Why we include Vitamin D in Juice Doctor

Why Vitamin D?

*Content revised and edited from NIH website

About Vitamin D:

Vitamin D (also referred to as calciferol) is a fat-soluble vitamin that is naturally present in a few foods, and added to others. It is also produced endogenously when ultraviolet (UV) rays from sunlight strike the skin and trigger vitamin D synthesis.

Vitamin D promotes calcium absorption in the gut and maintains adequate serum calcium and phosphate concentrations to enable normal bone mineralization and to prevent hypocalcaemia which can lead to muscle cramps and spasms. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts [1-3]. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Together with calcium, vitamin D also helps protect older adults from osteoporosis.

Vitamin D has other roles in the body, including reduction of inflammation as well as modulation of such processes as cell growth, neuromuscular and immune function, and glucose metabolism [1-3].

Who has potential to benefit from Vitamin D supplementation:

People with limited sun exposure:

People with occupations that limit sun exposure are among the groups that are unlikely to obtain adequate amounts of vitamin D from sunlight [62]. 

People with conditions that limit fat absorption:

Because vitamin D is fat soluble, its absorption depends on the gut’s ability to absorb dietary fat [4]. Fat malabsorption is associated with medical conditions that include some forms of liver disease, cystic fibrosis, celiac disease, Crohn’s disease, and ulcerative colitis [1,63]. In addition to having an increased risk of vitamin D deficiency, people with these conditions might not eat certain foods, such as dairy products (many of which are fortified with vitamin D), or eat only small amounts of these foods. Individuals who have difficulty absorbing dietary fat might therefore require vitamin D supplementation [63].

People with obesity or who have undergone gastric bypass surgery:

Individuals with a body mass index (BMI) of 30 or more have lower serum 25(OH)D levels than individuals without obesity. Obesity does not affect the skin’s capacity to synthesize vitamin D. However, greater amounts of subcutaneous fat sequester more of the vitamin [1]. People with obesity might need greater intakes of vitamin D to achieve 25(OH)D levels similar to those of people with normal weight [1,64,65].

Individuals with obesity who have undergone gastric bypass surgery can also become vitamin D deficient. In this procedure, part of the upper small intestine, where vitamin D is absorbed, is bypassed, and vitamin D that is mobilized into the bloodstream from fat stores might not raise 25(OH)D to adequate levels over time [66,67].  

Older adults:

Older adults are at increased risk of developing vitamin D insufficiency, partly because the skin’s ability to synthesize vitamin D declines with age [1,61]. In addition, older adults are likely to spend more time than younger people indoors, and they might have inadequate dietary intakes of the vitamin [1].

Bone health and osteoporosis

Bone is constantly being remodeled. However, as people age—and particularly in women during menopause—bone breakdown rates overtake rates of bone building. Over time, bone density can decline, and osteoporosis can eventually develop [71].

More than 53 million adults in the United States have or are at risk of developing osteoporosis, which is characterized by low bone mass and structural deterioration of bone tissue that increases bone fragility and the risk of bone fractures [72]. About 2.3 million osteoporotic fractures occurred in the United States in 2015 [73]. Osteoporosis is, in part, a long-term effect of calcium and/or vitamin D insufficiency, in contrast to rickets and osteomalacia, which result from vitamin D deficiency. Osteoporosis is most often associated with inadequate calcium intakes, but insufficient vitamin D intakes contribute to osteoporosis by reducing calcium absorption [1].

Bone health also depends on support from the surrounding muscles to assist with balance and postural sway and thereby reduce the risk of falling. Vitamin D is also needed for the normal development and growth of muscle fibers. In addition, inadequate vitamin D levels can adversely affect muscle strength and lead to muscle weakness and pain (myopathy) [1].

Clinical trial evidence on older adults

Among postmenopausal women and older men, many clinical trials have shown that supplements of both vitamin D and calcium result in small increases in bone mineral density throughout the skeleton [1,74]. They also help reduce fracture rates in institutionalized older people. However, the evidence on the impact of vitamin D and calcium supplements on fractures in community-dwelling individuals is inconsistent.

Can the Vitamin D in Juice Doctor (cholecalciferol) be absorbed if there is no fat in the hydration drink?

What we know from the following study is that:

A systematic Review on the topic showed “Vitamin D was better absorbed when it was consumed with fat-containing meals, but absorption also occurred without fat or oily vehicles.”

Silva, M. C., & Furlanetto, T. W. (2018). Intestinal absorption of vitamin D: a systematic review. Nutrition Reviews, 76(1), 60–76. 

An interesting study by Dawson in 2013, looked at whether a meal and its fat content influence D3 absorption and 25(OH)D levels. They looked at men and women between 50-59 years of age, and randomly assigned to one of three meal groups: no meal, high‐fat meal, or low‐fat meal; each was given a monthly 50,000 IU vitamin D3 supplement with the test breakfast meal (or after a fast for the no‐meal group) and followed for 90 days.

What they found 12 hours after the test dose was an increase in the plasma 25(OH)D in the low fat group in comparison to the high fat or no fat group.

However, at 30 and 90 days, although all groups had increased plasma concentration, there was no significant difference between the 3 groups.

Dawson-Hughes B, Harris SS, Palermo NJet al. Meal conditions affect the absorption of supplemental vitamin D3 but not the plasma 25-hydroxyvitamin D response to supplementation. J Bone Miner Res. 2013;28:1778–1783. doi: 10.1002/jbmr.1896.

In summary, Vitamin D absorption is complex. Although the traditional thinking has been that Vitamin D absorption is better with fatty meals, we now have data to say that is likely not the case. Although further studies are needed, we know that Vitamin D can be absorbed without fat or oily vehicles, and that the amount of fat with which vitamin D is ingested does not seem to significantly modify the bioavailability of vitamin D3 in the body.

What’s new in​​ the Vitamin D literature?

The landscape for Vitamin D is changing with respect to its impact on preventing fractures. It was previously thought that Vitamin D supplementation (up to 2000 IU daily), decreased the risk of fragility fractures. This high dose Vitamin D supplementation was previously recommended in Osteoporosis Management guidelines (i.e. Osteoporosis Canada), as recently as 2022. 

Although Vitamin D supplementation appears to have benefit in terms of bone density, recent systematic reviews suggest that Vitamin D supplementation alone, does not decrease the risk of fracture.

See Tools for practice Summary link which summarized the evidence.

These recent findings have led to a change in the daily dosing recommendations for adults. Whereas previously, recommended daily intake in most guidelines ranged from 800-2000 IU, guidelines are now suggesting 600-800 IU daily.

In light of this recent change to the guidelines that is reflected by high quality evidence, Juice Doctor has adjusted the Vitamin D per serving, from 800 IU to 400 IU. With a recommendation of 1-2 servings per day, the daily Vitamin D intake from Juice Doctor is now 400-800 IU, which is better aligned with the current evidence/recommendations.

Studies are ongoing and the data is always changing. Our goal at Juice Doctor is to continually review the literature and use high quality studies to help inform our decisions on ingredients and dosing.

REFERENCES

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