclear FXR receptors and TGR5 [an important target in the article discussed during Tutorial 6 and in my group’s editoral]. TGR5 play a role in energy expenditure, GLP-1 secretion and its activation may protect agains atherosclerosis. Researching the role of secondary bile acids can and has be done by wiping out the microbiome. This has been done in mice, and also in humans, through the use of anti-biotics.

Vitamins, minerals and trace elements

Vitamin A, D, E, and K are fat-soluble. Absorption goes up with increasing fat intake. Fat-soluble vitamins are incorporated with cholesterol into chylomicrons and transported to the liver.

Water-soluble vitamins are B1, B2, B3, B5, B6, B8, B11, B12, and C. Don’t discard the water in which you boil your vegetables. Vitamin B complex is important as a co-enzyme in energy metabolism. Vitamin B consumption in our group is sufficient. Present in high amounts in .
Reserve for a few weeks is stored in your body.

Light vitamin B1 (thiamine) deficiency can result in:

  • psychological problems, such as depression, headaches, increased irritability, concentration problems, and memory loss; and
  • fatigue, muscle weakness, decreased reflexes, lower appetite, weight loss, and stomach upset.

More serieus deficiencies can cause:

  • Beri-beri (characterized by muscle paralysis and coronary problems) affects demographics that subsist primarily on white rice or refined wheat flower;
  • Wernicke-Korsakoff syndrome (characterized by memory defects and disorientation) affects alcoholics who derive most of their calories from alcohol. These ‘empty’ calories cause malnutrition.

Vitamin D (calciferol) is fat-soluble and can be absorbed with fat in the small intestine as vitamin D₂ (ergocalciferol) or D₃ (cholecalciferol). Alternatively, Provitamin D₃ (7-dehydrocholesterol) is converted in the skin to vitamin D₃ (cholecalciferal) with the help of UV light. Dietary vitamin D (traveling to the liver via the lymphatic system and bloodstream) and sun-produced vitamin D are converted in the liver to calcidiol. Calcidiol is further processed in the kidneys, into calcitriol, the primary active form of vitamin D in the body.

Calcitriol functions in: calcium and phosophorus absorption; regulation of Ca levels in blood; the deposition of calcium and phosphorus in bones; the slowing down of cell proliferation; and the stimulation of cell differentiation.

Group C consumes around 2 µg/day on average, which is way below the 10 µg/day that we should consume during the winter. Sources of vitamin D are: fatty fish and liver, in smaller amounts in meat and eggs, and it is sometimes added to margarine.

Vitamin D (calciferol) deficiency can cause:

  • rachitis (in children) and osteomalacie (in adults);
  • osteoporosis; and it could be a
  • universal risk factor in chronic disease. Calcitriol forms a complex with VDR (vitamin D receptor), RXR (retinoid X receptor) and VDRE (vitamine D response element). VDRE promotes the transcription of genes that enhance anti-proliferation, apoptosis, differentiation, anti-inflammation and immune regulation.

Minerals and trace elements

Difference between minerals and trace elements is the amount that need to be ingested to avoid dietary deficiencies. For minerals, the ammount is > 100mg, and for trace elements < 100mg. Minerals and trace elements perform important functions as, for example, components of hormones and enzymes.


The number of centennials doubled in the last 14 years. To reach a 100, genes play an important role. To healthily reach 80, a healthy lifestyle is important. Janine: “Healthy nutrition has the right amount of energy and nutrients to avoid nutrient deficiencies and lower the risk of developing disease.” Most of the students in Group C get sufficient nutrients to avoid nutrient deficiencies. We have to be aware that portion sizes have gone up since the 1950s. Energy density as well. To avoid many of the risks involved with highly processed, energy-dense foods, it’s best to avoid eating too many empty calories.

1 Comment

  1. Rowan Rodrik

    David De la Mora reached out to me, asking me to link to his article on how to Turn Your Kitchen into A Gut-Friendly Oasis. I haven’t read it in full, but it seems like a good list of empirical pointers for people interested in improving their gut microbiome.

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