RALEIGH, N.C. — There’s a lot of truth in the old slogan “milk does a body good.” One reason kids are encouraged to drink milk is because it contains vitamin D. A new study finds this substance plays an even bigger role in growth and development than many realize. Researchers at North Carolina State University say a diet lacking vitamin D not only causes stunted growth, but also increases the risk of obesity.
Biological Sciences Professor Seth Kullman says tests on zebrafish reveal diets without the vitamin produce significantly smaller fish with much higher fat reserves. The study looks at the effects on these fish while on three distinct diets. For four months, the team fed three groups of post-juvenile zebrafish a no-vitamin D diet, a vitamin D-rich diet, and a control diet.
Kullman’s group then looked at the differences in growth, bone density, triglyceride, lipid, cholesterol, and vitamin D levels. In regards to obesity, they also compared the fat production, storage, and growth promotion in these fish.
‘Vitamin D plays important role in ability to channel energy into growth versus fat storage’
“The vitamin D deficient zebrafish exhibited both hypertrophy and hyperplasia – an increase in both the size and number of fat cells,” Prof. Kullman says in a university release. “They also had higher triglycerides and cholesterol, which are hallmarks of metabolic imbalance that can lead to cardio-metabolic disease. This, combined with the stunted growth, indicates that vitamin D plays an important role in the ability to channel energy into growth versus into fat storage.”
The zebrafish with no vitamin D in their diet were also found to be 50 percent smaller than their peers.
You might be asking, what does a zebrafish have to do with humans? Studies find this small freshwater species is extremely similar to humans on a molecular, genetic, and cellular level. This makes them very helpful to scientists studying vertebrates, animals with backbones.
Another bonus of using zebrafish, they grow from an egg to swimming freely in just five days. Thanks to their quick growth period, another recent study uses the species to examine vitamin E deficiencies in growing embryos.
Can you ever make up these deficiencies?
Following the initial tests, the NC State team attempted to help the vitamin D-deficient zebrafish catch up to the other groups. Despite switching to a vitamin D-enriched diet for six months, the fish never caught up in size with the others. Scientists note the fish lacking vitamin D did continue to grow and began to properly use their fat reserves. In the end however, they still retained more fat deposits.
“This work shows that vitamin D deficiency can influence metabolic health by disrupting the normal balance between growth and fat accumulation,” Kullman explains. “Somehow the energy that should be going toward growth is getting shunted into creating fat and lipids, and this occurrence cannot be easily reversed. While we don’t yet understand the mechanism, we are beginning to tease that out.”
Other foods that contain nutritious amounts of vitamin D include salmon, sardines, egg yolks, mushrooms, and cereals. The team says future studies will involve the babies of vitamin D-deficient mothers. They hope to see if nutritional issues can be passed down to children.
The study appears in Scientific Reports.