What Can Vitamin D Do?

What can—or can’t—vitamin D do? Results are in from three new studies testing vitamin D at or above the Recommended Dietary Allowance (RDA)—600 IU a day up to age 70 and 800 IU over 70.

Insulin sensitivity. Researchers randomly assigned 18 people with obesity to a low-calorie diet with either a placebo or a weekly dose of vitamin D equal to 3,570 IU a day. Most had low blood vitamin D levels to start with. After three months, insulin sensitivity improved only in the vitamin D takers.

Artery stiffness. Researchers randomly assigned 70 overweight or obese African-Americans aged 13 to 45 with low blood vitamin D levels to take either a placebo or monthly doses of vitamin D equal to 600 IU, 2,000 IU, or 4,000 IU a day. After four months, artery stiffness decreased in the groups that got 2,000 IU or 4,000 IU.

Diabetes control. Researchers randomly assigned 127 people aged 25 to 75 (average age: 60) with stable type 2 diabetes to take vitamin D (4,000 IU a day) or a placebo. Only 26 percent had low blood vitamin D levels. After 11 months, insulin secretion, insulin sensitivity, and hemoglobin A1C (a long-term measure of blood sugar) didn’t improve more in the vitamin D takers.

What to do: It’s too early to tell what high doses of vitamin D can do. But since it’s hard to get enough from food or, for most people, from the sun, take a multivitamin or a supplement with the RDA to play it safe.

You may need more if your vitamin D blood level is low (under 20 ng/mL). Just keep in mind that some studies find a higher risk of falls at 2,000 IU a day (see Jul./Aug. 2017). And stay tuned. VITAL, a larger study looking at vitamin D and more than a dozen conditions, is in progress.

Obesity 26: 651, 2018.
J. Endocr. Soc. 2: 310, 2018.
PLoS ONE 12: e0188424, 2017.

Stay Soft Hearted

In sedentary seniors, the heart chamber that pumps blood throughout the body can get stiff, which can lead to heart failure. Can exercise in middle age keep the heart muscle supple?

Researchers randomly assigned 52 sedentary people aged 45 to 64 either to moderate and high-intensity exercise or to a control group (balance, yoga, and strength training).

The exercise group took five months to work up to 5 to 6 hours a week of training, including 2 high-intensity interval sessions (4 minutes at 95 percent peak heart rate followed by 3 minutes at 60 to 75 percent peak, repeated 4 times).

After two years, the exercise group had less heart stiffness, more blood pumped per heartbeat, and greater aerobic capacity than the control group.

What to do: Get moving before your heart muscle stiffens. In an earlier study on older people, a year of exercise didn’t make hearts less stiff (though it has other benefits).

Circulation 2018. doi:10.1161/CIRCULATIONAHA.117.030617.

Is Gluten the Problem?

Can eating gluten give you GI symptoms even if you don’t have celiac disease?

Researchers gave 20 people with suspected non-celiac gluten sensitivity (NCGS) two muffins a day made with or without gluten (11 grams) for eight days each. The participants were all on gluten-free diets and didn’t know which muffins they were eating.

Only four of the 20 correctly identified the days on which they had eaten the muffins with gluten. However, they reported no more symptoms on those days. The other participants reported more symptoms on the days they ate the gluten-free muffins.

What to do: Got GI distress? Don’t assume that gluten is to blame.

Neurogastroenterol. Motil. 2018. doi:10.1111/nmo.13332.

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