Meat This has led to studies regarding the

as a Potential Source of Vitamin D

some time now, the human diet has been a topic of interest to our growing
population. In more recent years, that interest has fuelled extensive
scientific research. This has led to studies regarding the uses and effects of different
food sources on our bodies. With the vast range of information around us, it
can be difficult to deliver the facts. In this review entitled “Meat as a
Potential Source of Vitamin D”, it is my intention to deliver clear and
comprehensive facts under this heading.


D- It’s Sources and Benefits

D is a nutrient essential for maintaining a satisfactory calcium homeostasis
within the body, aiding bone development (Holick, 2004). Pure vitamin D3 under
application is a white or almost white crystalline powder, almost odourless
(EFSA, 2013). We are all familiar with the benefits of including Vitamin D in
our diet – it aids the absorption of calcium in our bones, strengthening bone
density. As it is a fat-soluble vitamin, it can be obtained from naturally
fat-containing foods (for example egg yolk, milk, butter). It is also known as
‘the sunshine vitamin’. This is because Vitamin D can also be obtained from natural
sunlight through the metabolism of 7-dehydrocholesterol to pre-vitamin D in the
skin by UV-B radiation. During the summer months, this exposure to direct
sunlight is the primary source of Vitamin D. Throughout the winter or reduced
periods of sunlight, one would rely on oral intake of Vitamin D (Holick, 2004)
perhaps in the form of supplements. The inclusion of Vitamin D in the diet has
been proven to decrease the incidence of osteoporosis which can be particularly
useful for the elderly as their bones become more porous and also for
menstruating females. Vitamin D occurs naturally in animal foods as cholecalciferol
(D3)  while ergocalciferol (vitamin D2)
is manufactured in the body (Deharveng, 1999).


 Role of Red Meat in International Dietary Guidelines

role of red meat in dietary guidelines can vary slightly from country to
country as generally, a country will have their own dietary preferences and
needs. The public often receive mixed messages in relation to the nutritional
value of meat. In recent years, the emergence of popular vegetarian and vegan
diets have led the population to believe that meat is ‘unhealthy’ and should
have no place in our diets. Meat is a valuable source of high biological value
protein, iron, vitamin B12 in the diet as well as other B complex vitamins. According
to the World Health Organisation, iron
deficiency is the most common and widespread nutritional disorder in the world
affecting both developing and developed nations (McNeill & Elswyk, 2012). Fat
content, a continuous area of concern when referring to meat consumption, depends
on animal type, feed type and quantity as well as the meat cut used. Pork meat
can have the highest fat content. Information like this can portray red meat in
a negative light.  In developed
countries, pork accounts for 50% of total red meat consumed, making it the most
widely consumed red meat (in those developed countries) (McNeill & Van
Elswyk, 2012).

1. International dietary guidelines for healthy eating in relation to meat

Country (Reference document)

Year published

Protein group
no. of serving/day

size (g)

Other meat-related comments

US (Dietary guidelines for americans 2015–2020,
8th edition)


~ 155 g/day from protein foods – as
part of a healthy US style eating pattern (2000 cal level).

No specific reference to meat serving size

Recommend a variety of protein foods.

Lower intakes of meats, including processed meats; have often been identified
as characteristics of healthy eating patterns. Specific recommendation to
include ~ 225 g of seafood/week.

Canada (Eating well with Canada’s food guide)


Females: 2 servings/day;
Males: 3 servings/day

75 g of cooked beef, pork or game-meat.

Meat and alternatives group provides important
nutrients such as iron, zinc, magnesium, B vitamins, protein and fat.

Ireland (Healthy food for life – healthy eating
guidelines and food pyramid)


2 servings/day

50–75 g cooked – lean beef, lamb, pork,

Lean red meat is good source of iron.

Limit processed salty meats such as sausages, bacon and ham – not every day.

UK (Eatwell guide)


No protein food group serving recommendation

70 g/day red and processed meat – average
daily consumption in the UK

If you eat > 90 g of red or
processed meat per day, try to cut down to ? 70 g/day.


from Cashman & Hayes, 2017).

is also worth noting that there is a difference in dietary quality of processed
and unprocessed red meat – processed meat was declared carcinogenic in 2015 by
IARC (Cashman et Hayes,2017). In the table above we see the term ‘lean’ meat.
Lean meat is generally defined as meat containing 5%-10% fat (Williamson et al,
2005) i.e 5-10g total fat per 100g meat.  As stated by Cashman & Hayes (2017)- “In
terms of optimal quantity of meat within a healthy diet, the Canadian and Irish
dietary guidelines suggest 50–75 g of cooked meat as a protein food group
serving” – leaving us with a guideline to follow, where lean meat would be the
preferred meat type. International bodies addressed in the table above have not
outlined a limit for daily lean meat consumption. However, there is agreement
amongst all bodies that a variety of protein sources in the diet is best,
placing particular emphasis on the inclusion of fish. (Cashman & Hayes,
2017). Pushing fish as a replacement protein source instead of red meat is an
attempt to lower fat intake. Meat and meat products are divided into subgroups
within the UK food composition tables including meat, poultry, game, offal, and
meat products (Cashman & Hayes, 2017).  NNR’s (Nordic Nutrition
Recommendations) RDA equivalents for vitamin D was set at 10 ?g/d for all
individuals aged 2-70 years. This RDA value was below the IOM’s
15 ?g/d for the same age range (Cashman, 2015). The Irish dietary
guidelines propose that processed meat should not be eaten every day while the
UK ‘Eatwell Guide’ specifically recommends that consumers
consume only 70 g/day of meat in the diet and urge those who consume over
90 g/day to reduce their intake (Cashman, 2015). Dietary requirement
estimates which form the DRI (Dietary Reference Intakes) values are based from the
EAR (10 ?g/d for persons aged 1 and over) and RDA (15 ?g/d ages 1 to
70, and 20 ?g/d for those over 70 yrs of age) (IOM
Institute of Medicine, 2011).


to Increase Vitamin D Concentration in Meat

D supplementation has been suggested as a means of bridging the gap between
current vitamin D intakes and new recommendations, but their usage appears to
be quite low. The fortification of food with vitamin D has been suggested as a
strategy for increasing intake (Cashman, 2015). These suggestions are an
attempt to reduce vitamin D deficiencies such as osteoporosis, a disease of the
bones, among the population. Increasing the vitamin D concentration in food,
and in this case red meat, can be done via a process known as biofortification
– the addition of vitamin D to animal feed to enhance vitamin D concentration
in the meat ahead of slaughter. Regarding biofortification with vitamin D, the
animal could have increased vitamin D and/or 25-hydroxyvitamin D contents by their
addition to the livestock feeds. Meat type, quantities fed and period of
feeding time will all have an impact on residual levels of Vitamin D in the
meat. Meat samples can be analysed for their Vitamin D content by undergoing
solid phase extraction followed with analysis by normal phase liquid
chromatography, after initial saponification. This method allows for the rapid
and sensitive analysis of vitamin D and 25OH-Vit D in meat (Strobel et Al, 2013),
giving us accurate measurements of residual vitamin D levels in meat.


of Animals and Residual Effect on Meat

D content of meat may be boosted through biofortification. This is a process in
which additional vitamin D is added to animal feed. Various trials have been
carried out involving vitamin D fortified feed being given to different animal
types (e.g beef cattle, lamb). One such trial was conducted to investigate the
influence of feeding vitamin D3 and aging on the tenderness of four lamb
muscles. In Trial 1, different levels (0, 250,000, 500,000 or 750,000 IU) of
vitamin D3 were fed to rams (n=26) for 4 days to determine the
most effective dose to increase calcium concentrations in the blood. In Trial 2,
feedlot lambs (n=40) were fed different levels (0 or 750,000 IU) of
vitamin D3 for 14 days to determine if vitamin D3 could
improve the tenderness of lamb muscles. Lambs were slaughtered and the M.
longissimus lumborum, M. biceps femoris, M.
semitendinosus, and M. semimembranosus were removed after
chilling, cut into chops, and assigned to an aging period (5, 10 or 15 days). Results
of Trial 1 showed weight gain was lower for rams supplemented with 500,000 IU
of vitamin D3. Trial 2 results showed that “Control chops from
the M. longissimus lumborum had lower (P<0.05) WBS values than chops from vitamin D3 fed lambs, but no other muscles were affected by vitamin D3 feeding".  Vitamin D3 supplementation was not an effective means of improving the tenderness characteristics of lamb muscles (Boleman et al, 2004). The rams used in Trial 1 weighed approximately 40kg. The doses of vitamin D3 were administered via bolus or feed supplementation to the rams. Vitamin D3 was mixed with corn meal for feed supplementation at a ratio of 1:2 During the trial, vitamin D doses were administered days 1 through 4. For Trial 2, lambs used were approximately 40kg and 8 months old. A control pen was created containing twenty lambs while the remaining 20 lambs (n=40), divided into 4 pens (5 lambs per pen) were administered a treatment of 750,000 IU vitamin D3.  Pens assigned to receive vitamin D3 supplementation were fed a mixture of the commercial feed ration and Rovimax D3 500. One week before commencing the trial, lambs were given free access to hay to allow them to adjust to the new environment. After adjustment phase, each pen received 4.54 kg of feed each day for a total of 14 days. Each day before new feed was given, refused feed was cleaned from feeders and weighed to calculate percent intake (Boleman et al, 2004). No significant differences were noted in blood calcium level between all treatment levels and controls. However, rams administered 750,000 IU vitamin D3 tended (P=0.0916) to have higher blood calcium levels at day 5 than control rams. Overall, results showed that feeding high levels of vitamin D3 to lambs did not improve the tenderness or aging characteristics of lamb muscles (Boleman et al, 2004). Another study involving 142 steers of 3 biological types was conducted; Bos taurus-English Bos taurus-Continental (predominantly Charolais and Limousin), and Bos indicus.  The steers were housed for 14 days, fed a 60% concentrate diet to start and then separated into the three respective breed types. For each breed type, steers were grouped by starting weight and grouped to one of the four dietary vitamin D3 treatments. Their diet was enhanced to a 90% concentrate diet over a period of 14 days. Day 1 of the study was marked by weighing and sorting each steer to a new pen after the 14 day period. The feeding system used to dispense the 90% concentrate diet was The Burnett Center feed milling system which is computer-controlled. Once the total diet was mixed, the feed was delivered via a belt-feeding system. The quantity of feed remaining in each bunk was recorded every day. Study outlined that feed troughs were cleaned, and unconsumed feed was weighed. Steers in all pens were weighed after 99 days on feed and allocated into final study pens based on their weights. The dietary treatments consisted of 0, 0.5, 1.0, or 5.0 × 106IU/(steer•(d) of VITD during the last 8 d of feeding (study d 116 to 123). Four pens of each biological type received one of the four VITD treatments for the last 8 d of feeding (d 116 through 123 of the study). Every day the VITD amount per pen was noted and diluted in 100 g of ground cornmeal. For the final 8 d of treatment, bunks were cleaned and leftover feed was collected and weighed. At study day 123, each steer was again individually weighed before being transferred to another facility for slaughter and carcass analysis on day 124. Feedlot performance data, carcass traits, and plasma Ca and P concentrations were analyzed using a 4 (VITD treatment) × 3 (biological type) factorial arrangement of treatments. Treating steers with VITD resulted in a quadratic increase (P = 0.007) in blood plasma Ca concentrations at slaughter. Supplemental VITD at 5 million IU/(steer•d) had the greatest effect on increasing plasma Ca2+ and P compared with the other VITD treatments. Results from research show that cattle can be supplemented with 0.5 million IU of VITD/(steer•d) to improve beef tenderness without adversely affecting feedlot performance and carcass traits but cannot raise residual level of vitamin D in the meat for it to be classified as a 'source of vitamin D'.  (Montgomery et al, 2004). A study outlined by Duffy et al, 2017, documenting the effect on vitamin D concentration of cholecalciferol supplementation in heifer diets has proved invaluable to this review. Thirty continental heifers (Charolais × Limousin crosses) were grouped according to weight and age and then randomly allocated to one of three dietary treatments: (Treatment 1) basal + 0 IU of vitamin D?/kg diet; (Treatment 2) basal + 2000 IU of vitamin D?/kg diet and (Treatment 3) basal + 4000 IU of vitamin D?/kg diet. These dietary treatments were carried out for the 30 day period before slaughter of the animal. The basal diet consisted of a standard ad-libitum finishing regime of concentrates and forage (straw) at a ratio of 90:10. The 4000 IU of vitamin D?/kg/feed is the maximum inclusion rate in bovine diets. Taking this inclusion rate into consideration, it was ensured that the treatments complied with EU regulations (Duffy et al, 2017).  Diets were created to meet nutrient requirements of finishing beef heifers. Typically, 2000 (half the maximum inclusion rate) IU of vitamin D? is the upper inclusion rate used in most commercially made feeds. Generally, farmers would choose a feed with maize as the main constituent, yielding a high-energy mix. Ingredients such as rapeseed and maize distillers may be used as a protein source, soya hulls as a fibre source, and then the inclusion of the required vitamin concentrate would then be added. The concentrate:forage ratio for the study was offered at 90:10. Composition of the concentrate was as follows:     Item (g/kg) Dietary treatments1 T1 T2 T3 Concentrate Dry matter 830.2 828.0 826.8 Ash 57.5 54.4 52.8 Crude protein (N × 6.25) 107.4 103.9 101.9 Ether extract 16.7 16.8 16.9 Neutral detergent fibre 192.1 200.8 198.0 Cholecalciferol (IU/kg)2 376.0 1680.0 4320.0 (Table taken from Duffy et al, 2017). A system was in place to monitor feed management and weight gain of the heifers while being housed in a slatted shed. A total of 5 pens, with 6 heifers per pen was set up. The Calan Broadbent controlled feeding system was used to feed each heifer individually. A unique key hanging from a neck cord was fitted to each animal. The animal's sensor key unlocks the feed door as it recognises the electronic circuit board on each feeder. This controlled feeding system also meant feed was weighed in and uneaten (refused) food was weighed out on a daily basis. For the duration of the experiment heifers were weighed weekly using a 'Weigh Crate' (Duffy et al, 2017).  Once animals reached slaughter weight, they were then stunned. After slaughter, the carcass was drained of blood and eviscerated and post-slaughter carcass weight (hot carcass weight x 0.98) was noted. The whole carcass aged for a total of 14 days at 4°C before the longissimus thoracis (LT) muscle was cut into 2.5 cm thick steaks for vitamin D analysis. The 'total vitamin D activity' of the 14-day aged steaks and vitamin D3 and 25-OH-D3 content of experimental diets were analysed using modifications of a sensitive liquid chromatography-tandem mass spectrometry (total vitamin D activity of longissimus thoracis muscle was defined as vitamin D3 + (25-OH-D3 × 5). In this study, supplementing heifer diets with vitamin D? "linearly increased (P < 0.001) serum 25-OH-D3 concentrations, the index of vitamin D status" (Duffy et al,2017).  Results showed that as dietary vitamin D? levels increased in the heifer's diet, vitamin D activity in the LT including, LT total vitamin D (R2 = 0.78), LT vitamin D? (R2 = 0.84) and LT 25-OH-D? (R2 = 0.75) content also linearly increased (P < 0.001). Heifers who were fed the highest EU acceptable diet of 4000 IU of vitamin D?/kg diet (Treatment 3) had a 42% increase in LT total vitamin D activity over heifers partaking in Treatment 2, the 2000 IU of vitamin D?/kg diet, and a 145% increase over those on the 0 IU vitamin D?/kg diet (Treatment 1). Results of the data from this study would indicate that eating beef derived from cattle fed a vitamin D? enriched diet (not above the EU limit of 4000 IU of vitamin D?) before slaughter has the potential to contribute up to 9% (per 100 g beef intake) of an individual's recommended daily intake of vitamin D (between 15 and 20 ?g/day as recommended by the IOM) and 13.5% of the EAR of 400 IU/day (Duffy et al, 2017).  In turn, with the use of vitamin D fortified feed to finish beef heifers, red meat can qualify as a potential source of vitamin D in the diet. Conclusion It is clear that for most populations there are a majority of individuals failing to meet the EAR for vitamin D (Cashman, 2015). Consumers should now be more aware of the gap between recommended intake of vitamin D and the current dietary intake. According to the EFSA, regarding vitamin D3 supplementation of feed concludes that the use of vitamin D in animal nutrition at the currently authorised maximum dietary content has not and will not cause the tolerable upper intake level to be exceeded (EFSA, 2013).  It must be acknowledged that there is a need for a solution to bridge this gap. This review shows us that biofortifictation of food, and in this instance the biofortification of meat by addition of vitamin D to feedstuffs, is an area that has attracted serious attention as a likely food fortification strategy.     References: Boleman, C.T., McKenna, D.R., Ramsey, W.S., Peel, R.K., Savell, J.W., 2004, Influence of feeding vitamin D3 and aging on the tenderness of four lamb muscles, Meat Science, Vol.67, p.185-190 Cashman, K., 2015, Vitamin D: dietary requirements and food fortification as a means of helping achieve adequate vitamin D status, Journal of Steroid Biochemistry and Molecular Biology, Vol.148, p.19-26 Cashman, K., Hayes, A., 2017, Red Meat's Role in Addressing 'Nutrients of Public Health Concern', Meat Science Journal, Vol.132, p.196-203 Deharveng, G., Comparison of nutrients in the food composition tables available in the nine European countries participating in EPIC, European Journal of Clinical Nutrition, Vol.53, p.60 Duffy, S.K., O'Doherty, J.V., Rajauria, G., Clarke, L.C., Cashman, K.D., Hayes, A., O'Grady, M.N., Kerry, J.P., Kelly, A.K., 2017, Cholecalciferol supplementation of heifer diets increases beef vitamin D concentration and improves beef tenderness, Meat Science, Vol.34, p.103-110 EFSA, Vol.11, Issue 7, Scientific Opinion on the safety and efficacy of vitamin D3 (cholecalciferol) as a feed additive for pigs, piglets, bovines, ovines, calves, equines, chickens for fattening, turkeys, other poultry, fish and other animal species or categories, based on a dossier submitted by Fermenta Biotech Ltd Holick, M.F., 2004, Vitamin D: Importance in the Prevention of Cancers, type 1 Diabetes, Heart Disease, and Osteoporosis, American Journal of Clinical Nutrition, Vol.79 , p. 362-371 IOM Institute of Medicine, 2011, Dietary Reference Intakes for Calcium and Vitamin D, The National Academies Press McNeill, S., Van Elswyk, M., 2012, Red Meat in Global Nutrition, Meat Science, Vol.92, p.166-173 Montgomery, J.L., Galyean, M.L., Horst, R.L., Morrow Jr, K.J., Blanton Jr, J.R., Wester, DB., Miller, M.F., 2004, Supplemental vitamin D concentration and biological type of beef steers. I. Feedlot performance and carcass traits, Journal of Animal Science, Vol.82, Issue 7, p.2050 Strobel, N., Buddhadasa, S., Adorno, P., Stockham, K., Greenfield, H., 2013, Vitamin D and 25-hydroxyvitamin D Determination in Meats by LC–IT-MS, Food Chemistry, Vol. 138, p. 1042-47. Williamson, C.S., Foster, R.K., Stanner, S., Buttriss, J.L., 2005, Red meat in the diet, Nutrition Bulletin, Vol. 30, p. 323-355