Meat This has led to studies regarding the

Meat
as a Potential Source of Vitamin D

For
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.

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Vitamin
D- It’s Sources and Benefits

Vitamin
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

The
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).

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

Country (Reference document)

Year published

Protein group
no. of serving/day

Meat-serving
size (g)

Other meat-related comments

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

2015

~ 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)

2011

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)

2016

2 servings/day

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

Lean red meat is good source of iron.

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

UK (Eatwell guide)

2016

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.

 

(Table
from Cashman & Hayes, 2017).

It
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).

 

How
to Increase Vitamin D Concentration in Meat

Vitamin
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.

 

Feeding
of Animals and Residual Effect on Meat

Vitamin
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