Monday, October 22, 2012

Older People And Vegetarians Risk Zinc Deficiency

Click to enlarge.
A recent post addressed the challenge of getting enough zinc on a vegetarian diet. Here's an excerpt:
Is zinc difficult to get on a vegan diet? The National Institutes of Health in their Fact Sheet on Zinc say:
"The bioavailability of zinc from vegetarian diets is lower than from non-vegetarian diets because vegetarians do not eat meat, which is high in bioavailable zinc and may enhance zinc absorption. In addition, vegetarians typically eat high levels of legumes and whole grains, which contain phytates that bind zinc and inhibit its absorption."
"Vegetarians sometimes require as much as 50% more of the RDA for zinc than non-vegetarians."
The RDA for adult men is 11mg, women 8mg. So, vegans may want to shoot for: men 16.5mg, women 12mg.
That's vegetarianism. Below is a recent study that describes how zinc deficiency can develop with age, independant of diet. Since zinc is an integral component of the immune system, defiency or sub-optimal levels can lead to a decline of the immune response (so, increased vulnerability to infection), and increased inflammation (so, increased risk for inflammatory diseases - heart disease, cancer, arthritis, and diabetes).

Increased Inflammatory Response In Aged Mice Is Associated With Age-related Zinc Deficiency And Zinc Transporter Dysregulation, The Journal of Nutritional Biochemistry, September 2012

From the abstract:
"Zinc deficiency ... was associated with increased inflammation with age. ... Restoring zinc status via dietary supplementation reduced aged-associated inflammation."
The research was conducted at Oregon State University which released a press release:

Zinc Deficiency Mechanism Linked To Aging, Multiple Diseases, Oregon State University, 1 October 2012
"[The study] suggests that it’s especially important for elderly people to get adequate dietary intake of zinc, since they may need more of it at this life stage when their ability to absorb it is declining.

[The study] found that zinc transporters were significantly dysregulated in old animals. They showed signs of zinc deficiency and had an enhanced inflammatory response even though their diet supposedly contained adequate amounts of zinc.

When the animals were given about 10 times their dietary requirement for zinc, the biomarkers of inflammation were restored to those of young animals.

“We’ve previously shown in both animal and human studies that zinc deficiency can cause DNA damage, and this new work shows how it can help lead to systemic inflammation,” [study author] Ho said.

In zinc deficiency, the risk of which has been shown to increase with age, the body’s ability to repair genetic damage may be decreasing even as the amount of damage is going up."
So ... The elderly, especially if they don't eat much animal food, are vulnerable to zinc deficiency. This raises the question, again, as to the suitability of supplements for this population. Taking any single nutrient in pill form can offset the amount of other nutrients we absorb. The authors said so much:
"Levels of zinc intake above 40 milligrams per day should be avoided, researchers said, because at very high levels they can interfere with absorption of other necessary nutrients, including iron and copper."
Nonetheless, Ho advised all seniors to take a supplement that includes the full RDA for zinc (11mg for men, 8mg for women). This doesn't sound like a bad idea.
The map of zinc deficiency areas is from Brian Alloway's 2008 Report: Zinc In Soils And Crop Nutrition. He says, "Zinc deficiency appears to be the most widespread and frequent micronutrient deficiency problem in crop and pasture plants worldwide." I wonder if soils were richer in zinc years ago.


Bix said...

Remember ... Zinc follows protein. So a low-protein diet is a low-zinc diet.

Healthy Longevity said...

Dr. Michael Gregor's released an informative video recently describing mineral absorption enhancers in allium vegetables:

A quick search through nutrient database may also be informative when selecting plant-based foods:

Bix said...

How about that. Eating the grains or beans along with onions or garlic increased bioaccessibility. I wonder what the mechanism is...

Good stuff!

Bix said...

Ok, here's the study:

Higher Bioaccessibility of Iron and Zinc from Food Grains in the Presence of Garlic and Onion

So, they looked at changes in bioaccessibility, in vitro. It doesn't reveal changes in actual absorption, in vivo. Not saying that alliums can't increase mineral absorption, but what is available to be absorbed, and what actually gets absorbed, are different things.

The mechanism in the study in my post involved epigenetic changes that affected the zinc transporter, and that resulted in decreased zinc absorption. What I thought was notable about it ... if I ate the same amount of zinc, say the RDA of 11mg, day in and day out, I might absorb progressively less of it as I aged, and could become zinc deficient even if I was eating adequate zinc.

A difficulty in trying to make up for decreased absorption by eating more food is that the elderly tend to eat less food ... for a number of reasons ... because they are less physically active, perhaps from disabilities, their taste sensations change, drugs and mental states reduce appetite, they have reduced ability to purchase food, cook food, chew food, and on.

Should seniors take supplements?