ONLINE DRIVERS MEDIA

Taking vitamin D pills on their own may be less effective than taking them with a meal containing 30% of the calories from fat - at least for older men & women and high doses of vitamin D3

This is science. Only 6 months ago, I wrote in an article about the effects of fat on the absorption and bioavailability of fat soluble vitamins that vitamin D would be the fat soluble vitamin with the lowest dependence on the co-administration of fat. Rather than the amount, it appeared as if the change in plasma 25OHD (nanograms per milliliter) during vitamin D supplementation was rather associated with the types of fat, i.e. MUFA = increased absorption vs. PUFA = decreased absorption (Niramitmahapanya. 2011).

Now, half a year later, it appears as if another, previously overlooked variables would force me to reformulate previous recommendations: Age and dosage!
In contrast to previous studies, Bess Dawson- Hughes and colleagues investigated the influence of fat on the absorption of vitamin D3 in older, not young men and women. In that, inclusion criteria for the study were

• no use of not more than 400 IU vitamin D or 1,000 mg calcium per day,
• serum 25(OH)D level in the range 20 to 29.5 ng/mL (49.9 to 73.6 nmol/L),and
• a body mass index in the range 20 to 29.5 (normal weight)

Subjects with kidney problems, hypercalcemia, general issues with malabsorption, Crohn’s disease, disorders of bone metabolism, kidney stones, cancer and those who were using proton pump in hibitors, lipid-lowering medications, fish oil, or flaxseed oil, hormones, osteoporosis medications, or high-dose thiazide diuretic therapy were equally excluded as those subjects who attended tanning salons, regularly.
This was yet not the only difference. Next to the subjects age, the amount of vitamin D3 in the capsules the subjects received differed, as well. While previous studies that reported little to no effect of fat on the absorption of vitamin D3 used small(er) amounts of vitamin D, like 1,000, 2,000 or 5,000 IU per serving, Dawson-Hughes et al. used a single serving of 50,000 IU(!) and thus more than 10x higher dosages than previous studies.

Figure 1: Composition of the test breakfast, lunch, and dinner meals, expressed as % of total energy the 50 healthy older adults consumed in the study at hand (Dawson-Hughes. 2014)

Alongside said vitamin D3 super-dose all 50 subjects ingested one out of three randomly selected meals that were either fat free or contained 30% of the total calories in form of dietary fat - albeit at two different PUFA:MUFA ratios (see Figure 1)

"[The m]eals were provided by the metabolic kitchen and consisted of real food. For example, breakfast consisted of egg whites flavored with small amounts of onion and tomato, fruit, toast, and cranberry juice. The groups were balanced for energy by adjusting the amount of sugar in the cranberry juice (diet or regular juice or a mixture of the two). Protein and fiber were balanced across all groups. MUFA:PUFA was manipulated by adding varying amounts of MUFA (olive oil) and PUFA (corn oil) to achieve a ratio of 1:4 in the low and 4:1 in the high MUFA:PUFA diets. The boxed lunch and the dinner provided to the study subjects on the test day had fat/protein/carbohydrate content similar to that of the test breakfast meals.

Importantly, the subjects were required to (a) eat all of the food provided and (b) refrain from pigging out on anything that was not on the menu for the study day.

Figure 2: Serum vitamin D3 levels in subjects after consuming fat-free or -containing meals (Dawson-Hughes. 2014)

What the scientists found, when they analyzed the vitamin D response of the subjects depending on (a) the fat content and (b) the type of the fat, Dawson-Hughes et al. found:

• In analyses of vitamin D absorption at baseline and the three follow-up time points, there was a significant interaction of fat-free vs fat-containing meal group with time (P < 0.001). As shown in [figure 2], there was no significant difference in plasma vitamin D-3 levels at baseline, but the fat-containing meal group had significantly higher plasma vitamin D-3 concentrations than the fat-free meal group at each time point thereafter.
  
  At 12 hours, the fat-containing vs fat-free meal mean difference in plasma D-3 concentration was 26.9 ng/mL (95% CI 9.6 to 44.1 ng/mL) (69.9 nmol/L). Differences at the other time points were for 10 hours, 30.5 ng/mL (95% CI 14.4 to 46.7 ng/mL) (79.3 nmol/L) and for 14 hours, 21.3 ng/mL (95% CI 4.6 to 37.9 ng/mL) (55.4 nmol/L).

• Vitamin D-3 levels at 12 hours after the dose were 116.0 3 ng/mL (301.5 nmol/L) in the low MUFA:PUFA group and 104.2 ng/mL (270.8 nmol/L) in the high MUFA: PUFA group.
  
  Potential covariates, body mass index, total body fat mass, and screening plasma 25(OH)D level were not associated with vitamin D absorption and neither modified the effect of fat on vitamin D absorption.

As the researchers point out, "[t]here were no serious adverse events during the study" and "[c]ompliance with the vitamin D supplement was 100%" (Dawson-Hughes. 2014). So, non of these obvious, but undesirable confounding factors could explain the observed differences between (a) the non-fat vs. fat-meals and (b) the influence of the PUFA:MUFA ratio.
References:

• Dawson-Hughes, Bess, et al. "Dietary Fat Increases Vitamin D-3 Absorption." Journal of the Academy of Nutrition and Dietetics (2014).
• Niramitmahapanya, Sathit, Susan S. Harris, and Bess Dawson-Hughes. "Type of dietary fat is associated with the 25-hydroxyvitamin D3 increment in response to vitamin D supplementation." The Journal of Clinical Endocrinology & Metabolism 96.10 (2011): 3170-3174. 
• Wortsman, Jacobo, et al. "Decreased bioavailability of vitamin D in obesity." The American journal of clinical nutrition 72.3 (2000): 690-693.

Red (meat) breast cancer alert!

Its not the first study and I am pretty sure its not going to be the last study to link red meat and cancer, but in view of the fact that I am pretty sure that the results Maryam S Farvid and colleagues present in their latest paper in the British Journal of Medicine are going to be all over the place this week, I feel that its worth to give you an unbiased overview of the results before you are confronted with the sensational press release celebrating the newest "Harvard science" - a source people trust, one that "propagates the truth" and one that is (ab-)used by press release writers to generate the impression that each and every word they write is true.

Well the truth is that we are dealing with yet another prospective epidemiological study which does not have the power to reveal causal links between parameter (a), in this case the dietary protein sources in early adulthood and parameter (b), which is the incidence of breast cancer.
The average ignoramus will still read the headlines as "red meat" causes cancer and think of poultry, fish, eggs, legumes, and nuts as "the cure". In contrast to the red meat intake which was associated with a 22% risk increase in the 2830 documented cases of breast cancer the scientists had been collecting and following for 20 years, the a higher intake of poultry, fish, eggs, legumes, and nuts was
not just unrelated to breast cancer, in postmenopausal women, a high poultry intake was even associated with a -27% reduced breast cancer risk.

Energy intake and cancer risk expressed relative to lowest intake quintile for red meat (Farvid. 2014)

The latter observation gives rise to one of the (imho) hilarious substitute this for that equations, where the "estimating the effects of exchanging different protein sources, substituting one serving/day of legumes for one serving/day of red meat was associated with a 15% lower risk of breast cancer among all women (0.85, 0.73 to 0.98) and a 19% lower risk among premenopausal women (0.81, 0.66 to 0.99). Substituting poultry for red meat was even associated with 17% and 24% lower breast cancer risk in all and postmenopausal women.

Unlike the fooled readers of the press release, the researchers are obviously aware of the weaknesses of the study, in the discussion of the results, Farvid et al. point out that "potential limitations need to be considered":

• participants were predominantly white, educated US adults, they cannot determine whether our findings are generalizable to other race or ethnic groups
• dietary intake was assessed by food frequency questionnaires, some degree of measurement error is inevitably present, and thus to reduce measurement error they used the cumulative average of
  multiple measurements in a sensitivity analysis
• residual confounders are always of concern in any observational studies; although they adjusted for a wide range of potential confounders for breast cancer, they still could not rule out the possibility that other unmeasured or inadequately measured factors have confounded the true association
• they only estimated the effects of substitution of legumes, poultry, and other protein sources for red meat on risk of breast cancer, when trials on dietary modification would be ideal to support these substitutions

In addition, the scientists made multiple comparisons (different food groups and nutrients, premenopausal and postmenopausal subgroups, and subtype of tumors) in this analysis, and can thus not exclude the possibility of type I errors. But (sarcasm) this is not so much of concern, "the central finding of an association with red meat was [after all] a prior hypothesis." (Farvid. 2014) - In other words: What do you want people, weve just made sure we confirm our hypothesis.
Reference:

• Farvid, et al. "Dietary protein sources in early adulthood and breast cancer incidence: prospective cohort study." BMJ 2014;348:g3437 doi: 10.1136/bmj.g3437